Antenna Engineer Vs Ham Radio Myths! True or False?
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- เผยแพร่เมื่อ 14 มี.ค. 2024
- This video includes a short True False test to see if you believe ham radio myths. Do you dare?
Great myth busting references!!!!
www.k3emd.com/downloads/Refle...
na0tc.org/lib/exe/fetch.php?m...
zs6wr.co.za/documents/SWR.pdf
www.ogdenarc.org/downloads/Ant... - วิทยาศาสตร์และเทคโนโลยี
It’s really does not matter if you do well on the quiz. It matters if it makes you think and understand why you have these miscomceptions. Thank you I will look up Walt.
Great point from @thuff3207
Everyone needs to read Walt Maxwells books reflections
There are a couple of very popular ham TH-camrs who I suspect would not perform well on this quiz . . .
True
Ham radio TH-camrs are worst…
Despite all that, some of them even get hired by the ARRL.
Talk about failing upwards.
@@mikesmith-po8nd 👀
@@TheSmokinApe You, sir, are a cut above the rest. Thank you for being educational in your content.
Excellent. Thank you. I've been advocating the same for years. It is amazing the power that myths have over people, and how hard they are to break. Good work, sir.
Well said!
I have brought up these same points multiple times with other hams. I have been challenged, dismissed and yelled down when pointing out the FACTS.
I big part of my masters degree was on antenna theory and receiver design; Yet I end up arguing with idiots who believe some of the most outlandish things.
Really sad. At least you know, and you tried.
As a technical professional, require them to pay for your advice. You'll get a lot less argument that way. ;-)
Excellent! As an EE I got them all right. I was a little slow on number 9 as the way it was worded left a little to be desired in my opinion. I wish and hope all hams see this. There is a wealth of misinformation out there in today’s world!
Agreed!. As a fellow EE, I also got them right, but have issues with the some of wording, #4 for example. Low SWR over a range of frequencies could mean that you have a diskcone antenna. Or it could be a problem with a higher resistance cable.
Maxwell was (and still is) THE quintessential antenna man.
I've long believed his science about antennas & transmission lines. Other hams who [still] believe the myths of SWR and reflected power, and who continue to perpetuate them, have always amazed me.
The truth is out there! 😅
BTW, I got 100% on the test!
Thanks for sharing!
73 from west Texas.
Agreed!
Thank you mate! For us beginners you are a breath of fresh air..
Happy to hear that!
Many will need a restart or a reboot or both, after something like this. As always, on point. Thank you Mark.
Very welcome
Btw, something this deep deserves a subscribe!
Thanks for the video. Very interesting stuff. It certainly changed some of my thoughts on the subject.
I missed a couple of them. Things I thought I knew. Fun Video. I have some stuff to go look up!
Simply brilliant! I felt alone like quixote when sharing similar conclusions. Thanks
Mark, great video to reflect on 😉, thank you.
For those who did not have an Elmer, information like this is so valuable. I know I’m have been enriched by you. 73 from the left coast.
Very welcome
Thank you for the information and making me aware of Walt Maxwell.
Amazing. I always learn from you.
Glad to hear that!
I am a foundation amateur and scored true on all but #6
I went back to see if I had miss read #6 question only to find I had indeed read the question correct and so my knowledge on that was flawed.
Thought hard about it and now I see.
I really like these very informative videos of yours.
Keep them coming
I've seen radars with high reflected power damage the transmitter. I'll need to dig into these references. I only got 50%.
Thanks for these videos - as a relatively new amateur radio operator, I am finding them very instructive. However, I have one question that I would like you to clarify please. If I have a good matching unit which lets my radio see a 1:1 match, even though, let's say, the SWR of the antenna is actually 5:1 - I surely won't get the same performance in terms of power output as I would if my antenna system was a perfect match and didn't require the AMU? In other words, if some of the power reflects and travels back towards the transceiver before being sent back to the antenna and eventually being radiated, is the only difference vs a perfectly matched system, the loss in the coax as it makes a few "unnecessary journeys"? From what I have studied, the loss in the coax due to length is more of an issue than a poor SWR - but if the power has to make that trip several times, the loss will be greater. If this is not correct and most of the power is transmitted even with a poor SWR, then what would be the point of a resonant antenna? Thanks again for your videos.
You are correct. The idea that a non resonant antenna cannot accept current as well as a resonant antenna is a myth. Of course you have to use a tuner with a non resonant antenna. Additional loss caused by SWR is not an issue in the HF bands with low loss coax like Rg8. And reflected power is radiated, minus some coax loss. Don't believe the myths.
