The Truth about SWR: Debunking the Myths and Misunderstandings

What is Standing Wave Ratio (SWR) and how does it impact your amateur radio antenna system? Is there really such a thing as “perfect” SWR and does it really matter? DX Engineering’s Michael Murphy, KI8R, covers the basics of SWR, including reflected power; factors that can influence SWR readings, such as lossy coaxial cables; the importance of measuring SWR at the antenna; and some of the myths and misinformation surrounding this widely used measurement in ham radio. Click on the links below for some great SWR resources, as well as low-loss coax cables from DX Engineering discussed in the video:
ARRL Antenna Book for Radio Communications, 25th Edition
www.dxengineer...
ARRL Handbook for Radio Communications
www.dxengineer...
Understanding SWR by Example
www.arrl.org/f...
SWR Reference Chart and SWR Calculator
www.dxengineer...
DX Engineering RG-213U PL-259 Low-Loss 50-ohm Coax Cable Assemblies
www.dxengineer...
DX Engineering 400MAX PL-259 Low-Loss 50-ohm Coax Assemblies
www.dxengineer...

[@matthewsteger9540]

As a ham of over 30 years and an electrical engineer, 2 thumbs up for a great video to educate about SWR.

[@timmack2415]

Great explanation. I've explained this to many folks over the years, but you crystalized it very well for a short video. Generally speaking, most hams understand SWR as well as they understand grounding and bonding - almost nill

[@off-trailseeking3965]

Nice job Michael! Made me think past the SWR standards. I would really like a video taking this a little farther using a RigExpert AA-650 Zoom or similar and talk about what the optimum X,Z,R numbers on the meter would be to strive for when tuning up an antenna.

[@kf7bws]

Very Good explanation. One thing to keep in mind, transmitter finals do not like a high SWR, especially solid state, ergo the tuner. By using a tuner to match your transmitter output to the antenna system (transmission line and antenna) you are protecting your radios Tx. I use as my primary antenna a 40 meter EFHW and LMR-400 with my Elecraft K3 which has a 10:1 tuner. This combination is pretty effective on ALL bands from 80 to 10 including WARC and most times on 160 and 6 meters. From the tuner out I don't care about the SWR, all I care about is protecting my radio and the tuner does this. The list of confirmed calls on every band proves this.

[@ekkiplicht7283]

Excellent, many thanks. Most important take-away: "If the SWR is low over a wide frequency range, something is very wrong." Please ask yourself if your super-wideband DC-to-Daylight shortened and heavily mismatched antenna really works so well or just heats up the atmosphere. 😄

[@BryanTorok]

I've been asking similar questions about the guy who sells a 40 / 80 meter antenna in a one-gallon plastic bucket for $450 and says to hang it in a tree. Snake oil magic antennas are generally just that.

[@leehyde6610]

This is a very complex topic....many radios fail because of out of tolorence amplifiers, so so transmission lines and over modulated signals. When running at the edge can get expensive. Great talk!!

[@KB9VBRAntennas]

This is a great presentation and illustrates the often overlooked effect that coax has on an antenna system. To paraphrase the editors of the ARRL Antenna Book: a sufficiently long enough piece of RG-8X will present a perfect 1:1 match from any antenna.

[@Cubasenet33]

This information is just gold. Thanks for it!

[@Texan747]

Interesting and most helpful. Thank you Michael and DX Engineering! W5JCS

[@CriticalThinker-42]

Another thing to Keep In Mind is that 1 S-Unit is 6db so 1/2 S-Unit is 3db, and in most cases 1 S-Unit signal loss at the other end will not be noticed UNLESS your close to the noise floor in Weak Signal Conditions where your signal could be lost in the noise. I have close to half a century as a ham and made my living as a radio tech, and I don't let lossy bands with high SWR and an Antenna Tuner prevent me from making a contact. 73 mike 🍺🍻

[@alanwoods4925]

Listening to this made me realize what knowledge I've been missing for 50+ years about SWR. Your video talks about voltage going from transmitter to antenna, or basically source to load. But electrically speaking, voltage doesn't travel, current travels. Now, if we were talking about DC current then we would expect that the voltage may fluctuate, ideally with some coherence if we were attempting to transfer data of some sort. And if some of that current was somehow "reflected" from the load back to the source, then I would totally understand SWR. But with RF, we are using AC, not DC. So I can understand that the voltage will be "traveling" along the feedline. But I also understand that the current will also be traveling along the feedline. And because the source power is AC, the voltage and power will be traveling back and forth on the feedline, sometimes moving towards the load and sometimes moving away from the load. And because feedlines are very often two conductors, the direction of travel will be, or should be, equal and opposite on the two conductors. So, coming back to SWR, how is it that we can measure and rationalize the "reflected" power when the "forward" power is constantly changing? If the forward power is swishing back and forth, how is the reflected power measurable? Does it have to do with time, or distance, or a combination, or something else? I have used SWR for decades, and understand that the power moves from source to load, and that reflected power is basically power bouncing back from the load. But the measure of the two doesn't yet make sense to me. Thanks for your great video and for taking the time to share your knowledge.

[@BustRadioMyths]

Great video. My only gripe is that he said to really know what's going on with your transmission line you have to measure SWR at the antenna. Yet earlier in the video he showed an ARRL graph that shows how you can measure SWR at the transmitter end and see what the actual SWR is at the antenna.

