[Boatanchors] 1930's era cw transmitter

[Howard Holden]

Link coupling is (or can be) efficient. I occasionally run a pair of 211s in 
a Hartley oscillator a la 1929 QST,  (expect 35-40% efficiency), 200W in, 80 
W out with link coupling, two links in series one on either side of the tank 
coil, with a 500 pF tuning cap in series from the links to ground. You just 
have to be willing to tinker with it a bit, it's rarely plug-n-play. But 
that's part of the fun.

Howie WB2AWQ/7



-----Original Message----- 
From: Bry Carling
Sent: Monday, June 03, 2013 2:40 PM
To: Rob Atkinson ; mac
Cc: boatanchors at mailman.qth.net List
Subject: Re: [Boatanchors] 1930's era cw transmitter

I guess then a Pi Network just ha sa whole lot of "inherent easiness" 
(grin!)

Yes, for those desiring period authenticity I think it would be a blast to 
build something link
coupled, designed only for a specific band, and antenna, etc., or use it 
with an external
tuner, which expands the number of componnets in the transmitter setup and
complicates things. Plenty of guys made good contacts using link coupling, 
but who
knows how much power some of them were actually  feeding to their antenna.

YMMV

Bry

On 3 Jun 2013 at 14:04, mac wrote:

From:           mac <w7qho at aol.com>
To:             Rob Atkinson <ranchorobbo at gmail.com>
Date sent:      Mon, 3 Jun 2013 14:04:22 -0700
Copies to:      "boatanchors at mailman.qth.net List"
<boatanchors at mailman.qth.net>
Subject:        Re: [Boatanchors] 1930's era cw transmitter

> No inherent difficulty with feeding coax from a link but the
> tank/link
> coil arrangement has to be designed with just the right turns ratio
> if
> fixed or, alternately, with a variable arrangement (swinging or
> rotating link, series cap, etc.) configured to provide a match over
> a
> range of load impedance values.
>
> Dennis D.  W7QHO
> Glendale, CA
>
> **************
> On Jun 3, 2013, at 4:53 AM, Rob Atkinson wrote:
>
> > 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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