That makes sense. I think different lengths coax does cause a propagation delays in the longer coax, resulting in an interference pattern, where out of phase signals cancel or at least diminish the signal strength. With same exact length coaxes, the signal propagation is matched and consequently no out of phase interference pattern.
I appreciate you taking the time to experiment. I’ve tried using using two antennas with a combiner before and had similar issues. I should have know separate lengths of coax would cause an issues with the same signal arriving at different time to the tv tuner. I guess the only other way it would not cause issues is if you use directional antennas that severely attenuated signals coming from the opposite direction, but nothing ideally attenuates a signal in the real world, haha!
I'm using a Televes SmartKom to combine two antennas on either ends of my house, as I'm right in between the two broadcast towers I want to receive from. It does a great job of evening out all the signals, despite vastly different coax runs.
What you can do is to get a bandpass filter from Arcom for the antenna that receives the single required channel, to just let through the frequency that you want before the combiner. You are correct that the channels being received by both antennas are cancelling out however if you just let through the channel that you want then it will work. Thanks again for a great video.
And notch filter for the other antenna to keep it from interfering with the antenna of the required channel. Such filters are pretty expensive though. Could feed each antenna into a separate networked tuner and set the display device to use the tuner based on channel. No combiner used this way and mismatched coax not an issue. For RG6 coax run longer than 30 feet or so put an amplifier at the antenna.
I live in an apartment and our broadcast towers are about 20-25 miles away and SSW in direction. I am using a Sling AirTV tuner with the antennas. My apartment building is ironically skewed by just about the same amount from true north/south. My apartment exterior however, does not face the broadcast towers but exactly in the opposite direction. I placed my antennas in my master bedroom closet. To point my antenna toward the towers, the signal has to pass through my next-door neighbor's apartment and their closet and my closet before reaching the antenna. This resulted in inadequate signal strength obviously, even with a small amplified antenna that worked better than any other that I had tried, including a large 150 mile yagi herringbone type antenna. Since I got almost good signal some of the time and weather played a roll in quality, I tried a combiner and another identical amplified antenna mounted to the same wall in an over/under configuration, about 1.5-2.0 feet apart, both pointing to the same towers. My signal isn't great and does have good days and bad depending on the weather, but it is much better with two identical antennas combined and pointed toward the same towers than it was with only one.
A few points: 1) If you have two antennas at right angles, different lengths matters less. 2) If your "base line" is at right angles to the direction to the transmitter, equal lengths work the best. 3) If your "base line" is so that the antennas are at different distances from the transmitter, unequal coax lengths works the best. The difference in coax is about 70% of the difference of the distance to the transmitter.
Phased arays are cool. And also very mathematically complicated haha. But wow - using non-identical lengths of coax in each leg from the Y-point in the coax is gonna cause big variations (at least in theory, though as you will already know working in the TV antenna business, there's more art than pure science to a lot of this stuff) Unless the coaxes are the exact same length (down to the millimetre, in fact) for any given frequency (eg: a single TV channel, keeping it simple) you'll get a directional skew in the gain pattern depending on the phase difference between the coax cables. (300/length n metres / velocity factor of the cable). You could in fact get away with using 3x or even 5x the length of one leg in the other leg, though that would lead to more loss especially at higher frequencies (based on more attenuation in the longer coax leg) A problem even if you use the same ength of coax in each arm, is that the two different antennas will present a reduced impedance to the main feedline. So two 75 ohm antennas will result in 37.5 ohms impedance (just like resistors in parallel). Any reactance (capacitive or inductive, will be additive or subtractive dependent on the reactance of the antennas in use at any given frequency. It is possible to use a specific length of coax that has a different characteristic impedance (often a 50 ohms section) to the main coax (which is usually 75 ohms) to transform the combined impedance of both antennas and make it closer to 75 ohms again, but the problem for TV use is that this transformation section length is frequency-dependent, so it won't work across a wide TV band. So the only sane way to do this is to use the exact same length in each leg of the coax harness, keeping the phasing accurate and losses identical in each leg of the Y harness. _ This is the point where my brain has already started hurting and beer seems like a very good plan B _ Sometimes easier results may be obtained if you use a narrow-band amplifier (of low gain) , one for each antenna (narrowband to reduce interference and noise problems) though amplifiers, as you probably know, give their own problems as well. The advantage to using 2 amplifiers here is that they present a known stable output inpedence to the splitter and the coax run-in to the TV receiver. A common problem ti this approach is the 2 amplifier can interact and sometimes go into spurious opscillation, causing all sorts of troubles. In theory, if you have good signal strength, you could just use a resistive or inductive splitter, which would be even better, though that would mean you would need a good striong signal in the first place, so it's Catch 22 - you *_already_* have signal strength problems if you are trying to combine antennas ! Phased array radar antenna arrays generally use an amplifier for each antenna right at the feed point, or very close to it, with the advantage that it can help beamsteering by altering the phase to drive each amplifier and can be steered electrinically. TV channel combiners (the ones I've seen anyways) seem to use a filter or a tuned circuit to keep the two two antennas more electrically seperate, in the RF sense, In the commercial transmission world, they would be known as diplexers. Each port would present a high impedance to the other port at the particular frequencies in use, preferably as close to pure resistance as possible to avoid reactance making things complicated (yeah - RF guys - I know it's just +j and -j, but that concept is quiet hard to explain to someone who doesn't already use complex matching on a daily basis haha) In theory, you could make your own combiner by making a good low-loss tuned circuit to accept the "extra" channel you want, and place that in line with the coax leg to the "extra" antenna. You would then probably have to make a high-pass, low-pass or band0pass filter and place that in the line to the "main" antenna that accepts all the other channels. Each installation would require it's own unique filtering because it's likely that no one site would have the same combination of channels. Combining two indentical antennas pointing in the same direction is known as either stacking or baying. Stacking is mounting one above the other, which narrows the vertical beamwidth of the array - this is sometimes used to reduce aircraft relections from planes on apparoach to a local airport) Baying is side by side mounting of two identical antennae that point in the same direction - this narrows the horizontal beamwidth - and so this is sometimes used to reduce problems caused by multipath from a large reflective object nearby. But the above descriptons only apply to 2 identical antennae phased up to point in the same direction, and operated at the same frequency. Combining (not stacking or baying) two different antennae from possibly two different directions is what you are trying to do (edit: maybe not deliberately trying, but having unequal length in each leg causes a squint like that) - it's like an interferometer - used in a type of directional radio telescope) and boy oh boy is it complicated in comparison. For ham radio use, phasing identical antennas is used to get extra gain (*), though they use a very limited bandwidth and are only receiving one frequency at any given time, or maybe a narrow band of frequencies, so the length tolerances in both the accuracy of the "phasing harness" (the two identical leg lengths) and the impedance transformation section (which of course varies in length with wide frequency changes) are less of a problem. Another bonus is that some ham bands are near-harmonically related. For example. 146MHz is approximately (for impedance purposes) 3x the wavelength of 440MHz, so a quarter-wave impedance transformation section at 146Mhz kinda works OK as a 3/4 wave section at 440MHz. Because odd multiples of quarter wavelenth sections work basically the same (I'm simplifying it here) a phased/stacked-or-bayed dual-band 146/440Mhz antenna with equal-leg phasing harness and transformation section of coax will generally work OK on both bands. If only TV was that simple - the extremely wide bandwidths you guys need to cover make things extremely complicated :( Also note that the physical spacing between the two antennae is a factor that can affect gain and pattern response - though this is more of an issue for narrow-band antennae of high Q factor than wideband TV antenna designs. I have a terrible headache just typing about all this haha. For more technical info, you could try a Google search for stacked/bayed/phased yagi antennas - there's some good literature in the ham radio research field dating back well over 70 years, because phased dipoles and yagis were used in early fixed radar arrays so it's an established technique. Just bear in mind that narrowband ham or commercial radio usage doesn't really pan out to very wideband domestic TV reception, unfortunately, though admittedly that is mainly due to the impedance transformation section lengths being more narrow-band as they are selected to be a particular fraction of a wavelength, adjutsed for coax velocity factor, at any given frenquency. For simple TV experimentation, you could just ignore the impedance transformation section and use 75 ohm coax and connectors throughout and just hope the wideband characteristics of the antennas don't give too much trouble. In general, TV antenna designs are rather flat in impedance response and are also designed to be minimally reactive (capacitive/inductive, -j/+j )across the wideband response, so it may not matter so much, especially if using log periodic antennas. (*) the extra gain from stacking or baying 2 antenna pointed in exactly the same direction, used at exactly the same frequency, with no additional losses due to the coax Y-arms or the transformation section, is a theoretical 3dB (a doubling of power). You can double that again to a theoretical 6dB (4x the power) by adding two more antennae, making 4 on total. HOWEVER - in practice though, due to coax line and extra connector losses as well as impredance matching inaccuracies, as well as the close-in effects of having two antennae in close proximity to each other (which can cause beamwidth anomalies and impedance changes due to near-field effects) about 2dB gain increase for a 2-antenna array is average for VHF, maybe 1,5dB at UHF, unless very high quality coax and connectors are used. This generally limits the advantages of phasing two or more antennae to right-on-the borderlines-of-possibility communication method such as moonbounce communication, or for extremely dedicated DXers.