@@NoMoreRadioMyths Thanks - that is very good to know. The feeder to my long wire is less than 10m long, so any loss will be minimal, even if the power travels back to the AMU a couple of times. That would explain why I am getting better results than I thought I should expect when I put it up. Keep up the good work :)
@@NoMoreRadioMyths The statement "The idea that a non resonant antenna cannot accept current as well as a resonant antenna is a myth." cannot be true and I will tell you why. First of all you have to understand what a Smith chart is. I don't mean to know what it represents but really understand it. The moment you say "non resonant antenna" it means a load of a different impedance than what is needed, which means that you can pick any point on the Smith chart to represent that impedance, as every possible impedance can be plotted on it. On the real part it represents everything from open to short and on the imaginary part everything from 100% inductive to 100% capacitive (including no reactance at all). Your statement implies that I can have a load that represents an open circuit and it will still be able to accept current just as well as say a 50 ohm resistor. This would be impossible. But I will indulge you for a minute and say that you mean that you are talking about a mismatch that is within reason. So now you're saying that there is a cut-off point that on one side, current is accepted just as well but once you go beyond this point then it is not true anymore. Let's stick with the resistor, so 50 ohm no problem, 51 ohm no problem, keep going, how are we looking at 60 ohm, 1,000 ohm, what about 99,999 mega ohm, at which point do you draw the line where current is accepted just as well to where that statement is no longer true. if you could possibly draw such a line, then it would be like a diver going down and the water gets darker and darker but still some light, but then one more inch down it becomes completely pitch black. physics simply don't work like that, it's a gradient. there is a gradient between 50 ohm and 99,999 mega ohm so technically 51 ohm already doesn't accept current as well as 50 ohm, so you see, your statement simply cannot be true.
That is ridiculous @wolfhorschtdad5443. I guess I have to produce a list of all the non resonant things that won't work as an antenna.
@yogipg2022 A non resonant antenna will radiate just as well as a resonant antenna if a proper trans match is used. That is the context of using a non resonant antenna. That is not "my statement." It is the statement of many antenna and transmission line engineers like Walt Maxwell. He has said it repeatedly in his articles and books which you should read.
I've only recently discovered your channel. You're terrific!! 73 de AE6DD, Daryl, California
Thanks!!
I understand that antenna efficiency doesn't change much with frequency, but I judge antennas more on gain - which does change with frequency. Am I wrong?
See number 4 Good question. Also, freq is just 1 variable and I don't think it is accurate to say gain changes with frequency. It may just seem that way because going up in frequency makes it easier to take advantage of other variables that do give us gain and efficiency.
A 7 element yagi for 80 meters is way more cumbersome to optimize with materials, height over ground, dielectric losses, and such, than an equivalent design for 2 meters.
I answered true to all the questions I did answer, but there were several that I just shrugged my shoulders and said, "No idea!". :-)
Responsible for the “Antenna Lavatory” ?😮
I have a couple of satellite tv dishes. Can these be used with CB radios?
Nope unless you make them into a table to set your transceiver on.
Thanks!@@NoMoreRadioMyths
I dutifully paused the vid, made an answer sheet in Notes app on iPhone.
Scored 100%.
I’m struggling to believe all of it, but I’m coming along. Cult Deprogramming is a process.
I got them all. 'Antennas' by Kraus is my antenna Bible. I'm an Extra, but one needs to know essentially nothing about RF to get that license. Too many people think a ham license is a license to talk, when it is in fact a license to learn. That's not just my opinion. It's the stated purpose on the creators of the Amateur Radio Service, the FCC, as detailed in the intro to 47 C.F.R. Part 97. Hams should be aware of why the FCC created the Amateur Radio Service if they hope to keep it. Learn it or lose it. Thanks for making this video. There is far too much drivel about RF on TH-cam from people who know nothing about RF or the various aspects of the hobby. There's even a channel where they are selling ham licensing videos, but called a distorted loop antenna a 'Yagi'. Unfortunately, there is no TH-cam policing of ignorant scam artists turning a buck by conning perspective hams, selling them videos of questionable validity to pass a test that a 7 year-old can pass. And yes, I knew a 7 year-old with her tech ticket. The VE's had to read her the questions because she hadn't learned to read yet. So again, thank you for bringing knowledge and reality to hams on your TH-cam channel. Hopefully it will start some curious hams on the road to actually learning about the hobby.
This is really a great post.
Dang, I'm not a ham but I was correct on all questions.
I am a electrician with a background in old style electronics from the 70s and 80s.
Am I reading that correct where if swr is 3:1, it won't damage the transmitter?
Not exactly. An SWR of 3:1 will not result in much loss in the transmission line at HF frequencies. If you have a modern solid state transmitter it will be powering down with a 3:1 SWR to protect the output stage from the impedance mismatch. Use an antenna tuner and your transmitter will be happy.
