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[AMPS] Tank coil question & other stuff

To: <amps@contesting.com>
Subject: [AMPS] Tank coil question & other stuff
From: wrt@eskimo.com (Bill Turner, W7TI)
Date: Sat, 05 Dec 1998 12:11:28 GMT
On Fri, 4 Dec 1998 10:40:34 +0000, Steve Thompson
<amps@txrx.demon.co.uk> wrote:
<snip>
>Should do - Often the accuracy on Z meters goes out a bit at 1000's ohms
>so it's also worth doing it the other way round - replace the tubes with
>equivalent R/C combinations and look for 50 ohms looking into the
>antenna socket. 
>
>Steve
______________________________________________
The MFJ-259 antenna analyzer works very well for this.  With the amp
off, connect a 1/2 watt resistor equivalent to the tube's impedance
from plate to ground, then connect the MFJ to the output connector and
set it to the frequency desired.  If there is a relay in there, either
activate it or bypass it.  Tune the input and load caps until the MFJ
is seeing 50 ohms and there you are.  Works like a charm.  Don't
forget to remove the resistor before you turn on the amp or you'll get
a demonstration of how well a 1/2 watt resistor dissipates a couple
thousand watts...  :-)

73, Bill W7TI


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