[@gordonwedman3179]

My understanding is that if you were to use a vector network analyzer, like a NanoVNA, you would connect it to the feed line.

[@timmotel5804]

9/2024: Hello & Good Day from The Future. I just found & subscribed to this site. Excellent tutorial and now, I want more. Thank You & Best Regards.

[@FrostyDog9186]

Thank you so much for this video! I have been preaching this gospel for years and now I finally have a terrific summary that I can just point people at! 73 de AA5SA

[@earlrichardet2102]

Great video and timely as well. A friend of mine is having a problem with his 80M antenna and he needed some understanding as to what he was seeing on his rig expert meter. Thanks for this post, it is very useful. 73!

[@robbannstrom]

Nice presentation, thanks Michael! There's actually an online antenna modeller website which can show, for a multiband wire antenna like an OCFD or EFHW, exactly how VSWR changes across a frequency range when using a user-defined length of a user-chosen coax type - all graphically. The site also shows radiation patterns, current diagrams, Smith chart ... all calculated and displayed on-the-fly.

[@eyesonly4451]

And it's not required that your coax run be a monolithic cable from your transmitter to your antenna. I have a 200' run of LMR-1200-DB (0.1 dB/100' loss @ 14 MHz) coax from just outside the shack, to near the base of a ground-mounted, 15/20/40 meter sleeve vertical. The first 10' on the shack end and the last 3' at the antenna is made up of RG-213. This has been in place for almost 20 years without an issue. As I'm HOA limited to a ground mount vertical, I expended more of my antenna budget on low-loss, buried coax rather than a tower, rotors, and Yagis. Excellent video, btw.

[@oldbassist60]

The only thing you could have mentioned would be CM chokes. Often, that will solve a lot of ills regearing SWR problems. Maybe another video for those less familiar with this very interesting phenomenon.

[@jamesaddis8726]

Agree I have had issues with 1:1swr antennas with stray rf however tuning 1:3 /1:5 has solved this for an endfed via a matching unit despite the settings being fine on an analyser it's truly a dark art especially with environmental factors such as moisture and rust bolt effect

[@3v068]

Thank you for this video. Studying for my first license and SWR has always thrown me off the hook.

[@flightstatic4662]

Good luck on your test!

[@williampeacock9473]

Good luck on your test. And ham it up when you pass your test. 73 AE4OY WILLIAM PEACOCK 🦚 EM-81UF Blackshear, Georgia USA 🇺🇸

[@Jerrythenerdful]

Just a few comments. 1.) The predominant loss in coax below upper UHF is conductor losses or current I^2 R losses. Below upper UHF, the dominant loss mechanism is not dielectric loss unless the cable is wet or has an exceptionally poor dielectric. 2.) Reflected power does not heat the source. Reflected power simply mismatches the operating impedance at the source terminals and this mismatch changes the PA load line. The mistermination at the load creates a standing wave that just "stands", and that wave changes the impedance along the line at stable predictable points. This is how a matching section works. The PA does not "absorb" reflected power. The PA simply sees a different load than the design target. The PA might run hotter, colder, or not change at all from that mismatch. If we add a tuner to make the PA happy, the system loss is primarily caused by increased current and increased I^2 R losses in the transmission line. 3.) It is important to point out that resonant half wave dipoles are not 72 ohms in the real world. The impedance of an infinitely thin zero conductor resistance half wave dipole in free space is absolutely 72 ohms, but a real dipole is normally not 72 ohms. Most of my dipoles are around 50 ohms, but a dipole can actually range from 20 or 30 ohms to almost 100 ohms at resonance in a typical real-world installation. Wire thickness, any wire insulation, the phase of ground reflection, and the surroundings all work to modify dipole impedance. 4.) It is possible to have a 10:1 or even a 20:1 SWR on a transmission line and still radiate almost 100% of the TX power. This is how Q-section fed or stub fed antennas work, and it is also how high efficiency doublets work. 11 percent reflected power or even 90% reflected power does not mean that amount of power is lost. That power does not reverse flow. All it does is set up a standing wave, which is an operating impedance change along the transmission line. Four of the biggest transmission line and antenna myths are: 1.) reflected power bounces around and heats the PA, or that power constantly moves both ways in a transmission line 2.) a dipole is always 72 ohms 3.) a high SWR means low system efficiency 4.) The dominant loss mechanism in a normal HF or VHF transmission line is dielectric loss

[@ucanliv4ever]

Look charlie

[@Elias-f4h]

60 degree phase shift at the transmitter final is at least DOUBLE the instantaneous peak heat dissipated in the output stage (that's on the very edge of properly designed consumer radios

[@Jerrythenerdful]

