If that antenna is resonant at 1900 kHz, and you have a suitably sized
inductor between the bottom of the vertical wire and ground, there will
likely be a tap-point on the inductor that will give you a low SWR. No need
for a transformer.
I think that is probably the simplest and most solid solution.
Further to Clive's point, I believe that inverted L-s can have substantial
high-angle radiation when the horizontal wire is a large portion of the
antenna. I always use a T, even if the wires have to slope down. Keep the
top symmetrical! (It also allows the antenna to be used on 80 and 40 meters
-- if you can match it. A 160 m inverted L will probably have mostly
high-angle radiation on those bands.)
Looking forward to the season!
73 and CU,
George
On Sun, 2 Sep 2018 19:29:51 -0000
"Clive GM3POI" <clive@gm3poi.com> wrote:
Or better still, Shorten the L until it is self resonant
at 1.9mhz, thereby
lowering the amount of horizontal polarisation. Then use a simple hairpin
coil across the feedline typically around 5microhenries. This will then when
chosen correctly match at your chosen ideal spot say 1825.
And provide a DC short to ground for the antenna. No Caps needed. 73 Clive
GM3POI
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Tom
Boucher
Sent: 02 September 2018 18:20
To: 160 reflector
Subject: Topband: Air wound coil
Bob W7RH - you don't need expensive hard-to-find vacuum capacitors to match
a quarter wave 'L' or 'T' on top band. I use cheap multilayer high voltage
disc ceramics and these have been working perfectly at QRO levels with my
inverted 'L' for years.
I use 1600pF made up from 1000pF + 470pF + 220pf all rated at 6.3KV and
available (over here) from CPC at less than $4 for 10.
Antenna is slightly longer than a quarter wave so it is inductive and the
capacitors form the other part of the L-match network.
73,
Tom G3OLB
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