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Author Topic: 9:1 or 49:1 unun for end-fed long/random wire?  (Read 1464 times)

Offline joczo

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9:1 or 49:1 unun for end-fed long/random wire?
« on: October 15, 2019, 1315 UTC »
Hi guys,not really hfu related,but I tought I might ask here as I have my account.
Before my house was built next to the older one and moved in,I used to have a 30m long long/random wire antenna.It was fed pretty "ghetto" way,with a simple speaker wire as a twinlead,and the house's metal gutter as the counterpoise.
Now in the new place,I can stretch out the old 30m wire to about 40m,and I would like to feed it with something better.The old twinlead was a bit too hard to match(tho I could do it more or less 80-10meters,with a beefy tuner),so I would like to add an unun.The radiating part would be the 40m long wire,the counterpoise could be the new and bigger gutter,or I can throw down another wire from the roof.
The question is:which unun would be more ideal?a 49 to 1,or a 9 to 1?The goal would be to have a not efficient but usable antenna 80m to 10m,until I can put up other and better antennas for the lower and higher bands.
Sorry for this short "novel" I wrote,I hope everything is understandable  ;D
Thanks in advance,73!

Offline Josh

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #1 on: October 15, 2019, 1748 UTC »
So you have the freq range of interest and the total length of the wire, figuring out wich balun will be a better match for 50ohm coax should be easy. The 9:1 may work best with that length wire and a tuner, but some say that length is undesirable for the hf HAM bands. I say run what you got and don't worry about it.

https://www.kb6nu.com/playing-end-fed-wire-antennas-91-ununs/
http://www.hamuniverse.com/randomwireantennalengths.html
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Offline joczo

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #2 on: October 15, 2019, 1803 UTC »
Thanks for your answer,I will probably go with the 9:1 then.
I've read the desirable lengths before as well,I will probably cut the wire to one of the lengths mentioned,it migth make tuning easier.
One more question,from the unun to the tuner,can I use simple 50ohm coax?

Offline ChrisSmolinski

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #3 on: October 15, 2019, 1933 UTC »
49 to 1 UNUN?  Do you mean 4 to 1?

Yes, from a UNUN you can use regular coax, 50 or 75 ohm.
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Offline Josh

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« Last Edit: October 15, 2019, 2231 UTC by Josh »
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Offline refmo

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #5 on: October 15, 2019, 2036 UTC »
Yes, with the recent surge in popularity of the end-fed half-wave antenna, the 49:1 balun has also become the defacto ratio for use with them.
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Offline Kage

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #6 on: October 16, 2019, 0249 UTC »
The "9:1 UNUN" are for random length wire antennas fed at the end. 49:1 or other high ratio transformers are for resonant "cut to frequency" antennas like the traditional zepp/fuchs antenna.

Generally the 9:1 has far more loss as the transformer/core takes on heat to make the non-resonant antenna be of any use across wide bandwidths and are often deaf across some range of frequencies because of the nature of a random length of wire. A tuner will help with that but introduces even more losses. Worse yet people who know no better will think they are performing great because they always show the user a good SWR, but remember even a dummy load shows good SWR  ;)
They have the benefit of being quick to throw up in the air and will get some signal in/out but are inefficient compared to resonant single/mono band antennas.

If you want a high performance monoband EFHW antenna you should always go with the 49:1 UNUN and cut the aerial to half-wave resonance and almost all your power into it gets out since it acts exactly as a traditional dipole, with the exception of being fed at the end.
The ratio doesn't need to be 49:1 2,400 ohm either, other ratios will transform to other impedance. Generally an EFHW will be in the range of 2,000 to 5,000 ohms at the very end of the dipole when resonant.
I usually go with a 3.2k transformation wire winding ratio of 8:1 which is a final impedance conversion of 64:1 (50ohm * 64 = 3.2k ohm). Antenna diameter and height above ground makes a difference here. Generally the fatter the radiator the lower the final impedance at the end. Thin wires might need as high as a 81:1 out at 4k ohm. Remember the large ratio number is the coil winding ratio squared, so for a 9:1 wire winding you end up with a 81:1 impedance conversion, not to be confused with a 9:1 UNUN for non-resonant types that convert to ~450 ohm.

