From: "James Moritz" <j.r.moritz@herts.ac.uk>
Organization: University of Hertfordshire
To: rsgb_lf_group@blacksheep.org
Date: Tue, 12 Jun 2001 16:44:07 +0000
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Subject: Re: LF: RE: 73kHz tests tonight
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Dear Andy, LF group,

>What sort of TX is it? 

It uses the Decca circuit configuration, together with my existing 
60V PSU and modulator. It uses a single PA rather than 3 in 
parallel, so the circuit is re-designed for about 2.5 times as much 
current. It has 4 x STW34NB20 MOSFETs. 

Only real problem so far was getting the gate driver to work - even 
with both sections of a TC4427 driver IC in parallel, the drive 
waveform had rather slow edges when feeding the 4 large-
geometry FETs in parallel, so I ended up adding a "booster" with a 
complementary pair of discrete MOSFETs in a circuit adapted from 
one of IR's application notes. The driver transformer now seems to 
be the limiting factor, but is OK for the time being.

Efficiency seems to be around 90%, as we have come to expect. 
The "guard" circuit seems to do it's job. Once I am sure the circuit 
has a reasonable life expectancy I will post some more details.

Cheers, Jim Moritz
73 de M0BMU