[AMPS] 3CX800

[Rich Measures]

>
>
>> Rich says;
>> 
>> >?  Unless one can tolerate the attn loss during Rx, one still needs a 
>> >high speed relay at the attn.  
>> 
>> No way! You have a c/o relay at the antenna. Antenna connects to common.
>> Amp goes to one contact (my preference is for n/c); Rx auxiliary antenna
>> input goes to n/o contact: the switch is moved on the xcvr to use the aux
>> ant input. No extra switching needed - just interlock or whatever to
>> ensure that the relay on the ant doesn't hot switch.
>> 
>> Reason for 'energise to receive' is that when you've switched off, the
>> antenna is connected to the plate of a big tube. That tube is more likely
>> to withstand high static discharges than a relatively small semiconductor
>> device.
>> 
>> I did design a receiver protection unit some 30 odd years ago for a marine
>> receiver: we protected against a discharge of 1.5 microfarads charged to
>> 15kV straight into an rx front end which used tuned circuits stepping up
>> to a JFET. Even so, I'd rather disconnect the antenna with the realy
>> switching.
>> 
>> 73
>> 
>> Peter G3RZP
>> 
>> 



Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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