Bifilar Cathode Choke ferrite rod material

[N3JBH]

Does it matter the mix for the ferrite rod when making a Bifilar Cathode Choke ? Any suggestions would really be appreciated... Jeff

[K6AER]

Type 31 would be my first choice for 160-10 meters.

[KI4VEO]

Matt Erickson (KK5DR) recommends an inductance value between 30 and 300 microHenries to be sufficiently robust to cover 160 thru 10M.  His writeup on "Building your own tube-type amplifier" is well done and has some excellent construction information and techniques.

The ferrite mix does not appear to be a critical factor.

Visit his web site http://kk5dr.com/ampbuilders.htm and send him an e-mail.  Matt is a great guy and is very willing to share his knowledge of amp construction.

On his suggestion, I changed my plate parasitic choke to a more stable design.  No longer is it the old, typical wire wrapped around the 100 ohm resistor.  And it is much more stable on 10M.

[KU3X]

Don't use a rod. Get an FT 240-43 ferrite core and wrap 10 bifilar turns of the proper size wire on the core. This is a W2FMI design.
You can use 43 or 31 material, either one offers more choking reactance than a rod will offer you.

KU3X