Construction details for yet another antenna, this time a 250 ft V Beam. It's a pair of 250 ft long wires, about 50 degrees apart, feeding a transformer located up 52 ft. The wires are sloped down to the ground, and terminate into 400 ohm resistors to ground.
The transformer has 3 turns on the RG-6 input and 10 turns on the output, wound on the standard BN 202-73 binocular core.
The goal for this antenna is good directivity towards Europe (especially on the 48 meter and other pirate bands), which is at about a 50 degree azimuth from me, hence the orientation of the wires at 25 and 75 degrees.
Construction was indeed a bit tricky, as I had to not only get the feedpoint high, but also run the two wires at the correct azimuth angles, and (relatively) equal slopes, dealing with numerous tree branches in the way on the two paths (although they also provided some support for the wires along the way). I ended up launching several temporary ropes over branches to pull the wires along the correct path, sort of weaving them into the trees. The Big Shot came in handy:
https://www.hfunderground.com/board/index.php/topic,60415.0.htmlSo how does it work? From early testing (it's not really DX season yet and there is a lot of storm static) quite well. I get noticeably better signal to noise when listening to stations from Europe vs my other antennas. Last night I had not only great reception from The Vault on 6985 (which often comes in well here anyway) but several other Europirates. I then took a spin down to the LW band, and was rewarded with audio from several LWBC stations which were just faint carriers on the 120 ft T2FD. I need to do some more one on one comparisons vs the 500 ft beverage and sky loop, at the time they were otherwise occupied.
Right now I have this antenna connected to KiwiSDR #2:
http://sdr.hfunderpants.com:8074/The 120 ft T2FD, which is also an excellent performer, is on KiwiSDR #1, for comparison purposes:
http://sdr.hfunderpants.com:8073/I found a V Beam drawing online which I marked up with the details for my antenna:
SWR (as measured in the shack):
Resistance and Reactance (as measured in the shack):
MiniNEC calculations of the radiation pattern for the 48 meter band. Note for the azimuth pattern it's assumed the antenna is aimed north, for ease of calculations:
Not bad on 20 meters:
11 meters, interesting if true:
Even on 75 meters it is not bad:
Not spectacular (in theory anyway) on MW as expected, here is 1700 kHz, but on the air testing shows it really works well, even down to LW: