QRPGuys Tri-Band Vertical Antenna - Hints for operating and tuning

Equipment Antennas
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Dear all,

I’ve been field-testing the QRPGuys Portable 40/30/20m Tri-Band Vertical Antenna for three SOTA activations in OK this weekend (some images i.e. here and here). The antenna seems to work great for 20 meters and I got decent reports from my usual chasers in EA and G-country ( :wink: ).

However, I have a hard time making any contacts on 40 meters. In addition to “no contacts” my FT-817ND complains about high VSWR at 40 meters (no such complaint for 20 meters). At this point I’ve got to note that I did follow the assembly-manual incl. tuning instructions to the best of my ability but I have a hard time squaring my head around a decent performance on 20 while there’s zero performance at 40.

Since I like the form factor of the antenna and relative quick-ness of erecting it I’d like to give it another try.

So - does someone own this thing and has inputs concerning tuning for 20 and 40 meters or how to best use this piece of hardware in the field? I’d like to use both 20 and 40 m :wink: .

Any inputs, insights, improvement suggestions, … would be greatly appreciated.

Thank you, Alex

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Hi Alex,
I built one of these a few years ago but was not particularly impressed with its performance. At that time - at the bottom of the Solar Cycle, I would have been trying to use it on 40m more often than 20m - so it seems I had a similar performance experience to you - but I don’t remember a bad SWR.
It got packed away somewhere in the bottom of a box and forgotten.

In general a 40m vertical will work better with more or longer radials than a 20m one, so you could try adding more radials.
Also by design, on 40m both ferrite ring wound coils will be used - so you might double-check that you have continuity when switched to 40m, if you have a bad contact to either of the ferrite coils you would only get the bad antenna effect when switched to 40m rather than 20m (which does not use the coils).
73 Ed.

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Alex,

I have one of these. I have the same experience as you: it seems OK on 20m but the SWR was really high on 30/40m.

I tried calculating how many turns should be on the coil to get it to work and got a different number to the instructions, but it was still not right so I played around a bit with the number of turns until it was a bit better.
Sometimes the SWR on 30m is lower when the switches are set for 40m (and vice versa) so just play around and see what happens.
I checked the PCB and the switches work correctly and turn on both coils when set to 40m, and just one of them for 30m.

I have 6 radials on mine 4 or 5m each (not 100% sure). Elevating them doesn’t seem to make much difference to the SWR (using a 6m pole they are usually elevated). It seems to work reliably and repeatably on certain summits but not others so I think the ground conditions affect it somewhat too.

Having said that, despite apparently having poor SWR and being a bit of a compromise I do make contacts with it so it does the job.

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First red flag for me is the length of the radiating wire to perform on 40m. Doesn’t matter what trickery pokery you may have wound at the bottom to “help” match it.
just sayin.
Ian vk5cz …

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Dear all,

Thank you very much for taking the time and sharing your knowledge and experiences :bowing_man: .

It seems that high SWR and “improvable” performance is something that everyone with this particular piece of hardware has experienced. This is comforting to know since I thought it might be just my problem.

For a plan of action I’ll follow the hints provided in the blog post shared by @MM0FMF and will double-check switches and toroid connections.

All in all the switches also do not give me a good feeling (= high confidence) and I’d rather have a dual-band antenna (no need for 30 meters) with no switches. My usual Inverted-Vee dipole works wonderfully for 40/20 and I do not even need to get up to open/close any switches (due to antenna traps). Would it not be for the Inverted-Vees very large on-summit footprint I’d never look for something else (I’m taking recommendations for any antenna offering small on-summit footprint, 40/20, no manual band switching necessary).

Thank you for your input so far,
All the best, Alex

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Apologies, this is a sidebar conversation and doesnt relate to the QRP Guys product, but is relevant to the trade-offs of tuned multiband compact antennas for SOTA.

@OE5LXR My 40 and 20m linked dipole was my go-to portable antenna, guaranteed to work well, no appreciable losses, no messing about, no tuning, but you have to drop each end to open/close the link when changing bands.

After tiring of this I tried a 20m wire (EFHW on 40m, EFFW on 20m) with a tuner (AA5TB) and this also worked well, and avoided the need to fiddle with the wire when changing bands. However you still have 20m of wire to put up which takes a bit of effort.

My solution (to this point) is a 10m length of wire, strung as an inverted L on a 6 - 8m pole, worked against a single 7 to 10m radial lying on the ground. A small matching unit at the base switches the RF either straight through from coax to 10m wire (making it a 1/4 wave vertical on 40m) or switches in the usual transformer (making it a EFHW on 20m).

Advantages: only 10m of wire to run up the pole, on a shorter pole the excess has to be tied off to a tree with a nylon chord; one radial to roll out on the ground; fully resonant on both bands, no tuner, no traps; change bands with a single toggle switch; compact and light.

Disadvantages: on shorter poles the excess has to be tied off to a tree with a nylon chord, although I have used this antenna with an 8m pole, taped to the top and strung as a sloper which worked fine.

This antenna has worked well on both bands, particularly 20m where I’ve been working VK-Eu QRP-QRP CW DX regularly. On 40m it may be 1…2 S-points down on the full sized 40m dipole, depending on conditions and distant station’s locale.

It should also tune 10m but I haven’t tried that yet.

I have a video which I posted on another thread a while back, let me know if you’d like to see it.

73 Paul VK3HN.

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Hello Alex. I have had good performance from this antenna on all three bands. I recall tuning it in terms of the turns on the toroids but it was so long ago that I cannot advise. It’s a good choice in a dense forest or undergrowth situation when it’s hard to swing a long wire up into a tree.
Scott
NZ4R

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Paul, thank you for your input :bowing_man: . My linked dipole is in fact a “trapped” dipole so no need to getting up for a band-switch. Very convenient and the only drawback of it is the large size requires on summit - which can become a challenge on :austria: :mountain:'s :wink: . Also it takes comparatively a long time to set-it up and the XYL - children patience is somewhat limited :wink: . Maybe you can send me a link to your video via PM?

Scott - good to hear that you got some results for 40 meters too. I’ve not given up on the antenna yet - need to take the time to attach my VNA and do some proper tuning session :fire: .

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