@@Elias-f4h The reflected power never makes it to the PA. It simply creates a STANDING wave. The mismatch simply sets up a pattern of operating impedance changes along the transmission line. At the PA, the mismatch simply appears as a mistemination. Thinking it appears in the PA at the PA device as some sort of power that has to be dissipated is irrational. Let me give you a working example group. A lossless 75-ohm line terminated with 112.5 ohms has a 1.5:1 SWR. If that line is a 1/4 wave long or any odd 1/4 wave, the standing waves caused a line operating impedance at the PA of 50 j0. The PA is perfectly terminated yet the line has a 1.5:1. The % reflected power in charts does not means a thing. (it is pretty much meaningless in the real world) A second example is a lossless 75-ohm line with 50 ohm termination. The line SWR is 1.5:1. At 1/2 wave the impedance at the PA port is 50 j0. The line clearly has reflected power and standing waves, yet power transfer to the load is perfect and the PA operates normally. The standing wave simply fills the transmission line with a static (standing) "wave" that changes the relationship between voltage and current along the line. We can have a 10:1 SWR or higher and if the line is very low loss transfer nearly 100% of transmitter power to the antenna or load. The "percent reflected power" and "reflected power heating the PA" is just meaningless blather. A mismatched load caused by SWR simply changes the loadline at the PA device. It can make the PA device run hotter, cooler, or not change it at all. ALL of this can be proven. If reflected power worked as the video says, and if it acted like the charts that show some percentage reflected power that was lost as heat, stubs and Q-sections would show that loss. They do not. I can build a combiner with mismatched transmission lines and while those lines might have some chart-indicated percent reflected power, they really only have the base transmission line loss. That loss is almost exclusively from conductor resistance losses, not from dielectric losses in normal cables operating below upper UHF.

[@Sonicgott]

Using RG-8X coax with my 20w G90 seems to work just fine, but if you have a more powerful base station and want to support a wide range of frequencies, then getting good coax is a definite must.

[@fredfenwick7047]

I have been a Radio Ham operator since 1984 and my advice is buy the best coaxial cable you can afford as it can be the weakest link in an antenna installation and as SWR increases this will in turn increase the coax losses especially at higher frequencies above 28MHz.

[@bill-2018]

5 Watts here and Mini 8 coax 25 feet so no great loss to 20m to 10m dipoles and works well. G4GHB

[@Homer19521]

Little surprised you talked about coax as if it is the only transmission line (no mention of balanced line). Also surprised to see the use of "Db". When presenting technical stuff, wrong units serve as a distraction. Good discussion on reflected power. 👍

[@turkeyman27534]

Coax? How about ladderline? Q very short coax run to the 4 to balun with the 450 ohm ladderline. It gives me frequency flexibility with lower loss.

[@Pioneer936]

On the whole pretty good info ,you could have mentioned that it's the impedance the radio sees that the feedline length and reflected wave have transformed that really kills you radio , for those who thought that it was the reflected power going back into radio

[@akiddoo8113]

Phase? No one ever mentions phase relationship. What is happening in that coax with signal ping ponging back and forth from load to source? Won't there be cancellations in signal because of phase shifts resulting in power loss?

[@DumbledoreMcCracken]

Exactly. There is a video that mentions phase, but I don't know where on KZbin. But power SWR should not be influenced by phase, only voltage SWR depends on phase.

[@Elias-f4h]

High VSWR on a transmission line means the voltage at some points is higher (V^2 losses increase) or where it is at null, the I^2 losses increase. Dielectric losses and conductor current heating both increase as the square of the VSWR. They both occur at different points (wavelengths) along the line at the same time. VSWR is a measure of how much above or below the normal RMS/PEAK voltages and currents of a sine wave are between a properly matched source and load. The phase (time) relationship between voltage and current of the sine wave is always changing, by how much extra at any given time (point, wavelength)? In a properly matched (resistive) system, they both change together at the same time (point, wavelength). VSWR means they start changing apart from each other (phase shift) - some energy is stored and released in the electric field or magnetic field until a different time (point, wavelength).

[@udx-483muddbucket5]

Good information. Well presented. Now I have to get to work and figure this out. ✌✌

[@MrTommy001]

Exactly right. As a new ham, much of this is still a bit boggling.

[@udx-483muddbucket5]

@@MrTommy001 After fighting never ending bad results I resulted to checking SWR via the transceiver vs the NANO VNA and I found I apparently was getting bad readings from the VNA. ✌✌

[@Quakeboy02]

@DXEngineering I would love to see a presentation about a 130 ft doublet fed with 1" twinlead/ladder line.

[@rj2para]

Thank you. Saved to rewatch.

[@franciscolopez3229]

This very informative since I try my best to make my own antenna. So please correct me if I am wrong. You said that on yagis, it has a low impedance, so in the 2 meter yagi that I am working on, if my analyzer reads lets say, 1.2 SWR, Reactance is 8 and the impedance is 38 ohms, does it mean the radio can take it with no problems in the long run? Sometimes when tuning an antenna, there readings like 1.7 swr, impedance is 50 ohms and 0 reactance. Which would be much better among the two readings? And on the part of taking your SWR reading at the antenna, can I use only a 6 foot coax? Before I forget, new ham this side of Asia. Thank you sir.

[@JustAThought1000]

Very informative and well done video.

[@G5STU]

Good stuff 👍

[@johnpawlicki1184]

Resistance can change by frequency. Impedance is resistanc + reactance. A perfectly resonant antenna (at one frequency) exhibits only resistance, i.e. radiatin resistance. The resistance (and reactance) will change when the frequency changes. A dummy load should exhibit only resistance and hopefully not change that resistance over the usable frequency rangs. Antennas, however, do change resistance ad reactance by changinf frequency.

[@2321brendan]

Reflected power is not lost power. Take a 50 ohm load ,at the end of a half wl of 500ohm open wire tx line. 10:1 SWR . If the power was lost only 33% of the power would reach the 50 ohm load. How much power do you think reaches the 50 ohm load?

