[AMPS] RF sensing

[Peter Chadwick]

Rich said:

>With RF switching. the amplifier's RF  relays can not begin transitioning until
RF is 
>present.  This is not good news.  

What about the situation where switching is done by PIN diodes? There must be a
finite time during which the transceiver and/or amp see a high VSWR, but this
could well be short enough that it doesn't matter - provided there's no funny
oscillations during it, which could give a key click effect each time the rx/tx
transition occurred.

You would also need to ensure that the switching took place at a low enough RF
level that a 'soft' word (such as 'electron') still had enough power to switch
it - probably meaning a 40 or 50dB range on the switch, in which case the
carrier leakage would probably hold it over. That shouldn't matter, though. 

Where the transceiver uses relay contacts to control the amp, you can get useful
speed up by bringing out the relay coil drive, and using that to drive a
transistor to switch the amplifier relay, rather than waiting for the internal
relay to close.

Although I have some suitably rated PIN diodes, I do have a certain (almost
certainly unfounded) suspicion about reliability.

73

Peter G3RZP







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