No, I do not have a cunning design for this, but would value some support.
Last weekend’s S2S across the pond got me thinking. Assuming I have lots of real state on my favourite summit, could I implement a Vee beam for the higher HF bands?
I do have a 30ft carbon pole and the legs for a dipole for 80m = 2Lambda legs on 10m.
Research suggests a feed impedance of 500-700Ohms so a 1:10 impedance conversion balun looks likely to be needed. A non critical 50degrees included angle is in the literature together with a forward gain of 7dBi. Looks interesting. Comments and experience welcome.
Many decades ago when I was serving as a soldier in Germany I often rigged up the antenna as a sloping V shape. The idea was it was directional and pointed to the rear rather than towards the “enemy”. Don’t ask me what the frequency was, this was in the 1980s.
It needs one of the expert antenna modellers on here for an informed answer!
A club member made some and tried them on one of the big 48hr HF contests. He did talk about the various antennas that were tried. I’ll ask him for comments but him and his partner in crime were located very close to a beach so that needs to be born in mind.
Why not try a doublet 3 half waves on 10m with a half wave of ribbon feeder into short piece of coax to your rig. I find my usual end fed 40m SOTA dipole has good results on 15m S2S to Japan most times I try it on SOTA or chasing in my back yards on 15m to JA ops on summits. That antenna is close to 3 x half waves on 15m, and in reality on 10m if the band is open even a simple 10m dipole will score contacts.
Regards
Ian vk5cz …
While this is true, I hesitate to encourage others to embark on building such a ridiculous antenna.
In all seriousness, it’s just not all that practical for most uses. It’s huge, slow to set up, and can’t handle much wind (at least not my ultralight design).
But beyond the yagi, a moxon is a good option for about 4 dBd of gain, and I have used half square and bobtail antennas with good success as well, particularly on 20 m where it’s hard to get a horizontal antenna high enough for a low radiation angle.
I have not tried a V beam but it could certainly work well. I’d recommend modeling in MMANA to compare. Remember that gain alone is not all the matters. Gain at a low radiation angle is key.
MMANA can’t model an antenna on a summit, only on a plain (and in free space). So it doesn’t give answers to the question which antenna would be best on a summit.
Although you can’t angle the ground in MMANA, you can get creative and angle the antenna relative to the simulated ground to get an idea of what performance might be like on a given slope. Give it a try.
I think the clever bit is going to be matching 50Ohms coax to 600 balanced.
I think a voltage balun, possibly with a self resonant choke may fit the bill.
Need to do a bench test
I won’t be building any kind of vee beam for the next TAS2S event, but I am considering a Moxon for 10 meters. According to the literature, it has impressive F/B ratio - it’s worth a try, it’s simple, has a feed-point impedance close enough to 50 ohms, it can be constructed fairly lightweight, and will be well supported by the 12-meter pole which is on its’ way to me as I write.
A 3/4 wavelength of 300 Ohm line, with a 4 to 1 balun might bring it somewhere near. That length of feeder might be practical, and would put the balun conveniently at ground level…
FWIW, although slightly off topic I’m running a rather big V-beam at home. I’m not that active at the moment, but on 20m (where it’s optimised) it seems competive to a 3el yagi at a similar height. But bi-directional, as mine is non-terminated. Each leg is around 70m long. I could dig up some details if anyone’s interested.
Fed with open wire line, into the built in 4:11 balun on a little MFJ-971 t-match.
Hi all,
Many thanks for the many contributions to this topic. We have a worldwide pool of valuable knowledge to tap into. I will report back after I have built and tested a beam.
PS lots of good aerial and balun practical tips in the reference section of German web site: “RF kits” 1:1 BalUn Archieven - HF kits
Regards
David
G0EVV
