[Boatanchors] The ORIGINAL Hammarlund Four-Twenty Transmitter

[Mike Clarson]

Bill: Maybe this will help. I do not know much about the particulat
transmitter, but I have some data on the B&W coils the unit aparently uses.
You mentioned the JEL and MEL series. There were other variations. The
"Junior" inductors for use up to 75 watts input, came in the JEL series,
with link on the end, the JCL series with link in the center, and the JVL
series with a variable link. The "Baby" inductors (up to 25 watts input)
came as the MC series, with a center tap; the MEL series, with an end link;
and the MCL series with an end link. No "Baby" units with an adjustable
link.--Mike, WV2ZOW

-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net]On Behalf Of williamhf
Sent: Thursday, May 26, 2005 9:32 AM
To: boatanchors at mailman.qth.net
Subject: [Boatanchors] The ORIGINAL Hammarlund Four-Twenty Transmitter


Gentlemen:

The Hammarlund Four-Twenty Transmitter manufactured only during 1947 and
1948
seems to be fairly scarce among Boatanchor afficionados.

 I acquired one recently. (I built the xmtr from a Kit in 1948; traded
it in a year or so later.)

I'm getting older now and everyone knows that old folk's memory banks
are kinda worn
and there's a certain amount of slippage.

But here's my memory of how the Final Tank Coil was tuned to the Antenna
output terminals.
My memory says that there was an *_/ADJUSTABLE/_* LINK in the middle of
the Final Tank Coil.

I have what seem to me to be fairly crisp memories of removing the top
cover and adjusting
the Link in, or, out to get more power to the Antenna output terminals.
I used a $4.95 Amphenol Folded Dipole
Antenna on 10 Meters and it was the only Coil for the four ham bands the
Four-Twenty covered.

Recently, I have "pinged" for 5-pin RF TankCoils on "Boatanchors" and
the Hammarlund Reflector and
happily have acquired some B&W MEL and JEL 5 pin coils.  Now please
understand that I
have not yet got the Four-Twenty refurbished/rehabilitated but and am
working along on that project.

But all these JEL and MEL  coils have either end or center  *_/FIXED
/_*output links.

Why am I writing to Boatanchors? I seek to learn if there's anyone among
the Boatanchor
ranks who happens to own a Hammarlund Four-Twenty Transmitter in_*
ORIGINAL*_
condition?
And/OR-------------Is there a ham out there who may not own the
transmitter but is confident
that he knows how the Antenna terminals were coupled to the Final Tank Coil.

Here's a direct quotation from the Hammarlund Four-Twenty Owner's Manual:
/*"Plug-in Coils are used in the Output Circuit of the Powr Amplifier.
These plug-in coils are accessible by removing the top cover of the
transmitter and are
 equipped with an output coupling arrangement with an adjustable tap to
permit matching
the output of the transmitter to any of the conventionally used antenna
feeder systems."

*/Doesn't that Quote make one feel scure and certain that somehow when
you reached inside the top
cover you could move something which affected the coupling of the Final
Amplifier circuit to
the Antenaa Output terminals?

Two current owners of the Hammarlund Four-Twenty that I have contacted use
FIXED LINKS in their RF output circuitry.

I am convinced that there was an adjustable link furnished by Hammarlund
in the ORIGINAL
Four-Twenty Transmitter.
/*
*/*E*xamination of the 4-20 Schematic shows a peculiar symbol (to me)
for the output link of
the Final Tank Coil System. (I don't know a simple way to reproduce it here)
Whereas the Final tank coil itself is shown connected to two definite
points, the Link
is  connected to two definite points which are the Antenna Input
Terminals- BUT, BUT
The link has an extra partial "loop" which is shown on the Schematic as
just free-ended,
that is, not fixed to a connecting point. The Electronics Draftsman was
showing
a different-than-conventional Link symbol.

The Photograph at RigPix      http://www.rigpix.com/hammarlund/four20.htm
 shows an upper central  front panel control marked  "Amplifier Tuning"
but it controls the variable capacitor shunted across the  Final Tank
Coil, not a Link coil.

Any help or clues will be greatly appreciated. Thanks, guys.

Bill
W4DSR
Florida