@@GrantsPassTVRepair Haha my pleasure - I love this stuff - antennas and arrays are all part of the super-secret black arts of RF. I just can't explain it any simpler, sorry - I really wish I could. I can't find the right words to describe it all without making it "just too wrong". This is a VERY complex topic - it really is far, far simpler for commercial radio transmission or ham use. The huge range of bandwidth you need for TV - especially in the US because I think you use some VHF TV too? - makes it an RF nightmare in practical engineering terms if you want to keep the cost down. I used to phase yagis, log periodics, dipoles and quads as a kid for extra gain and to reduce sidelobes - later I progressed to using variable phasing lengths to steer beam patterns and take-off angles. I've rarely thought about this stuff for the last 30+ years so it kinda all flooded out in one nig lumpy technical mess lol. Great channel by the way - keep it up.
@@gordslater Thanks. We have both UHF and VHF repeaters on different mountains around here, so my range of antennas can be a simple UHF loop or a full size yagi which attempts to cover a multitude of frequencies.
@@GrantsPassTVRepair yeah I noticed some larger VHF antenna sizes in some other vids. You certainly work in a very challenging area and those huge trees seem to be nightmares too haha
This is a very common issue for over-the-road truck driver dual antenna CB. Oftentimes in the overhead you'll find A rat's nest of wire but both are the same length.
#1 It all has to do with phasing, if antenna A is out of phase with antenna B you will get what’s called destructive interference. If the two antennas are in phase with one another you will get what’s called Constructive interference. *_“Destructive interference is when two waves traveling in the same direction are aligned at the crest of one wave and the trough of the other. The waves cancel out. Constructive interference is when two waves traveling in the same direction overlap, and their crests combine to produce a larger wave.”_* #2 If two identical antennas are co phased correctly you will get a gain of 3 db however, the length of the cables used for the phasing harness has to be a ¼ wave length for the frequency that you are trying to receive so they will be in phase for that frequency and only for that one frequency, and the antennas need to be spaced a 1/4 wave length from one another again this is for the frequency that you are trying to receive so they will be in phase for that frequency and only for that one frequency. This could contribute to losses at other frequencies. #3 Most signal combiners or antenna combiners, at best have an insertion loss of 3db this 3db loss will mitigate any gain that you would get from combining the two identical antennas. When you combine two antennas you get 3 db of gain. Note: I have used two identical antennas stacked one above the other with a ¼ wave phasing harness made from 300 ohm twin lead cut for the ¼ wave length of frequency that I wanted to receive. The phasing harness was between two antennas that I wanted to co phase I attached the twin lead to the 300 ohm terminals of each of antenna then on the bottom antenna where the twin lead connected to the 300 ohm terminals I attached a 300 to 75 ohm balun so I could run coax cable to the TV’s. It worked very well with very little loss on the other channels. The advantage of using the 300 ohm twin lead is that it eliminates the signal combiners and the 3db of loss that the contribute.
No argument on that. Someone suggested it could be beneficial to hook them up in series. Ether way I understand why two out of phase antennas could weaken their output.
The line length is matched on space diversity antennas in microwave communications. It used to be done by making the waveguide the same length, but now it can be made by an electronic adjustment. The receiver still only picks the best antenna.
The only way I can receive all the stations in my area is to combine 2 antennas. I have one set for downstairs and one set for upstairs. It is best to have an Amplfier for each set of antennas. Thanks for the video.
Tv towers in my area are in different directions so I hook 2 tv antennas together to get all the stations. I point one antenna southwest and one north west. @@XwpisONOMA
Let's be clear on this that a signal with a two-way divider isolates or combines two signals with significant amount of attenuation between one-another. The price you pay is a typical 3.5 dB loss by using it on each leg. Why not simply do what I do that and works well, buy two antennas, each must have a preamp to overcome any losses seen through the coax and signal divider. Take each pre-amp power supply and get a WYZE type WiFi AC power switch, two in a box, select the market you want to watch in my case it is NY and CT. Depending on signal of that day, if both are good I leave them both powered up. If it is a bad day with multi-path, I switch off the one that is causing an issue. About 1:00 AM in the morning they both default back to the on position with the build in clock. All controlled by a cell phone, isn't life sweet! 😊
@@jamesm568 I don’t quite see that thought, as one looses a significant amount of each antenna by coax losses, and what ever gain is left and divided by two further increasing signal loss significantly. I don’t suggest putting dividers at the antennas, other than the amplifiers I want to be able to make changes at the shack so to speak where it easier to get too. Unfortunately all bets are of with pre-amp as they need to be at the head end(antennas). Hence my suggestion of turning of the interfering preamp with choice when needed has worked terrifically, trust me!🙂
@@jamesm568 I do see your point if both antennas are pointing to the same market. My further explanation relates to two different markets(different directions). I actually do have an additional antenna pointing to the same market, it was availed to me, and selectively I switch between them when needed depending on propagation issues, but sometimes they do work well together. Maybe just has some favorable spacing and lead length by chance, but did not design for it.🙂
You can use any metal object as an antenna, but a good antenna is designed for a specific frequency, and cut to a specific size based on that frequency you are trying to pick up. You may find this video of interest. th-cam.com/video/vHVmJ5lD9jc/w-d-xo.html
It has always been when you combine two antennas to make sure they're the same antenna and to make sure the same cable length is used from each antenna to the combiner. Most of the time it works and then sometimes one antenna will cancel the other one out as it varies per setup and location. I found it works best to keep the antennas close to one another as possible. Sometimes I just use one transformer coming from both antennas.
@@GrantsPassTVRepair Every situation is different though. Sometimes two different antennas from different manufacturers work better when combined aiming at different markets.
I have a Televes two antenna combiner . I lose nothing at all with it. Pointed two different directions. One is getting my stations 27 miles west all UHF, the other is I think south east 5 miles away UHF and VHF…. All come in with no issues. ATSC 1.0 and ATSC 3.0…
Does the same thing running coax to different rooms. I been running two antennas for a couple years or so not for signal strength but to eliminate the rotor.
This was my recent experience, too. After putting up a new antenna, I found that the Ch 5 family of frequencies would not come in. So, I designed a yagi for the missing Channel family (Ch 5) but whenever the two antennas were combined, I lost the Ch 4 family. Cause? The antenna I purchased only has 3 dB of gain in the VHF section. That is not enough to pull in the missing Channel. IMO, 6-8dB of gain would be a minimum figure. Solution? Purchase an antenna with more gain in the VHF section and one that is designed for the low VHF, not just the high VHF band. As I have discovered, some manufacturers are building antennas now for the high VHF band only because TV stations are generally moving away from the low part of the VHF band. Where I'm at, the lower part of the VHF band is still used extensively.
Here in Grants Pass most of our channels are on UHF, but you can drive just a few miles away, and the same networks are broadcasting in VHF. I've been in some locations that pick up 4 different transmitters that are broadcasting the same networks on different frequencies, so sometimes I get doubles, triples, and even quadruples. Grants Pass can be a challenging place to install antennas.
When I coPhase to TV antennas I use the exact same length of 75Ohm coax from each antenna. You will loose some of the signal from the loose from the Combiner/Splitter. To over come the loose i install a small signal booster. NF1J 73s
P.S The problem is you can get the signals out of phase with different length coax. Be sure to use the exact same coax from the same spool . Different coax has different dielectric, etc that will cause issues when coPhaseing antennas
Thank you for taking the time. Did you also attempt to use the same cable manufacture? I'd assume different cables would cause a velocity difference too? Length and also same vs different manufactures would be interesting.
Hi i have an antenna with 2 coax leads 1 for each bay i am using a 2 way signal splitter in reverse (so 2 into 1) Is this not a good situation i notice you use a combiner or is that just a splitter ?? Thx in adv
So basically, different length cables may increase strength on some channels and weaken it on other channels, eg mis-matched cable lengths don't ALWAYS weaken signal for all channels.. interesting.
in my area (Grand Rapids, Michigan market), just about every station has its own tower. Most are in the same general area. However, two are in located in a totally different direction. It was common before everyone got cable to see antennae with elements pointing in different directions (south for CBS and NBC, west for PBS and north for ABC). Wonder how those worked? This would have been in the 70s and 80s.
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Just for the record, my video wasn'tt made to discourage anyone from installing two tv antennas, which can be beneficial in some locations, but to show the importance of coax length when joining two antennas together. I've since learned the distance between the antennas is also an important factor.
