What Unun for an End Fed Antenna? (

Jeremy, W1LKO, has been trying to experience himself in the realm of End Fed Half Wave Antennas, and he has noticed a wide variety of ununs being used. "How do you know which unun need to be used for an endfed?"
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#hamradio #endfedantenna #endfed

[@Garimeli]

Very nice explanation

[@jimsouthall1085]

Excellent presentation. Keep up the good work!

[@ths3900]

Always a good explanation

[@WilliamParmley]

Good, clear explanation. I sent the link to someone who has recently been asking about 49:1 transformers and I think it will help him.

[@Puttertorium]

The rule of thumb I use is if it’s a half wave then 49:1, for a random wire a 9:1. Btw, random wires are not random, they intentionally avoid half waves. My beast antenna is an 84’ inverted L with a home brew 9:1 unun. I can tune 80m to 6m with it. Most of that is with the internal tuner but a couple of bands I have to use the manual roller inductor tuner.

[@steveschroder8782]

Dave,
There is often confusion between a half wave end-fed and a random wire end-fed antenna.
Just to be complete. A 9:1 unun with certain non resident lengths of wire and a tuner with ground/counterpoise/radials create a multiband antenna. That set up will usually/often work on 60 meters, a non harmonic of other ham bands.
A half wave length long wire with a 49:1 Unun creates a multiband antenna for the half wave length band and its harmonics. Even with a tuner that set up probably will not work on 60 meters.
Steve KI0KY

[@mmlanger55]

@@steveschroder8782 Agreed Steve. I love using the 9:1 because I go from 160 to 6 including 60 and 12. The SWR might go as high as 5:1 but tunes out easily. Most bands are 3:1 or less. The wire is approximately 100' and the performance is surprising. Mike N0ANE
Good video from Dave. Excellent explanation.

[@johnbauman4005]

Hi Rick,
Please forgive my newby ignorance, but what is a "manual roller inductor tuner?" Is that a tuner you home-brewed or a marketed item?
Thank you!
73,
John - KK7JBZ

[@davep6977]

@@steveschroder8782 I've always been a beam person. But I just installed a NON-resonant end fed with a Palomar 9:1. I used 175 appox. feet of #12 solid wire and I get

[@rickmckee6698]

The problem with a 9:1 and a random wire is the fact that the 9:1 is designed to feed a 450 ohm load, not a random load like a random wire would present to it. Any balun or unun is most efficient when feeding it's design impedance and when you stray away form that, losses increase and the further you stray from it, the higher the losses are. Especially if the impedance is much lower that 450 ohms. You take say a 50 ohm load on a 9:1 and it gets down converted 9 times to around 5.5 ohms and this even increases losses in the tuner too! When the impedance drops that low, currents in the unun and the tuner skyrocket! Yes, you can make contacts with it, but only a small portion of the power actually reaches the antenna to be radiated. I've worked QRP at 100mW, but I did it with an efficient, resonant antenna too!

[@jimbennett2940]

Thanks for the explanation Dave - good info. I was going to build an EFHW with a 9:1 but after watching your video I've opted to build a 49:1 unun. 73, Jim / K7TXA

[@geirha75]

Thanks for great lecture. I have a question. We always talk about that efhw is high impedance like 2450 ohms at the end feedpoint. Is there a way we can actually measure and show the impedance we always talk about?

[@Lugeix]

If seen 64:1,49:1,9:1 4:1 and 1:1. Is there a variable ratio transformer for antennas? Var:1

[@sleeve8651]

Perhaps not important for your demo, but I thought Dipoles impedance at the feed point was closer to 73 ohms ?
Making RG - 6 75 ohm coax a better match ?
🤔....?

