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Anode inductor - why? - RF Cafe Forums
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Charl
Post subject: Anode inductor - why? Posted: Wed Jul 12, 2006
9:36 am
Colonel
Joined: Fri May 19, 2006 5:01 am
Posts: 25
Location: Netherlands
Hello folks,
I am still
working on my digital tube radio, and came across this setup in the
schematic of a Sherwood 3000 radio:
Both tubes are limiter
stages. The IF is 10.7MHz. I estimated the value of the inductor based
on size and core.
What does the anode inductor do? The thing
that really puzzles me is that it is tunable (I have the radio sitting
next to me). There is a turnable ferrite slug in there. What could it
possibly be tuned WITH?
Thanks,
Charl
Top
nubbage
Post subject: anode inductor - whyPosted: Thu Jul 13,
2006 6:13 am
General
Joined: Fri Feb 17, 2006 12:07
pm
Posts: 218
Location: London UK
Hi Charl
It is to resonate
roughly at 10.7MHz with the combination of stray capacitance around
the tube base plus the anode to suppressor capacitance of the EF89 first
stage plus the input capacitance of the following stage. Note the latter
will be magnified somewhat by Miller Effect
Since many of these
values can only be approximately estimated, the inductor is usually
adjustable
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