Ham Radio True or False #2. Test your knowledge on transmission lines and antennas and avoid myths!

Here's another true - false test to see if you know your stuff or believe ham radio myths. 12 questions. If you get any of these wrong you can probably find out why just by using Google Search. Also here are some great references on transmission lines and antennas.
www.k3emd.com/...
na0tc.org/lib/...
zs6wr.co.za/doc...
www.ogdenarc.or...

[@Calico5string1962]

11 out of 12... but once I re-listened (an reread) the question, I got it. LOL
Great stuff Mark.
I recently dug out M. Walter Maxwell's "Reflections" book, and started reading back through it... a book EVERY ham operator (and maybe CB too) should have available and read.
I'm certainly no mathematician, and while much of the complex calculations are way over my head, the concepts explained, in Maxwell's great and plain-language style, make it all easily understandable.
A must-read for anyone interested in radio & antennas!
73 from Texas!
~Alan
W5ARM

[@MrTommy001]

I missed two. And most of what I 'know' I learned during 35 years of OTR trucking and many CBs still sitting in my now ham shack. My shack used to be my "shop". I love your straightforward videos, Mark. I've only been in HF for about three months now and sucking up all the info I can.

[@W5KJD]

I’m learning, some I knew and others I learned by watching. 👍

[@dandypoint]

Good job! I have the ARRL Antenna book, in fact I have one dated 1949 and several more of various additions. I also think the ON4UN Low Band DXing Book (5th edition) is also a great resource for antenna info. I also have the John Kraus textbook on Antennas, Antenna Theory by Balanis and the Radio Engineers Handbook by Terman. What info one lacks another will have. I am constantly using these books to refresh myself. I also have numerous other Amateur Radio books and handbooks but the ones I mentioned are the best I have found.

[@kumasu]

I scored 8/12. I am now investigating to learn more. Thank you for these quizzes. They need to be required viewing for hams!

[@NoMoreRadioMyths]

I think such questions should be on the test at least for the extra class license.

[@cubicmaddness2052]

Exactly 50% had I thought a bit more. I may have managed a couple more correctly. Obviously I've either lost a little along the way, or fallen victim to commonly accepted fallacies. Thx for the vid. Put me in my place. I've learned today, and I'm better off for it. 73

[@Professzore]

50% right answers, though, three of the wrong answers may be cleared out in my brain by thinking it over a few more times...

[@javabeanz8549]

Unrelated to the content of the video: You have a high pitch squeal in the background of your audio. It seems to change in pitch when you switch scenes.

[@NoMoreRadioMyths]

No idea. I don't hear it.

[@javabeanz8549]

@@NoMoreRadioMyths I really didn't expect that you did. Audacity, or some similar sound editing software would probably show it though.

[@Calico5string1962]

I did not detect any "squeal" in the video's audio, on either my Android device or home desktop computer...
Perhaps it's your device?

[@javabeanz8549]

@@Calico5string1962 If it was "my device" I would get it in every video, not just this one. The high pitched noise is in there right from the start of the video.

[@Calico5string1962]

@@javabeanz8549
Watched (and listened) again, from the very beginning. No squeal...

[@theroguetomato5362]

I got about half wrong. Guess I need to study more.

[@bazzaar1869]

yeeaaahhh, I get the purpose of myth busting but its falling short in execution due to loose and conflicting terminology. For example is sounds like you at one time state SWR is the ratio of wanted impedance to antenna impedance and at another time that it ISN'T the ratio of impedance.
Solid state rigs DO have directional couplers to measure reflected power.
You say confusingly that impedance of transmission line/feeds changes with length. Feeder line is always its characteristic impedance at all lengths. What impedance may be presented to any equipment in an antenna system with some kind of mismatch can vary with feeder length.

[@NoMoreRadioMyths]

Never heard of a "wanted impedance ratio."

[@kumasu]

You may want to re-watch the video.

[@Calico5string1962]

Nothing conflicting nor confusing in his statements.
You may want to obtain and read Maxwell's book "Reflections - Transmission Lines and Antennas", as everything Mark presents are codified in that publication (as well as others).

[@DaDitDa]

When RF forward power from 50 ohm source is *initially* applied to a 50 ohm transmission line (TL) it travel down the TL until it meets the load. If the load is 50 ohms, forward power is fully absorbed. If load not 50 ohms, some power is reflected and superimposed/mixed with continuously applied forward power which creates standing waves on the TL Depending on length of TL, a certain standing wave V/I ratio (resistance) and phase relationship (reactance) will appear at the TL input -- this is known as TL input impedance. If the TL is 1/2 wavelength, the load's impedance will appear at TL input. If 1/4 wavelength, an inversion of the load's impedance will appear at TL input. If neither of these special TL length cases, some other impedance will appear. Whatever the resultant TL input impedance, it does NOT affect/change the TL's standing wave (i.e., SWR) due to the mismatched load; but it does affect efficiency of source forward power transfer to TL input.