----- Original Message -----
Sent: Thursday, January 22, 2004 7:44
PM
Subject: LF: 136kHz project
cancelled
Hi Dick
Get rid of your troubles immediately by building
the G3YXM or G0MRF designed 137 khz transmitters/amplifiers.
I have used a modified YXM design for
years and it has proved very reliable. There is no point re-inventing the
WHEEL
The components including chips are cheap. I have
replaced the output transformer 3C85 core with an old TV line output core and
it works just as well, I cannot detect any difference in RF output or heat
etc. I have always used a fan blowing across this transformer and the LPF
inductors plus another fan blowing across the MOSFET heatsink
compartment.
The amplifier runs very COOL, heatsink
just warm and the output transformer and LFP cold.
I use an ICOM 706 on 13.7 mhz and divide down to
the required 137 khz frequency.
I use 4 mosfets 75N10 type and with a suitable
PSU these are capable of nearly 1KW output. It depends what you have available
but try 12 - 20 Volts, the current could be up to 50 plus amps !!!!!!!.
Good Luck and be careful AVOID smoke
de Mal/G3KEV
