Re: RF Chokes


From: Alan Kaul (
Date: Wed May 25 1994 - 03:30:57 EDT

Hiya, Jeffrey: Here's a possible solution. Radio Shack catalogs list a
10uh choke. Obviously, you can use that one where specified. But buy a
second one, and count the turns! Now wind half as many turns in a
similar size wire around the body of the choke -- soldering the new wire
to one end of the axial lead, and making certain you wind the new wire in
the same direction as the old winding (you want to wires to ADD, not to
subtract). Remember, the axial lead where you soldered the new wire CAN
have to solder to the end of the wire that you added. The core has some
magnetic properties, so it is not easy to calculate the size of the
coil. If there is doubt, then solder TWO 10uh chokes together (get the
windings in the same direction for phase) and make due with 20uh instead
of 15, under the theory tis better to have more than less.
Once upon a time, I built a QST 1976 rcvr project called ''THE HERRING
AID FIVE'' which was a 5-transistor, 40-M, varactor-(sort of)-tuned, DC
rcvr which used Radio Shack 10uh choke and added several turns to it for
the frequency determining coil. It worked (I still have it--it <<almost>>
still works, only not very loud and takes a big signal to be heard!!).
GL, and 72, 73 de alan

                     [<Alan Kaul, W6RCL>]

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