What is SWR in Ham Radio?
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- เผยแพร่เมื่อ 13 ก.ค. 2024
- In this video, we discuss Return loss and SWR along with some different ways to measure.
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Is Ape the next Dave Cassler? Wow - I read the manual how many times and this is the first time it's made sense.
Ape is ape, man! He's just a guy figuring stuff out too! He usually makes things crazy easy to understand for me too
Thanks @Ben, I try to break thinks down in a way that's consumable. I find the in general Ham Radio isn't as approachable as it could be as much of the information is presented from an overly technical viewpoint.
Really appreciate your willingness to share your understanding. You're one of the few that I can watch/listen to for more than 10 minutes or until I get only what I really thought I needed. Your humility is refreshing.
Thanks for such a plethora of topical discussion.
Thanks Steve, I try to present material that will help folks learn and be better hams, not just unboxings of cheap crap or "buy this" type content. Ham radio is a lifetime of learning and we should be sharing content in a format that's consumable. That's one of the things that bothered me when I first got in the hobby; everything was commercial for something I didn't need or an overly complex explanation that I couldn't understand. Thanks for the feedback and for watching 👍
Been licensed for 6 years and done nothing with it. Decided to change that and, for all the knowledge I have (train on wireless MANET systems, mostly mil) there is always more I don't know than know. And know it alls annoy me so much that its probably why I stayed radio silent for so long on the amateur side. It is an unfair assessment, as I was ruined by just a few, but turned off nonetheless.
Keep putting the geeky deets to plain English, my friend. It's an art and a vital part of spanning generations.
Great job explaining. I definitely recommend an antenna analyzer as part of your toolbox. That way you can see what is truly happening with your transmission. 73’s
Totally agree, thanks for the comment 👍
Thanks for the video, Ape. And thanks for this tip byd3k, good point.
Another great video Ape! I have been a Ham for 26 years and I never considered line loss in calculating accurate SWR. Just goes to show, you can learn something new every day. Well Done!
Hey HoH, glad it was helpful. Thanks for watching!
Outstanding explanation!
Thanks Jim, glad you liked it!
Something I have seen asserted almost everywhere concerns reflection losses. The question is - what happens to reflected power in a feedline? What is the actual amount of power reaching the load or antenna? The reflected power reaches the transmitter output (or tuner output) then what happens? The power cannot just disappear. Nor does it go into the transmitter and cause heat. It undergoes a flip in phase and combines with the forward power and goes back in the feedline, until it meets the antenna feedpoint, where again a small amount becomes reflected power. The aggregate effect is that most of the power produced is absorbed by the load. At HF frequencies coax feedline loss is not significantly great. As in a previous post, a matching device at the feedpoint is only partially effective with a wire antenna on HF. For VHF and up, with a Yagi antenna for example, you can use a gamma match or similar. For a simple multi-band dipole, the impedance is going to be all over the place, so a transmitter located tuner works best. It's all about impedance matching and system losses. On a feedline, the impedance changes constantly, but SWR is constant. The actual transmitted power includes reflected-reflected power and is greater than the table suggests at the end of the video. For a clear and concise description of this phenomenon, see Walter Maxwell's "Reflections". (Free download) - www.k3emd.com/downloads/Reflect.pdf
Awesome Ape ! Great info and you make it easy to understand!
Why thank you Chuck, glad you liked it!
The inherent loss in coax along with loss due to SWR is one reason why I use balanced line whenever possible (and in reality that's quite often). Inexpensive ladder line will have MUCH less loss than even the best coax when any significant SWR is present on the feedline. A doublet fed with ladder line is an excellent multiband antenna and is highly efficient.
Just to stress a point that I believe you infer near the end of the video - locating a tuner at the feedpoint of the antenna is another way of avoiding loss due to SWR if the antenna is being fed with coax. Doing so won't eliminate the inherent loss in the coax but it does remove the losses caused by SWR from the equation.
Thanks for the detailed comment Brian, I agree with both points.
What I like to do is use concepts that most hams are exposed to, in this case SWR. I wanted to show that measuring at the radio and the feed-point will give different results, and to your point coaxial transmission line being a huge factor. On the channel I get lots of questions about SWR and antenna performance, I wanted folks to know that there is more to the story than just what is on the shack SWR meter.
The ubiquitous SWR boogeyman! At HF frequencies, the average run of coax being less than 100 feet will produce fairly low or insignificant losses. Balanced feedline is basically lossless at HF frequencies, but requires a lot more care in installation. A feedpoint tuner will correct the feedpoint mismatch, but not the transmitter - feedline mismatch. For example, a half wave dipole (let's say cut for 7100 kHz) at resonance will show a feedpoint impedance of about 73 ohms. With 50 ohm coax that is an SWR of 1.5:1, and there is nothing you can do to improve that. You can try to match the feedpoint, but what's the point? You will gain nothing. A transmitter tuner will essentially make a conjugate match along the whole system with maximum transfer of power to the antenna, minus aggregate feedline losses. Now, whether your antenna is radiating well and efficiantly is entirely another matter. So much confusion!