Combining antennas can and often does lower the dB signal strength. There is only so much possible gain from each direction, so when you use two, you divide the signal strength between the two antennas. Also, adding an additional antenna changes the radiation pattern and SWR for each frequency. I recommend getting a NanoVNA meter to understand further how antennas' alterations affect the Standing Wave Ratio (SWR) for each channel. A good signal meter is critical as well. The only time I ever use dual antennas is if the signals pull from two different directions and there is enough gain for both positions. A spread of more than 45 degrees will often diminish most distant signals. Ultimately, an antenna only needs two elements for each channel. The length of the elements is very specific to the frequency you are tuning in. Yes, much like the old rabbit ears. LOL, but really. Yagi and Log Periodic-style antennas have multiple elements on them, and this is not by accident--it's to accommodate for all the channels. In contrast, if a person only cared about one channel, then you only need two elements to optimize for that channel. For example, RF channel 7, not virtual channel 7, but RF 7/183 MHz, is a wavelength of 64.49 inches, so divided by two is 32.245-inch elements on each side to accommodate the entire wavelength. You must consider wire connections between the elements as part of the measurement as well. For fine-tuning, the NanoVNA can show you in real-time when you get it right. As you clip the element inch by inch, or simply move them around, you can see the SWR marker on the meter move towards or away from that perfect 1:1 desired position for that channel. Long story short, every single tiny adjustment to an antenna changes things drastically from one channel to the next. Optimizing for one channel is easy with the right equipment and knowledge, but optimizing for ten channels from multiple directions, well, that is when it gets challenging. Adding a second antenna totally messes with the SWR for every channel, and that's a bad thing if one does not fully understand these multiple channel changes. Glad to see you are still at it. I started as a TV repair tech too back in 2009 and have always been inspired and learn from your videos. Hope we can learn from each other. We once used to share repair tips, if you recall. Formerly Jer's TV Repair from Grand Have, now TransitionTV. Have a great day and stay cool over there. I too like to be off roofs by noon. :)
Hi Jer, Thanks for all the information. Your right about getting off the roof early. I recently tried to do Two in a day and really paid for it. Good to hear from you.
Did you try this with directional antennas pointed in different directions? Directional antennas pointed in different directions have side and rear attenuation!
Could feed each antenna into a separate networked tuner and set the display device to use the tuner based on channel. No combiner used this way and mismatched coax not an issue.
Note that most antenna I see on yt are wired in series and same element length. In parallel I will need to keep the wires to different elements, tuned to different channels, the same length to the balun?
Interesting. Does it apply the other way around ? On the TV in the lounge I get all the channels at 98%-100% strength, From a splitter it goes to the bedroom, where I get about 70%-80% of the channels with 60%-80% strength. But then it goes off to the music room where I get only about 30% of the channels with 30% or less strength. All the Coax's are different lengths.
Assuming you use proper (good quality) splitters, then the difference in strength is usually just due to plain old coaxial cable losses and the normal splitter losses. However, if you don't use proper splitters at all, just Y-connectors in the coax, then all sorts of additional bad interactions can occur as well as very variable losses. The worst example would be someone cut the coax with a penknife and taped it all up after they twisted the relevant cables runs together with wire nuts - this will rarely, if ever, work at all - so beware of that. Edit - daisy-chaining one split cable from another split cable is also asking for big problems - see below None of the problems you describe will actually be related to phasing of 2 antennas as seen in this video, though what happens is kinda similar at a scientific level - it's all related to the physics and mathematics of phase differences between RF sources and sinks, impedances and reactances in parallel, as well as the complexities of individual cable lengths and characteristics. To a theoretical radio guy - a specialist - yes it's almost the same thing mathematically - but to anyone who doesn't do quite advanced mathematics - it's easier to explain it as - "something different is wrong with your setup" We are off down the rabbit hole of transmission line theory here if we keep taling about phasing antennas, so I think the best thing I can say is:- "No, but yeah, maybe kinda" haha. Check that where the cable join to each other that there is actually a proper device - called a splitter or a divider. Some look like small rectangular boxes, or triangular shaped angled boxes. If all you have where they join is a thin/narrow 3-way joiner not much thicker than the coax itself, then that;s just likelya simple 3-way joiner or "Tee" - you may need to buy a real splitter/divider. Without that, strange things will happen and signal losses will increase dramatically especially on the longest run. In any case, you must bear in mind you are dividing your signal up and it;s getting weaker with every split. If you have a poor signal before you start, then it will weaken with every split. Special amplifiers called distribution amplifiers are sold for your specific problem - you install them nearest the good strong signal from the antenna (often in the attic space, or at least at the rear of your main TV where you have the antenna signal coming in from outside. They amplify the signal there - they need mains power - before spliting it to overcome splitting losses. I would caution to avoid high-gain ampifiers - you only really need to overcome the 6dB or so splitting losses at each port. Devices that claim stupid gain figures are usually rubbish. 6 to 12dB gain is more than enough most of the time for a distro amp. The higher quality ones in fact provide no more than 6dB of gain per port. Too much gain can cause lots of problems including interference between devices and noise. Some of these distro amps have more gain of certain ports to cope with longer coax runs to distant TVs - might be useful in your longest cable run for example. Bear in mind that if you run from one device, to the next, then split it again there, then do it again, you are dividing your signal away to nothing VERY quickly. Far better to do a full run of coax from each distant TV all the way back to the main TV antenna socket. That way you only have one split per device and you won't be daisy-chaning all your problems. This is a common amateur mistake and could be where your problems are. So in your case I'd run a direct cable from the music room direct to the main TV, another one from the bedroom to the main TV, and have a modest-gain distribution amp there. If you have good strong signal from your antenna, running direct runs to the main TV antenna socket may mean you can just use normal splitters and get away without an ampifier/splitter - which would be cheaper and more reliable. But if you currently have badly-taped connections, or simple coax Tees and not real splitters, then you might as well by a small distribution amp/splitter all in one unit. These distribution/splitter amps are common in larger houses and your local TV antenna specialist will sell you a good one or recommend where to get one. Residential-grade ones aren't that expensive. Maybe 30-40 US dollars. But best to invest in direct cable runs to main TV antenna socket, or better again, in the attic if you are in a very poor signal area (this usually gives less coax length from the antenna and best signal:noise ratio by keeping the actual antenna cable that feeds it as short as possible).
sorry for the longwinded reply - I'm trying not to over-simplify it for some more advanced readers or be technically incorrect, This is a complex topic and it's likely your problem is just daisychained cables and/or not using good splitters. Both problems are common in houses where the previous owner has done it DIY, adding on one cable after another until nothing works properly.
@@gordslater No, it's not the previous owner. It's my shoddy DIY. LOL I just got a lot of coax and through one end out of the top storey window, and, like you say, I got cheap splitters. The cables are going though open windows into the different rooms. LOL. I know nothing about RF. (Can you tell ?) Ha ha.
@@frankowalker4662 Ah ok - so yeah, if you run coax from the furthest points to the rear of the main TV, then put all of the existing splitters there, you should be in a better situation. Don't buy expensive splitters, becase at least you seem to have splitters, not just simple coax T's. If that doesn't fix it, install a small disrtibution/splitter amp there, and you won't need to buy new splitters because the distro amp has the splitters inside anyways.
Doing it this way combines two antennas in a parallel connection. That's what a coax splitter used as a combiner will do. They're for splitting signals, not combining them. The length of coax cable is practically irrelevant here as the signal is not significantly slower on a 20ft cable vs a 5 ft cable. If one wishes to combine two antennas, or even more, one must do it in series, not parallel. Doing that then basically takes the two antenna and makes them as one. The best way to combine in series is to connect them before the balun, or before the 300 ohm to 75 ohm transformer. Modern antennas may have this hidden within a housing. You'd connect 300 ohm wiring between the two antennas and then use the transformer in the lower antenna to go to coax cable connected to the TV. It's a chore alright, so an A-B switch is much easier, and maybe better in the long run as most people understand them. Another alternative is to get a better antenna.
@@GrantsPassTVRepair It can be confusing because we're basically talking about a connection of two separate lead wires, each in a series connection. The cursory thought is that they must automatically be connected in parallel because it's two-wire 300 ohm cable, but that's a misconception. We're basically talking about a series connection between the antennas of each one of the 300 ohm two wire strands to the balun, or transformer. Think of it as being somewhat similar to the multiple bow-tie antennas where you see perhaps 4 bow-tie antennas in a vertical row on a support, each one connected to the next one below by a wire. The bow-tie angles are next to each other, each in a horizontal V-shape but the metal part of each V-side does not touch, they just look like a bow-tie. Then each side is connected vertically. Then those two connecting wires are where the two connectors of the balun transformer are attached, making it a doubled series connection, and not a parallel type, turning each separate element of the antenna into one antenna. If it's hard to visualize, this might help: th-cam.com/video/DU9g92LlAxg/w-d-xo.html
@@themoviemaniac8416 I can't follow everything you wrote, but looking at the video got me thinking about the cross over wires in between each set of horizontal Vs on a bow tie antenna, and why they are designed this way.. I'd guess it's much like hooking up two transformer outputs in series. If done incorrectly their outputs cancel each other out due to the phase or angle of the sign wave being out of sync. I suppose the space between each antenna is what determines what phase angel is captured.
@@GrantsPassTVRepair You've got it! Sorry to be so specifically detailed. That comes from having taught upper level classes. I was an FFC licensed broadcast engineer before I went to Grad School for other things.
I've got 2 DIFFERENT types of indoor Ota antenna(1st- Flat type attached to window, 2nd- Round Ball sitting in window). Each hooked up to 2 dif tvs in the same room cuz each antenna picks up a few channels that the other does not. What I was wondering is... if I could use a dual female to male splitter to hook both antenna to ONE TV so that I could get ALL CHANNELS without having the need for separate tvs? 🤷♀️ I've ordered the splitter so I guess I'll find out. 😫
I don't believe anyone here can answer your question without trying this experiment, as you intend to do, and every location is likely to have different results.
