[Amps] filament supply options

[Bill Fuqua]

    This reminded me of something. Sometimes while listening to your own 
signal (CW) in your shack you may notice some  hum. This may not be real. 
What happens (QRP Guys notice this a lot when using direct conversion 
receivers) is a lot of the signal in the shack may be radiated by the power 
lines or other wires and not the actual feed line or antenna.  And this RF 
may be modulated by the switching on and off of the rectifier diodes in 
various power supplies thus it will modulate the Carrier that you receive 
in the shack. The solution is to put RF bypass capacitors across the 
rectifier diodes or don't worry about it.

73
Bill wa4lav


At 11:36 PM 4/25/2004 -0400, jeff millar wrote:
>If Voltage across the filament caused bias/linearity/gain variation 
>problems, then all amplifiers with AC on their filaments would have hum on 
>the transmitted signal.
>60 Hz on the filament varies very slowly compared to RF...its almost 
>DC...so DC doesn't hurt...except for hypothetical wearout issues.
>
>jeff, wa1hco
>
>Steven Grant, W4IIV wrote:
>
>>thanks for the tip...your correct...wouldnt using DC cause a bias 
>>condition that may cause linearity problems?.......steven
>>
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