Re: Johnson MatchBox Answer

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From: Vic Rosenthal (rakefet@rakefet.com)
Date: Sun Jan 26 1997 - 17:45:28 EST


Craig J. Sterling wrote:
>
> Greetings,
>
> In my quest for the ideal tuner for QRP, I found a mint, pristine &
> just out of the box Johnson MatchBox at a local ham-fest. It's the
> small one with a meter and SWR bridge...$175.00...gulp!
>
> Question: WILL THESE UNITS TUNE THE WARC BANDS?
>
> Before starting the negotiation process, I better find out about it's
> tuning range since it's band-switching control ONLY indicates the
> original 5 bands...80,40,20,15 & 10M.
>
> Anyone have one of these boatanchors?

Craig,

I have one. The circuit is very well balanced is is excellent for use
with ladder line. It does not match as wide a range as the t-match plus
balun circuits that are common in present-day tuners, but provides
better attenuation for out-of-band signals. I can't guess about the
efficiency; maybe someone has tested it. The fact that you don't need a
balun should be a plus. As far as the WARC bands are concerned, it
depends on the particular mix of resistance and reactance that you
have. I use mine to match my full-wave 20 meter delta loop on 30, 20,
17, 15, and 10 meters (there is an imperfect match on 12). I had to
diddle with the length of the feedline to obtain this. I use it on 40
for 30 meters, 20 for 20, 15 for 17, 15, and 12; and 10 for 10.

Finally, I think $175 is high for this. $125 would probably be more in
line with prices that I have seen.

Vic K2VCO


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