TopBand: Top feed verticals?

[Steve Ireland]

Dear Vic,

John Heys G3BDQ has done a lot of work with this kind of antenna - he used
to run an inverted-L, which was earthed at the base of the vertical with
lots of radials and fed via a horizontal wire which ran from the top of the
vertical section into the shack.

John used to feed the antenna with a L-network in the shack, which was in a
upper bedroom of his house.  I think his antenna was just over 200' long in
total, maybe a bit less, but the length of the antenna is not critical.  If
you make the overall antenna length a quarter wave long, that gives it a
very high Z feed - it is better at three eighths to a half wave in length.

G3BDQ used this system very successfully on the low bands and had one of the
best signals out of the UK on 160m - with only about 50' of vertical.  This
arrangement also gives you an excellent all-band antenna.

The only problem you can have with this kind of antenna is that, depending
on the length of the inverted-L, you can end up with RF in the shack.  This
is easily solved by attaching a quarter wave radial to the chassis of the
ATU - the radial is best made of heavily insulated wire (you don't want
anyone touching the voltage end of it!!!) and can be wound around the room,
under the shack carpet.

Vy 73,

Steve, VK6VZ




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