From: Wes Stewart on Fri 12 Aug 2005 10:09

On 12 Aug 2005 06:30:47 -0700, "Tim Shoppa"
wrote:

I'm fixing up some older ham transmitters. 811 or 6146 finals, etc. in
the 50-200 watt class.


The idea behind the multiple section windings on these chokes is the
prevention of unwanted resonances.

Absolutely. A self-parallel-resonant inductor above its
resonant frequency will appear as a CAPACITOR.

Here is an example of a solenoid wound choke that uses different
winding lengths and diameters to place resonances outside the range of
operation:

http://www.qsl.net/n7ws/RF_Choke.jpg

Excellent photo quality there, Wes. Also, it amused me to see
so MANY sections on that RFC assembly! :-) I've seen quite a
few and "dipped the plate, peaked the grid" on many an HF
transmitter of olden times using such RF chokes.

I see no theoretical reason why ferrite loaded chokes cannot be used
as long as all of the design caveats are observed.

I can only add that the Micrometals *free* toroid calculator
incorporates approximate self-resonant frequencies in their
program's calculations. Excellent program for toroidal inductor
design...can't beat the price! :-) www.micrometals.com

Problem is, if this is a restoration kind of project similar to
old automobile restoration, toroidal forms won't do...just
weren't many in the old transmitters of the 1950s and before.
Anything of the same construction type is going to be an
expensive special-order thing now. :-(