Date: Sun, 06 Nov 2016 12:04:59 -0500
From: "N2TK, Tony" <tony.kaz@verizon.net>
To: <towertalk@contesting.com>
Subject: [TowerTalk] Matching 40M
Years ago some of us used an L-C network made from a variable cap and a coil
to make the amp happy at the top end of 40M with our shorty-forty's.
I now have the same problem with a 3-EL 40m that is tuned for CW. The amp
does not like to put out much power at the high end of the band. Is it
possible to update that old circuit with a ferrite core and some doorknobs?
Has anyone tried this? Would I have issues with circulating current or very
high voltages trying to put this into a box to put on the output of the
1500W amp for phone contests?
I realize this does not treat the high SWR on the coax. I could put the box
at the base of the tower so that there would only be about 50' of coax to
the antenna if that makes things "better".
Tnx for any feedback
N2TK, Tony
## exactly how was the L-C network configured ?? Was the C on the
input side, from hot side of coax to grnd....with the coil going from hot
side of input to hot side of output ??
## I would not mess with ferrites. A small coil is easy to wind from cu tubing.
Once u know the exact value of cap to use, it could be replace with a few
NPO doorknob caps. NPO doorknob caps dont drift, but are typ only available
in lower pf values. Ferrite is the wrong item anyway. If you went that
route, you
want to use powdered iron core, like a T-225-2A type. 8 ga solid wire, or
.125
inch od cu tubing is easy to wind..and bomb proof. It would never heat up.
Jim VE7RF
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