Resonant vs Non-Resonant Antennas (
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- เผยแพร่เมื่อ 2 ต.ค. 2024
- Richard, AE6XO, is wondering what the difference is between resonant and non resonant antennas. Why no just get a non resonant and use a tuner? He asks. Is there any difference or advantages to either of them? Watch to find out.
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My son asked what that thing was over your right shoulder..had to explain the typewriter to him..he was perplexed..could not under stand that the printed paper came out immediately..I had a good laugh!!!!
Next, show him a dial telephone and have him dial a number correctly.
I don't think his question was really answered. I think he simply wants to know if the antenna will radiate as good say for example with a non resonant 6 meter antenna using a tuner to a perfectly tuned 6 meter antenna.
And the short answer is yes. Simply saying "yes" is too short for a video, hence I used his question as a "basis" for a video.
@@davecasler I really appreciate Dave taking the time to discuss the math involved here, something most hams don't relish. I didn't truly understand the complexity of electronic theory until I took trigonometry .... wow, who knew! Dave answered the ham's question in his original video, just follow the math...../k6sdw
It might be easy to say the current is low at the feed point of non resonant antennas is because the Impedance center feed point would be very high creating a high voltage and forcing the current to be low. (P=IxE) voltage goes up Current has to go down for a given power. The losses are low on balance line because the capacitance between the 2 lines is low compared to coax reducing the losses for long lengths of open line vs. coax. Now it doesn't matter where the tuner is located at the antenna or at the transmitter end because the line losses are very low. There is a great book by Walter Maxwell called "Reflections Transmission Lines and Antennas" that took all the magic out of transmission lines and tuners for me"
I do not agree with much of anything with you or what is broadcast here
Why not think in basics of basic antenna theory
A antenna does not need to be resonant
There is no magic or sacred reason a radiator needs to be perfectly resonant or even really close
What is most important is
The TX sees a 50 ohm load purely resistive
There is no excessive feedline losses
And a efficient radiator is used
The antenna being resonant at some specific frequency is less important than everything above !
Much easier to just build a antenna than endevor to pursue some pseudoscience that has to do with some magical resonant antenna
Long wires and rombics are not resonant antennas and still they hold the title
String up a 1/2 wavelenght of wire use a transmatch between the tx and the feedline and presto
You have a damn efficient antenna
It really is quite simple
No misconstrued theory or pseudoscience
I guess I missed the part where you answered the question "Why bother with resonant antennas if a nonresonant antenna and tuner are just as good."
Thanks Dave. One thing you didn't mention is the change in pattern between resonant and non-resonant, particularly with large antennas at higher frequencies. Thanks for all you do.
Good point! Pattern distortions can be downright weird.
Thanks so much for the wonderful videos Dave. Your channel is a treasure. On this video, I feel like I’m missing a key point though. Say I have two antennas, resonant and non-resonant. The non resonant antenna has a tuner directly on the antenna base. Is there any reason besides tuner component cost that I should prefer the resonant antenna? I feel like your answer in the video was that they are equivalent. However, I never read about someone using a one foot random wire and a very expensive tuner to do DX 160m. That makes me think there is something besides matching impedance for low SWR that I’m missing. Thanks so much!
Congrats on the QST gig!
Dave, Thank you for the TH-cam programs and your QST articles. I look forward to both. I'm in an apartment with severe space restrictions. I wanted to see if I could possibly work HF on multiple bands using 100 watts or less. Center fed resonant antennas and verticals with radials just weren't feasible at my location. I now use a 71' non resonant sloper going from a 25' balcony down to a 6' wooden fence, a 9:1 unun at the high feed point, two 15' counterpoises on the balcony, 50' of coax, common mode choke at the and of the feedline going to a manual antenna and into the transceiver. Using this setup and 80 watts LSB from California on 7.204 MHz, I was able to work VK4KW in Australia on 10/1/21 at 10:30 UTC (3:30 am PDT). I've made made many contacts using just 1 to 5 watts. I regularly check into nets using 20 to 100 watts and have had extended QSOs on 80, 40 and 20. The SWR indicator on my little 100 watt amp and also on an external SWR meter shows 1 to 2 or better on all HF bands after careful antenna tuning. I've also tried a MagLoop but the non resonant antenna works better for me. My point is there's plenty of fun available on HF even for those of us with severe space restrictions if we're willing to learn about and experiment with antennas. Keep up your excellent work!