[@Johann-ZS6L]

Great article. One thing, after 52 years in RF coms and other sevices, it still remains a hidden secret on why hams dont use ballanced feedlines in the majority of cases. And.. why hams dont look and UV protected (as well) and much cheaper 50 and 72 ohms CATV, CELL PHONE BTR co-axes. It shows a low loss at freq's even at 10GHz!!!!. And where only 75ohm. MOB COMMS CO-AX is available, learn how to apply the 1/12 wavelength co-ax impedance matching stub option. It works like a charm!!!!

[@RodrigoForrequi]

Thanks for the video. I’ve a question: why reflected signal from antena, arriving the transmitter, is reflected back if at this point we don’t have impedance mismatch (between transmitter and cable)?

[@surgingcircuits6955]

Thx for the informational video. Interesting statement that "Reflected Power is NOT Lost Power". Seems technically correct, but not practically correct. I presume that reflected power has latency, and would be out of phase, so not useful or problematic. Just thinking out loud. Cheers.

[@redmesa2975]

That would explain why I have an SWR of 1.5 with the radio turned all the way down. Then as I turn up the output, SWR also goes up.

[@sleeve8651]

I have a question ! Having an SWR meter in the radio, and an SWR meter in an antenna tuner, which do you believe, as they both change as you adjust the tuner ?

[@davemichaeli5339]

Thank you, this is helpful. If you are receiving only, and not transmitting, is the SWR reading at the feed end a good indication of the antenna’s resonant frequency? I use some SDR dongles for receiving signals from passing weather satellites and have tuned the antennas based on the SWR numbers. Is that a correct method?

[@gartnl]

Tricky question. If RX only the feed end is the antenna, not the receiver..

[@capt.mike73ahoy14]

Thanks Mike. Good presentation. Is that a Hallicrafters SX110 on the top shelf of the bookshelf behind you,?

[@mikemurphy1940]

Yes. If it hadn't been for that radio, I probably wouldn't be in Ham Radio today

[@TheEmbeddedHobbyist]

I find the best VSWR is when you connect a 50Ohm lump of carbon across the antenna, but i don't seem to hear much. My ERP is very bad as well. But i'll live with the great VSWR 🙂

[@FixItStupid]

LOL

[@Johann-ZS6L]

Don't be lazy. Get to ant to resonate at the operating freq with a 50ohm load... That carbon dummy is absorbing unnecessary RF power.

[@TheEmbeddedHobbyist]

@Johann-ZS6L but my 50 carbon load works on all frequencies giving me a perfect swr of 1:1, its a joke man, swr can be great with shit coax and no antenna. Back in the 80's a new ham on 144MHz had a great 1:1.5 swr but could not work anyone. Checking his set up he had the thinest coax I've seen and it was snapped at the antenna. We calculated that with 10 W in a out 1 or 2 watts reflected back so bugger all at the swr bridge gave a great reading.

[@Johann-ZS6L]

@@TheEmbeddedHobbyist seems you want to talk shjeet. Qrt de zs6l

[@TheEmbeddedHobbyist]

@@Johann-ZS6L no I was just pointing out that a good vswr does not mean that the antenna is doing anything. Long runs of coax, antenna mismatch, etc need to taken into account. I check my antennas with the vswr bridge as close to the antenna as possible or use a NanoVNA which gives a better view on the mismatch. Makes it easer to decide if it is too long or too short. 73 a radio ham since 1980

[@geirha75]

Is a wire antenna more capacitive when too close to the ground?

[@bobwall3]

What did I learn? That I know less than I thought. 😢

[@althepal6818]

Peuple always explain the effects of swr on TX, rarely on RX😢

[@c.a.r.s.carsandrelevantspecs]

Very well done and important video for ham radio! Thank you so much! ~ 73 ~ AC7WH

[@lostinspace280]

I was all cocked and ready to tell you that you do not have it quite right, until you said check SWR at the antenna. Most of us QRP operators adjust our antenna to be resonant at the frequency we intend to use using an analyzer at the antenna, which also gives the SWR reading. I might add it is also a good idea to check the SWR at the coax before it inters the transceiver because running portable operations the coax is put thru more bends and connected and re connected many times. Good to know if your coax is in good working order.

[@jeffmachul9562]

Well done! I going to be ordering by 100 foot runs of lmr- 900. Boy is my wife going to be upset.

[@Tsachyl]

If one needs only one thing from this clip it is the part from minute 5:30 to 6:00.

[@MrDmjay]

Excellent insight. Thank you.

