----- Original Message -----
From: "jerome schatten" <romers@shaw.ca>
To: "Amps" <amps@contesting.com>
Sent: Friday, January 01, 2010 5:37 PM
Subject: [Amps] 813's on 160.
>
> I'm looking at getting my venerable 813's amp to play on 160. Works fine
> on 80 -> 20, but I'm thinking I need to increase the plate choke bypass
> and the output coupling caps in value.
>
> The plate choke is a Hammond 1515x (.25MH) which hopefully will be OK
> (~2.83k @ 1.8mhz). But, is that enough reactance or not?
That should be OK with an adequate bypass.
> Both the plate cap and the choke bypass cap are at present .001/5kv WW2
> micas.
Those are waiting to become firecrackers. Replace with a .001 disc ceramic.
I'm thinking of replacing them with .1/5kv Glass Mike 'ASG
> 104-5M's. Are these appropriate for what I'm planning? I couldn't find
> any info on them -- they live in my junk box, thus the choice.
Those may be better for a scope and not RF, dont know for sure. Id use a
.01 disc cap in parallel with the .001.
>
> Finally, I'll need to add more inductance to the pi. The inductor that's
> in there now is a nice big mother roller inductor (square copper wire
> wound on a ceramic form - about 16uh., horizontally mounted). I was
> thinking to add a vertically mounted additional inductance wound on a
> piece of 1.5" pvc pipe to make up the needed 'L'.
A toroid takes up a lot less space.
Do I need to worry
> about the 'sense' of the winding being the same as the original if they
> are mounted in different planes as described?
Yes
Carl
KM1H
>
> Thanks for any insight on these questions!
> jerome - VA7VV
>
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