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

To: <w7ry@centurytel.net>, <amps@contesting.com>
Subject: Re: [Amps] 200-ohm tank and "un-un" in HF amp design?
From: "Jeff Blaine" <keepwalking188@yahoo.com>
Date: Sun, 20 Oct 2013 09:27:35 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
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@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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