@@NoMoreRadioMythsso #2 is correct only if you have an antenna tuner
@@EvgeniX.Reflected power doesn't flow back into radio at all ,the difference without a tuner is power is reduced to the difference of the amount of reflected power
@@paulm0hpd319 reduced by the transmitter not to damage itself? Power have to go somewhere, if its not transmitted, then its reflected. If your tx reduced power due to bad swr, out of the new reduced power still the same ratio is reflected, just the reduced amount is not enoug to damage anything.
@@EvgeniX. the transmitter can't put full power into an impedance mismatch ,it will overheat itself trying to ,all reflected power that reaches the transmitter is reflected back towards antenna
Thank you very much for the papers Mark, I missed one so back to homework 😃😃😃
Great job!
Somaeone commented everyone should read Maxwell’s book(s)..I’d love too but good like trying to buy one. Selling used for over $75 . Any suggestions.
www.k3emd.com/downloads/Reflect.pdf
@@NoMoreRadioMyths but is this article just a summary or the whole book?
@@pakeck1 reflections 3 is a free download, it's the complete book
Thanks very much M7AUC
But the online H.A.M. radio "experts" tell me that they know everything!
Thank you sir.
Most welcome
Always great to hear the other side of perception, on how things work. 73
KN6JHC
The correct side ?
The multiple frequencies antenna's biggest problem is interaction, if you can tame that the rest isn't a big deal.
As a new ham, my main question then is: why care about SWR at all? If an SWR of say 10:1 doesn't cause damage and the energy mostly just gets re-radiated from the antenna eventually after making a few round trips at relatively low loss, why do we even bother thinking about resonance?
Care about the impedance the transmitter sees ,if not using a tuner power isn't produced, the tuner allows the transmitter to produce its maximum power into the system
The transmitter will shut down because of the impedance mismatch. Now if you insert a trans-match (antenna tuner) you may be able to lower the SWR so the transmitter can transfer power. The term antenna tuner is misleading. It does not tune the antenna. It only adjusts the impedance between itself and the transmitter. In your example the SWR is still 10:1 between the tuner and antenna.
To add to what others have said, the filters in your transceiver are designed to operate into a 50 ohm load. If they do not see a 50 ohm load they will not operate as specified. This is why, for example, the receiver comes to life when the antenna is matched because you get maximum power transfer. 73, VK7IAN
@@doc145a tuner does a little more than that ,with providing a conjugate match it tunes the whole system to resonance, it changes the phase of the reflected power to add to the forward power correcting the mismatch loss
As a new ham, my main question then is: why care about SWR at all? If an SWR of say 10:1
Well in his explanation he speaks the truth, A bad SWR does not damage your finals because the power does NOT go back into your transceiver. But you do have an impedance mismatch and your finals do not like a mismach. That is why the ALC reduces power if it is mismached. So yes a high SWR does not damage your finals. But mismach does. Better use an antenne tuner.
BTW the higher the frequency, the more SWR gets important. Special on VHF/UHF where coax-loses are way more higher.
Remember he is talking about HF, not VHF-UHF and much much higher.Where feedline losses are higher.
The same laws apply, but the losses will be higher.
Great voice, better mind!
I think what he is saying is a g5rv antenna is a great antenna. With external tuner.
They pretty good
They are better on the higher bands (except 20) if you do away with the coax and use 450 ohm twinlead all the way. Louis Varney G5RV designed it as a 20 meter 3/2 wave antenna.
Despite the SWR, I agree all power, less a few losses, does eventually reach the antenna. But with each bounce, power arrives delayed. It all adds, but much of it will add negatively due to the phase delays. So, out of those 100 forward watts, don't begin to think you are radiating it all. As the SWR goes up, your radiated power will go down. Pick a T-Line length and coax type and you can graph radiated power versus SWR. That sounds like another homework problem to me.
Phase delay is only a problem for TV and FM broadcasting.
Well, you are right in that SWR phase delays for TV and FM do cause delayed images and distortion. But in the case of ham transmissions, the vector additions of each bounce don't cause objectionable interference. But they hardly add in-phase. The worst they can do is subtract. Your presentation was indeed an eye opener! Keep it up.
@@user-oj5mo7xq7p using a tuner corrects the phase
All very true
Whew! 11/11.
Thanks for this spirited attempt to get some truth out there. Incidentally, I get them all right, but I was uncertain about a couple of them. Old beliefs die hard.
True!!
another great video,I did get 1 wrong !! the last question. 73 es DX
The feedline radiates because of an antenna imbalance not feedpoint impedance mismatch
Close!
Q10: If thats true, why does a matching unit get warm if the feeder VSWR is high? Some of that power is being dissipated as heat in the matching unit, and not being 'reflected' back to the load.
