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Re: [Amps] SB-220

Subject: Re: [Amps] SB-220
From: Jim <>
Date: Wed, 24 Mar 2021 17:47:49 -0500
List-post: <>
Why do you need more L?
On what band or bands?

Jim W7RY

On 3/24/2021 9:46 AM, Joe wrote:
Need advice,

I am assuming some of you here are also on the Heathkit HF Amps E -Mail list. So I won't go into the long drawn out story here unless asked to do so if needed.

I re-built this old SB-220 practically from scratch. And changed a lot of stuff to make it better. But one change it has been determined, has made it in the Need of needing more "L" in the output network.

That of course if even possible would be some major surgery to say the least. Trying to think of how I can add some more "L".

At 2 AM last night I had a thought. How about like an old Drake VFO!? Drakes varied the "L" in their VFO's not the "C" as most others did.
And they varied it by inserting a ferrite bar into the coil.

Research says that inserting Ferrite into a coil will increase the amount of "L" the coil has.

I wonder if I could cheat and do the same on the L7 coil of this amp?
Get some ferrites like on a plastic threaded rod and insert them into the coil.

What Mix of Ferrite would be best for such an application?

And anyone thoughts of possibility of success?


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