[TowerTalk] Feedpoint Choke

[Wilson Lamb]

The choke is essential with small numbers of radials.
Friends recently helped me with a great T Top loaded vertical for 160m.
We used 57' for the vertical element and four 75' radials, up 7', and a small loading coil from radial junction to ground.
Radials were carefully tuned, starting with EZNEC and then tweaked.
The performance was excellent, Z=35 Ohms, fr=1820, no prob working EU, VK, KH from NC.  EU easy with 100W.
The important thing was that with only four radials the coax looked very large.  We couldn't even tune properly until two big clamp ons were installed at base and about 50'!
The warnings about high voltage on the radials are no joke.  I made a nice char mark on the side of a tree trunk, just before the radial melted.

My only contribution was realizing that the 132' T top loading wire was a half wave on 80m.
We made the vertical of window line and did not short the line at the top, so I could unshort the line at the bottom and have a great 80m dipole nearly 1/4 wave high!
Tuned with a little L network, it worked VERY well!  Worked well on 40m too, but I didn't have time for much testing there.

I took it down for Field Day, but hope to get it up for the upcoming 160m season.

Wilson
W4BOH