I have done the same thing here......But used it in "reverse". I wanted to
find the plate load impedance of an amplifier. (Viewsrtar PT-2500). Tuned
the amp on all bands and logged the "dial" settings of the plate load and
tune caps. Disassembled the amp, with the tubes in the sockets and POWERED
OFF !!!......Set to the logged settings of the tuning and loading. Hooked
the MFJ 259 to the output jack. Wedged a piece of paper in the contacts of
the T-R relay.......Substituted some different values form the plate to
ground to obtain 50 ohm reading on the MFJ-259. Appeared to be very
accurate a test. Same resistor value for all bands. (One would expect).
Good luck on your project Lane....
73
Jim W7RY
-----Original Message-----
From: Jon Ogden <jono@enteract.com>
To: zeitler@ibm.net <zeitler@ibm.net>; amps@contesting.com
<amps@contesting.com>
To: <amps@contesting.com>
Date: Sunday, June 27, 1999 11:52 PM
Subject: Re: [AMPS] fine tuning amp pi-network
>
>>Anyway, in optimizing the L for the output pi-net what are the recommended
>>methods?
>
>HI Lane,
>
>Here's how I would do it:
>
>First of all calculate the "ideal" (theoretical) tank component values
>based on the tube's optimum load impedance and 50 Ohms and an appropriate
>Q. The load impedance (am I using the right term?) of the tube can be
>calculated using : Vplate/(Iplate*1.6) -> I believe 1.6 is the right
>"fudge" factor. Someone correct me if that's not right I forget the
>exact number.
>
>I would make up a tank coil based on those calculated inducatances. Then
>I would assemble everything into the amp. With the tube in socket (not
>powered mind you) I would connect a resistor of a value equal to the load
>impedance calculated above from the anode to ground.
>
>Then I would take my MFJ-259 attach it to the tank output and measure
>away. If tuned properly the tank will look like a "perfect" 50 Ohm
>match. Adjust caps and tank coil for optimum matching.
>
>This is the way I would do it. Others may have a better way.
>
>GL es 73,
>
>Jon
>KE9NA
>
>--------------------------------------------------------------------------
>The Second Amendment is NOT about duck hunting!
>
>
>Jon Ogden
>
>jono@enteract.com
>www.qsl.net/ke9na
>
>"A life lived in fear is a life half lived."
>
>
>--
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>
>
--
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