[Amps] Filament Choke Inductance

2 2@vc.net
Fri, 3 Jan 2003 17:23:54 -0800

>Can anyone tell me what inductance do I need in the filament choke for a
>3CX3000A7 for 80M.  

The SB-220 uses 9uH.  This even works well on 160m if c. 900pF is added 
to C-out in the 160m tuned input pi-network.  

>I built one back in the mid 90's and had to wind one
>around 3
>ferrite 1/2" rods in order to keep the AC out of the tube(or was it to keep
>the RF out of the transformer?).  I have some filament chokes wound made
>with 10ga wire and they measure 45uh. I guess I could always put 2 of these 
chokes in
>series but they would take up more real estate under the chassis.
To save real estate and greenbacks. float the 3cx3000A7  filament xfmr on 
a G-10 insulating plate, bypass all leads/terminals to the core, and put 
a 3a, bifilar choke in series with the primary.  


cheers, Bob

-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,