[Boatanchors] Link coupled output?

[Dave Brown]

Steve,
I dont know the details of the B&W hardware you mention (suppose I 
could go plough thru the ads in the back of some of my old ARRL 
handbooks- wish I had the time!!) but I expect the link IS adjustable.
 That being the case then impedance of the load is not going to be all 
that critical-have you tried loading it into a standard 50 ohm dummy 
load yet?  Link adjustment will of course be part of the tuneup 
process- aiming for recommened PA stage operating conditions, while 
achieving the expected level of output power. Start with the link well 
out - get the tank resonant and and go from there.
You should probably get a good indication of whether you are in the 
ballpark-impedance wise- by just grounding one end of the link for 
initial testing, taking output from the other end against ground. (Try 
a ground on either end -you should get similar results if all is 
symmetrical in the PA stage)
But you may need a balance to unbalance xfmr in a final setup if the 
link output is just a pair of terminals and has no other components 
included. Ratio depending on what you find from initial tests-start 
with 1:1 and work up.
73
 Dave, ZL3FJ

----- Original Message ----- 
From: <StephenTetorka at cs.com>
To: <boatanchors at mailman.qth.net>
Sent: Friday, September 09, 2005 1:57 AM
Subject: [Boatanchors] Link coupled output?


> Hi all:
>
> I am trying to determine what characteristic impedance transmission 
> line to
> use with my homebrew 1948 transmitter.
>
> The unit uses two 1625's in the RF deck with a B&W type JVL link 
> coil for the
> output to the antenna terminals.
>
> In this arrangement, the B+ goes into the center tap of the coil 
> with one
> section of a two gang variable across each half of the coil from 
> center tap.
>
> The antenna terminal output comes from a separate 3 turn coil 
> located in the
> middle of the coil between the two halves..thus obtaining the RF 
> coupling.
>
> This arrangement is typlical of 1940's - 1950's rigs.
>
> Would appreciate any assistance in this matter.
> Regards,
> Steve
> WA2TAK
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