[Amps] Plate Choke Query

[Carl]

Delrin has a low melting point so that has to be considered. Ceramic forms 
are readily available and a combination of tape and Q Dope keeps the wire in 
place.

The old Dentron choke is 130uH using a 1" x 3" ceramic form and #25 wire.

Carl
KM1H




----- Original Message ----- 
From: "Jim Garland" <4cx250b at miamioh.edu>
To: <amps at contesting.com>
Sent: Saturday, September 14, 2013 9:09 AM
Subject: [Amps] Plate Choke Query


>            I'm making a plate choke for a duoband 80m-160m amplifier and
> want to solicit any comments. The tank compartment is space-limited, and 
> at
> most I can have 4 inches of winding length on a 1 inch diameter form.
> Ideally, I'd like to have even a shorter winding length and smaller 
> diameter
> form. I'm thinking 150-200 uH would be satisfactory, but if 100 uH would
> work, that would be better. Four inches of close-wound 24 AWG wire on a 1
> inch diameter form should give about 200 uH. I'll be using either a teflon
> or delrin rod for the choke. I don't have experience with delrin, but I 
> like
> the fact that it's not as slippery as teflon (and hence easier to 
> stabilize
> the coil winding). I've heard delrin has good RF properties, but don't 
> know
> that for a fact. (I know nylon can't be used.)
>
>            The plate impedance of the amplifier is about 700-750 ohms, and
> 200uH is about 2.2K reactance on 160m. I have no idea about the Q of the
> choke, but it will probably be 100 or a bit more. I'll bypass the cold end
> of the choke with several 1000pF caps. Since the choke is only for use on
> 80m-160m, I don't think self-resonances will be a problem. Any comments or
> suggestions?
>
> Thanks!
>
> Jim Garland W8ZR
>
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