Suggestions for a practical small area 80m antenna for SOTA portable use

Or you could use a German cuting edge antenna Ham Radio Site - [CUTTING EDGE ANT]

73 de Pedro, CT1DBS

Yes, I thought I was going to hit those damn Physics laws again. I just need to find a workable compromise - I still have some good ideas from the thread - so thanks to all who have contributed.


Got that one direct from Rick this morning, thanks Pedro,

Thanks Heinz - text corrected.

The responses so far have been great, food for thought as the cycle goes down. Now to just find some antenna wire that’s strong enough to support a long antenna wire (I currently use 13x0.12mm).

It might also be the only 160m activity I do as my backyard isn’t really big enough for a 40m dipole.

Silly question and the answer is probably “sometimes”, but is 80m likely to be useful at all in the sunny part between grey-lines?

check on the SOTA news for Sept 2015 An Antenna Story by PA7ZEE.

The article is actually in Oct 2015, not Sept

73, Barry N1EU

More likely in winter than in summer. During the summer daytime D layer absorption can leave 80 dead, sometimes 60 and even 40 can drop out.


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Hi Ed,

Many use the G5RV or ZS6BKW on 80m quite successfully. No coils to wind or adjust. Plain straight wire. Twin line feeder. Usable impedance on 80m, with ATU. Not as short as 40m dipole but shorter than standard half wave dipole.

Query on your loaded dipole. Is the coil made as a closely spaced coil on a former, as per the article, or is it scramble-wound. Photo appears to show it as uneven, but maybe that’s ice? What wire did you use? I’m just surprised that it is not performing well.

I learned some time ago that loading coils need to be high quality and wound with low loss wire, as heavy as possible and ideally silver plated. Like in a rotary inductor.

73 Andrew VK1DA/VK2UH

Perhaps the answer is to go vertical.
A kite or helium balloon sky hook (or hybrid) is all you need.

Helium has the advantage that you can inflate the balloon at the trail head and then use the balloon as a pack goat,to take the weight of your pack!

I’m planning on playing with some kites during the summer months.


Careful Pete, didn’t you loose a bothy bag sometime ago :slight_smile:

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Hi Ed,

Yes, you are hoping for a bit much as others have pointed out. I have used half a dozen different antenna systems for SOTA over the last few years and IMO the gold standard for local contacts is a resonant dipole for contacts out to about 700 km and a vertical for longer distances. The vertical however requires more real estate as 3 minimum quarter wave radials above ground are needed for best performance.

The 44 foot doublet is as long as you can use for 14 MHz and above if you don’t want too many nulls. It’s OK on 30 m and usable on 40 m but is certainly shaded by the full size dipole. That’s where the 88 ft doublet picks up the pace and it is usable on 80 m but with some nulls on the high end of the HF spectrum.

If the 44 ft doublet is small enough you could make it work better on 80 m by having clip on coils with wire tails of say 6 ft each. That still makes it a bit shorter than a 40 m dipole. Or you could insert the coils 6 ft in from the ends of the 44 ft doublet. Requires some time experimenting but a coil with self resonance on 14.3 MHz would be my starting point.

Good Luck


Re 80 m in daylight.

The answer is “Yes, but…”

As Brian said, the D layer soaks up the signal and this absorption increases as the sun rises. 80 m typically loses its effectiveness a couple of hours after sunrise and does not recover until after sunset. It is latitude dependent.

VK3CAT and VK3BYD have used 80 m CW to get into the 40 m skip zone in mid morning and up to UTC rollover but it’s a desperate measure that doesn’t always work.


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Hi Andrew,
The coils are wound tidily and closely packed using the “magic SOTA wire” that I bought while still in Australia from - was it it Peter? who imported it in bulk and then sold off shorter lengths. Great quality wire that I have used in many projects. The scrambled look is from the ice on the coil.

The G5RV / ZS6BKW with twin feed wire may be worth a look - another one for the list to investigate.

With the centre loaded 80m dipole, it could of course be it’s location that impacts its performance and impedance (which seems low at 24 ohms) - I think I might take it out to a summit late afternoon and try it there, however the Balun that it currently has is quite heavy as it was not intended as a portable antenna. Perhaps I should simply build this design again but with lower weight components and try that out.

All things to plan - all good inpit, thanks.

73 Ed.

Now there’s a good idea - thanks Pete. Actually I bought a cheap kite about a year ago to try out a kite held antenna on a SOTA activation, but the work to keep it airbourne while operating, probably would be easier with someone along at the activation (idealy another amateur).


Sorry, but must take exception to a few of Ron’s points:

An 88ft doublet still has two main broadside lobes on 14MHz. It doesn’t get multi-lobed until you’re above 14MHz.

A 44ft doublet is down only a fraction of a dB compared to a full size dipole on 40M and is not “certainly shaded”.

My personal experience on summit activations is that a horizontal dipole will outperform a vertical for dx, The down slope in all directions on a summit means that effectively the dipole is very high off the ground and the elevation angle of propagation very low. I’m sure everybody’s experience will vary but I disagree with it being stated as a rule that the gold standard for dx from a summit is a vertical.

