The QRPer Board

Reading around, it sounds like a lot of SOTA folks, either use verticals (and I can understand that, due to low takeoff angle) or EFHW, and in the second case, folks often complain about "not being able to get on air on band X due to the antenna..."; now... why such a "refusal" for "random" wire antennas ?

All in all, it's just a matter of using a "proper" length of wire

https://www.hamuniverse.com/randomwirea ... ngths.html

https://udel.edu/~mm/ham/randomWire/

add a counterpoise with a length of at least 0.05 lambda at lowest frequency (about 26ft on 160) and then using a good 9:1 unun

http://vk6ysf.com/unun_9-1_v3.htm

and a decent wideband choke

http://vk6ysf.com/balun_choke_balun_hf_reisert.htm

so... why such a "preference" ?

just curious

Hi Andrew,

I can only speak for myself, but I have and use both 9:1 random wire and 49:1 EFHW antennas. I prefer using resonant antennas (EFHWs or dipoles) for radios without a tuner to avoid carrying extra kit. I love the random wire with my KX2, because it has an excellent built-in tuner. The 9:1 random wire antenna works well when you keep the radiator length away from resonance on bands of interest, so a tuner is necessary for operation. Also, I have not used a counterpoise other than the feed line (typically 15 ft of RG316) with either type of end-fed antenna at QRP power levels, and I have been quite pleased with antenna performance.

73 de Brian - K3ES

Brian - K3ES wrote: ↑Sun Jun 12, 2022 9:16 pm Hi Andrew,

I can only speak for myself, but I have and use both 9:1 random wire and 49:1 EFHW antennas. I prefer using resonant antennas (EFHWs or dipoles) for radios without a tuner to avoid carrying extra kit. I love the random wire with my KX2, because it has an excellent built-in tuner. The 9:1 random wire antenna works well when you keep the radiator length away from resonance on bands of interest, so a tuner is necessary for operation. Also, I have not used a counterpoise other than the feed line (typically 15 ft of RG316) with either type of end-fed antenna at QRP power levels, and I have been quite pleased with antenna performance.

73 de Brian - K3ES

Brian, I perfectly understand you; and I know that for portable/temporary use, and in QRP, the use of a length of the coax feedline is perfectly acceptable; my reference to the counterpoise and choke was just due to the "classic" setup, which won't hurt in any case, also since it will allow to maximize radiation from such an antenna; my wondering was mainly about the fact that I read that a lot of people "complains" about being unable to (e.g.) cover a given band since the EFHW won't work there, and since a number of QRP rigs have embedded ATU, plus QRP small ATU are available (and easy to build if not willing to buy them), I started wondering for which reason people doesn't use the "random" antenna as an "allbander" for POTA and similar operations, nothing else

Thanks for your reply !

Hi Andrew,

I understand. For multi-band antennas, I have been working with linked EFHWs to extend resonant capabilities to other bands. They trade off time for raising and lowering the antenna to manipulate links against access to more bands. You might be interested in the Frequency Agile Antennas topic on the Questions & Advice forum.

73 de Brian - K3ES

Brian - K3ES wrote: ↑Mon Jun 13, 2022 11:04 am Hi Andrew,

I understand. For multi-band antennas, I have been working with linked EFHWs to extend resonant capabilities to other bands. They trade off time for raising and lowering the antenna to manipulate links against access to more bands. You might be interested in the Frequency Agile Antennas topic on the Questions & Advice forum.

73 de Brian - K3ES

Hi Brian; yes, I saw that discussion but didn't want to "pollute" it with my question which is (I believe) marginally related to that discussion about the "best" frequency agile antenna (or multiband antenna, that is), hence I decided to post my question here; I understand that having a linked EFHW allows to work w/o a tuner, but as you stated the disadvantage is the need to lower/raise the antenna whenever one needs to close or open a given linked section, whereas, with a random one should just adjust the tuner (or let the rig run the tuning, if the tuner is embedded) and I think it's something worth considering

Another thing which puzzles me is the fact that such endfed antennas are often installed as inverted V or, either, with the feedpoint low on ground; running some NEC simulation shows that in inverted V config, the antenna will offer an NVIS pattern, which may be ok for short to mid range contacts, but won't play well if one is chasing DX, especially with QRP power, also, if the feedpoint is low on ground, losses due to nearby ground will be higher and this is an issue too, I believe, since we should try pushing the few W we have at hand to the antenna, and not on ground losses; am I wrong ?

Hi,

My operating practice has always been "linked dipoles", I opted for 40, 30, 20, it takes me one minute to lower the mast and change the band setting on the antenna. I've been able to work JA, VK, ZL and stateside with only 5W in CW. On summits where there is not much space or very crowdy I'd use an HF-P1 ( https://youtu.be/A8NSC4WllH0 ). When on summits where there was a lot of space I occasionally have used an end fed antenna, I was not convinced having the feedpoint close to the ground.
In my opinion "random" is using a BNC to banana plug adaptor and putting "random wires" on it. Or you trim the wires to one frequency/band (making them no longer random .... .. ) or you let the internal tuner of the trx do the work. The last method is described in all field equipment by Elecraft (KX1, KX2, KX3 ... )

Either way, all what matters is you're having fun on SOTA, POTA, GMA or whatever you're doing in the field/back yard ...

