Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: Anode inductor - why? Posted: Wed Jul 12, 2006
Joined: Fri May 19, 2006 5:01 am
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?
Post subject: anode inductor - whyPosted: Thu Jul 13,
2006 6:13 am
Joined: Fri Feb 17, 2006 12:07
Location: London UK
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