[hpsdr] New T/R Switch for >100W without external blocking voltage.

[Phil Harman]

Hi Kjell,

Congratulations on a great idea!  The usual DC to DC converter that is need 
to generate the high voltage to provide sufficient attenuation for the PIN 
diodes can generate a lot of noise and spurs.

With your idea the more power you run the more bias voltage you generate - a 
very elegant solution.

73 Phil...VK6PH

-----Original Message----- 
From: Kjell Karlsen
Sent: Sunday, May 18, 2014 4:27 PM
To: hpsdr at lists.openhpsdr.org
Subject: [hpsdr] New T/R Switch for >100W without external blocking voltage.

***** High Performance Software Defined Radio Discussion List *****

Hi All.

I have uploaded 2 files to HamSDR. One is an update of the schematic for
ApolloRev4 and one is a 100W T/R Switch without any external blocking
voltage.

Using an electronic T/R Switch at power >50W normally needs an external
voltage of 150V or more to give enough isolation for the RF signal to the
RX. When I worked with Apollo, I discovered that by using the negative
voltage detected by one of the diodes in the switching path to the RX, it
was possible to get better attenuation of the RF to the RX during TX. This
detected voltage is the peak of the RF and added to the +12V, the blocking
voltage is around 70V at 50W.

For higher power levels, a higher voltage is needed. By using a voltage
doubler, the detected voltage is >200V and this is sufficient for a 150W
T/R Switch.

By using components with higher ratings, it may be possible to use this
principle also for higher power levels.

73, Kjell.

-- 
Sendt med Operas e-postklient: http://www.opera.com/mail/
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