[Amps] 200-ohm tank and "un-un" in HF amp design?

Jim W7RY w7ry at centurytel.net
Sun Oct 20 09:31:44 EDT 2013


What kind of power?  What plate voltage and current on the tube?

73
Jim W7RY


On 10/20/2013 12:51 AM, Jim Barber wrote:
> Assuming adequate core/wire sizing and airflow, can anyone think of a 
> solid reason *not* to design a legal-limit HF amp output tank for 200 
> ohms, then use a 4:1 "un-un" transformer to step it down to 50?
>
> I'm curious because doing so would bring the loading cap requirement 
> for a 4000-ohm plate impedance down to under 1000pF at 1.8 mHz, which 
> can be done with a large air variable alone.
>
> Note: Yes, I know it *has* been done already, but I'm asking for 
> opinions as to whether you think it should be.
>
> Thanks and 73,
> Jim N7CXI
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