[@n0vty873]

I have tried to explain this to some people so much that I just gave up

[@VP2EIHonAnguillaIsland]

Thanks 👋🏻Good Stuff👍🏽 thanks 73 🎙Ira

[@pierfrancescograzioli4080]

Ciao Michael, complimenti ottima spiegazione, ti faccio un appunto, nelle slide dove si vede la radio, la linea di trasmissione e l'antenna, il termine decibell e scritto in modo sbagliato! Hai scritto Db ma si scrive "dB" perché è l'acronimo di deci-Bell "Bell e il nome del fisico che l'ha inventato" per quanto riguarda il Rosmetro o SWR meter, in stazione sono pienamente d'accordo che leggerà più o meno correttamente i valori di SWR solo alle basse frequenze, diciamo le HF fino a 30MHz, poi salendo di frequenza in VHF e soppratutto in UHF e quasi inutile se non si utilizza un cavo veramente corto e a bassa attenuazione! Anche in condizione di adattamento di impedenza tra Tx e antenna, se l'attenuazione e elevata, si rischia leggere valori di SWR talmente bassi da non distinguere se l'antenna funziona oppure e scollegata o in cortorcuito, quindi pensare di leggere il vero valore di SWR in shak a frequenze nell'ordine dei 450MHz e una chimera, ma questo vale non solo per il SWR meter, ma anche per un Bird, o un Nano VNA dove si vedrà una traccia più ondulata a basso valore di SWR! Quello che hai spiegato lo si trova anche sul sito della BirdRF nelle application notes, e si chiama "Cable Masking Effect" Ti seguo con interesse, un caro saluto 73 Pier Francesco Grazioli

[@ericnepean]

An SWR of 2:1 measured at the antenna is good enough for most purposes. This is a return loss of 10dB, 10% of your Tx power is reflected, and 90% is transmitted, for a loss of about 0.5dB. Most feeder lines have a loss well over 0.5 dB, and at the receiver end a power fluctuation of 3dB is perfectly normal. An SWR of 1.2:1 (return loss of 20dB) is close to accuracy of most regular lab equipment. If you think you have measure a better VSWR you are probably just measuring the result of the inaccuracy of your equipment combined with the reflected signal. You may just as well say the SWR IS 1.2:1 within instrumentation error.

[@marklowe7431]

S/n should be more of a focus. Yeah for rx loops

[@dapperdave4952]

Thank you Michael from a Ham that was licensed as a Novice shortly before he could legally drive a car....that was 54 years ago. I have never heard these SWR/VSWR myths debunked so well.

[@AC9BXEric]

"my antenna has been up there for 30 years and the SWR is getting better"

[@calbrabandt5967]

You say, "To really know what's going-on, you need to measure your SWR at the antenna." That's often very difficult to do so why not measure SWR at the shack and correct your SWR reading for the coax losses given the length of your coax feed line and frequency of operation, which are published and well known? Thanks for the video!

[@Wizardess]

There is another large gorilla in the room, impedance presented to the transmitter. Transmitter power amplifiers are designed for optimum IMD performance and efficiency at a specific load resistance. Ham equipment sacrifices transmit IMG performance for oomph out the antenna. Still, varying that load resistance from 50 ohms to a lower impedance means the output waveform will flattop at a lower current than the transmitter tries to supply. The waveform distorts. Other hams complain. If the load resistance is higher than the design load the PA will go into voltage saturation at a lower instantaneous voltage. That gives more IMD and more complaints from hams on adjacent frequencies. Both cases can also reduce how well receivers can decode most of your modern digital waveforms. The only cure is to reduce transmitter power so BOTH instantaneous voltage peaks and instantaneous current peaks are less than the design levels. In effect this is another "loss" in the over all system performance. Of course, remember that a 1 dB (about 25%) power loss is usually not going to make a difference in your ability to communicate. But that is yet another aspect of the overall system design to consider. "What things are worth developing intestinal upset over?" {^_-} Joanne/The design is not over until you have looked for ALL the problems/ W6MKU

[@Pioneer936]

@@Wizardess that's why we use a tuner at the transmitter

[@Wizardess]

@@Pioneer936 Duh - but tuners were not part of the discussion. {o.o}

[@Pioneer936]

@Wizardess duh it's the cure to the issues you mention

[@Wizardess]

@@Pioneer936 And that "cure" an excuse to put in as much as a dB extra loss and a high pass filter to enhance EMI into your system. (That is the topology of almost every tuner out there. I built my own back in about 1970 with a little more loss and a serious lot more harmonic suppression.) {^_-}

[@Pioneer936]

@@Wizardess absolutely bs ,a tuner doesn't introduce loss it main function is to allow the transmitter to produce its full power into the system

[@n1qeh62]

I use LMR low loss coax

[@miroslawkaras7710]

@10:22 . That statement is not entirely corect or a list for same type of ampliers use in transmiter. Reflected power do reflect back from transmiter. It will be partially absorb by power amplifer. I am doing some power handling on components in the company that I work for, and let me tell you one thing. If the load have savire mismuch and the power is reflected back to the source with out much loss in transmission line, the power will be absor it as it have own load characterystics. In such case the output power may drop due to prezents of signal in both direction - forward and reverse. Remedy is to use additional attenuation on the transmision line with penaly of loss of power, or use some isolator or circulator to redirect reflected power to dummy load. Some amplifer have aleady build in such protection so they might not effected. Just be aware that you may see something like that.

[@paulm0hpd319]

Power is not absorbed in the transmitter it's just not produced,the reflected wave joins the forward wave back towards antenna hence an swr measurement,

[@josegerardoalvarez2601]

XE2ZZ Good Info.

