Dan Zimmerman N3OX wrote:
> On Sun, Feb 1, 2009 at 10:40 AM, Richard Thorne
>> I have a vertical in my backyard that I currently feed at the base with
>> an SG-239 200 watt tuner. I want to increase my power from 100 watts to
>> 400 watts. In order to accomplish this I either need a tuner at the
>> base like an SG-235 or CG-5000 both expensive.
> A couple of other options:
> Fixed tuned matching networks:
> or motorize your tuner
> There are more elegant ways to do that, stepper motors, etc.
> You could also do a mix of approaches.... bands where the coax loss isn't
> too bad, you use a shack tuner, bands where it is unacceptable to you, use
> an external matching network. VK1OD's page could give you a guide to which
> bands are worst, and you could start there.
A remote antenna switch, used to switch among networks or taps in a
network might be a handy thing with this approach. One potential bummer
is that some autotuners aren't happy about passing control signals up
the coax (if you're using one of the MFJ 1:4 switches). The 60 Hz might
cause issues with the fwd/rev power bridge.
Personally, I figure putting the tuner at the feedpoint is your best
overall option. You're up against a power issue, but maybe you need to
look at your actual power and frequency and impedance, and your existing
tuner will do ok. The limits on the tuner are a combination of current
in the inductors and voltage/current on the capacitors. A bit of
tinkering with an analysis program might show that it will work ok. The
mfr has to pick a sort of compromise power rating for all cases, and you
might not be in one of the corners (or, you can adjust your antenna a
bit to make sure).
A 2:1 power difference is only going to be a 1.4:1 voltage/current
issue. But I sympathize.. going from the 100-200W class tuner to the
kilowatt class is a BIG cost shot (hey, it's keeping me from running a
linear in the car.. I can rationalize the kilobuck for the amp, but
another kilobuck for the tuner too!... ouch)
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