No yeah, read this many times, never could wrap my head around it. The way you explain this, I finally get it. Thank you so very much. Keep on teaching man.
Thanks No Code, glad it was helpful 👍
Very nice and clean but very informative video!
Thanks Anton, glad you liked it 👍
Very informative. Thanks Ape!
Thanks for checking it out Jason 👍
Excellent explanation and graphics. This is teaching quality material!
Thanks Izzo, trying to set up my game 👍
Once again you've made me more knowledgeable in this hobby. Thank you so much man.
Hey Man, thanks for checking it out! We all learn from each other and that’s what makes it cool 👍. Be on standby for the help with the DigiRig 🍻
Great explanation Ape, you makes it so much more easier to understand,,
Thanks👍👍
Thanks Ed, glad you liked the video!
Nicely explained and clearly put. Thank you.
Thanks for watching Daniel, glad you liked it 👍
Hi,good video well explained 👍,I didn't realise the losses were so much,,,good to know,,,thanks from Rotterdam
Glad you enjoyed it, thanks for watching Joe!
Great Video Ape
Thanks for checking it out Molson!
Excellent!
Tango! Thanks for checking it out.
You opened my eyes. Thanks,KD2RLB
Thanks for watching Greg, glad the videos was helpful.
Great info! I've been thinking about line loss lately 👍👍
Glad it was helpful, thanks for watching Skeeter!
Here's an idea for a HF dipole. Use cheap 16 gauge speaker wire. Use a good quality balun/center insulator. Feed it with cheap/free TV type 72 ohm coax. At the resonant frequency and either side of it, you will get a near perfect match and no reflection loss! Another misconception is that an antenna must be resonant to work well. This is incorrect and it even states this in the ARRL Antenna Book. At resonance, the feedpoint is purely resistive but can still have a mismatch and reflection losses. A good old half wave dipole is cheap, easy to make and is a good performer. And you made it yourself!
I like this idea, thanks James 👍
Nice talk !
Thanks!
great information. Now to just learn how to calculate the line loss, and how to adjust any that can be adjusted to make it the best it can be.
Glad you liked the video, there will be more on this topic 👍
Hey Ape, great video. There are a few common things that as hams we accept or believe. 1. 100 watts, that is the setting on the radio and not the actual output. 2. SWR reading at radio, we are told anything under 2.0 you can operate so we just say ok. 3. This is why we try not to use cheap coax, better coax has less line loss (in most cases). 4. Antenna tuner will help catch the line loss and reflect it back playing a game of ping pong with forwards and reflective. IMHO those are just a few things some Hams believe when talking about this subject. Using SWR vs math is like electricity….take the path of least resistance
Awesome post Blackheat! Thanks for watching, glad you liked it.
To understand indicated power vs. actual power, take a look at good old Ohm's Law. You can look up losses for all types of feedlines on the web. At HF frequencies, coax feedline losses are almost insignificant. Look up S units and power ratios.
well put, in a way that anyone should understand
Thanks Buzz, glad it was helpful 👍
As stated above, reflected power is not lost power. It goes back to the antenna and is radiated minus what is lost in the feedline.
@@andyw6ad131 so it’s not lost except the lost power from the feed-line? I suppose you will tell me that the ping pong back and forth is efficiencies next…. The video was about SWR and Return loss, where it’s measured and how line loss plays a role. Please Mr Helper, instead of regurgitation of what others posted, direct me to your cinema-graphic master piece…
Ape. Just tryin to be helpful. Don't know what you mean by cinema masterpiece but please read Maxwell as you are spreading a myth that reflected power is lost power. Spot on with the coax loss though. I don't usually frequent your channel but enjoy the Coffee and Ham Radio episodes and wanted to see if there were any here to watch. Where does this return lost power go? Maybe time for a new episode to explain this. Regards andy w6ad
@@andyw6ad131 thanks for helping Andy.
Ape, that is a great explanation, but only half the story, I am afraid. Check out 'SWR - the persistent myth' by John Fielding, ZS5JF, for example (it's a free pdf presentation, just google it). Actually the reflected power is relected again with a phase shift at the tranceiver, going back and forth until it is radiated at the antenna. So the only added loss throuh a mismatch is happening in the coax. The misconception of assuming the reflected power is lost probably comes from viewing the trx final as a generator with an inner resistance. In reality there is usually some sort of transformer or matching network. So we are talking impedance mostly formed by reactance and not resistance. Reactance in contrast to resistance can not consume power (converting it to heat) but store it to give it back during the next cycle. Ot is'sort of a virtual resistance only applying to AC. In reality there are still small resistances in the components and the feed line, of course, but the effects are much less critical than one would assume. I am not saying you shouldn't care about matching, especially with very high power, but It is not like all reflected power would be burned up in your transceiver (or tuner, as some say). All the best es 73
Thanks for that post, its really well stated. The point you make is a fair one, the angle I wanted to take in this video was in reality the effects of line loss in most ham shack installations. I used the topic of SWR / Return loss as the topic to illustrate what actually happen when folks just rely on the SWR meter in the shack.
