Those of you that have seen my recent alerts may have seen that I’m looking for QSOs on 80M CW.
My antenna, like all antennas, is a compromise. I’ve been using an EARCHI UNUN with some extra radials, fed with RG-174 and matched by the LDG autotuner.
The question: What are some better antennas out there for these low bands?
I’ve thought about increasing the length of wire, and stringing it out among the trees. I’m thinking 40 meters of wire or so, to yield a quarter wave on 160 or a half wave on 80. Given that the antenna would be quite close to the ground (in terms of wavelength), I think this might be a bit of a “cloud-warmer”, but that’s fine. With SOTA, the clouds are often very nearby.
This may be great fun if I’m able to camp out on a summit here in Virginia. Making 80 and 160M QSOs at night is good fun!
Good topic, I’m interested in what people are using. I’ve activated with loaded verticals for 80m and that yielded close contacts that couldn’t hear me on 40m. The two issues I had with that set-up were 1) the bandwidth of low SWR was narrow (for a particular coil tap) and 2) I had fiddle with the antenna (inserting the coil and chosing the tap). I recently made a ZS6BKW doublet (as a result of my S2S QSO with Gerard VK2IO, which is what he used), and my KX3 tuner allows me to tune anywhere in the band. It’s very nice for for 80m-17m, there’s no fiddling with the antenna to change bands. The KX3 wouldn’t tune 15m on the two peaks that I tried. I’ll make a short section of connectorized feed line to solve that. Gerard said that he has a double-sized ZS6BKW for 160m, I might try that. I have a future activation in mind that I’ll be operating at night.
because of the down turn in local conditions on 40m here in vk5 when activating I have used a couple lengths of wire with alligator clips on one end and normal tie off strings on the other. Now I erect my 20/40 metre link dipole in the usual fashion stringing it normally 8m high, then I clip on the extension wires for 80m to the end of the dipole and continue out further and tie off the extensions to make the antenna resonate on 80m. The extensions are 9.5 metres each side and that made it resonate on 3.680 as that is the frequency most of my local chasers use on ssb. If you needed to be in the cw part of the band well you may need to check for a differing resonant point. When not in use I just roll them up around my finger and thumb into a bundle KX0R style and keep then in my SOTA bag. What you have to do with the 40m dipole on the end near the insulator is bare back some wire and tin it with solder so the Alligator clip can bite on to it and make contact if you use plastic coated wire. I make good contacts around vk5 when my local chasers can not hear me on 40m and it has saved a few of my activation’s to qualify last year by having 80m as another option.
From memory 9.5 m was the starting point and i did snip it back a bit i think.
works for me
Ian vk5cz …
I’m currently experimenting with some loading coils to make my link dipole for 40m and 60m also work on 80m. The coils are designed to fit where the 60m/40m link is and uses the same connectors. I’m hoping to give it a SOTA trial the weekend after next while out grabbing some winter bonus points in G/WB
Dr OM Nate,
My KX1 with build in tuner is happy with the W3EDP; 84’ in a tree and 17’ on the ground. Works on 20-, 30-, 40 and 80 m.
No balun no coax.
I have been told ones: KISS Keep It Simple Stupid!
73 de geert pa7zee
You beat me to it, Geert! The only difference is that I use an FT817 so I built a simple parallel tuner, a coil and a capacitor. As it stands it tunes 80, 60 and 40, and just about does the job on 20 metres - with no switch. I am about to modify it with a bigger coil and switched taps so that I can cover 160 metres and perhaps a couple of higher bands. Most of the UK summits do not have trees so I set the main wire up as an inverted V with a 7 metres roach pole.
The W3EDP antenna is an ancient design dating back to 1936. It was regarded as a DX magnet then and it still works well today!
I am not at all clear about the use of loading coils. My portable aerial is a 60/40/20 linked dipole with end strings to keep the wire ends clear of the ground. It does not need tuning unless used on the wrong band for the link setting. The full (60m) length tunes quite well to 80m, so I could continue using that.
I could add some more wire to make it into an 80/60/40/20 linked dipole but the extra length could be a problem when setting up or packing up .
I could fit coils as suggested above.
I’ve been using 80m loading coils for quite a few months now in response to the changing band conditions. My antenna is a three band linked dipole for 60/40/20. I fix the coils on the 60/40 croc clips and I have wound the coils so that I am able to work around 3.765 Mhz although I do have considerable lee way each side of this even without an ATU which I don’t carry. I did experiment with adding extension wires from the 20m link to give me 80m but reverted back to the coils as they they keep the antenna compact but not so efficient. Radiation pattern…who knows?..but it works.
See my blog for my latest activations and contact results on 80m. Try it and it’s fun to experiment.
A good match does not mean you have a good aerial.
My dummy load has a 1:1 match but makes a poor aerial.
If you feed your dipole with coax, then there can be a big loss in the coax feeder between the tuner and the antenna when you use the antenna on the wrong band. The tuner makes the radio see 50Ohms (or whatever you want) and the radio is happy. The loss could waste 90% of your power.
If you add loading coils then the antenna still looks like 50Ohms and so there is much less loss in the coax.
Its the tuner “just about does the job”, Geert, I built it for 80 and 40, it will just about tune 20 with the capacitor close to minimum but it takes a delicate touch to find the best setting. I hope the mark 2 version will be better, if not I will have to put a small slow motion drive on the control!
Yes, Andy, I know. My G5RV tunes to 1:1.1 on 160m - and I don’t even hear anything, let alone transmit successfully. It is probably too near the ground.
Thank you for pointing out why the loading coils are better than an AMU; I knew they would permit operation without AMU if selected carefully but it looks as if I may need to carry them as well as the AMU. I shall have to experiment but WX is not too good for that at present. Allan’s solution looks very neat.
Yes, I think the loading coils will work well then, although I think I won’t use a dipole.
I really like the simplicity and ease of deployment of random wires fed against a counterpoise. I’ve had great success with my EARCHI (I worked OH9XX and DJ5AV from San Diego and Riverside Counties in Southern California–roughly 11000 mile paths, using 5 watts on CW).
I think I may experiment with a loading coil paired with the EARCHI. I’m not 100% certain about where I’ll put the coil–my sense is that it probably belongs near the end of the wire since, theoretically at least, that should be the highest voltage/lowest current area of the antenna, and therefore will affect the strength of the signal the least.
I don’t have much experience with EZNEC. If I did, I would model this.
My 20 metre extended double zepp works quite well on 80 metres. Fed with 300 ohm twin feeder (old TV ribbon) direct into the KX3 tuner. This antenna actually works OK on all bands 80m through to 6 metres.
Recently used a top loaded 7 metre squid pole vertical on 160m and quite happy with the performance.
I chose the 40/60 links to position the coils as it meant a) max wire length (radiating) from centre of dipole to coil and high above the ground b) easy to change band/ remove coil without dropping the antenna in inverted vee configuration. You will need to experiment with the length of wire that you wind on to form your coil as it is not a direct replacement to the lost antenna length, however, it is a good starting point…obviously start longer and trim back carefully…various inductances come into play. I wound my 80m coils on readily available kitchen waste pipe (35mm diam) and did the testing in back garden…made quite a few mistakes but the wire was cheap enough Have fun.
It seems that this was the case on 1st March when I started my activation of GW/SW-002 on 80m. SWR was 2:1 rather than 1.2:1 which I normally get on 60m. Six contacts were made; all but one with signal report of 44 or worse. In contrast I was giving 57 or above in all but one case. 60m and 40m were much better; 41 contacts, mostly reporting 56 or above.
Time to get to work on some loading coils.