[AMPS] Re: Filament Chokes

[222WAS7]

OK here's the question......

What about an 8877 with separate cathode/filament on 6 meters?
I have seen with, and without, in published designs.  What do the gurus say?

73

Peter
VE3AX

measures wrote:

> >
> >> I was reading the HF amps section the other day, and was surprised to read
> >> the flat statement that the filament choke is not necessary in
> >> grounded-grid amplifiers at HF.  Or did I misunderstand?
> >>
> >> 73,  Pete N4ZR
> >>
> >That is true if you are talking about indirectly heated tubes with a separate
> >cathode pin(s). The old glass tubes still need one.
> >
> >BTW, I see lots of ridiculously high bids for B&W FC-15's and FC-30's on
> >E-Bay. Bear in mind that these do not cover 160 meters when you are bidding!
> >
> The 9uH fil. choke in the SB-220 works quite nicely on 160m.  To cancel
> the reactance of the choke, add approx 900pF to C2 in the 160m tuned
> input.
>
> cheers
>
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