Have a lot of fun,
72
Frank

Andrew (grayhat) wrote: ↑Sun Jun 12, 2022 7:20 pm Reading around, it sounds like a lot of SOTA folks, either use verticals (and I can understand that, due to low takeoff angle) or EFHW, and in the second case, folks often complain about "not being able to get on air on band X due to the antenna..."; now... why such a "refusal" for "random" wire antennas ?
...
just curious

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

Hi Rob,

I guess this falls under the category of "no such thing as a perfect antenna". I have been playing with 49:1 EFHW and 9:1 "random wire" antennas for POTA activations over much of the past year. I have no doubt that I am working with a compromised station, because:

1. At most my antenna is up about 30' (inverted V).
2. Most of my activations are under forest canopy.
3. Coax feedline (about 15' of RG316) is my only counterpoise.
4. I'm only running 5 watts anyway.

For me, the end fed antennas make sense, because they are quick to set up and retrieve, and they can cover many bands. I willingly pay the price to have rapid deployment and multiple bands.

In any event, the proof is in the contacts. I have had good success with contacts, and I am able to switch bands when conditions require it. I have even had some unexpectedly good DX (like VK on 5 watts from north-west Pennsylvania).

Best 73 de Brian - K3ES

Brian, I'm 100% onboard with EFHW as a solution, because in most essential ways they're he same as a dipole, and often a lot more convenient to deploy. Do you have any comparisons with random wires? I'm guessing more noise & less gain with the random wire, but have no data on this.

I will say, my little Par Trail-Friendly EFHW 40-20-10 has phenomenal performance, and I ought to use it more often. I really need to spend a weekend next fall out in the woods doing head-to-heads on various designs.

Waters-Stanton has a nice video about EFHW's based on those little LDG 49:1 UNUNs: https://www.youtube.com/watch?v=UcuHTWWOg7c Think I'll pick one up now and be ready when the weather and bugs settle down here in N FL. It'll be much the same as the Par TF-EFHW, except able to handle QRO levels out of the FT-857. That, and it'll be something new and cool to play with.

ps: Waters & Stanton also has a video on random wires and 9:1 UNUNs: https://www.youtube.com/watch?v=IpGzBPtkxRg Always a wealth of knowledge at their channel.

Rob-W4ZNG wrote: ↑Wed Jun 22, 2022 1:52 pm Brian, I'm 100% onboard with EFHW as a solution, because in most essential ways they're he same as a dipole, and often a lot more convenient to deploy. Do you have any comparisons with random wires? I'm guessing more noise & less gain with the random wire, but have no data on this.

I will say, my little Par Trail-Friendly EFHW 40-20-10 has phenomenal performance, and I ought to use it more often. I really need to spend a weekend next fall out in the woods doing head-to-heads on various designs.

Waters-Stanton has a nice video about EFHW's based on those little LDG 49:1 UNUNs: https://www.youtube.com/watch?v=UcuHTWWOg7c Think I'll pick one up now and be ready when the weather and bugs settle down here in N FL. It'll be much the same as the Par TF-EFHW, except able to handle QRO levels out of the FT-857. That, and it'll be something new and cool to play with.

ps: Waters & Stanton also has a video on random wires and 9:1 UNUNs: https://www.youtube.com/watch?v=IpGzBPtkxRg Always a wealth of knowledge at their channel.

Hi Rob,

I have done no direct comparison tests between EFHW and Random Wire, but my subjective bias is that the EFHWs tend to work a bit better.

The up-side for EFHWs is that they are resonant, so they don't require a tuner. All of mine are based on a 40m EFHW, which gives 20m, 15m, and 10m, because the 40m base is a multiple of the half-wavelengths of the other bands. By installing a link (or a switch) in the radiator, it can be shortened for resonance on non-harmonically related bands (e.g., 30m, 17m, and 12m).

The down-side for EFHWs is that moving to or from 30m, 17m, or 12m, requires moving out of the operating position to lower the antenna, adjusting links, re-hoisting the antenna, then getting back to operation.

Random wire antennas can be switched to essentially any band from the operating position just by adjusting a tuner. It saves time, but requires extra kit (tuner and patch cable). Also, my random wire is a 9:1 unun with a 71' radiator, and my ZM-2 tuner easily matches 80m (160m has been elusive to date). Surprisingly, 40m can be touchy to tune with the ZM-2. This is a problem, since 40m is usually my most productive band.

I have not noted any difference in noise level between the EFHW and random wire, partly because I do most of my work in the north-west Pennsylvania woods where noise floor is usually quite low.

Best 73 de Brian - K3ES