I have looked at Channel Master on line help trying to figure out how to get channel 10 out of Springfield. Apparently whomever put their summary list together expects the rest of us to have an advanced degree in electronics. And seemingly none of them has ever held a compass much less flown an aircraft. Just what is so hard about giving me the compass direction to point. I pick up most of the other stations over here in Cabool, but CBS is on 10. I like watching what few football games that have not been gobbled up by ESPN. First they shat upon MLB. Now they want to do that to the NFL. And forget watching bowl games unless you pay. Well, dudes, seniors are more worried about keeping our homes a little above freezing. I put up a 3 leg Rohn tower to clear the hill behind my house. Finally after 2 years I could actually rotate the antenna and scan. The wind would blow and I would point it west again . . . then the motor stopped working. It will be quite a feat for me to get it back to ground level again and I want to add a second antenna to pick up channel 10. But without knowing the right direction, I'll just be spitting into the wind 😢
The clearstream 4 anthenna is the best in the market. I get 98 channels crystal clear indoors l live in the 6th floor building in New Jersey..depends on where you live...find the right place inside your living room
I’m still an RF noob, but imagine you would want at least two filters involved for the best results. So the filter on antenna a should block the signals you want on antenna b and vice versa. How far off am I?
Someone suggested I should have had these two antennas in a series circuit. I'd guess that having the antenas the right distance apart so their two phases add together rather than collide could enhance the signal.
I believe the reason the signal was reduced with Two antennas is because of Two signals are coming in slightly out of phase with each other creating multipath signals and somewhat cancelling each other out.
It can be done If using 2 same antennas Then both coax runs need be the same if pointed same direction. Different directions you need experiment. Different antennas again experiment. I used to use 3 different Antennas. Combined 2 as a single antenna The 3rd as a 2ed antenna Using different coax lengths. In the end Worked Very well indeed. Yet it was a month long trial and era of several antennas Method of combining them etc Nothing Wrong with Experimenting Hapoy New Years to EveryOne
Now I'm assuming your experiment is based on one certain channel from what you had said in the video. With that being said I have two antennas one pointing in One direction and the other facing another direction. Obviously what I'm doing is trying to pull from one set of towers and One direction and another set of towers and the other. That method I was able to double my channels. However obviously some of them are just the exact same channel so you want to get rid of some of your doubles for instance here I get PBS on 36.1, 36.2, 36.3, 36.4 I also get the very exact channels on 12.1, 12.2, 12.3, 12.4. in this situation I look at the antenna strength and whichever one is more consistently stronger I delete the other channels. Interesting video by the way I honestly had no idea that the length of coax cable makes that big of a difference.
Polarization problems. So, line of sight is a real EM transmission problem. He is describing a tower within the flat earth range and combing up to 4/8 antennas. Neat trick you don't passively combine antennas. You select which spectrum (channel) from which antenna. Remember polarization cancels...
Also, for $79 Televes has a 2 antenna input auto gain per channel booster which will balance. Of course, that's no fun and cheating, as well as more expensive.
Multipath interference and its gets worse the bigger the difference in cable length and if using different models of antennas. It was more pronounced back in the days of analog signals (it would look like a duplicate ghost image on the TV screen), these days it just pixelates or drops out completely. A lot of times the old-style antennas that look like a central bar with rods along its length work better in this situation as they don't have a rear 'reflector' that blocks reception from another direction (note the antenna you have in the baseball field picture). If the problem station is in the VHF bands then it might be as easy as getting a VHF adapter antenna and hooking it in series; that's what I did for mine and the one VHF station (NBC) that was a problem now comes in great.
You didn't answer the question. Did two antennas improve the signal vs. the one antenna? You answered the question "Did unequal length coax affect the signal? Please answer whether two antennas (with equal length coax) improve the reception over one antenna.
Yes I should have been more clear. It's my understanding that two TV antennas can help the signal, but only if both signals are in perfect phase with each other, otherwise it can cause problems and reduce the signal strength.
@@GrantsPassTVRepair it is known that the frequency bounced off from the satellites decreases as it reaches the dish at your house to reach the proper frequency so in other words the distance traveled effects the frequency reached
if 40 miles or more in the woods just spend the $600 for 6 items ..........1-channel master 80 extreme antenna for all uhf , 2 - stellar labs fringe vhf antenna , 3-channel master pre-amp , 4-channel master tv joiner , 5- 20 foot telescopic flag pole , 6- channel master amp , and enjoy all the channels crystal clear ....just raise pole high enough for the antennas to be out of the way and pointed in general direction ....exact pin point wont be needed ........ attach preamp to the extreme antenna at top , then the joiner just below that , then the stellar labs vhf antenna , then the amp to the tv......this will allow a minimum of 100 foot run of coaxial with zero signal loss on any of the channels ......me and neighbor have same set up with trees directly if front of the antennas and all around ...zero issues
Having the antenna up high on the mast is generally a good idea, but I have been on 3 jobs where lowering the antenna brought in the channels I could not get,. In one case I ran about 300 feet of coax from the TV to the antenna, and I was sure I would need an amplifier, but the signals were great without one. When it comes to finding the perfect antenna around here, what seems to be tbhe best in one location, isn't so great in another, I'm sure the antennas you mentioned are good ones, but when I think I know which antenna is best, I'll discover that sometimes I'm wrong in a particular location.
with those two particular antennas combined, its a monster system high or low trees or no trees ,...but if you want it up like a flag in the wind you can ....ours are about 12 foot from ground to bottom antenna to 16 ft to top of other antenna...you can spin them both 45 degrees and never lose a channel ..they are locked in to the stations...as expensive as cable tv and labor is these days , no need in seeing how little one can get by with and just put a complete monster system up if in rural area @@GrantsPassTVRepair
That makes sense. I think different lengths coax does cause a propagation delays in the longer coax, resulting in an interference pattern, where out of phase signals cancel or at least diminish the signal strength. With same exact length coaxes, the signal propagation is matched and consequently no out of phase interference pattern.
I appreciate you taking the time to experiment. I’ve tried using using two antennas with a combiner before and had similar issues. I should have know separate lengths of coax would cause an issues with the same signal arriving at different time to the tv tuner. I guess the only other way it would not cause issues is if you use directional antennas that severely attenuated signals coming from the opposite direction, but nothing ideally attenuates a signal in the real world, haha!
Very interesting experiment. Glad to see you're still putting out content. Drive by your shop all the time.
Thanks Robert.
I'm using a Televes SmartKom to combine two antennas on either ends of my house, as I'm right in between the two broadcast towers I want to receive from. It does a great job of evening out all the signals, despite vastly different coax runs.
What you can do is to get a bandpass filter from Arcom for the antenna that receives the single required channel, to just let through the frequency that you want before the combiner.
You are correct that the channels being received by both antennas are cancelling out however if you just let through the channel that you want then it will work.
Thanks again for a great video.
And notch filter for the other antenna to keep it from interfering with the antenna of the required channel.
Such filters are pretty expensive though.
Could feed each antenna into a separate networked tuner and set the display device to use the tuner based on channel. No combiner used this way and mismatched coax not an issue.
For RG6 coax run longer than 30 feet or so put an amplifier at the antenna.
I live in an apartment and our broadcast towers are about 20-25 miles away and SSW in direction. I am using a Sling AirTV tuner with the antennas. My apartment building is ironically skewed by just about the same amount from true north/south. My apartment exterior however, does not face the broadcast towers but exactly in the opposite direction. I placed my antennas in my master bedroom closet. To point my antenna toward the towers, the signal has to pass through my next-door neighbor's apartment and their closet and my closet before reaching the antenna. This resulted in inadequate signal strength obviously, even with a small amplified antenna that worked better than any other that I had tried, including a large 150 mile yagi herringbone type antenna. Since I got almost good signal some of the time and weather played a roll in quality, I tried a combiner and another identical amplified antenna mounted to the same wall in an over/under configuration, about 1.5-2.0 feet apart, both pointing to the same towers. My signal isn't great and does have good days and bad depending on the weather, but it is much better with two identical antennas combined and pointed toward the same towers than it was with only one.
A few points:
1) If you have two antennas at right angles, different lengths matters less.
2) If your "base line" is at right angles to the direction to the transmitter, equal lengths work the best.
3) If your "base line" is so that the antennas are at different distances from the transmitter, unequal coax lengths works the best. The difference in coax is about 70% of the difference of the distance to the transmitter.
Phased arays are cool. And also very mathematically complicated haha. But wow - using non-identical lengths of coax in each leg from the Y-point in the coax is gonna cause big variations (at least in theory, though as you will already know working in the TV antenna business, there's more art than pure science to a lot of this stuff)
Unless the coaxes are the exact same length (down to the millimetre, in fact) for any given frequency (eg: a single TV channel, keeping it simple) you'll get a directional skew in the gain pattern depending on the phase difference between the coax cables. (300/length n metres / velocity factor of the cable). You could in fact get away with using 3x or even 5x the length of one leg in the other leg, though that would lead to more loss especially at higher frequencies (based on more attenuation in the longer coax leg)
A problem even if you use the same ength of coax in each arm, is that the two different antennas will present a reduced impedance to the main feedline. So two 75 ohm antennas will result in 37.5 ohms impedance (just like resistors in parallel). Any reactance (capacitive or inductive, will be additive or subtractive dependent on the reactance of the antennas in use at any given frequency.
