Topband: Fwd: Capacitor for Inverted L

[John K9UWA]

With a 30 foot high vertical section and the rest around 105 feet horizontal
And having two above ground radials. The "Real Impedance" Of this
antenna is about 12 ohms. The fact that the antenna matches 50 ohm coax
says that your "Ground Loss" of this antenna is about 38 ohms. So your 
warming the worms with about 3/4 of the power going into that antenna 
and only 1/4th of the power is actually being radiated into the air. If you keep 
adding additional radials you will find that the match will keep lowering until 
eventually at around 80 to 100 radials you would eventually get to a ground 
loss of maybe 5 to 10 ohms the antenna would be much more efficient. It 
would then require a 2 to 1 Un Un to match the now around 25 ohm antenna 
to your 50 ohm coax. Your signal will be considerably stronger as you won't 
be warming the worms as badly as you are now.

John k9uwa


> Although I'm far from being an antenna "expert", I second Wes' comments about
> matching a 160 meter Inverted L.
> 
> I recently made my first ever Inverted L and am very, very pleased with the
> results. Mine has only 30 feet or so of vertical rise, and the remainder of the
> "hot" side runs pretty much horizontal. Being very space constricted, along with
> having to be stealthy due to HOA and CC&R issues, I was only able to get two
> radials installed. Both are 16" off the ground. When I first installed the
> antenna and hooked my MFJ-259B to it, it was resonant at about 1.700 MHz. I
> pruned back the radials several feet and left the "hot" wire alone. Doing so got
> the antenna to resonate at 1.840, with a 60 KHz 2:1 bandwidth. I feed it with
> 115 feet of RG-8 and have a huge coax RF choke at the feed point. With this
> "crummy" antenna setup I've worked the east coast of the USA during the recent
> California QSO party, in addition to easily working the guys at T32C. This has
> been with 100 watts from an Elecraft K3. The auto-tuner in the K3 has no problem
> getting a match up in the phone part of the band. N
>  o external matching network needed here...! :-)
> 
> I put my final measurements into EZNEC and the far field plot shows the antenna
> being omni-directional (expected), but with a fairly low take off angle - about
> 25 degrees. I fully expected that I'd wind up with an NVIS cloud warmer, but the
> on-air results pretty much compare with the modeling data.
> 
> Jim / W6JHB

John Goller, K9UWA & Jean Goller, N9PXF 
Antique Radio Restorations
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