Whew think I typed that all correct. Check out http://www.aa5tb.com/efha.html for info on the traditional high performance resonant EFWH.
For random wire non-resonant types plenty of plans and examples exist online but keep in mind there is no free lunch as they say, being non-resonant and wideband means they might perform as good as a wet noodle on some bands and somewhat acceptable on others, but any wire in the air is better than nothing.
« Last Edit: October 16, 2019, 0257 UTC by Kage »
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Offline joczo

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #7 on: October 16, 2019, 0815 UTC »
I'll get a 9:1 unun,and use a suggested random wire length to avoid half-wave and it's multiples then,that sounds like the best things I can get out of this setup.
I was only thinking about the 49:1 due to the random high impedance spikes a random wire can produce,and I tought it would be easier to match a super low impedance than a too high one.
Actually,the old one did a fairly decent job for me.Especially on the higher bands,where the 30m wire was at least 2x wavelength.It is true that it has some directivity,it may be deaf in some directions,and it may perform really well in others.
I don't want to live with this one antenna forever,but right now this should be fastest and easiest way to get on the air with somewhat decent signals.
Thank you for everyone,I can't wait to install it and see the results  ;D

Offline ChrisSmolinski

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #8 on: October 16, 2019, 1026 UTC »
Yes, with the recent surge in popularity of the end-fed half-wave antenna, the 49:1 balun has also become the defacto ratio for use with them.

Interesting. Maybe I need to make a 49:1 version of the Cyclops  ;D
Chris Smolinski
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Offline Kage

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #9 on: October 16, 2019, 1404 UTC »
I'll get a 9:1 unun,and use a suggested random wire length to avoid half-wave and it's multiples then,that sounds like the best things I can get out of this setup.
I was only thinking about the 49:1 due to the random high impedance spikes a random wire can produce,and I tought it would be easier to match a super low impedance than a too high one.
Actually,the old one did a fairly decent job for me.Especially on the higher bands,where the 30m wire was at least 2x wavelength.It is true that it has some directivity,it may be deaf in some directions,and it may perform really well in others.
I don't want to live with this one antenna forever,but right now this should be fastest and easiest way to get on the air with somewhat decent signals.
Thank you for everyone,I can't wait to install it and see the results  ;D
If you have a facebook account check out the group EndFedHalfWaveAntennas. Don't need to be a ham to join. They focus mostly on the non-resonant type EFHW transformer and antenna designs and are very active.
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Offline Josh

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #10 on: October 16, 2019, 2201 UTC »
The key is you want to stay at least 1/2w long but not near 3/4w for any band of interest. When you're 1/2w long you're around 2k ohms or more where the balun won't under or over xform; as you approach 3/4w your z is going to drop to where a coax match can be made just by soldering the wire to the center conductor sans balun - more or less the principle of the windom and ocf dipole. When you're antenna (or radial) length's an odd multiple of the operating freq, you may not need a balun or even a transmatch.
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Offline ThElectriCat

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #11 on: October 19, 2019, 0624 UTC »
This may not be relevant to HF stuff, but the antenna I use for NDB reception has a 400:1 transformer (20:1) turns ratio. I have never tried to transmit through it, but it proved the optimal ratio for receiving with my setup.
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Offline Josh

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #12 on: October 19, 2019, 1922 UTC »
The beauty of the halfwave antenna is it's a complete antenna in the sense it needs no counterpoise. For example, when adding a 1/4w tiger tail to a 2m ht with a halfwave for antenna will likely show no improvement at all in tx or rx strengths.

Comparing the halfwave to a typical 1/4w vertical, the vertical will give up power to groundplane loss (unless it has myriad well connected radials), where the halfwave should be about as efficient as any dipole for the same band in the same location, ie about as efficient as you can likely get in the real world. This obviously applies to rx as well as tx.
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Offline joczo

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Re: 9:1 or 49:1 unun for end-fed long/random wire?
« Reply #13 on: November 14, 2019, 0953 UTC »
Update guys:made the unun,the antenna was extended to about 37m length,and I added a counterpoise which is about 10m.The whole thing is much higher in the air,compared to where it was before.
It performs much much better than the old one  :D I get reasonable swr on most bands,down to 1.2 on some of them.
At the moment,it seems I lost 80m,though it even works on 160m,most likely horribly inefficiently.
So a tuner would be a good idea.I tried my old one,which I used to tune the twin-lead one but it does not perform well with this setup.Can you please recommend schematics that are designed to tune setups like these?

Offline Josh

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