It is possible to use a specific length of coax that has a different characteristic impedance (often a 50 ohms section) to the main coax (which is usually 75 ohms) to transform the combined impedance of both antennas and make it closer to 75 ohms again, but the problem for TV use is that this transformation section length is frequency-dependent, so it won't work across a wide TV band.
So the only sane way to do this is to use the exact same length in each leg of the coax harness, keeping the phasing accurate and losses identical in each leg of the Y harness.
_ This is the point where my brain has already started hurting and beer seems like a very good plan B _
Sometimes easier results may be obtained if you use a narrow-band amplifier (of low gain) , one for each antenna (narrowband to reduce interference and noise problems) though amplifiers, as you probably know, give their own problems as well. The advantage to using 2 amplifiers here is that they present a known stable output inpedence to the splitter and the coax run-in to the TV receiver. A common problem ti this approach is the 2 amplifier can interact and sometimes go into spurious opscillation, causing all sorts of troubles.
In theory, if you have good signal strength, you could just use a resistive or inductive splitter, which would be even better, though that would mean you would need a good striong signal in the first place, so it's Catch 22 - you *_already_* have signal strength problems if you are trying to combine antennas !
Phased array radar antenna arrays generally use an amplifier for each antenna right at the feed point, or very close to it, with the advantage that it can help beamsteering by altering the phase to drive each amplifier and can be steered electrinically.
TV channel combiners (the ones I've seen anyways) seem to use a filter or a tuned circuit to keep the two two antennas more electrically seperate, in the RF sense, In the commercial transmission world, they would be known as diplexers. Each port would present a high impedance to the other port at the particular frequencies in use, preferably as close to pure resistance as possible to avoid reactance making things complicated (yeah - RF guys - I know it's just +j and -j, but that concept is quiet hard to explain to someone who doesn't already use complex matching on a daily basis haha)
In theory, you could make your own combiner by making a good low-loss tuned circuit to accept the "extra" channel you want, and place that in line with the coax leg to the "extra" antenna. You would then probably have to make a high-pass, low-pass or band0pass filter and place that in the line to the "main" antenna that accepts all the other channels. Each installation would require it's own unique filtering because it's likely that no one site would have the same combination of channels.
Combining two indentical antennas pointing in the same direction is known as either stacking or baying. Stacking is mounting one above the other, which narrows the vertical beamwidth of the array - this is sometimes used to reduce aircraft relections from planes on apparoach to a local airport) Baying is side by side mounting of two identical antennae that point in the same direction - this narrows the horizontal beamwidth - and so this is sometimes used to reduce problems caused by multipath from a large reflective object nearby. But the above descriptons only apply to 2 identical antennae phased up to point in the same direction, and operated at the same frequency. Combining (not stacking or baying) two different antennae from possibly two different directions is what you are trying to do (edit: maybe not deliberately trying, but having unequal length in each leg causes a squint like that) - it's like an interferometer - used in a type of directional radio telescope) and boy oh boy is it complicated in comparison.
For ham radio use, phasing identical antennas is used to get extra gain (*), though they use a very limited bandwidth and are only receiving one frequency at any given time, or maybe a narrow band of frequencies, so the length tolerances in both the accuracy of the "phasing harness" (the two identical leg lengths) and the impedance transformation section (which of course varies in length with wide frequency changes) are less of a problem. Another bonus is that some ham bands are near-harmonically related. For example. 146MHz is approximately (for impedance purposes) 3x the wavelength of 440MHz, so a quarter-wave impedance transformation section at 146Mhz kinda works OK as a 3/4 wave section at 440MHz. Because odd multiples of quarter wavelenth sections work basically the same (I'm simplifying it here) a phased/stacked-or-bayed dual-band 146/440Mhz antenna with equal-leg phasing harness and transformation section of coax will generally work OK on both bands.
If only TV was that simple - the extremely wide bandwidths you guys need to cover make things extremely complicated :(
Also note that the physical spacing between the two antennae is a factor that can affect gain and pattern response - though this is more of an issue for narrow-band antennae of high Q factor than wideband TV antenna designs.
I have a terrible headache just typing about all this haha.
For more technical info, you could try a Google search for stacked/bayed/phased yagi antennas - there's some good literature in the ham radio research field dating back well over 70 years, because phased dipoles and yagis were used in early fixed radar arrays so it's an established technique. Just bear in mind that narrowband ham or commercial radio usage doesn't really pan out to very wideband domestic TV reception, unfortunately, though admittedly that is mainly due to the impedance transformation section lengths being more narrow-band as they are selected to be a particular fraction of a wavelength, adjutsed for coax velocity factor, at any given frenquency.
For simple TV experimentation, you could just ignore the impedance transformation section and use 75 ohm coax and connectors throughout and just hope the wideband characteristics of the antennas don't give too much trouble. In general, TV antenna designs are rather flat in impedance response and are also designed to be minimally reactive (capacitive/inductive, -j/+j )across the wideband response, so it may not matter so much, especially if using log periodic antennas.
(*) the extra gain from stacking or baying 2 antenna pointed in exactly the same direction, used at exactly the same frequency, with no additional losses due to the coax Y-arms or the transformation section, is a theoretical 3dB (a doubling of power). You can double that again to a theoretical 6dB (4x the power) by adding two more antennae, making 4 on total.
HOWEVER - in practice though, due to coax line and extra connector losses as well as impredance matching inaccuracies, as well as the close-in effects of having two antennae in close proximity to each other (which can cause beamwidth anomalies and impedance changes due to near-field effects) about 2dB gain increase for a 2-antenna array is average for VHF, maybe 1,5dB at UHF, unless very high quality coax and connectors are used. This generally limits the advantages of phasing two or more antennae to right-on-the borderlines-of-possibility communication method such as moonbounce communication, or for extremely dedicated DXers.
I'm unable to keep up with everything you're saying in one read, but I appreciate your effort to share so much information here.
@@GrantsPassTVRepair Haha my pleasure - I love this stuff - antennas and arrays are all part of the super-secret black arts of RF.
I just can't explain it any simpler, sorry - I really wish I could. I can't find the right words to describe it all without making it "just too wrong".
This is a VERY complex topic - it really is far, far simpler for commercial radio transmission or ham use. The huge range of bandwidth you need for TV - especially in the US because I think you use some VHF TV too? - makes it an RF nightmare in practical engineering terms if you want to keep the cost down.
I used to phase yagis, log periodics, dipoles and quads as a kid for extra gain and to reduce sidelobes - later I progressed to using variable phasing lengths to steer beam patterns and take-off angles. I've rarely thought about this stuff for the last 30+ years so it kinda all flooded out in one nig lumpy technical mess lol.
Great channel by the way - keep it up.
@@gordslater Thanks. We have both UHF and VHF repeaters on different mountains around here, so my range of antennas can be a simple UHF loop or a full size yagi which attempts to cover a multitude of frequencies.
@@GrantsPassTVRepair yeah I noticed some larger VHF antenna sizes in some other vids. You certainly work in a very challenging area and those huge trees seem to be nightmares too haha
This is the best comment I've read on TH-cam in 13 years
This is a very common issue for over-the-road truck driver dual antenna CB. Oftentimes in the overhead you'll find A rat's nest of wire but both are the same length.
Worth every second invested
#1 It all has to do with phasing, if antenna A is out of phase with antenna B you will get what’s called destructive interference. If the two antennas are in phase with one another you will get what’s called Constructive interference.
*_“Destructive interference is when two waves traveling in the same direction are aligned at the crest of one wave and the trough of the other. The waves cancel out. Constructive interference is when two waves traveling in the same direction overlap, and their crests combine to produce a larger wave.”_*
#2 If two identical antennas are co phased correctly you will get a gain of 3 db however, the length of the cables used for the phasing harness has to be a ¼ wave length for the frequency that you are trying to receive so they will be in phase for that frequency and only for that one frequency, and the antennas need to be spaced a 1/4 wave length from one another again this is for the frequency that you are trying to receive so they will be in phase for that frequency and only for that one frequency. This could contribute to losses at other frequencies.
#3 Most signal combiners or antenna combiners, at best have an insertion loss of 3db this 3db loss will mitigate any gain that you would get from combining the two identical antennas. When you combine two antennas you get 3 db of gain.
Note: I have used two identical antennas stacked one above the other with a ¼ wave phasing harness made from 300 ohm twin lead cut for the ¼ wave length of frequency that I wanted to receive. The phasing harness was between two antennas that I wanted to co phase I attached the twin lead to the 300 ohm terminals of each of antenna then on the bottom antenna where the twin lead connected to the 300 ohm terminals I attached a 300 to 75 ohm balun so I could run coax cable to the TV’s. It worked very well with very little loss on the other channels. The advantage of using the 300 ohm twin lead is that it eliminates the signal combiners and the 3db of loss that the contribute.
No argument on that. Someone suggested it could be beneficial to hook them up in series. Ether way I understand why two out of phase antennas could weaken their output.
The line length is matched on space diversity antennas in microwave communications. It used to be done by making the waveguide the same length, but now it can be made by an electronic adjustment. The receiver still only picks the best antenna.