My question as well.
I've done temperature testing between a low and high swr with the high swr producing substantial more heat.
Inadequate components for the situation
The coil in your tuner is made out of wire that is too thin. Cheap tuner.
As the impedance transformation ratio goes up, the Q-factors of the matching-network components must also increase for low-loss operation given the increase in circulating current in those components. It the Q's are not there, then the "match" is partially into the antenna's radiation resistance and partially (or mostly!) into resistive heating of the matching network components.
In other words, don't try to use your 40 meter dipole on 160.
I also challenge Q7. Most bc towers I know of are 1/4 wave and are resonant. Yes, there are many that are not, so employ a matching unit at the tower, but I don't think that's 'most'.
To know for sure, you'd need to conduct a survey of radio towers. That would be a challenge, indeed.
The ideal non-directional radiator for medium-frequency groundwave service is a half-wavelength-high tower fed against buried ground radial wires... BTW, the antenna heights for all AM stations in the US can be found in the FCC license database.
@@k7jebI think you’ll find its quarter wave, i.e. 90° height with a ground field. The feedpoint impedance is then about 35R which is easily matched to 50R coax feeder.
If it were half wave the impedance would be up around 2500R - much harder to match.
@@andylinton2798
@@andylinton2798 A half-wave vertical has the desirable property of suppressing high-angle radiation which, when reflected off of the ionosphere at night, interferes with the ground wave in the outlying parts of the service area. The antenna doesn't have to be exactly a half-wave to do this, +/- 10% will work just fine and the impedance-matching is manageable. The "spare no expense" clear-channel stations in the 30's and 40's generally went with such antennas; the smaller market stations were constrained by the station owner's wallet to more modest installations.
Great. All correct.
Now tell C.B.'ers (mostly) about trimming their coax to ½λ by cutting off one inch pieces is not required. I've seen videos and argued with so many C.B.'ers about this. They seem to think that trimming the coax then adding more coax through an SWR meter will not alter their carefully trimmed ½λ coax as if the meter isolates it. They can't grasp the fact it becomes one coax cable. I've been told even after telling them this they want the best out of their system and will continue trimming their coax.
I've seen only one video where an amateur said coax length does matter.
G4GHB.
Was that Mr dx commander saying coax length doesn't matter ,I don't think he gets to grips of the feedline becoming an impedance transformer with standing waves
@@paulm0hpd319 Not one radio book talks of cutting coax to a specific length.
Even coax manufacturers don't say it.
@@bill-2018 there's plenty in the books about the feedline being an impedance transformer especially in the book reflections that mark is talking about in this video
@@paulm0hpd319 I know there are but not for feeding aerials. If you need a precise length you have common mode current on the outer.
@@paulm0hpd319 You can waste your time trimming coax if you think it's better but I won't be doing it, never have, never will.
It's all so mysterious ,radio wave phenomonon
And facinating!
Q2. The FM transmitter manufacturer I used to work for went to great lengths to build in high VSWR protection, as if the VSWR was too high it did indeed damage the output stage of the transmitter. I watched their design engineer demonstrate this - the STAC2942 output FET went pop. All tx manufacturers do this. So I question this answer.
The SWR itself is not what blows up solid state final stages, it's the high voltages and currents that result during an impedance mismatch condition that destroys PA components.
So the high VSWR does damage the transmitter! The high V and A are caused by the reflected power.@@richb.4374
The damage is due to high voltages resulting from high VSWR and not from absorbing reflected power.
My antenna has been up there for 20 years and the SWR is getting better.
😄
That kind of antenna can't be modeled.
It can. Add a few ohms of resistance that represent the failing coax. Add more resistance every year.
@@j3gum Exactly. Your antenna isn't getting better. Your measurement is getting worse.
Your feed line is getting lossy.
6 , 7 , 9 wrong for me i said F ... hahhahahaa 8 out of 11 isnt to bad hey
Haha don’t give up!
its crazy how many A-R operators have... NO !! F#CKING !! IDEA !! ...
what the rediculasly mis-named, a.t.u 'IS' and DOSE. it makes me wonder who sat the exam for them and how much it costs !!
What does the atu do
In my VERY humble opinion, the level of misunderstanding about antennas and transmission lines is only exceeded by the misunderstanding of the bible. Perhaps; MAYBE!
73 and thanks.... de K4WRF
Probably true
Praise the Lord
If people understood both more we'd have more hams and fewer Christians. 😅
OMG, I cant watch all the way through! Im going to watch paint dry now. Its less boring!!😩😩😩
What is the point of this comment? This video is meant to disabuse radio operators of long-held misconceptions. If that's not your thing, don't watch. I feel the same way about golf.
In other words you flunked the test LOL