[TowerTalk] Matching 40M

[David Robbins]

Maybe, but I would worry about the ferrites at high power.  I do something
like that with coax transformers and/or stubs to flatten out some bands or
compensate for the mismatch caused by 75ohm hardline transforming some of
the stack combinations.  You can also just put a tuner like an mt-3000a
inside and either switch it in and out or do like I did on 40m and use it to
level out the whole band so no adjustment is necessary between cw and ssb,
that is a neat use for a vna since you can watch the whole band and not have
to sweep it with the radio.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373



-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of N2TK,
Tony
Sent: Sunday, November 06, 2016 17:05
To: towertalk at 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

 

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