Without looking at the best (amp) itself, but knowing that the 8877 has an
indirectly heated cathode, no filament choke is needed, only some bypass
caps. The heater (filament) only "indirectly" heats the ctathode to cause it
to emit electrons, that's its only role. This means it's not part of the RF
circuit. The only time a filament choke is used in on indirectly heated
cathodes.
Will
-------Original Message-------
From: Paul Christensen
Date: 03/04/05 09:30:45
To: AMPS
Subject: Re: [Amps] Alpha 77Dx -Adding Grounded Grid Filament Choke
Whoops - my mistake. The 77Dx's 8877 does not tie the cathode and filament
together. One side of the filament is grounded. Would it still be
advisable to add the common-mode filament choke anyway?
-Paul, W9AC
----- Original Message -----
From: "Paul Christensen" <w9ac@arrl.net>
To: "AMPS" <amps@contesting.com>
Sent: Friday, March 04, 2005 9:22 AM
Subject: [Amps] Alpha 77Dx -Adding Grounded Grid Filament Choke
> Last week's discussion of GG filament chokes got me thinking about
modifying
> my Alpha 77Dx which I believe, ties one side of the filament to the
cathode.
> I would like to cut this tie and user a R.F. Parts Co. FILRFC-30 filament
> choke.
>
> http://www.rfparts.com/choke.html
>
> I am assuming that a combination of HV-rated 0.01 uF and 0.1 uF disc caps
> could be used to bypass each side of the filament tube terminals to
ground.
> Anything else I should consider before doing this? Thanks!
>
> -Paul, W9AC
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
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