[amsat-bb] Re: need plans for 70 cm preamp
G0MRF at aol.com
Tue Feb 26 00:27:28 PST 2008
In a message dated 26/02/2008 03:39:11 GMT Standard Time, rlasso at zianet.com
Need recommendations for plans for an easily constructed homebrew 70cm
mast mount preamp with built in RF sense TR switch (VOX controlled). I
will not be running more than 50 watts in New Mexico or possibly 100
watts in CA when I move there.
thanks and 73, Robert W6RQR
That's really tough Robert. Unless there is some sequencing going on inside
your radio then any RF sensing circuit will mean that the relay contacts
will be hot switched on transmit.
A couple of seriesed limiting PIN diodes may help, but with 100W across them
for a few 10s of milliseconds even that may not be enough to protect the
On the preamp side, the design that was published in the journal in August
(2006?) works well and has a noise figure of 0.5dB and is a no tune design.
Details are on g0mrf.freeserve.co.uk
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