Reading about the best counterpoise installation I find that there are opposing recommendations. In the instructions of the Switched Longwire Tuner Plus (SLT +) of Pacific Antenna Switched Longwire Tuner - Plus - Pacific Antenna it is indicated that the counterpoise “should be 180° from active element direction” but in the instructions of the Sotabeams Bandspringer end fed antenna the recommendation is that “ideally one would lay it under the radiating element.” Any idea why such opposing indications for a LW counterpoise?
73
Antonio, EA4MY
Interesting question I’d like to see argumented.
My favorite way to install my SOTA antenna is this:
Heinz @HB9BCB told me he would simulate this setup on EZNEC and I asked him to try to confirm if there’s some directivity in the sens indicated by the arrow on the image above.
73,
Guru
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The SLT+ ATU is designed for the impedance matching of end-fed half-wave antennas (EFHW) - these are very high-resistance at the feed point (very low current), so the orientation of the radial is practically irrelevant.
The Bandspringer Midi Antenna from SOTABEAMS is an end-fed antenna of random length, which is chosen so that an impedance matching is possible with most of the available ATUs. Because the radial of the same length has an influence on the impedance matching, its orientation is important.
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In general, I consider all antennas with two different wire positions as OCFD Off Centre Fed Dipoles.
Depending on the wire length and ratio to the ground, this results in different impedance and steepening characteristics. The impedance helps the antenna tuner get into a range where it can work and match.
If one wire is on the ground and the other is sticking up vertically, it becomes vertical (ground plane)… as opposed to horizontal…
This is a wide field for experimentation. There will probably be some experience here.
73 Armin
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Some good hints about counterpoise types for vertical antennas… elevated vs. ground can be found here: https://consumer.steppir.com/radial-systems-for-elevated-and-ground-mounted-antennas-2-2-12_2018/
short summary… ground counterpoises with 0.1 lambda work well…
Works well for Sota. Tested with MP1 and HF-P1 antennas.So no need for 0.25 * lambda elevated radials…
73s
Ingo
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There was a talk about antennas on the last online Hamradio fair, where a similar antenna was simulated confirming your thoughts.
Unfortunately, it is only in German… but you should be able to understand the slides.
73s
Ingo
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As said, there are three categories.
-
Radiator has a length of half a wavelength and a multiple (EFHW)
Impedance approx. 3k Ohm and low supply current → counterweight practically does not radiate -
Radiator has a length of approx. a quarter of a wavelength and uneven multiples (endfed 1: 9 unun)
Impedance approx. 450 ohms and average supply current → counterweight emits a nominal value. -
Radiator has a length of 1 to 2 meters with an extension coil (HF1, mobile vertical)
Impedance a few ohms (plus loss resistance - usually significantly higher) a very high supply current → counterweight must be very low-resistance, is an essential part of the antenna, radials should definitely be matched and hang at least 50cm above the ground and contribute significantly to the tuning and radiation
73 Chris
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Well, it depends on whether you want to follow the technical meaning of counterpoise, which was originally a mat of conducting wires that created a capactive connection to conducting ground, to substitute for a network of radials buried under the surface.
One single wire dangling somewhere in mid air can not be regarded as equivalent to a counterpoise.
I am with Armin @DL6GCA in regarding most antennas of the configuration in Guru’s diagram to be off centre fed antennas.
73 Andrew VK1DA/VK2UH
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My most successful End Fed Random Wire is a radiating wire 58 feet long or 17.678 metres long with one radial 13 feet or 4 metres long.
I use a 6m long telescoping pole as support and antenna is an inverted L config.
The reason I arrived at these wire lengths was mostly influence by the tuner in my KX3 or the MT1 LC manual tuner I use with my FT817. Both tuners seem to tune this combo the easiest on all bands from 40m to 10m. It also radiates very well for a none resonate antenna with QRP. I have chased many SOTA activators from my back yard around VK ZL and JA. Had a S2S qso on 20m one time with EA2CW on 20m CW using this antenna on afternoon greyline for me.
The antenna is set up with 5 metres of the wire vertical up the pole the remaining wire is horizontal across the yard to another support. I have a plastic home made winder to insulate between the two wire with a short length running to the tuner or kx3 binding post on the antenna socket of the rig. If the “feed” junction is about half a metre off the ground the radial is run out under the antenna in the same direction as the antenna. I find a short stick and tie the ground radial to it and poke it in the ground, the radial is insulated from the earth. I saw a DL station do it this way on YT he liked to have an angle of 135 degrees between the vertical part of the L and the ground radial sloping down to the tie off stick a few inches long. My LC tuner has several selections of inductance and I like to tune with a more centered capacitor so its not jammed fully one way or the other and as for the KX3 well the excellent tuner does its own thing for me. My FT817 loves this combo and as you will know if the rigs not happy it won’t give full power. Done a few WSPR tests with it as well and been heard in a few dx countries and locally in VK on a few bands. I am no Techno Weeni on the theory of it all just a practical person with the above results to show. There also have been some famous U.S. QRP CW SOTA ops using a 58 foot antenna of varying incarnations for several years its where I got the idea from working them from my home station.
Regards
Ian vk5cz …
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Ian,
I’m with you, this summer I’ve been using more or less the same setup on my activation’s and find the 58’ wire really sings on 20m, maybe a little less so on 30m, and again on 40m works very well. Certainly feel it out performs my trapped EFHW for sure on 20m (EFHW trapped has the edge on 30m) No science here just gut feeling. By way EFHW seems to work the same whether I use a Sotabeams mountain tuner with a counterpoise or a Fuchs tuner without. What I do find helps is to run the wire down the slope in the direction of interest if at all possible.
Dec
ei6fr
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Seldom using a 22m EFHW with Fuchs tuner. It works well on 40,20,15m.
Not so good on 30m and 17m. But it still works somehow… 
A trapped EFHW for 40,30,20,17,15m would be worth a try.
73s
Ingo
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I’m very interested in the length, number and arrangement of counterpoises for end-fed non resonant antennas in terms of antenna theory, modeling, and actual real-world performance. My perspective is that there are many variables in the environment of actual physical antennas that impact their impedience and radiation patterns, so experimenting with actual antennas is important. For example, I have a 71 foot sloper that’s end-fed with 50 feet of RG8x coax into a 9:1 unun at the high end. The antenna runs from an apartment balcony 25 feet high down to a 6 foot wooden fence. Two 15 foot counterpoises go down and away from the unun at the high end about 20 and 35 degrees from the radiating element and seem to increase the bandwidth without needing to readjust a manual MFJ 904 tuner. There’s a common mode choke at the transceiver. This antenna runs down over a concrete parking area that has metal rebar underneath. The coax runs across the concrete floor balcony into the apartment away from, but in line with the 71 foot wire element. VSWR can be tuned to 1:1.2 or better on all bands 80-10. From California in the US, I’ve worked Japan, Australia and the East Coast of the US with 100 watts SSB on 40 meters. I get up to S9+ reports on West Coast 80 and 40 meter SSB nets and have had QSOs on 20 and 15. I’ve also made QRP SSB 40 meter contacts with 1 - 10 watts. For me, antenna experimentation is a fun and critical part of ham radio.
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The main reason I use the MT1 tuner with a selection on inductances give more choice options rather than a 9 T 1 balun which is a fixed middle of the road inductance for all desired bands to tune. JP1QEC did a model for me some time ago and it showed 20m would work the best in this config. I quite often work him when he is on his summits in Japan as Mot is a great antenna builder who tries different set ups.
Ian vk5cz .