On 3/24/2010 5:18 AM, DF3KV wrote:
> I tried that [RF Parts] choke in one of my amplifiers without testing it
> first with the
> GDO and it just turned into smoke on 10m.
I've been working on a choke for a new amplifier project. I've noticed some
things which
experienced builders probably already know, but I thought would be worth
mentioning:
a) Even if the gdo has decent calibration to begin with and even if you are
careful to use
it properly (move it away from the choke to get the smallest perceptible dip)
the
frequency is pulled a lot near a resonance. I've found it necessary to use it
together
with a counter to get accurate, repeatable measurements.
b) It makes a big difference when the choke is mounted on a chassis (and
probably when it
is inside a box) compared to sitting on a wooden workbench.
I am trying out an idea as follows: I wrapped the choke with Teflon tape and
made a copper
band about 1/4" in width which I can slide up and down. The plan is to test the
choke
installed and wired with everything mounted and use this to fine tune it before
applying
power.
For what it's worth my choke is 3-7/8" close wound no. 28 on a 1" diameter
ceramic form.
I've used the RF Parts choke before successfully, but why pay for something
that you can
make for nothing?
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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