DJ5SE I have just finished reading John Fieldings document. What a brilliant engineer and what an excellent document. It should be made MANDATORY reading for any amateur radio exam ! DJ5SE... THANK YOU for bringing this to my (our) attention, i had never heard of this wonderful document.
Albert EI7II.
@@albert7ii also reflections by Walt Maxwell goes into great detail on this subject
DJ5SE totally agree ,reflection gain where the reflected power joins the forward power needs to to be taken into account to determine loss within a system, an swr figure alone is not the full story, for example different types of feedlines will have a different loss figure with the same swr
@@paulm0hpd319 Thanks Paul. Appreciated !
In laymans terms that a lot of new and experienced ham needed to see tl start to clear the fog on VSWR. If you have time, a real life walk thru would be a great help. I for one do a lot better with visual, much better than reading about it.
Would a video of how to correct VSWR be possible? Say, introduce a UNUN or BALUN and/or a Line Isolator to assist in matching impedence be possible?
I appreciate all of your videos, and always look forward to each one. Thank you Ape for all the work you put into them. KI5IQE
Thanks for watching Joe, I'll see what I can do about future videos.
How badly do you need to "correct VSWR"? Would it be worth it to correct from, say 2:1 to 1.2:1? The difference to the receiving station would be insignificant. The use of baluns is not primarily an impedance matching device and these things are usually lossy and can saturate and overheat. Best to keep it simple and eliminate parasitic stuff in your feedline. A balun at the feedpoint of a dipole can help prevent common mode currents in the coax, if it is good quality and would properly.
This was a great video. Now can you make a video explaining how an antenna can have gain?
It's on the list, thanks for watching Ron 👍
Great explanation Ape, thank you. I will have to upgrade to some LMR coax one day to try to minimize the line loss.
For the record I run rg8x (hangs head in shame) it works fine for me and I am aware of the losses and plan accordingly. Thanks for watching Keith!
For a typical HF installation an expensive upgrade to LMR400 or similar is not worth the money. Now if you're a serious QRPer, it might be worth the effort where every milliwatt is precious.
@@TheSmokinApe I run QRP into a vintage vertical antenna. I have tested various coax types and can find no difference. So I use RG58!
@@James-ci3lx use what works for ya, thanks for watching James 👍
S.Ape, as always. Clear, great audio and to the point. For the love of me... I find it hard to understand that people invest a fortune in good kit and then throw it away by using 2nd/3rd rate feed cable. I used to be a die hard own cable smith but these days I only use Messi&Paolini cables and connectors. As I now only do VHF/UHF work I have standardized on their HYPERFLEX 13. as I want to wring every watt of power out of the system. Short of going the Andrew Heliax route.... you cant beat that cable. I will enclose a link to their website. Ape... I have seen a BIG stacked UHF array fed with RG213 !!!!!! the loss must have been horrific.
If anyone would have told me that I would sink so low as to buy ready made jumpers.. I would have had 'em shot... but now I get their ready made CERTIFIED jumpers. With bad arthritis in my hands I finally caved and By God... I am glad I did !
Anyway.... anyone interested..,check out their website and especially their technical info pages on their cables. About the best any money can buy. U put a lot of effort in your station.... does it not deserve the very best cable too? Yes... they ship to the USA and bloody fast too.
messi.it/en/home.htm
Albert EI7II.
Thanks for the link Albert and for the kind words 👍
@@TheSmokinApe What sets YOU apart from so many others is that you take the time, which MUST be very precious, to reply to us... yr subscribers. As you will know better than most, time is precious, there are never enough hours in the day. Allow me one final point if I may. Even if God himself created videos He still would get lots of Thumbs down, I can guarantee you that those come from people who have never in their entire life produced one micro second of worthwhile video.So....? IGNORE them. The people who care about yr channel will comment if they want to highlight something or bring a matter to your attention. An excellent case in point is the Gentleman that brought John Fielding's brilliant document to your attention. Those are yr goldmine subscribers whose opinions matter ! I loved the way in which he gently did so, (corrected you), a sign of a TRUE gentleman AND a CARING person.
S.Ape... better one good quality video than two/three lousy ones. Long may yr channel be with us !!!
Albert EI7II.
Thanks Albert. I try to reply to as many comments as I can, if someone takes the time to make a post I feel that I should follow up with them, admittedly I do not get to them all.
