Why so few "random" wire antennas ?

[Rob-W4ZNG]

Thanks Brian, it's always good to have real-world reports. Personally, I'm itching to get back into the woods here in N FL, but realistically that's not happening until mid-October. In the meantime, I need to draw up an experiment plan and get the gear ready.

As you said, it is awfully handy to have the easy multi-band capability of the random wire, even if its performance is a little off the EFHW. No free lunches, I suppose.

[Andrew (grayhat)]

I really like the idea of a random wire – OK, call it a quasi-random wire, to avoid the near 1/2 wavelength antenna lengths. However, a couple of years ago I did some A/B testing with a low-mounted dipole (i.e., NVIS), and the dipole won hands-down, both for the signal strength and for noise levels. Here are the full results: https://coyoteswamp.blogspot.com/2020/0 ... sults.html

The bottom line is that noise levels were 18 dB higher and signal strengths (transmit or receive) were 3 to 6 dB lower. Random wires do work, but they're just not worth the signal loss and noise gain issues. Almost anything else is better. For compact multi-band, I've moved on to a variation of the W3EDP: https://coyoteswamp.blogspot.com/2019/0 ... w3edp.html

Late on this !

Rob, I've checked your blogpost and would like to make some observations; first of all, I was thinking to a (not so) "random" antenna used for outdoor activations, and in that case, noise will be lower than the one near a homestead, then, you placed the random at 7' and that's really low for an horizontal antenna, raising it to (say) 33' or more would allow the "random" to radiate better, then, it would be advisable to place a choke on the coax feeder and use a counterpoise (not connected to ground) otherwise the coax (braid) will both disperse RF when transmitting and pick up noise when receiving, so if you want, it would be interesting repeating your experiment but raising the "random" a bit more (at least raising the feedpoint, then the antenna may be sloping), using a counterpoise and placing a choke on the coax (18 turns of coax around a #43 toroid will serve well)

Then ... ok, the "random" is by nature a compromise antenna, on the other hand, it's easy and cheap to setup and if the need arises, it's easy to build it and, with the help of an ATU, cover whatever [1] band

[1] to have a bit of efficiency the "random" lenght should be choosen to be at least longer than 1/4 wave on the lowest frequency we want to use it on

[Rob-W4ZNG]

Hi Andrew, Well, that antenna farm went with the sale of my old house last year, so that avenue of experimentation is a closed chapter, and now I'm a downtown apartment dweller. However... fall is just 3 months off, and I'll be ready to go camping in the N FL woods with a spool of wire, SWR meter, a variety of ununs – 9:1, 4:1, & 49:1 – a tuner, and a few spare days. Can't wait to experiment with randoms, W3EDPs, and EFHWs again. Oh and a dipole, for reference. In the meantime while the bugs are out and it's 95F during the days, I'll make do with my apartment antenna and try to filter out most of the local power line noise.

[Andrew (grayhat)]

Hi Andrew, Well, that antenna farm went with the sale of my old house last year, so that avenue of experimentation is a closed chapter, and now I'm a downtown apartment dweller. However... fall is just 3 months off, and I'll be ready to go camping in the N FL woods with a spool of wire, SWR meter, a variety of ununs – 9:1, 4:1, & 49:1 – a tuner, and a few spare days. Can't wait to experiment with randoms, W3EDPs, and EFHWs again. Oh and a dipole, for reference. In the meantime while the bugs are out and it's 95F during the days, I'll make do with my apartment antenna and try to filter out most of the local power line noise.

Rob, thank you for the reply, as for "random" (ok not-so-random) antennas while the reference for lengths you posted (https://udel.edu/~mm/ham/randomWire/) is good, I usually stick with the shorter list found here https://www.hamuniverse.com/randomwirea ... ngths.html since I found that the "green number" half down the page are pretty good, a couple notes, first of all as I already wrote, pick a length which is (even slightly) longer than a quarter wave on the lowest frequency (band) you want to use the antenna, not that shorter lengths won't work, but having a bit more efficiency is a good thing especially when it comes to QRP, then... use a choke; place the choke at the point where the coax, coming down from the 9:1 UnUn at the feedpoint hits the ground, that way the external of the coax braid will work as your counterpoise (assuming the coax isn't running inside a wall, that is, but that shouldn't be a problem when camping )

As for your current QTH limitations, sorry to hear that, but maybe I could help you a bit, at least for reception; have a look at this (receive only) antenna design, it's small so it should fit pretty well even in a limited space, yet it gives you good directivity and low angle, so may help you "pulling out those signals" and fighting the noise

[Andrew (grayhat)]

Rob, regarding power line noise, see here

http://www.ka7oei.com/syn_blank.html#:~ ... y%20strong.

no miracles, but it may help

HTH

[Wize1]

I just throw a 28 1/2 foot wire up on a pole or tree in a sloper configuration, and lay 17 feet or more wire on the ground as a counterpoise. They both connect directly to my G-90, which has no problem tuning it! Works great on multiple bands!

[K9EI]

I'm in the EFHW or resonant dipole method category for my activation sessions. At 5W every DB counts, so I would rather use a dipole and tuned coax length. Plus, I don't want the extra kit. An extra point of failure, too. But, that's just what I like to do. I say use what ever you like and keep having a good time.

Matt
K9EI

[Andrew (grayhat)]

I'm in the EFHW or resonant dipole method category for my activation sessions. At 5W every DB counts, so I would rather use a dipole and tuned coax length. Plus, I don't want the extra kit. An extra point of failure, too. But, that's just what I like to do. I say use what ever you like and keep having a good time.

Matt
K9EI

I hear you, and it's a good reason, but then there's a tradeoff between frequency agility and efficience, sometimes one may prefer being able to jump on whatever band is open at that given moment, since that may make the difference between having a successful activation or not, and I think that this is something to consider when going for POTA/SOTA, in particular if the spot one is going to activate isn't so easy to reach

[KL7MJ]

It depends on which radio/gear I'm using. My KX1 has an ATU, so no issue with a random wire, but my FT817 doesn't have an ATU (I have a T1, but that's another piece of equipment and two more coax cables) so I like the EFHW for that. My next antenna will be a 40-10 EFHW with links for 17 and 30m.

73,
Mike, KL7MJ

[Andrew (grayhat)]

Here are some worth reading notes about EFRW antennas

https://www.k0ehr.tech/2023/02/the-ins- ... re-hf.html

and, aside for a couple details, I agree with K0EHR