[Amps] HV for Ameritron QSK-5PC

[k6xx at juno.com]

I'll take both sides of this discussion!

1. The HV is sufficient for proper operation. Remember, these are PIN diodes, not switching diodes. The wide intrinsic region slows down their switching speed so RF will pass through--or be blocked. Even momentary voltages/currents exceeding the biasing level. That's the magic of PIN diodes. Like a relay, they can carry/block HF, but are limited in how fast they may toggle ON/OFF. But their toggle speed is a few orders of magnitude faster than a mechanical relay, of course.

2. The MFJ QSK switches are poorly designed. I have both the internal and external versions. Both versions have blown up multiple times. Neither has ever seen even 1500W (maybe 1200 or so). SWR over 1.5:1 at over 1000W exceeds their capability. I lose the HV switching transistors, not the PIN diodes...


73 de Bob, K6XX

Date: Mon, 13 Jul 2009 22:14:18 -0400
From: "Joe Subich, W4TV" <lists at subich.com>
Subject: Re: [Amps] HV for Ameritron QSK-5PC
To: <philc at texascellnet.com>, "'k5jv'" <k5jv at kingwoodcable.com>,	&qu
ot;'Amp
	Reflector'" <amps at contesting.com>
Message-ID: <8065C86008A246DC9F7AFEFA0165C460 at laptop>
Content-Type: text/plain;	charset="us-ascii"


> My stand-alone QSK-5 has a HV of 380 volts.

That's only enough reverse bias for a matched load in a 
50 Ohm system.  With 2:1 SWR the peak of the RF crest is 
almost 800 V (535 - 540V RMS). 
 
73, 

   ... Joe, W4TV 


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