Thank you sir!
Get rid of as much coax as you can for any non-resonant antenna!
I simply use a 102' dipole with 450 14ga. window-line that is about 70+ feet long (you usually have to tweak the length to hit all the bands).
I get rave-reviews on my signal, much more than any coax-fed antenna I've ever used period!
Also, don't be afraid of all the nonsense about field spacing on the window line; I even run it right through the wall to 2-banana-jacks whereby I either plug in the tuner or a heavy double-ground wire when not in use. The only time you will ever have problems with routing, is long parallel runs longside metal objects or wires; short right-angles are not a problem as I've watched all of this while trying different placings. If you need to run along the ground, just buy some of the non-metallic sticks available at home improvement centers and cable-tie to them.
Also, people get too hung up on patterns; I've never noticed directional deficits on any band 80-10m; as in life, you go with the lobes you have!!!
The efficiency gain with open-feeders is well worth the trouble! 73...
Thanks for the info Dave - more for me to chew on as I mess around with wire antennas. I do things by gut/trial and error rather than theory and math and enjoy my successes and failures. I am now deep into playing with traps and seeing the effects they have on long lines both resonant and non-resonant together with un-uns ranging from 9:1 to 49:1 in value, together with ATU's. Some surprising results are emerging. As Yoda said - Do or Not Do ! 73 . M7BLC
For a strictly receive only antenna does it matter if it is resonant or not?
Long winded, didn't really answer the question 🤷🙄
Dave spent a lot of time with the 43 ft vertical but never explained it ws a 5/8 wave on 20 M and never explained the significance of that length.
OK, so Dave's personal preference is to use resonant antennas to avoid the reflected power loss in the coax when non-resonant antennas are used. Great, but seems half the conversation is missing here... As a practical matter, since this is about multiband antennas, the way most so-called "resonant" antennas achieve "resonance" on multiple bands at the same time is through the use of lossy components in the antenna system, ie, traps, loading coils, etc...(where the actual loss of such components seems to be a mystery to most people). All of these "trick" components create losses of their own even when the SWR is very low.... So, there's that, which still leaves the question, which is better and why... I think the answer is that it depends totally on the specific configuration details and specific antenna design of any system. I'd like to see this bigger picture discussed in more detail. But, it would be nice to hear an analysis of both sides of this story to help people better understand whether, for common scenarios, it is better to have loss mainly in the coax after the tuner (the non-resonant case) or in the trick components used by most "resonant" systems to get SWR down on multiple bands (I'll call that pseudo-resonance for lack of a better term). If people only wanted to operate on one portion of one band then obviously a resonant antenna is better, but since multi-band operation is usually the goal, the answer does not seem so obvious.
Alas, not so. Modern verticals (unfortunitally there are still a bunch of "non-modern" antennas out there) use more interesting tricks such as 1/4-wave transmission line stubs and so on. One of the most interesting antennas is the DX Commander Classic, which is a fan vertical, so no traps at all. You can get it from DXEngineering.
@@davecasler -- since I wrote the above, I'd decided to go with the AVR-640 as it seems to have good blend of features -- will be assembling it over the next couple days... Uses 3/8 wave radiator with parallel stubs for the higher bands (so it's able to not need long wire radials and uses 6 ft counterpoise radials at its base instead, and the parallel stubs eliminate the need for traps and their associated problems/band-narrowing issues)... unlike most 1/4 waves, it actually wants to be higher, so it will be mounted around 25 ft in my case), has end-loading coils and cap hats for some bands to get the needed electrical length needed for the lower bands. So, while resonant, this falls in the category of non-1/4 wave solutions. Has a 4:1 unun to get from 50 to 250 ohms at the feedpoint. Seems to perform very well from the reviews I've seen (low-angle dx is its strong point) with broader low SWR range than most trapped antennas can achieve. Now that I'm beyond the point of verifying all the parts were included and there are no loose, missing, or broken parts in the matching unit, I'm hoping I've survived the hit or miss quality crapshoot that is MFJ these days.