[@AC3HT]

Thanks, Dave. Very interesting topic. 73, AC3HT

[@jimbennett2940]

Dave - built my QRP 49:1 unit yesterday and it seems to work OK. I connected a 2,500 ohm resistor across the two terminals and then read the SWR on my AA-55 Zoom. Got readings under 1.5:1 on 80 - 15 meters, so that was good; 10 meters was 2:1. I've seen several other videos where the builder(s) put a 150pf / 2kv capacitor between the output terminals, supposedly to help lower SWR at the higher frequencies. I put a 220pf / 3kv cap on mine and it didn't do the same. It slightly lowered the SWR on 80, 40, and 30, but on 10 meters it went up a bit. Any comments on the use of a capacitor?
Jim / k7TXA

[@azarellediaz4892]

If you hear from anyone on this subject, pls let me know, I need the same information.
73

[@ericdee6802]

Great explanation Dave, one question for anyone. what is a 1:1 balun used for, I hear people using a 1:1 for 10m alot???

[@williamshepherd1128]

Mainly to suppress common mode from getting back to the shack.....kind of like an isolator

[@eddy2561]

I understand the math and the concept, it's clear and easy to understand....however, 9:1 endfed antennas are sold (like the kit EARHCI ham group in Hawaii) and if your tuner will match the 450 ohm or so impedance the antenna works FB,. The penalty would be the losses in the tuner...is this correct? 73/K6SDW

[@nevmarr]

Eddy, keeping things very simple ... tuners are a matching device and in theory don't have losses (they do in practice). The 49:1 is used on a length of wire that is a half wave (or multiple) of the frequency you want to use. The 9:1 is also end fed and connects to what people call "random" length wires, but the length of the wire is far from random ... these wire antennas have very precise lengths. These "random" wire lengths, by design, present an impedance of approximately 450R on the desired frequency. Clever math people have figured lengths of wire that present 450R on many frequencies, hence these antennas are sometimes referred to as multiband.

[@eddy2561]

@@nevmarr And the kit I bought from EARCHI and used for 3 years worked great running my IC7300 and the MFJ 939i tuner on all bands except 60meters. If the 939i could tune the swr betlow 2:1 then the IC7300 was "happy" and I worked the world with tha 9:1 endfed setup. The wire length I used was suggested by the EARCH club, you can read it on their website.
I got talked into the 49:1 unun and it too works FB. What you wrote makes sense. However, using the 9:1 wire antenna I worked the world. Regarding tuner losses, many years ago QST published an article on measured losses operating some popular manual antenna tuners and while all were close, all had some losses but not enough to lose sleep over...the article was probably 30 years ago.
73

[@nevmarr]

@@eddy2561 Re 60M working/not working ... another crazy antenna thing is the length of the coaxial feed line, it can make a difference ... adding say a 6 foot length of coax between the antenna and tuner will change where the impedance sits on a Smith Chart and that "change" is sometimes enough to get things in the range your tuner can handle/match.

[@eddy2561]

@@nevmarr Kurt Sturba (RIP) use to write in his monthly column a garbage can or grocery store cart will radiate RF if you can get the SWR low enuff the xmtr doesn't shut down....aw the days of tube transmitters and Pi networks....everything worked then...73

[@tomcook5813]

I bought a 9:1 and plan running 250’ wire, did I buy the wrong Balun?

[@billlamb8944]

As usual this is another great show, but can you do somthing about the lighting. You are sitting in a shadow and the reflections of the white board. Maybe you are running off grid power and saving money. Thanks again. KD9HWH said that.

[@davecasler]

We are working on this.

[@earlymann1954]

Wish I was smart enough to understand these complicated explanations. It's like Chinese to me.

[@davecasler]

On most of my videos, I assume you have your Technician license already and are at least studying for or recently achieved you General class license. To become a technician, see my training videos at www.ke0og.net/training.

[@mk12pickle]

This is not a clear explanation at all. He never does the math for the end of the antenna with actual end fed impedance, he just skips right to substituting the Un Un. So its not clear in terms of scale, how the center impedance is different than the end fed impedance. He skips the representative math and adds the un un directly into the equation, without exact reasoning.

[@glenmartin2437]

Thank you, Dave. N0QFT