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Author Topic: Bifilar Cathode Choke ferrite rod material  (Read 2798 times)
N3JBH
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Posts: 2358




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« on: February 18, 2012, 05:55:51 PM »

Does it matter the mix for the ferrite rod when making a Bifilar Cathode Choke ? Any suggestions would really be appreciated... Jeff
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K6AER
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Posts: 3515




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« Reply #1 on: February 18, 2012, 07:50:06 PM »

Type 31 would be my first choice for 160-10 meters.
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KI4VEO
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Posts: 166




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« Reply #2 on: February 18, 2012, 07:58:21 PM »

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.
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KU3X
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Posts: 142




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« Reply #3 on: February 20, 2012, 11:43:48 AM »

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
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