Date: Mon, 13 Aug 2012 21:12:51 -0400
From: "Joe Subich, W4TV" <lists@subich.com>
Subject: Re: [Amps] ALC Overshoot FTDX-5000
What is the time constant of the Powermaster? Then only clear way to
measure the sub 5 ms spikes is with a scope.
73,
... Joe, W4TV
## I should try the scope. I have 4 of the power master watt meter’s
and any of them will easily show the 3% ripple of any of my 4 x Drake L4B
power supply’s. With any cxr over 700 watts, and when slowly increasing the
PO control on the MK-V or 1000D, each bar on the bar graph would slowly
light up. Then when fully lit up, the next bar would slowly light up, and so on
and so on.
## slam it with a 1200 w cxr.... and sure it sez 1200w on the
digital...Numerical display,
but the last segment was.. dithering. It was not on solid nor off, it was
pulsing !
## I hooked up my old yaesu scope and instead of a solid green bar... it wavy
on top and
bottom. I could clearly see the ripple on the HV supply. 8 x 200 uf caps.
## with amp off... and 1000-D xcvr cranked to 290 watts out, and scope padding
changed so full height display with 290 w, I get a flat bar on the scope.
## replaced caps with higher value ones and ripple vanished on the scope.....
and
no more dithering segments on the power master display units.
## IF your xcvr does have gross amounts of overshoot, the cheap and easy way
to fix
that is to just put 9 v dc across a 50 k pot.... and feed the NEG output to
the ALC jack on the
xcvr. Set po on xcvr for max. Tweak 50 k pot for desired PO. No more
overshoots.
The –3 to –6 vdc from the 50 k pot is fed directly into the alc jack... and
sits there at all times,
rx and tx. You don’t have to develop alc voltage in the normal fashion. End
of overshoot problem.
Jim VE7RF
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