[Amps] electronic switching

[2]

>  One problem with PIN's is if the RF voltage
>the PIN is subjected to in its "off" state exceeds the
>bias applied to the PIN to turn it off, the RF voltage will
>attemp to turn the PIN back on.
> In the limited ampunt of PIN diode work I've done here
>it seems the PIN "off bias" should be at least twice the
>applied RF voltage if any sort of SWR may be
>present. So in a 50 ohm circuit at 1500 watts you'd need
>about 5-600 volts reverse bias. 

**  1500W into 50-ohms =s c. 775v p-p.  To prevent a PIN diode from 
conducting at any point during the cycle, at least 800v of reverse bias 
is needed, provided the SWR was 1 to 1, otherwise the PIN diode could 
short.

>.  In a Hi-Z cicuit such 
>as a plate tank I.E. 2000 ohms, you'd need about 3500 volts.
>Thats a tall order.
>
**  indeed, Mark.
>
>
>On Wed, 18 Jun 03 13:10:12 -0700 2 <2 at vc.net> writes:
>> >Hi Rich,
>> >
>> >PINs are readily available to 1000Vpk and of course can be placed 
>> in series
>> >for higher voltage applications.  
>> 
>> **  Hello, Steve --  For 10kW @ 50-ohms, a minimum piv of 2000v is 
>> needed.
>> 
>> >Remember, a PIN is not a P-N junction
>> >device and doesn't really have a "PIV" rating...when biased OFF, 
>> its a large
>> >value resistor and when biased ON, it's a small value 
>> resistor....using
>> >power devices that can be biased ON with amperes of current, that 
>> resistor
>> >can become *really* small......-WB2WIK/6
>> >
>> >"Success is the ability to go from failure to failure with no loss 
>> of
>> >enthusiasm." -Winston Churchill
>> >
>> >> -----Original Message-----
>> >> From:	2 [SMTP:2 at vc.net]
>> >> Sent:	Tuesday, June 17, 2003 7:15 AM
>> >> To:	Dr. William J. Schmidt, II; on4kj; AMPS
>> >> Subject:	Re: [Amps] electronic switching 
>> >> 
>> >> >Well, we do..... there are diodes that will handle as much as 
>> 10kW....
>> >> but
>> >> >they are expensive.  Harris uses them in their gear...
>> >> >
>> >> **  What is the piv rating of such diodes, William?
>> >> 
>> >> >Sincerely,
>> >> >
>> >> >Dr. William J. Schmidt, II  K9HZ
>> >> >
>> >> >"Collector of Edison Wind-up Phonographs... Do you have one for 
>> me?"
>> >> >Email: bill at wjschmidt.com
>> >> >Alternate Email: wmschmidt at charter.net
>> >> >WebPage: www.wjschmidt.com
>> >> >
>> >> >
>> >> >
>> >> >----- Original Message ----- 
>> >> >From: "on4kj" <on4kj at skynet.be>
>> >> >To: <amps at contesting.com>
>> >> >Sent: Sunday, June 15, 2003 2:44 PM
>> >> >Subject: [Amps] electronic switching
>> >> >
>> >> >
>> >> >> Hello Folks,
>> >> >>
>> >> >> About steatite wafers used for band switching.
>> >> >> Why dont we see switching systems based on pindiode, for input 
>> ( 100 w
>> >> )
>> >> >> must be possible nowadays. Even for high output power !!
>> >> >> What say ?
>> >> >>
>> >> >> Jos on4kj
>> >> >>
>> >> >>
>> >> >> ----- Original Message -----
>> >> >> From: "Osten B Magnusson" <sm5dqc at algonet.se>
>> >> >> To: <amps at contesting.com>
>> >> >> Sent: Saturday, June 14, 2003 10:35 AM
>> >> >> Subject: [Amps] 572B's WARNING
>> >> >>
>> >> >>
>> >> >> >
>> >> >> >
>> >> >> > STAY AWAY FROM RICHARDSON ELECTRONICS, ENGLAND      
>> www.rell.com
>> >> >> >
>> >> >> > 572B's are sold here in Europe by different dealers, the 
>> tubes are
>> >> >> distributed by Richardson Electronics in England, and they 
>> claim that
>> >> it's
>> >> >> Cetron tubes manufactured for National. Sorry to tell, but it 
>> isn't the
>> >> >> truth - it's newly produced Chinese tubes re-badged by 
>> Richardsons as
>> >> >> National and also have ''Made in USA'' printed on them. So be 
>> careful,
>> >> >> before buying. I have been offered, not by Richardsons, but by 
>> the
>> >> >> distributor to get a full refund if sending the tubes back. 
>> Richardsons
>> >> >does
>> >> >> not even answer e-mails...
>> >> >> >
>> >> >> > This is part of an e-mail from a serious distributor in 
>> England:
>> >> >> >
>> >> >> >      >>Hello Osten,
>> >> >> >      >>Taylor is a brand name for RF parts but these can be 
>> re-badged
>> >> >any
>> >> >> type!
>> >> >> >      >>We have National 572B which are badged by Richardsons 
>> which is
>> >> >the
>> >> >> main
>> >> >> >      >>outlet for Eimac, but need not be Eimac !
>> >> >> >
>> >> >> > There are original Cetron NOS 572B's available here in 
>> Europe, have a
>> >> >look
>> >> >> at   www.clhi-fi.it   It's in Italian, but click on 
>> ''Surplus'' and
>> >> than
>> >> >> ''avanti'' to go to page four. There are no prices on the WEB, 
>> but in
>> >> an
>> >> >> e-mail they asked 500 ''euros'' for a matched pair, plus 
>> postage.
>> >> That's
>> >> >> totally USD 645 for a matched pair!!!   I know that there are 
>> also NOS
>> >> >> Cetron 572B's available in USA, but unfortunately we have to 
>> pay more
>> >> >> postage, customs, 25 percent VAT etc. so here we always try to 
>> buy from
>> >> a
>> >> >> European Community country, this was no customs and other 
>> extra charges
>> >> to
>> >> >> pay.
>> >> >> >
>> >> >> > Probably time to get all ''glass tubes'' amplifiers marked 
>> ''junk''
>> >> and
>> >> >in
>> >> >> the future only get amplifiers with ceramic tubes!
>> >> >> >
>> >> >> > 73 de Osten SM5DQC    e-mail:  sm5dqc at algonet.se
>
>
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Rich, AG6K, 805-386-3734, www.vcnet.com/measures