Random Wire Antenna Balun or ???
I am presently using a random length long wire with a counterpoise under it tuned by an SGC-235 coupler. It works pretty well but the SGC-235 has been less than robust. I would like to use an in-shack tuner and I have found conflicting advice as to what feed point balun is needed. Some say 1:1 and others say 4:1.
So who is correct?? I have a MFJ 259B to hook up to it, it's been raining and I'm not sure the exact way to do it, coax, no coax... Any suggestions on how to get rid of the SGC-235 coupler and run the longwire???
No experience here with long wires & baluns??
I run a 55 ft end fed wire here to a home brew tuner . the shack is on the 2nd floor. The wire comes in thru a window insert straight into the back of the tuner. No ground or counter poise , no balun , just a wire screwed to the out point of the tuner. It works great. I use it 40 and 30m and it has worked a ton of dx. Also worked all sates with this end fed.
As far as I know, you cannot run a random length wire antenna without using a tuner, most of which have built in baluns.
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I believe you can do it with or without an impedance transformer of some sort, and you'll get similar results either way.
The difference is that you'll get a different impedance at the tuner. Without a BALUN or UNUN, your tuner will see a higher impedance and will have to work a little harder to tune the antenna. However, if you happen to be working a frequency that's close to the antenna's resonant frequency, you may also find that the balun gets in the way when your match is already near 50Ω, and it actually reduces performance. This is one reason I never cut a long wire to a resonant frequency: while it does give you better performance on one band, it also means you're going to have a very hard time tuning up on that band's even harmonic. (IE: a 40 meter antenna will not work for 20 meters.)
A 4:1 UNUN is not too expensive; I am currently using an S9V31 antenna and the 4:1 UNUN that LDG sells to go with it. I think the UNUN only cost around $100, and it should work at barefoot power levels. (I would never run an amp on a cheap antenna system. $1 of antenna is probably worth $100 of amplifier.)
Here's what I would do: either pick up a 4:1 UNUN, possibly the LDG unit meant for their S9 antennas, or go with a remote tuner mounted at the antenna base. That's the best way to go, as your transmission line is always working at 50Ω. The only down side is the need to run power out to the tuner, but since you seem to want to do this right, maybe this is an opportunity to give that a try.
If you take a fixed-length, end-fed, single-wire, and feed it with coax as a multiband antenna with a tuner at the shack end, the SWR on the coax will likely be very high on some bands; depending on the length of that coax run, and the quality of the coax, losses could be unacceptable on some bands.
Introducing an impedance transformation at the feedpoint will reduce the high SWR on some bands, but may increase it on others; overall, an impedance transformation of 4:1 or 9:1 tends to produce lower losses averaged across all bands.
I did an analysis of that type of system here:
Please note that the conclusions are specific to my wire length and coax feedline!
My understanding and my general rule is that unbalanced coax fed dipoles like 4:1 and balanced ladder lines work best with 1:1.
Well that was sure helpful
Originally Posted by N4MTB
De Oppresso Liber.
Couple of questions; is this an end fed longwire?, are you trying to use it on multibands?, how long and high is it and how long is the "counterpoise" ?baluns are the least of your concerns until further info.