[Amps] Help constructing filament choke for pair of 3-500Zs on 6 m

Paul Baldock paul at paulbaldock.com
Fri Jun 28 18:23:58 EDT 2013


The standard ferrite rod that you use for 10-80M works fine. I've 
moded quite a few amps for 6 M and I remove half the turns from the 
original choke. This reduces the inductance by a factor 4 and works 
great for 6M.

- Paul



- At 10:20 AM 6/28/2013, Carl wrote:
>Do the math.
>
>A reactance of 10 times the input impedance of the tubes is 
>sufficient to have the choke "invisible" to the input RF.
>
>Carl
>KM1H
>
>
>
>
>----- Original Message ----- From: "John Farber" <kg6i at comcast.net>
>To: <amps at contesting.com>
>Sent: Friday, June 28, 2013 12:02 PM
>Subject: [Amps] Help constructing filament choke for pair of 3-500Zs on 6 m
>
>
>>I could use some info on constructing a suitable filament choke for 
>>a pair of 3-500Zs on 6 m, my current amp project. My gut feeling is 
>>a standard choke design for 80-10 would not be correct due to too 
>>much inter-winding capacitance would effectively bypass the RF 
>>around the choke and into the filament transformer. Use of the 
>>standard ferrite rod as a coil form/inductance magnifier would also 
>>be excessive. So what are folks using in this type amp?
>>Thanks, John
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