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Re: LF: Varistor spike management

To: DK7FC <[email protected]>
Subject: Re: LF: Varistor spike management
From: Chris Wilson <[email protected]>
Date: Fri, 28 Apr 2017 14:29:23 +0100
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Hello Stefan,
28 April 2017


They go bang when run as 2 amps in parallel with the W1VD combiner.
They then even blow the Varistors to kingdom come. I will try with the
combiner into my big water cooled dummy load, to see if the energy at
close down is from the loading coil / antenna. Without combining Jay's
original, cheap as chips FQA34N20L 200V LOGIC N-Channel MOSFETs work
fine. I have 1500pF and 10 ohms low inductance in series, drain to
gate, 1 per pair of FETs.

http://www.gatesgarth.com/FQA34N20L.PDF


Thanks Stefan, very few UK domestic properties have 3 phase,
unfortunately ;)


Best regards,
 Chris  2E0ILY                          mailto:[email protected]

 My part time LF grabber is at http://www.chriswilson.tv/grabber.html

> Hello Chris,

> These FETs are a good choice :-) You still manage to make them dead? And
> your supply voltage is 50V? That's not ideal. You can use 320 V directly
> from the mains, no heavy transformer needed, just a ferrite transformer
> on the RF side, to decouple the RF signal from the mains.
I was running >> 1.5 kW on 137 kHz (WSPR-15, no problem, not even in 100% 
> TX mode) with just 4x IRFP460A, which are not as good as yours. So i 
> don't really understand why you need a combiner at all. The 900V types
> would be fine for a 3-phase PA running at 560 V DC in a H bridge 
> arrangement. A nice thought :-)

> 73, Stefan






-- 
Best regards,
 Chris                            mailto:[email protected]


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