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LF: 500 khz TX

To: "rsgb" <[email protected]>
Subject: LF: 500 khz TX
From: "mal hamilton" <[email protected]>
Date: Mon, 21 Jul 2008 11:09:59 +0100
Reply-to: [email protected]
Sender: [email protected]
My 500 khz TX is made out of recycled components from the junk box.
1940 xtal in osc
IC osc chip/IC divider chip/IC driver chip/FET PA class E, then on the drain side
1940's ceramic inductor (tinned copper wire) out of a TU5B tuning unit, 1950's tube TV line output core, rewound for impedence matching FET/50 ohms.
LPF using unmarked cores similar to FT200 type.
FET out of an old marine tx 1960's vintage.
CCT board for chips reworked from an old pre used board.
Ferrite chokes in V +  line from old smpu, decoupling capacitors and misc items, small heatsink and fan from junk box.
Psu for chips 12 regulated, ex surplus
Psu for FET rebuilt using ex surplus high capacity capacitors, not regulated
The finished package looks neat and tidy and is totally reliable, and no SMOKE
The secret to avoid smoke in class E  is to get the FET drain matching network spot on to avoid voltage/current spikes during switching. If designed properly you will be in the ball park and just need minor adjustments ie adjusting coil tappings while making observations on a 'scope.
I used components that I had lying around in junk boxes and the cost was NIL.
This is the TX that I used on 500 khz to work VE1ZZ and RW3ADB on normal CW.
73 De Mal/G3KEV
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