Message-ID: <000001c382db$4ebf1460$5967fea9@p4o2b7>
From: "Ian Kyle" <ianj.kyle@virgin.net>
To: rsgb_lf_group@blacksheep.org
References: <AAEBLFEBLAPDIHJAGBICGEHFCDAA.g4wgt@talkgas.net>
Date: Wed, 24 Sep 2003 13:31:35 +0100
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Subject: LF: Re: Output Power.
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Hi Gary,

Easy to measure power at 136.  I use  " V squared over R"  in a dummy load
consisting of four wirewounds in series/parallel and measure the peak
voltage with an very ordinary "cooking"  chopped beam 'scope.
Same system used to calibrate the current meters,and as the basis for a
"scope-match" unit.
A 'pick-and-shovel' way of looking for match is to set up the TX for a given
power into the dummy (say 25W) and note the input DC current. Leave the
settings alone and put the antenna on. Adjust tune and/or match to get the
same current. You'll be in the park - if not exactly in the Directors Box.
I have given up on the BK having tried Jims mods and found that ANY
departure from the manufacturers component values banjaxes either voltage or
waveform or both at the drive stage, and now intend to simply use  the PSU
and two of the MOSFETS in push-pull into a tuned cirrcuit and drive them
with a commercial 10W audio chip good to 120KHz that my "technical adviser"
GI1PHF found whilst clearing up his garage - thus maintaining my policy of
minimum expenditure.
Have been running captures pretty well every night for the last few weeks
without getting anything other than a reduction in free disc space.
Have fun.

Ian GI8AYZ/MI0AYZ