[Amps] SB-220

Jim jimw7ry at gmail.com
Wed Mar 24 18:47:49 EDT 2021

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?
> Joe WB9SBD
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