[Amps] Plate Choke Issue

[Jim Thomson]

Date: Thu, 4 Jan 2018 18:38:47 -0500
From: AJ <iamfromcanadaalso at gmail.com>
To: amps at contesting.com
Subject: Re: [Amps] Plate Choke Issue

<Interesting that Henry had a 20 uh choke for 20,15,10. That seems to be
<where it blew apart. 

> ##  His  larger choke really requires 2-3  x  4700 pf ceramic bypass
> caps. His smaller choke should have its uh increased to 50 uh.   The
> smaller choke should ideally use  1-2  x  500 pf doorknob style
> bypass caps, like a  HT-50 or HT-58 series, which are available in 5
> kv..and also 7.5 kv.    

<This would require me to add another relay at the feed point if I
<understand you correctly.


<A flash over to the chassis through the ceramic insulator to the ss
<bolt is possible, it was excessively long and reused. I have ordered
<some ceramic bolts to eliminate that possibility.


<Sincerely AJ___ VE3HJ

##  The henry radio setup was a dogs breakfast.   They originally used
3 x 150  ohms,  at 5 watts each,  resistors in parallel + a few turns of strap..for the parasitic
suppressor.  Later versions used just a single 1 inch wide, and thick, chrome plated strap
coil for the suppressor.  Last version had no suppressor at all.  The 3x3 tube does not require a
suppressor !  Their  2 x piece plate choke setup was changed a few times.   The 20 uh  coil
was wound with 18 ga wire.  The 180 uh coil was wound with, I think, 24 gauge wire. 

##  No 2nd relay required with the   2 chokes, when using different values of bypass caps. 
The 500 pf ones are a better bypass on the upper bands.  The 4700 pf  disc ceramic types,
are a better bypass on the lower bands.     Any residual RF that gets past the respective plate
choke being used at the time, will  route to the respective bypass cap that functions better. 

##  The 8 K ultra  used 3 x 4700 pf caps  +   2 x 500 pf doorknobs, all in parallel, at the base of the
larger 180 uh choke.   20 uh choke was in series, and at right angles to the large choke.  Base of small
choke was  mounted to top of big choke, via an  aluminum L bracket.  A modified HV solenoid was used
to short out the larger choke, when amp used on 20-10m. 

##  The bypass capS at the base of the plate  chokeS  is not a critical issue. Your 5000 pf is probably ample.   

## Either use a shorter SS bolt for mounting the chokeS, or better yet, ur idea of using ceramic bolts.

Jim  VE7RF