[Elecraft] KPA500 does not use "EBS", and doesn't have any associated bias noise

[Edward R Cole]

A side note to this topic for RF amplifiers, in general:

I have not heard of this "paper crunch" noise description, before 
this, but it's well known with VHF and up operation that one does 
want to remove bias during receive on many amplifiers due to "white" 
noise being generated.  Perhaps this is not detected from HF 
amplifiers because sky noise is much higher and it is not heard.

I initially ran a 50w modified 900-MHz amplifier on 1296-eme and 
making a quick connection did not bother with switching the keying 
line which enabled/disabled bias.  I was puzzled why my noise floor 
was 6-dB higher than normal (I monitor the noise floor in receive 
with a SDR-IQ set for maximum span (190-KHz)).  Someone replied to my 
e-mail comment suggesting that bias might not be set to cutoff.  That 
was the solution and once I connected up a TR line to key the amp for 
Tx (and unkey it in Rx) Rx noise was back to normal (sky noise at 
1296-MHz is in the region of 10K vs 20,000K at 28 MHz).

This is probably not related to the "paper crunch".

73, Ed - KL7UW
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