73, Barry N1EU


Hi Barry,

We may have to agree to differ.

According to the antenna analysis program EZNEC, on 14.2 MHz the 88 ft doublet in inverted Vee arrangement has two good lobes at right angles to the wire with 4 nulls of 30 dB approx at angles of 35 degrees to the wire. Except for the area covered by the two lobes the signal is several S units down cf a dipole. On 21 and 28 MHz there are more nulls. Now I know the program has it’s limitations but the old ARRL handbook antenna patterns support this. I also know that often in the field theoretical shortcomings can be reduced by the nature of the ionosphere and the topography.

The biggest single factor about mountain top operation is the low noise level. You can hear the other QRP guys very well.

On Wednesday I did a A/B check on 7.032 MHz and found the dipole on the same mast in the same alignment to be a good 6 dB better than the 44 ft doublet. How much of this was due to the balun and ATU I’ve yet to find out. However the balun did well in back-to-back testing at 100 W and the tuner is an LG model so it’s unlikely that they would soak up as much as 1 dB each.

The strongest 20 m SOTA signals out of the UK from summits are all from verticals. Only when the dipole is up at 20 m or more - worked a couple of DL activators who have done that - does the dipole do as well or better. For short hop distances the vertical is not as good as the dipole.

Poorly performing verticals IME have problems with the radials. Being on or close to the ground can give a good VSWR but it likely will warm up the worms. ie they have reduced efficiency and the radiation pattern in elevation may be affected.


It is probably best not to argue about the performance of antennas for SOTA on the basis of theory, there are too many uncertainties involved - the effect of the slope of the surface, which will only very rarely be the same in all directions, the depth to the effective ground (both rocks and snow are good insulators but organic soil can be a good conductor) and the geometry of each individual set-up (how vertical is a vertical in practice!) Even a straight-forward A/B comparison may be more about the site and set-up than it would be about real differences!

As one who has performed soil resistivity surveys, I can tell you that the resistivity of soil in a location can vary by a couple of orders of magnitude in a few metres!


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If we come back to the 40m inv-V with coil loading so it works on 80m, Ed says it doesn’t work very well. In what way is the performance sub-optimal? Compared to a full size 80m inv-V? Compared to an 88ft doublet? 44ft doublet?

Is it not working as well as something loaded and half sized should work or is the performance bad allowing for it being shorter?

Perhaps investigating if there are some setup/design/construction (*) issues, or installation issues may be time well spent. Moving the apex up or down or altering the height the ends are located may change it from a dummy load to something acceptable.

As for the possibly radiation pattern strengths and weakness of 44 or 88ft doublets. Maybe it would be worth going chaser portable to a local park etc. and setting up the coiled loaded antenna and doublet and trying to chase with them to see if the nulls are an issue in use? Also I should point out the design requirements were for an antenna that was space optimal for 80m and didn’t necessarily mention it had to be FB on 10m at the same time. A radiation pattern that reminds you of a porcupine/hedgehog’s bottom on the higher bands may be totally acceptable if the thing works on 80/60/40 etc.

Just thinking out loud here, please do shoot down any daftness I may be suggesting! :wink:

(*) Ed’s has been licensed for many years so I think he can wind a coil and solder a connection OK, but there could be silly errors being overlooked as the antenna may have an acceptable match.

At home, I have a loaded 80m dipole that is the length of a full-size 40m dipole. Calculations show it about 3dB down from a full-size dipole.

But I expect that most of the problem is trying to get an 80m dipole high enough.


Hi Ed,

The impedance of 24 ohms is not far off what I would expect for a low dipole. If your dipole is 7 to 9 metres above ground, that’s a good figure because it includes ground resistance. Was the bandwidth fairly narrow, eg <100 kHz for 2:1 SWR?

If you look up the antenna handbooks you will find a graph showing the impedance of a dipole at various heights. The heights are in wavelengths. A 9m height is about 0.11 of a wavelength on 80m and you may find the graph indicates an impedance of 15 ohms or so, the other 9 ohms of your measured impedance would be the sum of the resistive losses including ground and in the coil. My books are still in storage so I can’t refer to the graph here, but I know the convenient 50 ohms impedance of a dipole is shown at a somewhat greater height than 0.11 wavelength.

As others have mentioned, efficiency suffers with low loaded antennas. 80m is reasonably tolerant of an antenna that is only 50% efficient, so if you can achiever 50% you have done well. That’s only a loss of 3db.

If you have access to a Q meter it would be interesting to measure the Q of the coil.

Another approach you might consider is a trap dipole 40/80, Sotabeams have some interesting designs available and I think you’d find the 80m extension past the trap would be only about half the full size extension (best check with others who have tried them), again that’s not much different from a G5RV. The bandwidth can be expected to be half what a straight wire would be, so I’d not expect better than 100 kHz for 2:1 SWR. For ssb only (no CW required) that should permit enough bandwidth to be useful as a SOTA station.

Good luck, have fun.

Andrew VK1DA/VK2UH