----- Original Message -----
From: "Tom Rauch" <w8ji@contesting.com>
To: "jeff millar" <jeff@wa1hco.mv.com>; <amps@contesting.com>; "William
Fuqua" <Wlfuqu00@pop.uky.edu>
Sent: Wednesday, November 01, 2000 12:58 PM
Subject: Re: [AMPS] DC Filaments???
> The only problem is with directly heated filament-cathodes and low
> bias voltage tubes, the voltage drop across the filament can be a
> significant portion of the bias voltage. That would mean the filament
> is not supplying equal current over the entire area of the filament.
Even with AC on the filament, the voltage between grid and filament
varies along the length of the filament at any instant in time. The
filament voltage varies very slowly compared to both the RF
carrier current pulses and most of the modulation envelope.
> That shouldn't hurt life, but it certainly could affect IMD and other
> parameters.
I can't see how DC could effect IMD. DC creates less variation
in filament to grid voltage than AC because it doesn't have the
peaks over RMS that exist with AC.
jeff
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