[@oldbassist60]

Great explanation debunking the myth. There are antennas that will give you a flat response across the entire HF band without the need to retune. It's called a terminated coaxial cage monopole or TC2M for short. Mine is 0.8 meters in diameter, 44 feet tall (I purposely tuned it long for 6.9MHZ, has six cage wires, ten-wavelengths of wire at 40 meters under it for radials, is terminated in the antenna's characteristic impedance - about 260 ohms, has a broad-banded, bifilar wound 3.5:1 Unun and a 3,000-ohm Common Mode choke at the input. The worst SWR is at 5 MHz (2:1) but I don't care about that band. It requires no tuning from 1.8 to 60 MHz and is 1.2:1 or less. In fact, enabling the internal tuner actually raises the SWR - to the detector anyway. To RF it looks like a big fat pipe with 1-meter long, tapered ends - Look way back in the books and look for a 4 to 6 wire cage dipole. It is a beast. This vertical is half that and is only the weight of the DXE telescoping 46' fiberglass mast. It's guyed at the half-way point. It has very little to no gain, but nothing affects it either (very low "Q"). Neither rain, snow, trees, or me standing beside it making measurements affects it. I use LMR-400 series coax and N or BNC connectors. I'm too old to climb so a vertical is my choice. The CM split ferrite beads placed randomly along the feed line help a lot with QRM. If running under 500 watts, use RG-58 or LMR equivalent cable and wind a 4-turn choke on a 1-inch split bead, and stick it at the input of any antenna to decouple it from the third path (the outside of the coax braid) back to the rig. OK, I'm done. 73's all.

[@norbertdapunt1444]

Awesome.

[@mikeault5335]

Good Video Mike! 73 ghw

[@dalependleton6420]

Now talk next about a conjugate match for the antenna system when a tuner or the tuner in the rig is used. What are the losses then? de W4AUV.

[@charleswoods2996]

Well that was entertaining and educational! Explain how "grounding" has NOTHING to do with achieving a low SWR - AND - how "earth grounded antennas" are both dangerous and illegal according to the National Electric Code. KD8EFQ/73

[@BusDriverRFI]

Interesting that you don't mention CMC. CMC and reflected signals is like Clark Kent and Superman. You never see the two of them mentioned on a YT video at the same time.

[@Pioneer936]

@@BusDriverRFI maybe because they are two separate issues and not related

[@user-ef3nu1eh7z]

Old operator here which is more accurate? Quality swr meter or antenna anylizer ?? Havent used the anilyzers yet always trusted calibbrated swr meters Or is plotting meter responses on graphs ( old school) just as accurate?

[@lifegettingintheway2710]

Reflected waves are subject to the same losses as the primary wave, and also travel twice as far along the coax. And because the wave reflected back to the antenna is going to see the same impedance mismatch as the primary, part of it will be reflected back to the source and of course reflected back to the antenna. It is continuous. So not all the reflected power reaches the antenna. On a modulated transmission the modulation on the reflected wave is displaced in time by the time spent traveling back to the antenna after the primary wave has been radiated. In broadcast television this shows up as ghost images. All the power that is traveling to the antenna is measured by the directional watt meter, including reflected waves. Same with the reflected power. The watt meter has no way to differentiate the primary wave from reflected secondary waves.

[@kayleesotiseesa3625]

13689 Hettinger Drives

[@TheScottClifton]

Please explain how reflected power eventually gets radiated. Before you do, place an RF ammeter at the feed point of the antenna, as well as a bridge or VNA to determine the exact resistance. Then using the standard formula of (I x I x R) current times current times resistance, and then tell us what that calculates out to. Now, use your VNA or impedance bridge and measure the impedance of your transmitter’s output. This would require activating the antenna switching relay to actually do so, but in most cases you’ll find the output if a transmitter, or amplifier, is lower than 50 ohms, which will create more power loss as a terminator. But let’s assume it’s 50 ohms for easier calculation and our transmitter is 100 watts. A coax loss of 3db at the antenna that causes a 10% loss of power means 45 watts is flowing forward into the antenna and 5 watts gets sent back to the radio. If what you’re saying is that this power is then reflected back from the radio to the antenna, the power at the radio is now 2.5 watts and by the time it would presumably get back to the antenna, it’s now 1.25 watts. So, it is getting wasted, and nothing of any consideration would be sent back to the antenna. Now, if you assume the load is actually much lower, like in the 5-10 ohm impedance, then even less power would be sent back to the antenna. Now, I haven’t even began to discuss the phase of the forward and reflected waves, but length DOES play a role here, where it could be possible that any amount of power that is reflected back to the radio, or the antenna from the radio, could be phase cancelled or attenuated. Simply put, reflected power is mostly lost power and very unlikely to make round trips and find its way onto the antenna.

[@paulm0hpd319]

Lossesd power until you put a tuner in line to correct the phase and return it back to antenna

[@artbremer4076]

I guess you can go ahead and contribute to the next update of the ARRL Antenna Book, if you so sure that the authors, including those who were designing antenna systems for deep space programs, didn't know what they were talking about... And yes, many people have measured the power the way you described on a low loss coax.. And each time it would measure forward power plus whatever gets reflected back to the antenna. 3db loss coax was used as a more of a dramatic example to stress the point. No one is using such a lossy TL in real life, at least intentionally...The caveat is LOW LOSS coax

[@yakovdavidovich7943]

If the output impedance of the transmitter is low (can be 5 ohms or less!), then you will have a discontinuity, which is a 50-ohm cable driving a 5-ohm load. This is a 10:1 mismatch, which is 1.743 dB return loss. This means 1.67W is reflected back into the coax to make the journey... drop another 3dB, and it's 837mW, which hits that 2:1 mismatch, meaning 89% is radiated, putting 745mW onto the antenna.

