Topband: 160 antennas

[Greg Chartrand]

AF4OD wrote:

> 	i was reading your post to topband tonite. Believe
> it or not, i built up a
> inverted "U" today. I had been using a inverted "L".
> but i wanted to try
> lengthening the antenna, thus i created a inverted
> "U". Mine is up 55' over
> maybe 40' and down 50'.
> 	You mentioned grounding the end of the "U". What
> does this do to help the
> antenna? Mine is floating on the end, but it would
> not be hard to ground
> it. I was just wondering what results you found or
> read about. I'm using a
> series "air capacitor" to tune it.

Bill,

The K8RRH inverted U as I recall (after about 30 years
ago) was close to your configuration. Fed at one end
with coax and a ground radial system and terminated at
the far end with another ground radial system. The
interesting twist I just learned is adding a coil
between the far end and the ground system. That would
allow you to adjust the electrical length of the
antenna (assuming it is shorter than 3/8 wave) so you
would end up with a perfect 50 ohm match at the
desired fq. Probably a good idea since the match is
the radiation resistance plus your ground losses thus
you don't know what antenna length will actually give
you a 50 ohm match.

I use a top loaded vert on 160 and just added a
decoupling wire to it to form a 3/8 wave stub for
75/80 meters. It gives me a nice match I can tune both
bands with my motor driven cap. 

Good luck with it. Let me know how it works for you.

73's,

Greg
W7MY


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