Dave - Why do people say a nonresonant vertical shouldn't be resonant on any band? What's the downside to using a 1/2 wave 33ft vertical on 40 meters and higher frequencies? (With a transmatch/tuner)
There are several non-resonant multiband antennas that employ either a 9:1 or 4:1 transformer (unun or balun) that do not require a wide band tuner. Some require no tuner on select bands.
The endfed varieties generally require RF grounding and/or counterpoises, and a common mode choke to be used without a tuner.
Its hard to beat the efficiency of a resonant single band antenna, but for the slight loss in efficiency I generally opt for multiband non-resonant antennas for the frequency agility.
The only non-resonant antenna I haven't had stellar success with is the 53' random wire antenna. The performance was not that exciting, but it did work. I suspect I need to research optimizing performance through better use of counterpoises or ground radials and grounding.
I've seen for schools of thought on ground radials and counterpoises: being 0.05 wavelength counterpoise for lowest frequency, 0.25 wavelength counterpoises for bands of interest, and a total of 2X wavelengths of for lowest frequency of ground radials of any length, or one counterpoise at approximately one wavelength.
Some of the variation depends upon grounding and whether the antenna is resonant or non-resonant and if the transformer is grounded and location of choking.
After watching Steve Ellington's EFHW experiments I setup my EFHW and it is now working like gang-busters. The 49:1 transformer is grounded, choked, and mounted close to the ground with antenna in an inverted-L.
The manufacturer of the 53' random wire antenna suggest mounting the 9:1 transformer high with the antenna sloping and counterpoise a full wavelength of lowest frequency about a foot off the ground. That will not work at my condo, so need a next best installation. The first time out was with the transformer about 4' off the ground and 130' counterpoise laying on the ground and 50' with the choke at the TX, and no grounding. The next iteration will use ground at the 9:1.
The transformers do the impedance matching. In the case of a windom or something like that, the tuner does the impedance matching.
Some ignorant people buy "antennas" with Flat SWR in a wide frequency band. They don't realize that their "antennas" maintain a good match by pulling a 50 Ohm resistor into it that just dissipates a power of their transmitters to heat...
The question could have been answered in about 5 minutes. A resonant antenna at the feed point is at or close to 50 ohms or can be matched with a transformer (e.g. a 49:1 unun for an EFHW). A non-resonant antenna cannot and an ATU must be used for the transceiver to see a match. Also, non-resonant antennas require a balance feed line like 450 ohm window line to prevent significant line loss due to high VSWR which is inherent with NR antennas.
Also, Dave is confusing the Carolina Windom, which is a coax fed OCFD with a doublet, which is non-resonant dipole fed with parallel window line.
I think you did not realy answer the question. The answer is not yes. The difference is in the radiation pattern which changes kind of chaotic with the frequency
Really good question?.
My mfj269c has me resident and the swr reads 2.3 but the vswr reads 3.0 which is correct
The power dissipated in an open wire feeder due to I2R will only scale in the way described if it is terminated in its' characteristic impedance.
Yes, like any transmission line, the losses go up with SWR.
@@davecasler that is true, but your maths assumes a 450 ohm load.
If as an example you consider a low half wave dipole with 100w AT THE ANTENNA the current will be the same whatever the feeder. I appreciate that the impedance will change as you vary the length of feeder to the transmitter due to the normal effects of a feeder not terminated in its characteristic impedance.
