What Does Weird Length Feedline do to Impedance? (

[@TFuzz58]

Dave I always learn from your videos, even if some of it’s over my head. I do know more now than I did a year ago and a lot of it is due to you (and Cal, the DX Commander). I now am better informed about transmission line, and tuners. Cheers from Moose Jaw. Tim

[@edwymer2226]

Thank you for the information Dave, Yup You are looking better. Glad to see it, 73. KC3GHC,..

[@michaeldina1103]

I really appreciate the antenna tuner/impedance/ SWR content! Thank you!

[@brianchandler3346]

Got an analyzer over the holidays. Exactly what I was puzzled about. Well explained. ☺️👍

[@dougtaylor7724]

Had to take a liquor break at 9:00. Just got too heavy for me.

[@Mark19960]

Great explanation. Succinct and to the point. I don't see this discussed much if at all in the Amateur radio community either but *I* think that's because most of us understand what is going on and we "get it" for the most part. We just do what we need to do to get the RF out to the antenna where it belongs. No doubt you have seen or heard some of the coax length legends elsewhere. *breaker breaker*

[@daveN2MXX]

Very interesting presentation!

[@watthairston1483]

Most tuners deal with wide range of resistances but not very wide ranges of reactance without external compensation. Great video Dave!

[@RobB_VK6ES]

Dave, A general obsrvation on your videos. The LED flood light you are using is making you look like death warmed up. The colour temperature is too high. LEDs are frequently labeled warm white and bright white. Go back to some of your earlier videos and you will see much better skin tone rendition. You might also try modifying the colour balance in the camera settings to give a natural image colour rendition.

[@ReedAB8AS]

Appreciated the explanation. 👍🏻

[@dans115]

Such great content even thought it gets complicated! Its on me to make it simple (by educating myself) . Great job!

[@clems6989]

If at 1/2wl it is a reflection of the opposite end. And at 1/4wl it is inverted. Then at lengths between the two, you can obtain any impedance between these two. So the feedline can be an impedance transformer.

[@normjacques6853]

So.....my understanding is that, since I'm using a multi-band antenna, simply cut coax as short as possible (to minimize loss) and use a good tuner after making any available adjustments to the antenna, so that the antenna is as close to resonant as possible. Right? Thanks and 73 de W1NLJ

[@davecasler]

Basically, but don't worry about coax losses at HF. They're just too small to worry about.

[@clems6989]

Back down to the golden rule. "Everything affects everything" !

[@BaldurNorddahl]

Does the tuner have any effect on receiving signals? If not, should it be bypassed to lower losses?

[@danluzurriaga6035]

Bottom line is: Oftentimes you see statements like "ensure your transmission line is not an odd integer of quarter wave to the feed point" etc.. But that is not for a resonant antenna. For a resonant antenna, length of coax doesn't matter. For a non-resonant antenna, voltage at the feed point from high SWR gets out of control especially at odd quarter wave multiples (may be too high for insulation at feed point!). VSWR max may be 5X or more transmitted forward voltage. And tuner may not be able to handle the complex conjugate impedance at feedpoint (also too high of a voltage for tuner components, especially C). This situation does not exist when VSWR = 1:1.

[@Homer19521]

The "Tuner/Matcher" tunes/matches the Antenna "System". Anything that affects the impedance is in the system, like an earth ground.

[@rogerlafrance6355]

As usual, how to do it depends on the band. At VHF and UHF matching can be done with short pieces of coax or line. On the low bands, it still works if you don't mind big rolls of coax but not practical. For low bands, lumped constants ( inductors and capacitors) are used . Whats that? At low bands an antenna tuner and/or matching transformer/balun keep the coax in a reasonable low impedance range and not radiate or blow out with high power. Confused? Don't be, because with modern transceivers, modes and antennas are the only things left to experiment with. Its all online from simple how to, to engineering level.

[@francismcclaughry3794]

I wonder if the phasing of the antenna's the three of them would be like the old super scanner of days of old because you could kinda talk in one direction because of it being squeeze at the transmit point. ?

[@samgrieg2542]

Non related question.. can I pass coax feedline through grounding block (it grounds coax shield to earth) at the entry point to the shack if it feeds a dipole? Would that mean that one shoulder of the dipole is electrically grounded? All examples I've seen show coax grounding done for verticals. Thank you David.

[@larryak0z672]

Dave rarely reads or replies to comments.

[@samgrieg2542]

@@larryak0z672 Apparently.. it's been a year :) but my hope is still alive, maybe someone else will answer.. what would be the correct way to ground a dipole (both shoulders)

[@clems6989]

Would it maybe be better to say. The tuner becomes a variable part of the antenna system. It all becomes the antenna system as seen by the transmitter ?

[@clems6989]

TRUE!

[@lorensteele2962]

Very informative, appreciate it!

[@rickeaston3228]

Do people who like to use Smith charts also like slide rules too???????

[@mostlypostie1]

Hey Dave - 11:42 why do you say that an Antenna Tuner at the feedpoint of a loop antenna, is impractical? Is this just because of the physical mounting complexities? I'm thinking about a remote coax fed ATU mounted on a tower, feeding a loop directly. I would appreciate your thoughts!

[@davecasler]

Yes, you're correct. But if you can mount an outdoor-type tuner right at the feedpoint, you'd probably do well.

[@mostlypostie1]

@@davecasler thanks David! That's my plan. 🙂

[@chrisjones8741]

Ok, all very interesting, but is that typewriter about to fall of the desk behind you? 😲

[@chrisjones8741]

On a more serious note, now that I’ve watched the whole thing: thank you! Informative and worthwhile.

[@pixeluser8243]

Is 'oggie' a term that existed before KE0OG? Greetings from The Netherlands

[@davecasler]

It means "a follower of OG (KE0OG)". I understand that the same name, different spelling refers to a type of Cornish pastry.

[@pixeluser8243]

@@davecasler Well, I'm a worldwide Oggie. Along with Callum DX Commander, the German TRX Bench, Dave Tadlock and the man of RSD Academy, you are one of the influencers that took me to passing my full license. I want to thank you for that and the many hours of enjoyable video's.

[@davecasler]

@@pixeluser8243 Thanks for the kind words! Congrats on your full license!

[@davecasler]

@@johnmilton7578 Apologies! Someone told me Cornish. I don't suppose you could send me a picture of one?

[@cr6925]

Oh! I'm First to comment! And... I see an Oggy video I automatcally press Like, then watch it in it's entirety :-) Thanks for puting this together Dave, as always interesting well explained and expertly put together :-)

[@battlestarone]

Why ate radio hams hell bend on having the atu in the shack,,the atu should be at the antenna end of the coax,,that how marine syatems do it and broadcast sysyem do it,,ham just dontvwantvto go out in the rain at one time,,but remote tuners or making a external L or Lc match at the antenna end will make everything work more efficiently,,thus better signal and less losses.

[@eddy2561]

Hey Dave, the xyl seys you need to have your nails done......HI HI / k6sdw

[@k8byp]

Nothing. Transmission lines do not have impedance so the whole topic has no merit. Says REAL experts on the topuc, not Amateur opinion based on myth. Brown Sharpe Grove and Post... Impedance opposes current flow in circuits. Tlines are not circuits and current does not flow on them. They are field conduits. If they had impedance, the losses would be more than just dielectric loss. Tlines do not have impedance. .The term is " characteristic resistance" which is a TERMINATING RESISTANCE RESULTING IN NO REFLECTED POWER. Its about the load not the line. Lines, Waves and Antenas- a book by PHd experts, not 100 year old myths.