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Re: LF: RE: pictures of my new 136kHz stn

To: [email protected]
Subject: Re: LF: RE: pictures of my new 136kHz stn
From: Scott Tilley <[email protected]>
Date: Mon, 01 May 2006 01:13:23 -0700
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Dick, Dave and LF Group

Using a design here with 4 FETs (W34NB20) in a module with the two pairs combined this nets about 900W with 37V input.
Now on the MO_ALFA we have 8 FETs in two modules of 4 arranged in pairs
of 2 combined for 2KW and when loafing on the 'stun' setting we're able
to get 1200W+ without much heating at all, in fact she runs very
cool(much more efficient then a single module running balls to the
wall)... At 2KW forced air is a must... Nothing paralleled and no
traditional LPF required as the Wilkinson does the job and provides some
port to port isolation.

We could push for maybe 3KW as the 8x400W PSUs are loafing still... But
after the Tesla display when we commissioned it at 2KW in my backyard
cooler heads prevailed...!
The highest voltage we can reliably push out a signal with without
'strange' events is 41V. However, I run lower at 37V as a nominal
safe choice.
I found the W34NB20 better in my application then the IRFP450...

73 Scott VE7TIL

[email protected] wrote:
In a message dated 30/04/2006 21:43:09 GMT Standard Time, [email protected] writes:
    Hi Dick, LF Group,
What power supply voltage will you be using for your new TX, and
    what RF power do you hope to get out with 4 times IRFP450?
73, Dave G3WCB IO91RM
Hi Dave / Dick.
If it helps: I converted on of my 250W linear amplifiers which used 4 IRFP450s to class D(ish) The power output went to 700W on 136kHz. I just replaced the input phase splitting transformer with the normal class D 4426 driver chip. I also used the same amp in Scotland at 300W on 73kHz to work Jim M0BMU and Derek G3GRO who were nr Lands End. PSU was adjustable 35 to 48V. Thanks David G0MRF

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