[Boatanchors] 1930's era cw transmitter

[Roger Ruszkowski]

Fellows,

The other things going on was tubes had a much higher 5 - 10K
output impedance than todays transistors or cathode followers.

It was 'simpler' to match the antenna, balanced line, output link, 
output tank, and tube finals all as one lump sum, where the link 
varied to give a match. You built in enough fixed capacitance to
get the variable link coils to provide a match.

It was a mechanical solution that you could build from
available parts.

As coax had not yet been invented, (WWII stuff) open lines
were the norm.

Roger AI4NI


-----Original Message-----
From: Rob Atkinson <ranchorobbo at gmail.com>
To: Brian Carling AF4K <bcarling at cfl.rr.com>
Cc: boatanchors <boatanchors at mailman.qth.net>
Sent: Mon, Jun 3, 2013 7:53 am
Subject: Re: [Boatanchors] 1930's era cw transmitter


On Sun, Jun 2, 2013 at 8:47 AM, Bry Carling <bcarling at cfl.rr.com> wrote:
> Another popular (but tricky) circuit from the 1930s was the LINK COUPLED RF 
final.
>
>

It was "popular" because the feedlines of the day were balanced
parallel wire.  What you are probably really referring to is the swing
link output.  Since just about everyone (not exactly sure when
unbalanced line became common but I think it was after WW2) used open
wire line, a balanced link coupled output was pretty much a standard
arrangement.   The Meissner 150B from WW2 used a pi network because it
was originally made to work into a random length wire (unbalanced) in
the field.  That's about the earliest rig I know of using a pi network
output (but my knowledge is far from complete).

you don't say what feedline you were using.  If you were trying to get
the link coupled to work directly into 50 ohm coax then of course
you'd have difficulty.  It was designed to work with twisted pair or
parallel line to either a balanced dipole or a floating link input to
a balanced tuner like a EFJ matchbox (but with its link connected to
the twisted pair).

73
Rob
K5UJ
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