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[AMPS] Plate choke

To: <>
Subject: [AMPS] Plate choke
From: (km1h @
Date: Fri, 27 Mar 1998 14:09:26 EST
On Fri, 27 Mar 1998 13:41:29 -0500 (EST) (Paul
Hrivnak) writes:
>        The choke cofiguration I used when I was at Drake in 1995 when 
>did the new L85 single tube 3-500Z ( now cancelled ) is as follows
>(1) 1" dia x 6" ceramic steatite form unglazed
>(2) wound with #22 nypol magnet wire for a total of 110 turns. There 
>was a
>split silver plated slip ring in the middle of the choke at 55 
>essentially I had two 55 turn windings on the form connected in 
>series. The
>ring was used for a soldering point.
>(3) Soldered a 50pf 10Kv disc, HT57 or equivalent capacitor between 
>TOP(tube connection) and the middle of the winding. This cap must be 
>high quality and capable of high currents and dissapation capability. 
>disc cap was 1" dia and 3/8" thick with leads mounted at 180 degrees
>apart.( This was a custom made unit )
>(4) This placed the resonance of the choke at 5.5Mhz (gap between 
>(5) Coated the choke with dielectric varnish etc
>(6) In line choke for 160 meters in series with the plate choke, 1/2" 
>dia x
>2 1/2" long with 30 turns for the first layer and another 30 turns for 
>second layer wound on top in the reverse direction.
>        We did not try this at power levels more than 1000watts , but
>worked very well for all the bands from 1.8 to 29.7 Mhz for a single 
>running at 3400vdc. This was exhaustively tested with the usual 3 100? 
>watt metal film resistors wound with 4 turns #16 tinplated buss wire 
>the vhf suppressor. We also used 4 different new tubes with the same
>                                Regards  Paul
>Bramco Palstar Inc.
>Piqua, OH  45356

Sounds like a lot of work and expense for just a single 3-500Z  amp IMO.
Why not just copy the AL-80A/SB-1000 design and be done with it? They DO
work in case you were not aware of it. 

Or is there Engineering Revenue involved here?

Sometimes it does not pay to re-invent the wheel. It is also a shame that
Drake found themselves priced out of the market...again.

I'm just wondering Paul, how many times are you going to flog that same
basic single 3-500Z  design? Hammond,  Viewstar, AEA , Vectronics, Drake
and I may have missed a few.

Cheers  Carl  KM1H

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