Yet Another KPA500 Question

[Bill - K6WLM]

Since there does not seem to be any schematic diagrams posted yet for the KPA500 I am wondering what the 270 volts from the power supply is used for.  My guess would be that it maybe used for the T/R swithching and the higher voltage insures faster switching but that is just a guess.  Don or anyone do you know?
 
Thanks & 73,
Bill - K6WLM
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[Richard Squire - HB9ANM]

You are right, Bill: the 270V are required for the T/R switching  through the PIN diodes.

73 - Richard

Bill - K6WLM wrote

Since there does not seem to be any schematic diagrams posted yet for the KPA500 I am wondering what the 270 volts from the power supply is used for.  My guess would be that it maybe used for the T/R swithching and the higher voltage insures faster switching but that is just a guess.  Don or anyone do you know?

[Don Wilhelm-4]

Bill,
I don't know about "faster switching", but normally in a T/R switch, the
diodes must be reverse biased with a DC voltage higher than the peak RF
voltage to be encountered.

73,
Don W3FPR

On 8/7/2011 3:25 PM, Bill wrote:
> Since there does not seem to be any schematic diagrams posted yet for the KPA500 I am wondering what the 270 volts from the power supply is used for.  My guess would be that it maybe used for the T/R swithching and the higher voltage insures faster switching but that is just a guess.  Don or anyone do you know?
>  
> Thanks&  73,
> Bill - K6WLM
>
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[Guy, K2AV]

Yup, 270v times .707 = 191v to get max RMS RF properly blocked.  Using E
squared divided by R, gives you 728 watts blocked by 270 VDC on diodes for a
well matched 50 ohm load. Various tricks increase this range, but that
explains the order of magnitude.

73, Guy.

On Sun, Aug 7, 2011 at 4:26 PM, Don Wilhelm <[hidden email]> wrote:

> Bill,
> I don't know about "faster switching", but normally in a T/R switch, the
> diodes must be reverse biased with a DC voltage higher than the peak RF
> voltage to be encountered.
>
> 73,
> Don W3FPR
>
> On 8/7/2011 3:25 PM, Bill wrote:
> > Since there does not seem to be any schematic diagrams posted yet for the
> KPA500 I am wondering what the 270 volts from the power supply is used for.
>  My guess would be that it maybe used for the T/R swithching and the higher
> voltage insures faster switching but that is just a guess.  Don or anyone do
> you know?
> >
> > Thanks&  73,
> > Bill - K6WLM
> >
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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