From: Chris Wilson <dead.fets@gmail.com>
Date: Fri, 28 Apr 2017 14:29:23 +0100
Message-ID: <116328997.20170428142923@gmail.com>
To: DK7FC <rsgb_lf_group@blacksheep.org>
In-Reply-To: <59033D72.80705@posteo.de>
References: <1106627522.20170427150315@gmail.com> <5901FD30.5010902@posteo.de> <1907129228.20170428123626@gmail.com> <59033D72.80705@posteo.de>
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Subject: Re: LF: Varistor spike management
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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:chris@gatesgarth.com

 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:dead_fets@gmail.com