Monday, August 3, 2015
Initial Notes on the 6BTV Vertical Antenna
Things have finally come together on this thing. So far it's all working well, but relative to my existing antennas the results are ambiguous. With 16 22 gauge ground radials, all bands tuned easily: 10, 15, 20, & 30 have SWRs < 2 across the bands, right out of the box. 40m took a few minor adjustments on the telescoping sleeve, but is < 3 from 7.0 to 7.275 MHz, and with a little bit of autotuner persuasion it will reach up to the 7.3 MHz band edge. So that is a success. On 80m... after trimming the whip extension down do 16.5", SWR is < 3 from 3.810 to 3.880 MHz, for a relatively narrow 70 kHz bandwidth. The autotuner stretches things out to nearly 200 kHz, which is perfectly useable.
As for performance, the vertical seems to have legs on 30m with PSK31. Last night I was able to receive three stations in eastern Europe, and had a conversation with a guy out in Oregon, both things that the low dipole has never managed. OTOH, it may have just been band conditions. I did have a conversation with a group in the Jackson area on 80m to compare performance with the low dipole on that band, and the vertical came out the loser by a factor of 30 dB. No surprise there, because that 150 mile hop is best done with NVIS off of a low dipole. No comparisons yet on 40m. 10 & 15m sound a bit more noisy than on the A99, but those comparisons will have to wait for daytime.
So if anything, this vertical is a step up on 30m, and may yet prove to be a step up for DX on 40m as well. It is certainly a compact, functional antenna. Its footprint, ~1 sq ft when raised, and 25 ft length when lowered, is much much smaller than the 80/40 antenna's 85 ft length and its pain-in-the-rear 4 guy-lined center support mast. I strongly suspect that when the summer lightning noise fades and the ionosphere improves this fall, this vertical will prove its worth.
As a side note, on 30m the predictions for the vertical are for a step up in performance:
which is noticeably but not overwhelmingly better than the low dipole's modeled performance:
But that's just rough modeling, and reality may be quite different. With time and a bit of patience, we shall see.
Taking a look at winter propagation on 40m, things look much more promising. Here's the vertical's predicted performance:
vs the same for the low dipole:
Again, we shall see.
ps: If you're looking for one of these for your very own, DX Engineering has them.