The only way I can receive all the stations in my area is to combine 2 antennas. I have one set for downstairs and one set for upstairs.
It is best to have an Amplfier for each set of antennas. Thanks for the video.
your comment makes no sense
Tv towers in my area are in different directions so I hook 2 tv antennas together to get all the stations. I point one antenna southwest and one north west. @@XwpisONOMA
Let's be clear on this that a signal with a two-way divider isolates or combines two signals with significant amount of attenuation between one-another. The price you pay is a typical 3.5 dB loss by using it on each leg. Why not simply do what I do that and works well, buy two antennas, each must have a preamp to overcome any losses seen through the coax and signal divider. Take each pre-amp power supply and get a WYZE type WiFi AC power switch, two in a box, select the market you want to watch in my case it is NY and CT. Depending on signal of that day, if both are good I leave them both powered up. If it is a bad day with multi-path, I switch off the one that is causing an issue. About 1:00 AM in the morning they both default back to the on position with the build in clock. All controlled by a cell phone, isn't life sweet! 😊
Geez you made that complicated. Buy an actual combiner solves the issue. Stay away from preamps when using combined antennas.
@@jamesm568 I don’t quite see that thought, as one looses a significant amount of each antenna by coax losses, and what ever gain is left and divided by two further increasing signal loss significantly. I don’t suggest putting dividers at the antennas, other than the amplifiers I want to be able to make changes at the shack so to speak where it easier to get too. Unfortunately all bets are of with pre-amp as they need to be at the head end(antennas). Hence my suggestion of turning of the interfering preamp with choice when needed has worked terrifically, trust me!🙂
@@jamesm568 I do see your point if both antennas are pointing to the same market. My further explanation relates to two different markets(different directions).
I actually do have an additional antenna pointing to the same market, it was availed to me, and selectively I switch between them when needed depending on propagation issues, but sometimes they do work well together. Maybe just has some favorable spacing and lead length by chance, but did not design for it.🙂
What I want to know if is there a way to connect a coax to a existing chain fence and use the fence as a antena for a tv?
You can use any metal object as an antenna, but a good antenna is designed for a specific frequency, and cut to a specific size based on that frequency you are trying to pick up. You may find this video of interest. th-cam.com/video/vHVmJ5lD9jc/w-d-xo.html
It has always been when you combine two antennas to make sure they're the same antenna and to make sure the same cable length is used from each antenna to the combiner. Most of the time it works and then sometimes one antenna will cancel the other one out as it varies per setup and location. I found it works best to keep the antennas close to one another as possible. Sometimes I just use one transformer coming from both antennas.
Thanks for the info. I was told the same thing from a channel masters rep.
@@GrantsPassTVRepair Every situation is different though. Sometimes two different antennas from different manufacturers work better when combined aiming at different markets.
I have a Televes two antenna combiner . I lose nothing at all with it. Pointed two different directions. One is getting my stations 27 miles west all UHF, the other is I think south east 5 miles away UHF and VHF…. All come in with no issues. ATSC 1.0 and ATSC 3.0…
Does the same thing running coax to different rooms. I been running two antennas for a couple years or so not for signal strength but to eliminate the rotor.
This was my recent experience, too.
After putting up a new antenna, I found that the Ch 5 family of frequencies would not come in.
So, I designed a yagi for the missing Channel family (Ch 5) but whenever the two antennas were combined, I lost the Ch 4 family.
Cause? The antenna I purchased only has 3 dB of gain in the VHF section. That is not enough to pull in the missing Channel. IMO, 6-8dB of gain would be a minimum figure.
Solution? Purchase an antenna with more gain in the VHF section and one that is designed for the low VHF, not just the high VHF band. As I have discovered, some manufacturers are building antennas now for the high VHF band only because TV stations are generally moving away from the low part of the VHF band.
Where I'm at, the lower part of the VHF band is still used extensively.
Here in Grants Pass most of our channels are on UHF, but you can drive just a few miles away, and the same networks are broadcasting in VHF. I've been in some locations that pick up 4 different transmitters that are broadcasting the same networks on different frequencies, so sometimes I get doubles, triples, and even quadruples. Grants Pass can be a challenging place to install antennas.
@@GrantsPassTVRepair Thanks - I believe a higher gain antenna is going to be the answer in my situation...
When I coPhase to TV antennas I use the exact same length of 75Ohm coax from each antenna.
You will loose some of the signal from the loose from the Combiner/Splitter.
To over come the loose i install a small signal booster.
NF1J 73s
P.S The problem is you can get the signals out of phase with different length coax.
Be sure to use the exact same coax from the same spool .
Different coax has different dielectric, etc that will cause issues when coPhaseing antennas
Thanks Grant. Thanks for the info. I'm guessing you meant to say 75 ohm coax from each antenna. :-) 73s
Good info. Thanks.
great video my location RF 34.1 fox 61 pax 31 same RF signal cant watch both
with to different antenna s
Thank you for taking the time. Did you also attempt to use the same cable manufacture? I'd assume different cables would cause a velocity difference too? Length and also same vs different manufactures would be interesting.
It's been a while since i made this video, so I'm not sure, but I'd guess the wires were likely the same manufacture.
Hi i have an antenna with 2 coax leads 1 for each bay i am using a 2 way signal splitter in reverse (so 2 into 1)
Is this not a good situation i notice you use a combiner or is that just a splitter ??
Thx in adv
So basically, different length cables may increase strength on some channels and weaken it on other channels, eg mis-matched cable lengths don't ALWAYS weaken signal for all channels.. interesting.
in my area (Grand Rapids, Michigan market), just about every station has its own tower. Most are in the same general area. However, two are in located in a totally different direction. It was common before everyone got cable to see antennae with elements pointing in different directions (south for CBS and NBC, west for PBS and north for ABC). Wonder how those worked? This would have been in the 70s and 80s.
Just guessing that they were more directional.
However, now days tbe frequency spectrum has been changed😢
Vertical tv antenna with 2 horizontal lines with one of the lines horizontaly diagonal
sar vs sal
I'd think the different lenghts are changing the tuned circuit of the antenna, cables and input circuits.
That sounds like another possibility.
Possible. The coax cable itself is an antenna.
WOW! IM NOT KIDDING YOU!!!! You Have Helped MANKIND TODAY! You Saved Me Absolutely No LESS than $100 For Two Antennas, Coax Cables, Splitters! THANK YOU! 40k Views and 40K subs! ITS ALWAYS The REALLY GOOD Guys That Get The Least Support It Seems! YOU REALLY WENT ALL OUT TO PRODUCE THIS RESULT!!!
Well Done My Good And Faithful Servant - You Have Blessed Your Fellow Man and Made The World a Better Place - LOOK AT ALL THE PEOPLE YOU SAVED FROM GOING TO HELL AFTER WASTING $100 AND NOT GETTING A BETTER SIGNAL! I KNOW I WOULD HAVE DONE SOME CUSSING!!! LOL. I took all I was going to buy today Out the cart TWICE!!!! Before I Ran Into This VIDEO!!! LOL! THIS IS THE BEST TH-cam VIDEO I HAVE EVER EXPERIENCED! LOL!
Just for the record, my video wasn'tt made to discourage anyone from installing two tv antennas, which can be beneficial in some locations, but to show the importance of coax length when joining two antennas together. I've since learned the distance between the antennas is also an important factor.
I use 2 antennas to get both Phoenix and Tucson which are in different directions. Works fine since they have different channels.
If the signals are fairly strong I think it's less of a problem.
What kind of antennas and set up did you do? I like install 2 antennas to get Tucson and Sierra vista Bisbee area since they're in different towers
Combining antennas can and often does lower the dB signal strength. There is only so much possible gain from each direction, so when you use two, you divide the signal strength between the two antennas. Also, adding an additional antenna changes the radiation pattern and SWR for each frequency. I recommend getting a NanoVNA meter to understand further how antennas' alterations affect the Standing Wave Ratio (SWR) for each channel. A good signal meter is critical as well. The only time I ever use dual antennas is if the signals pull from two different directions and there is enough gain for both positions. A spread of more than 45 degrees will often diminish most distant signals.
Ultimately, an antenna only needs two elements for each channel. The length of the elements is very specific to the frequency you are tuning in. Yes, much like the old rabbit ears. LOL, but really. Yagi and Log Periodic-style antennas have multiple elements on them, and this is not by accident--it's to accommodate for all the channels. In contrast, if a person only cared about one channel, then you only need two elements to optimize for that channel.
For example, RF channel 7, not virtual channel 7, but RF 7/183 MHz, is a wavelength of 64.49 inches, so divided by two is 32.245-inch elements on each side to accommodate the entire wavelength. You must consider wire connections between the elements as part of the measurement as well. For fine-tuning, the NanoVNA can show you in real-time when you get it right. As you clip the element inch by inch, or simply move them around, you can see the SWR marker on the meter move towards or away from that perfect 1:1 desired position for that channel.
Long story short, every single tiny adjustment to an antenna changes things drastically from one channel to the next. Optimizing for one channel is easy with the right equipment and knowledge, but optimizing for ten channels from multiple directions, well, that is when it gets challenging. Adding a second antenna totally messes with the SWR for every channel, and that's a bad thing if one does not fully understand these multiple channel changes.
Glad to see you are still at it. I started as a TV repair tech too back in 2009 and have always been inspired and learn from your videos. Hope we can learn from each other. We once used to share repair tips, if you recall. Formerly Jer's TV Repair from Grand Have, now TransitionTV.
Have a great day and stay cool over there. I too like to be off roofs by noon. :)
Hi Jer, Thanks for all the information. Your right about getting off the roof early. I recently tried to do Two in a day and really paid for it. Good to hear from you.
Did you try this with directional antennas pointed in different directions? Directional antennas pointed in different directions have side and rear
attenuation!
I just tried this in one direction.
Could feed each antenna into a separate networked tuner and set the display device to use the tuner based on channel. No combiner used this way and mismatched coax not an issue.
You can do that just by remembering which tuner for which channel. Your TV can receive from one antenna and use the tuner to receive from another.
Note that most antenna I see on yt are wired in series and same element length.
In parallel I will need to keep the wires to different elements, tuned to different channels, the same length to the balun?
Thank You
Interesting. Does it apply the other way around ? On the TV in the lounge I get all the channels at 98%-100% strength, From a splitter it goes to the bedroom, where I get about 70%-80% of the channels with 60%-80% strength. But then it goes off to the music room where I get only about 30% of the channels with 30% or less strength. All the Coax's are different lengths.
Assuming you use proper (good quality) splitters, then the difference in strength is usually just due to plain old coaxial cable losses and the normal splitter losses. However, if you don't use proper splitters at all, just Y-connectors in the coax, then all sorts of additional bad interactions can occur as well as very variable losses. The worst example would be someone cut the coax with a penknife and taped it all up after they twisted the relevant cables runs together with wire nuts - this will rarely, if ever, work at all - so beware of that. Edit - daisy-chaining one split cable from another split cable is also asking for big problems - see below
None of the problems you describe will actually be related to phasing of 2 antennas as seen in this video, though what happens is kinda similar at a scientific level - it's all related to the physics and mathematics of phase differences between RF sources and sinks, impedances and reactances in parallel, as well as the complexities of individual cable lengths and characteristics. To a theoretical radio guy - a specialist - yes it's almost the same thing mathematically - but to anyone who doesn't do quite advanced mathematics - it's easier to explain it as - "something different is wrong with your setup"
We are off down the rabbit hole of transmission line theory here if we keep taling about phasing antennas, so I think the best thing I can say is:-
"No, but yeah, maybe kinda" haha.
Check that where the cable join to each other that there is actually a proper device - called a splitter or a divider. Some look like small rectangular boxes, or triangular shaped angled boxes.
If all you have where they join is a thin/narrow 3-way joiner not much thicker than the coax itself, then that;s just likelya simple 3-way joiner or "Tee" - you may need to buy a real splitter/divider. Without that, strange things will happen and signal losses will increase dramatically especially on the longest run.
In any case, you must bear in mind you are dividing your signal up and it;s getting weaker with every split. If you have a poor signal before you start, then it will weaken with every split.
Special amplifiers called distribution amplifiers are sold for your specific problem - you install them nearest the good strong signal from the antenna (often in the attic space, or at least at the rear of your main TV where you have the antenna signal coming in from outside. They amplify the signal there - they need mains power - before spliting it to overcome splitting losses. I would caution to avoid high-gain ampifiers - you only really need to overcome the 6dB or so splitting losses at each port. Devices that claim stupid gain figures are usually rubbish. 6 to 12dB gain is more than enough most of the time for a distro amp. The higher quality ones in fact provide no more than 6dB of gain per port. Too much gain can cause lots of problems including interference between devices and noise.
Some of these distro amps have more gain of certain ports to cope with longer coax runs to distant TVs - might be useful in your longest cable run for example.
Bear in mind that if you run from one device, to the next, then split it again there, then do it again, you are dividing your signal away to nothing VERY quickly. Far better to do a full run of coax from each distant TV all the way back to the main TV antenna socket. That way you only have one split per device and you won't be daisy-chaning all your problems. This is a common amateur mistake and could be where your problems are.
So in your case I'd run a direct cable from the music room direct to the main TV, another one from the bedroom to the main TV, and have a modest-gain distribution amp there. If you have good strong signal from your antenna, running direct runs to the main TV antenna socket may mean you can just use normal splitters and get away without an ampifier/splitter - which would be cheaper and more reliable. But if you currently have badly-taped connections, or simple coax Tees and not real splitters, then you might as well by a small distribution amp/splitter all in one unit.
These distribution/splitter amps are common in larger houses and your local TV antenna specialist will sell you a good one or recommend where to get one. Residential-grade ones aren't that expensive. Maybe 30-40 US dollars. But best to invest in direct cable runs to main TV antenna socket, or better again, in the attic if you are in a very poor signal area (this usually gives less coax length from the antenna and best signal:noise ratio by keeping the actual antenna cable that feeds it as short as possible).
sorry for the longwinded reply - I'm trying not to over-simplify it for some more advanced readers or be technically incorrect, This is a complex topic and it's likely your problem is just daisychained cables and/or not using good splitters. Both problems are common in houses where the previous owner has done it DIY, adding on one cable after another until nothing works properly.
@@gordslater No, it's not the previous owner. It's my shoddy DIY. LOL I just got a lot of coax and through one end out of the top storey window, and, like you say, I got cheap splitters. The cables are going though open windows into the different rooms. LOL. I know nothing about RF. (Can you tell ?) Ha ha.
@@frankowalker4662 Ah ok - so yeah, if you run coax from the furthest points to the rear of the main TV, then put all of the existing splitters there, you should be in a better situation. Don't buy expensive splitters, becase at least you seem to have splitters, not just simple coax T's.
If that doesn't fix it, install a small disrtibution/splitter amp there, and you won't need to buy new splitters because the distro amp has the splitters inside anyways.
@@gordslater Brilliant I just looked on ebay and found a booster for £10. That should do something. Thank you. (I never thought of it. LO).
Doing it this way combines two antennas in a parallel connection. That's what a coax splitter used as a combiner will do. They're for splitting signals, not combining them. The length of coax cable is practically irrelevant here as the signal is not significantly slower on a 20ft cable vs a 5 ft cable. If one wishes to combine two antennas, or even more, one must do it in series, not parallel. Doing that then basically takes the two antenna and makes them as one. The best way to combine in series is to connect them before the balun, or before the 300 ohm to 75 ohm transformer. Modern antennas may have this hidden within a housing. You'd connect 300 ohm wiring between the two antennas and then use the transformer in the lower antenna to go to coax cable connected to the TV. It's a chore alright, so an A-B switch is much easier, and maybe better in the long run as most people understand them. Another alternative is to get a better antenna.
I've never heard anyone suggest putting the antennas in series. Thanks for the suggestion.
@@GrantsPassTVRepair It can be confusing because we're basically talking about a connection of two separate lead wires, each in a series connection. The cursory thought is that they must automatically be connected in parallel because it's two-wire 300 ohm cable, but that's a misconception. We're basically talking about a series connection between the antennas of each one of the 300 ohm two wire strands to the balun, or transformer. Think of it as being somewhat similar to the multiple bow-tie antennas where you see perhaps 4 bow-tie antennas in a vertical row on a support, each one connected to the next one below by a wire. The bow-tie angles are next to each other, each in a horizontal V-shape but the metal part of each V-side does not touch, they just look like a bow-tie. Then each side is connected vertically. Then those two connecting wires are where the two connectors of the balun transformer are attached, making it a doubled series connection, and not a parallel type, turning each separate element of the antenna into one antenna. If it's hard to visualize, this might help:
th-cam.com/video/DU9g92LlAxg/w-d-xo.html
@@themoviemaniac8416 I can't follow everything you wrote, but looking at the video got me thinking about the cross over wires in between each set of horizontal Vs on a bow tie antenna, and why they are designed this way.. I'd guess it's much like hooking up two transformer outputs in series. If done incorrectly their outputs cancel each other out due to the phase or angle of the sign wave being out of sync. I suppose the space between each antenna is what determines what phase angel is captured.
@@GrantsPassTVRepair You've got it! Sorry to be so specifically detailed. That comes from having taught upper level classes. I was an FFC licensed broadcast engineer before I went to Grad School for other things.
Thanks for confirming this. I've always wondered about the cross over connection I've seen on TV antennas. @@themoviemaniac8416
I've got 2 DIFFERENT types of indoor Ota antenna(1st- Flat type attached to window, 2nd- Round Ball sitting in window). Each hooked up to 2 dif tvs in the same room cuz each antenna picks up a few channels that the other does not. What I was wondering is... if I could use a dual female to male splitter to hook both antenna to ONE TV so that I could get ALL CHANNELS without having the need for separate tvs? 🤷♀️ I've ordered the splitter so I guess I'll find out. 😫
I don't believe anyone here can answer your question without trying this experiment, as you intend to do, and every location is likely to have different results.
Try using lengths of coax in the precise wave lenthh. In metres, example two metre band two metres of ciax. And equal multiples there of
Good job!
Parallel feed or the antennas in series?
The antennas were in parallel.
series adds parallel divides
I have looked at Channel Master on line help trying to figure out how to get channel 10 out of Springfield.
