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

[Jeff Blaine]

Didn’t the QRO 2500 have this format?

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Jim W7RY
Sent: Sunday, October 20, 2013 8:31 AM
To: amps at contesting.com
Subject: Re: [Amps] 200-ohm tank and "un-un" in HF amp design?

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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>

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