I've attempted to educate people on this, including hams, and they just don't get it. One guy was running over 100ft of RG58 to an expensive, high gain UHF antenna. I tried to explain that you're wasting your money and potential because effectively, you're back to unity gain or less. Even at 27mhz he was only getting 55% of the power to the antenna, with no real idea of the SWR at the antenna.
Another ham was so ignorant, he just would not acknowledge that the feedline loss was masking his SWR readings... not to mention meter placement (won't get into that). He was saying how flat the SWR was (and it read 1:1) across so many channels. He was also using a very long run of RG58.
Something worth mentioning about running low loss coaxial like Heliax, even at 27mhz, is when you have a very high gain antenna. The advantages when considering the ERP are considerable, not forgetting your receive as well.
Good video.
What I have noticed is that sometimes folks, regardless of RF service have a hard time being open minded ESPECIALLY if they are wrong.
@@TheSmokinApe having an original thought is good for development.
As a noob this was very informative. How do I measure or determine my line loss?
Glad you liked it, the best way so to use coaxial line loss charts.
This is very informative, thanks. A question: When using an antenna tuner (either at the radio or the antenna) to lower the SWR to 1.2 or lower (impedance matching), does this actually increase the useful power going to the antenna or does it simply reduce the reflection back to the radio (or both)? 73 KJ7YBK
It just reduces the reflection back to the radio, thanks for watching Dan.
@@TheSmokinApe Thanks. From all of the videos I have watched (including David Casler), this is the first time my brain heard this. It is what I suspected but do not think anyone said. My guess then is that the power not reflected back nor sent forward to the antenna is consumed in the form of heat. Would this be accurate?
@@danev1969 a tuner next to the transmitter will allow the transmitter to put its maximum power into the system also creating a resonant system by canceling out the reactances, the reflected power will join the forward power back to the antenna, the key to efficiency in this system is the feedline, the lower the loss the more power is available to the antenna to radiate
Awesome show! New HAM. What part of the coax does the return loss come back through? The calculation takes into consideration the coax line loss, makes sense. My other question is how to calculate the power loss? Is that losss based on the coax or is it due to the throtttling at the load on the antenna?
Louis KK7AAG
73’s
It comes back on both the shield and center conductor as I understand it. The loss can best be measured in terms of attenuation on the feedline. There are websites that show loss in dB per 100" of various coaxial types.
The loss is created anywhere there is current flowing (review Ohm's Law) - it is mainly I^R loss with some dielectric loss. The power is not "throttled" at the antenna. A basic principle of RF states that a perfect impedance match throughout a circuit causes a perfect transfer of power. Where there is an impedance mismatch, a percentage of the power is flipped in phase and travels as a wave in the opposite direction, causing an interference pattern in the feedline. The wave consists of voltage and current, nothing more, nothing less. It is AC current, the same stuff that runs in the walls of your house, only at a much higher frequency.
thanks for the video. i'm trying, but still not getting it. in the summary, if i see 100w incident at the transmitter with some return loss and a swr of 1.6, i would not assume 100w transmitted.
Correct, less than 100 would make it to the antenna.
Ape thnx
Glad you liked it Paul 👍
Have you ever bought a car before? The sticker price is like the line loss. It's out there all defined and advertised really well. You look at it and you say to yourself, "Self, that sticker price is all this car will cost me!" And you shake hands with the dealer. Maybe you live in a state with no sales tax. I don't. So I have to add in sales tax as more loss, like the SWR losses at the feedpoint. You talked about that, but wait. There's more losses. You still have to pay title and license fees as the ADDITIONAL cable losses due to VSWR. A 2:1 VSWR feedpoint measurement gives us an additional ~0.22dB of cable loss in addition to the stated loss. It's not much, but if you are messing with a 4:1 SWR, you can tack on an ADDITIONAL ~1dB loss to the cable losses. It can be staggering.
This is mostly incorrect. "with moderate lengths of low-loss coax, such as we
commonly use for feed lines, loss of power because
of reflected power in the hf bands can be
insignificant, no matter how high the SWR. For
example, if the line SWR is 3, 4, or even 5 to 1 and
the attenuation is low enough to ignore the
reflected power, reducing the SWR will yield no
significant improvement in radiated power because
all the power being fed into the line is already
being absorbed in the load." That from antenna engineer Walter Maxwell who wrote extensively on this subject. If you transmit 50 watts to the antenna and 25 watts is reflected back, that in turn is reflected back to the antenna. So now you have 75 watts (50 watts + 25 watts) headed to the antenna, and the antenna radiates full power of 50 watts. The only important thing is use an antenna tuner so the transmitter sees about 50 ohms or an SWR of now more than about 1.5 to 1.
Awesome "art skills" !
Haha, thanks man!