Apparently whomever put their summary list together expects the rest of us to have an advanced degree in electronics.
And seemingly none of them has ever held a compass much less flown an aircraft.
Just what is so hard about giving me the compass direction to point.
I pick up most of the other stations over here in Cabool, but CBS is on 10. I like watching what few football games that have not been gobbled up by ESPN. First they shat upon MLB. Now they want to do that to the NFL. And forget watching bowl games unless you pay. Well, dudes, seniors are more worried about keeping our homes a little above freezing.
I put up a 3 leg Rohn tower to clear the hill behind my house. Finally after 2 years I could actually rotate the antenna and scan.
The wind would blow and I would point it west again . . . then the motor stopped working.
It will be quite a feat for me to get it back to ground level again and I want to add a second antenna to pick up channel 10.
But without knowing the right direction, I'll just be spitting into the wind 😢
If you google TV direction finder, you can come up with several sites to help you find where to point your antenna. I often use tvfool.com
The clearstream 4 anthenna is the best in the market. I get 98 channels crystal clear indoors l live in the 6th floor building in New Jersey..depends on where you live...find the right place inside your living room
I've also had good results with the clearstream antenna.
I’m still an RF noob, but imagine you would want at least two filters involved for the best results. So the filter on antenna a should block the signals you want on antenna b and vice versa. How far off am I?
Someone suggested I should have had these two antennas in a series circuit. I'd guess that having the antenas the right distance apart so their two phases add together rather than collide could enhance the signal.
Can we put a oscilloscope on it to confirm they are out of phase or have bucking voltages.
Sounds like an interesting experiment, but my scope only goes to 20 MHZ.
@@GrantsPassTVRepair We will have to get you a 2 ghz oscilloscope for Christmas.
Could you be able to inform us all as to what actually is happening that causes this issue ???
I believe the reason the signal was reduced with Two antennas is because of Two signals are coming in slightly out of phase with each other creating multipath signals and somewhat cancelling each other out.
@@GrantsPassTVRepair Thank you for letting us all know. Well appreciated Grants Pass TV Repair. Look forward to more great videos Sir.
Also, I assume you point exactly in the same direction. Ever tried at 90°, null of each other?
Yes. both antennas were pointed in the same direction,
It can be done
If using 2 same antennas
Then both coax runs need be the same if pointed same direction.
Different directions you need experiment.
Different antennas again experiment.
I used to use 3 different Antennas.
Combined 2 as a single antenna
The 3rd as a 2ed antenna
Using different coax lengths.
In the end
Worked Very well indeed.
Yet it was a month long trial and era of several antennas
Method of combining them etc
Nothing Wrong with Experimenting
Hapoy New Years to EveryOne
Now I'm assuming your experiment is based on one certain channel from what you had said in the video. With that being said I have two antennas one pointing in One direction and the other facing another direction. Obviously what I'm doing is trying to pull from one set of towers and One direction and another set of towers and the other. That method I was able to double my channels. However obviously some of them are just the exact same channel so you want to get rid of some of your doubles for instance here I get PBS on 36.1, 36.2, 36.3, 36.4 I also get the very exact channels on 12.1, 12.2, 12.3, 12.4. in this situation I look at the antenna strength and whichever one is more consistently stronger I delete the other channels. Interesting video by the way I honestly had no idea that the length of coax cable makes that big of a difference.
Polarization problems.
So, line of sight is a real EM transmission problem. He is describing a tower within the flat earth range and combing up to 4/8 antennas.
Neat trick you don't passively combine antennas. You select which spectrum (channel) from which antenna. Remember polarization cancels...
Out put ota antenna satellite antenna connection oru video podunka
Also, for $79 Televes has a 2 antenna input auto gain per channel booster which will balance. Of course, that's no fun and cheating, as well as more expensive.
I don't understand all of your comment, but do you have a model number of the Televes amplifier you suggest?
Multipath interference and its gets worse the bigger the difference in cable length and if using different models of antennas. It was more pronounced back in the days of analog signals (it would look like a duplicate ghost image on the TV screen), these days it just pixelates or drops out completely. A lot of times the old-style antennas that look like a central bar with rods along its length work better in this situation as they don't have a rear 'reflector' that blocks reception from another direction (note the antenna you have in the baseball field picture). If the problem station is in the VHF bands then it might be as easy as getting a VHF adapter antenna and hooking it in series; that's what I did for mine and the one VHF station (NBC) that was a problem now comes in great.
Also, I am clueless on the physics as to the chosen dipole lengths and the loop length people are recommending on home made antenna. 23 inch loops, 7 inch elements. I am not sure about space between elements. 2'+ seems to work, but not tighter unless 90 deg out of phase, but polarization matters.
Here is a table of the half-wavelengths for TV channels 7-36:
| Channel | Frequency (MHz) | Half-Wavelength (m) |
|---------|-----------------|---------------------|
| 7 | 174-180 | 0.86-0.83 |
| 8 | 180-186 | 0.83-0.80 |
| 9 | 186-192 | 0.80-0.78 |
| 10 | 192-198 | 0.78-0.76 |
| 11 | 198-204 | 0.76-0.74 |
| 12 | 204-210 | 0.74-0.71 |
| 13 | 210-216 | 0.71-0.69 |
| 14 | 470-476 | 0.32-0.31 |
| 15 | 476-482 | 0.31-0.31 |
| 16 | 482-488 | 0.31-0.31 |
| 17 | 488-494 | 0.31-0.30 |
| 18 | 494-500 | 0.30-0.30 |
| 19 | 500-506 | 0.30-0.30 |
| 20 | 506-512 | 0.30-0.29 |
| 21 | 512-518 | 0.29-0.29 |
| 22 | 518-524 | 0.29-0.29 |
| 23 | 524-530 | 0.29-0.28 |
| 24 | 530-536 | 0.28-0.28 |
| 25 | 536-542 | 0.28-0.28 |
| 26 | 542-548 | 0.28-0.27 |
| 27 | 548-554 | 0.27-0.27 |
| 28 | 554-560 | 0.27-0.27 |
| 29 | 560-566 | 0.27-0.27 |
| 30 | 566-572 | 0.27-0.26 |
| 31 | 572-578 | 0.26-0.26 |
| 32 | 578-584 | 0.26-0.26 |
| 33 | 584-590 | 0.26-0.26 |
| 34 | 590-596 | 0.26-0.25 |
| 35 | 596-602 | 0.25-0.25 |
| 36 | 602-608 | 0.25-0.25 |
You didn't answer the question. Did two antennas improve the signal vs. the one antenna? You answered the question "Did unequal length coax affect the signal? Please answer whether two antennas (with equal length coax) improve the reception over one antenna.
Yes I should have been more clear. It's my understanding that two TV antennas can help the signal, but only if both signals are in perfect phase with each other, otherwise it can cause problems and reduce the signal strength.
If the antenna has an earth and the antenna is elevated it's possible the. Earth becomes part of the antenna lower the height of the antenna
present day 2022 this idea cant work due to shared RF signals
👍
Double stack antenna
I tryed that and it did not help
Not much of an experiment since dish does this with its lnb 110 119 satellite frequency
How so?
@@GrantsPassTVRepair it is known that the frequency bounced off from the satellites decreases as it reaches the dish at your house to reach the proper frequency so in other words the distance traveled effects the frequency reached
lose the combiner and just use a T connector
Why?
@@GrantsPassTVRepair Just try it, you will see
Buy a Rotor!
Nice video but misleading title. You're not comparing 1 ant to 2 ants as the title says. You're comparing various lengths of coax.
Yea your right. Thanks for the info.
To much information
if 40 miles or more in the woods just spend the $600 for 6 items ..........1-channel master 80 extreme antenna for all uhf , 2 - stellar labs fringe vhf antenna , 3-channel master pre-amp , 4-channel master tv joiner , 5- 20 foot telescopic flag pole , 6- channel master amp , and enjoy all the channels crystal clear ....just raise pole high enough for the antennas to be out of the way and pointed in general direction ....exact pin point wont be needed ........ attach preamp to the extreme antenna at top , then the joiner just below that , then the stellar labs vhf antenna , then the amp to the tv......this will allow a minimum of 100 foot run of coaxial with zero signal loss on any of the channels ......me and neighbor have same set up with trees directly if front of the antennas and all around ...zero issues
Having the antenna up high on the mast is generally a good idea, but I have been on 3 jobs where lowering the antenna brought in the channels I could not get,. In one case I ran about 300 feet of coax from the TV to the antenna, and I was sure I would need an amplifier, but the signals were great without one. When it comes to finding the perfect antenna around here, what seems to be tbhe best in one location, isn't so great in another, I'm sure the antennas you mentioned are good ones, but when I think I know which antenna is best, I'll discover that sometimes I'm wrong in a particular location.
with those two particular antennas combined, its a monster system high or low trees or no trees ,...but if you want it up like a flag in the wind you can ....ours are about 12 foot from ground to bottom antenna to 16 ft to top of other antenna...you can spin them both 45 degrees and never lose a channel ..they are locked in to the stations...as expensive as cable tv and labor is these days , no need in seeing how little one can get by with and just put a complete monster system up if in rural area @@GrantsPassTVRepair