[@TheScottClifton]

No, Art, Chapter 9 supports my position just fine, they too promote line matching at the antenna. They even include the broadband matching concept, which I also agree with to minimize our losses as we go above and below our resonant frequency. Since reactance varies, your antenna’s resonant point might need to be skewed high, while another’s may be lower. The point is to balance the 2:1 points equally above and below your favorite operating area. This makes the tuner corrections slight, which minimizes loss.

[@Pioneer936]

​@TheScottClifton if it's mostly lost power ,how is it that a doublet antenna with 10.1 swr has most of the power radiated by the antenna

[@DumbledoreMcCracken]

There is a lot wrong in the video. Let's start that a length of coax is exactly a *_circulator_* circuit, at some center frequency, with respect to a reflected wave.

[@TelstarElectronics]

Sorry, I don't agree with your statement about reflected power is not dissipated in the output stage of the transmitter. There are only two places that the reflected power can go... either the coax or the transmitter. I think there is reflected dissipation loss by both... but the vast majority is consumed by the transmitter. After all, that's the real danger of reflections. The other more benign issue from reflections is the loss of ERP of the system.

[@KeiDys774]

There is a third place it might "go". Forward and reflected power are concepts that do not represent anything tangible. They are values computed from the voltage and current measured at one point on the transmission line, and these values have the units of power, but they do not represent an actual energy flow. The two values have the nice property that when reflected "power" is subtracted from forward "power", the result is the actual average energy flowing at that point in the line. Since "reflected power" does not represent a tangible energy flow, the question "where does the reflected power go?" is not meaningful. Treating forward and reflected power as tangible energy flows causes much confusion and inhibits understanding what is actually happening. It does not help that many authors colloquially describe power as being reflected at an impedance discontinuity. A more precise description would describe the reflection of voltage and current waves, not power. For sure, it is not the intangible reflected power that damages PAs.

[@bobbyt3451]

ive got my swr down to 1.3 but when i talk into the microphone it goes up to 3 is that bad ?

[@Sonicgott]

Short term that isn’t an issue, but make sure to use an antenna tuner if you have one.

[@bobbyt3451]

@@Sonicgott yes i tuned my antenna dead key down to 1:4 with an swr meter its just when i talk into the mic it jumps to 3 and above

[@fredfenwick7047]

​@@bobbyt3451That is very strange are you sure you have the SWR meter set correctly ?

[@bill-2018]

R.f. getting back? Common mode currents on the coax? I'd check for r.f. on the coax. If yes, put a ferrite ring on. G4GHB

[@ClaraMag-g6i]

4826 Barton Lodge

[@ElviraScott-l9f]

Orie Plains

[@TheScottClifton]

Oh my, now we’re tuning coax! Tuners belong at the antenna, not the transmitter. Are you putting your half-wave antenna baluns at the transmitter, too? All you’re doing is creating more loss in power by bouncing the impedance of the 50 ohm cable on both ends. Phase would only be affected by the output coil, but what you’re adjusting it for is to wipe out the reactance. The SWR or reflected power from the forward coupler metering circuit is not looking at phase, it’s looking at energy flowing in a particular direction. I need a Tylenol. This is why resonant antennas work best folks. This is why the DXCommander and similar resonant antennas work well. Keeping the load as close to 50 ohms and minimal reactance is the key. And when it isn’t, matching/tuning it at the antenna will provide the most effective results, not the tuner in the shack. All that reflected power coming back into the shack is really getting lost in the coax, your output tuning network and final amplifier transistors or tubes, and not slingshotting back out into the antenna. Again, use your basic training; place an ammeter on the antenna and calculate your results. Or… Place a remote tuner at the feed point and tune/adjust for maximum power from the shack. 😊

[@bill-2018]

I like resonant aerials. I have 5 dipoles 20m to 10m in my attic and an outdoor inverted vee for 60m. I was given an MFJ 16010 tuner with two SO239 sockets, one to the tx and one to the aerial. All I use it for is one to the tx (changed to BNC as I run QRP) and a banana plug fits nicely into the other SO239 to a long wire. I've never thought a tuner on coax to an aerial works well. Before I built my resistive SWR meter I adjusted my tuner and long wire, a roller coaster and variable cap. at that time for maximum r.f. out as indicated on an r.f. pickup meter at the wire. It served me well for years. I used a similar set up at a special event station with three 5 foot lengths of aluminium tube which slotted together for a vertical. G4GHB

[@Pioneer936]

@@TheScottCliftonreflected power joins the forward power it doesn't go back into the radio and damage it ,the radio damages itself trying to put power into a mismatch that's why we use tuners at the transmitter

[@joeboxter3635]

Why is the first number always bigger. I dont like that. The swr by following this method fails to tell you which side has higher resistance.

