[AMRadio] FS: 1930's and Homebrew AM Rack Transmitters


Don Merz n3rht at yahoo.com
Sun Jun 24 13:05:36 EDT 2007


FOR SALE: AM RACK TRANSMITTERS. E-mail n3rht at yahoo.com
for pictures and more info.

“Globe King 500”-based Homebrew Transmitter. This is a
homebrew transmitter in a 5 foot tall rack. It has 5
decks in the rack: 500B on top, speech amp, PP 811A
modulator, modulator supply and RF deck supply. The
key to this transmitter is the stock WRL 500B RF deck
(bandswitching 160-10 meters). The rest of the rig is
homebrew. But the circuit very closely follows the
original WRL 500B transmitter. The modulation
transformer is a fine-sounding Thordarson 300W
Multi-match. Uses 3B28’s in the power supplies. Rack
has been repainted and looks great with stainless
steel rack hardware. The mod deck has a cool windowed
panel with a door that opens to allow access.
Electrically, the transmitter is in good shape and
working--I’ve had it on 80 meters. It sounds very
good. I started to re-do the AC wiring to the various
decks and it is done, but still needs some tweaks
(like power switching!). The modulator deck had a bad
KV meter on it. I have a replacement meter for it, but
you need to build the correct multiplier resistor to
go with it. But you don’t need that meter to
operate--in fact, you could just eliminate the meter.
The only other thing that you may want to add is a T/R
relay. The 500B RF deck has a good, strong 4-400A in
it instead of the WRL-specified 4-250. The 4-400A is
loafing. The speech amp section was re-built by a
prominent Pittsburgh-area AMer and now sports a
compressor that can be switched in or out. With
original WRL Globe King 500B manual and some builder’s
handwritten notes. Pick-Up only in Pittsburgh, PA.
$625

GWE III AM Transmitter. This is in a 5 foot wooden
rack--very pretty with many matching meters. It uses
plug-in coils and puts about 120 watts. This seemed to
be working perfectly when I bought it but then
discovered a strong parasitic in the exciter. This was
fixed and the TX tests out good on 40 meters. No other
bands were tested. Needs AC power rewired using
3-conductor grounded line. It could also use new HV
connectors for safety. It was all built by N3GWE, Ed
Mantick. It was purchased by me in September, 2002
after Ed needed to sell it due to the onset of health
problems. Final: 812, Exciter: 6AG7’s driving 807s,
Modulator: 45s driving 809s, Power Supplies: Solid
State. Ed’s original documentation goes with it. This
uses Ed’s modified Eico 722 VFO. This rig uses plug-in
coils and a full set is included. $450 with coils and
modified Eico 722 (N3GWE Modified Eico 722 VFO notes:
Modifications include 6AH6 in place of 6AU6 and power
supply changed to full wave rectifier using a better
transformer. Repainted nicely with black case. Looks
good. Working perfectly and quite stable after 20
minutes.) Pick-up Only In Pittsburgh, PA.

Gross CB-80 transmitter. This is the only one of these
transmitters that has survived--there are no others
anywhere on Earth. This is a 1936-vintage 5-foot high
rack transmitter for AM and CW covering 10 through 80
meters with plug-in coils. It has a 42 crystal osc
into a 6L6 buffer driving an Eimac 35T in the final.
The modulator is a pair of 6L6's. I think it is all
original looking, though it may have some very old
mods that I can't tell from original. The one
unoriginal appearing thing about it is the RF ammeter
in the antenna matching section, which is definitely
not original--though it looks very close. Also, the
antenna matching section has been basically gutted and
will have to be rebuilt. The matching section
originally had two caps and some coils in it. But only
the caps remain. This rig has the optional meter panel
with 4 surface-mount Gross-logo'ed meters that plug
into various spots on the rig with 1/4 inch phone
plugs. The one coil installed in this thing probably
isn't right--it's a EFJ edgewound type. So you should
plan on building a set of coils for it. I have most of
the original documentation including schematics. The
documentation is very fragile but I also have
photocopies. The rack is made for this rig and each
chassis can be slid out on metal flanges. It has the
original paint, Gross name tag and looks pretty sharp
for its age. Naturally, this is pickup only in
Pittsburgh, PA. If you want something absolutely
unique and one-of-a-kind in your shack that connects
you to the first golden age of ham radio in the
1930's, then this will be quite a conversation piece
for you. This rig appeared in CQ Classics calendar in
1999. $750.

1939-vintage PP 250TH open rack TX with pp 810
modulator and 1930’s UTC kit speech amp. The exciter
is a Gross CW-55 (the only one known to exist--it is
featured in the 2007 CQ Classics calendar). This
vintage transmitter is in the classic open rack
style—the rack is home made of riveted steel
angles—the shelves are wood. The PS on the bottom deck
may need some help from an external PS--it does not
look beefy enough to run the whole rig--exciter, the
RF amp and modulator. The speech amp is a separate
unit—it was a 1930’s UTC kit. It’s in 2 ventilated
cabinets—one for the speech amp PS and one for the
speech amp itself. I believe it uses PP 6L6’s.
Beautiful transmitter from the first golden age of ham
radio. $975.

Package Deal: Take all 4 rigs in one load for $2,350.

Contact Don, N3RHT at n3rht at yahoo.com. Please pass
this along to anyone you think might be interested.
Date: June 24, 2007




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