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Re: [Amps] filament supply options

To: jeff millar <wa1hco@adelphia.net>, stevengrant98@yahoo.com
Subject: Re: [Amps] filament supply options
From: Bill Fuqua <wlfuqu00@uky.edu>
Date: Mon, 26 Apr 2004 09:52:33 -0400
List-post: <mailto:amps@contesting.com>
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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