[@JessicaHall-d3c]

9846 Eldridge Course

[@margaqrt]

To say that the reflected (and re-reflected, and re-reflected and so on) wave does not impose a current and voltage upon the final output stage of the transceiver would be to say the incident wave does not deliver energy to the antenna. The reflected power is lost. And is done so in several parts of the system. Each reflected, and re-reflected wave experiences transmission line loss. Energy is lost as current is imposed in the final transistors opposite to the direction of normal flow (collector->emitter). Not much current flows, but some does, and it does exhibit additional strain on the output stage. The majority of the energy is lost in the reflections. If you wish to refute my position place a wattmeter ammeter at the end of the transmission line and simulate the mismatch conditions cited in your presentation. The reflected power, in an impedance mismatch scenario, is not delivered to the load in any appreciable way. That, my friend, is why we have 'antenna tuners.' Also, odd and even multiple electrical lengths of transmission lines, have impedance transformation characteristics. One very common application is matching stubs.

[@Starbuckin]

I was thinking the same thing. I've seen several amplifiers destroyed because of high SWR and they always heat up quickly. Does he really think that power reflected back into the final output device isn't at least partially or mostly dissipated by it??

[@Pioneer936]

Without a tuner the power isn't produced to the difference of amount of reflected power ,the reflected wave will reflect back towards antenna at the mismatch radio coax junction, the impedance at this junction is what causes the transmitter to heat up trying to put power into a mismatch, place a tuner at this point the radio produces its maximum power ,the reflected power is in phase with the forward power back to antenna, at hf frequencies with moderate swr and low loss cable loss isn't too much of a worry

[@sure5291]

Sorry mate, I totally disagree with you. Higher VSRW not only affect the transmission but weakens the o/p electronic devices, as per my experience.

[@Redbelly357]

Apparently we don't even need SWR meters. Just run it.

[@bill-2018]

For many years I didn't have an SWR meter. I simply tuned for maximum r.f. out at the aerial as seen on an r.f. pickup meter. G4GHB.

[@rickyodom1201]

Been C B nearly and Ham 60 years 1:1 is best you get on S W R

[@rjy8960]

If power isn't reflected and absorbed by the transmitter, why are finals damaged by having a high SWR? My personal take on feeder losses is that if you have a loss anywhere near 3dB you need to give your head a wobble and give up - especially at HF.

[@Pioneer936]

It's the impedance the radio sees that causes the radiobto heat up ,reflected power joins the forward power back towards antenna

[@rjy8960]

@@Pioneer936 How does an impedance cause the radio's PA to heat up? For a PA to heat up and fail it implies energy does it not? I'm asking where that energy comes from.

[@Pioneer936]

@rjy8960 the radio is trying to put its maximum power into a mismatch line which causes the radio to over heat ,the power that leaves the radio is less the difference of the reflected power

[@rjy8960]

@@Pioneer936 I'm sorry but I really don't accept this. The fundamental problem with this argument is a 3dB loss in the feeder. This is BS. As I mentioned in my initial post, a 3dB loss in a feeder is a stupid assumption to begin with. Even at 2.4GHz over a 24m run of feeder my losses are better than 1.6dB. At HF they are a fraction of a dB. Have a look at some of the reports for finals failure for the QRP Labs QRP radio's where a mismatch of over 1.5:1 causes the output MOSFETs to fail. Why does this happen if all of the reflected energy gets reflected back to the antenna?

[@Pioneer936]

@@rjy8960 it happens as I've mentioned before because the radio is overdriving itself to put power into the mismatch

[@daveengstrom9250]

Your charts are too small to see.

[@robertmethia7080]

another words , buy new coax from dx engineering with deluxe connectors

[@throttlebottle5906]

cheap coax or too long a run on undersized coax and you may as well just talk on the dummy load or rubbery ducky antenna. 🤣

[@IainDavies-z2l]

It's not very good, it cancelled a lot of it's trains like SWT. No way as good as SW section of BRSR.

[@robbannstrom]

Ian, great comment - you should have your own YT channel!

[@SA5OHR]

Dont know the name or channel of the person that for about a year (?) ago spoke about exact the same as you do. For me it sounds correct, but i went into doubt when there where several "famous youtube hams" that made videos stating this person was so wrong and should stop making things up and stop spread false information about SWR. Will be interesting to see if they do the same with your video, or maybe you have better credibility in the HAM-world (?) so that they may consider to relearn themself...

[@ernestb.2377]

dB not Db 😆

[@danieljohnson8437]

Nope,Dope. Length matters.

[@donepearce]

Return loss is a far more useful presentation of reflected power than SWR. Please stop using SWR.

[@Gw0wvl]

What's SWR ? ..... If you're going to make a video. Refer to SWR as it should be. ..... VSWR. ..... Come on get the basics correct !

[@4Nanook]

If you want to fry your transmitter, ESPECIALLY if it is solid state, go ahead and run your system with a high SWR. The reflected power is NOT reflected again back to the antenna, it is mostly dissipated as heat in the final, also standing waves can result in voltages that will punch your final transistor if a solid state amp. I hope people don't take your talk seriously, final tubes and transistors tend to be expensive at the higher power levels where damage is likely to occur.

[@XPFTP]

why would i listen to this channel....... they over charge for everything they sell... the place is a joke and a rip off. even before c19 hit. they were over priced

[@James_Bowie]

9:59 ... make that resonant, not resonate.

[@KevinBasilMagnus-sy7rm]

Michael THANKUOU ❤🎉🎉 & DXE Thankyou, 73s 9V1KM KK7QGL SINGAPORE

[@dianeschultzviseth9794]

bravo. thank you. kb7pfu