[Amps] Best source for Gigavac GH-1 ?

[Jim W7RY]

Jim
Can you tell me why sequencing is a requirement? I have found that the 
RF never flows (6 ms after the tranciever control circuts energise)until 
way after the relays and cathode bias has switched which as you have 
pointed out is  3-4 ms.

Thanks
73
Jim W7RY


>> In researching the subject during the past year, I've looked at the 
>> relay
>> circuits of a number of commercial amplifiers. Most seem to treat T/R
>> switching pretty cavaliearly, without adequate protection for the 
>> relays. In
>> my own design (the circuit mounts on a 3"x5" PCB), I've tried to 
>> prevent any
>> situation that can damage the contacts. This involves several 
>> precautions:
>> (1) sequencing the amp so the output relay, bias switch, and input relay
>> operate sequentially in that order, after allowing for the relay closing
>> times and contact bounce. (2) Having an RF "lockout" sensor that 
>> prevents
>> the amplifier switching sequence from beginning if RF is present on the
>> input line. (3) Having an RF "lockon" sensor that keeps the relays 
>> closed so
>> long as RF is present. My new amplifier completes its T/R switching 
>> in 4 mS,
>> which is suitable for QSK speeds up to about 60 wpm, far beyond it's
>> builder's capabilities.
>> 73,
>> Jim W8ZR
>>
>>
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