When you think about it, a run of antenna wire has both resistance by the wire itself and radiation resistance. Ask yourself what percentage on a resonant antenna wire is radiated on the first transit to the end point before being reflected. The remaining signal is minus the amount radiated for the first transit, then minus the radiation on the next etc. on a declining exponential rate. The resonant wire is just rejuvenated on each cycle by the transmitter. A very long wire radiates all along its length and also declines exponentially as it goes. What is the difference? The wire resistive loss is greater with resonance as the source energy must keep adding to the un-radiated. It is just that a resonant length must coincide in wavelength for the frequency being used, otherwise the back forth transit from the two reflective end points become destructive and appears to be a different impedance load. VA7WN
Nice video and nice try with the maths but unless you're willing to embrace fully COMPLEX numbers lets not go there at all. A congugate match is exactly what an antenna tuner should give you which also gives the best possible SWR or VSWR. A fully agree that when practical the ATU should be as close as possible to the base of the antenna. However, I'm not going to lose any sleep over my 20m of coax. Ladder line is dead, long live coax! You forgot about the losses in the matching transformer going from 50 ohms to 450ohms or whatever! But my main gripe is that there are a lot of people out there thinking that they can avoid the "Copper Losses" I2R by eliminating the ATU!!! What utter nonsense, they are impossible to eliminate, you can only reduce them as far as practicable. Use what you need to people and if an ATU helps then use it. Try buying one of the older more robust units with the larger coils and variable caps to further reduce losses.
Dave, would you please explain ", especially in connection with antenna efficiency and bandwidth. Listening to all these YT videos about different kinds of antennas, I usually hear that the antennas have low SWR, but rarely do I hear anything about how efficientt the antennas are. My dummy load has an SWR of 1.0:1. There are also "cloud burners" and "ground warmers." So, what is antenna efficiency, how can I measure it, and does it really matter? Thanks in advance David SV0SGS. PS I enjoy your videos and have learned much from them.
Resonance vs matching - two different aspects of every antenna. An antenna could be resonant, but don't match and will require some matching network. A tuner usually don't change antenna resonance and does matching only.
"Put the antenna right at the base of the antenna"... I suspect you meant to say something else for one of those nouns. Did you mean "tuner" right at the base of the antenna?
And if so, what are the downsides of that?
okay, you go on to answer that. Thanks!
Yes, he meant the tuner.
I just re did my G-five rv. I had to add three feet on each end of the hundred feet of wire. I also have a wind om in my radio room.
To answer my own question, the impedance of free space is 377 ohms. VA7WN
Some non-resonant when set up correctly, have a flat swr on all bands.
flat, but relatively high, right?
@@davidbinkowski4825 No less then 2
Would a cob web antenna work if it is mounted in a vertical orientation instead of horizontally?
What is the impedance of free space? An infinite wire without an end reflection point has no resonance, no "Q" and no bandwidth and works at any frequency. A rhombic antenna approaches this condition. Even with multi wavelengths, it is still finite and therefore requires a termination resistance to match that of free space to prevent reflections. An ideal antenna that is very directional. In theory, an infinite wire would reach all the way between the transmitter and distant receiver; Haw Ha! Anyone own an abandoned railway with remaining telegraph wire? You would just need to do an impedance match to the radio to that of free space. VA7WN
I recall that the Z of free space is 166 Ohms.
I don't like to use lots of words when not required. As a rule I look forward to and enjoy your videos. This video was absolute gibberish, you were past 12 minutes before you even began to answer. Sorry, Maybe I' just to dumb to watch.
I didn’t know you were working on Sunday!
EXCELLENT PRESENTATION
Appreciate your videos!
Thanks so much
thx, 73, dg2r?
Didn’t you draw the G5RV?
nope, a doublet.
It would be more accurate to call the feed point as resonant or non resonant. A 1/2 wave length antenna has a resonant feed point in the middle of the antenna but at other locations along the wire the jX does NOT equal zero. Does the antenna magically change from resonant to non resonant as we pick different feed points???