[AMRadio] interesting items


Geoff/W5OMR ars.w5omr at gmail.com
Wed Jun 27 08:33:24 EDT 2007


on the e-place...

item #290133329556 is four AM transmitters, including a Gross (that's
the brand, not a description) transmitter.

You'll have to go there to see the photos... but here's what the
description says:

Anyone know the guy, near Pittsburg, that's getting rid of these?
-Geoff/W5OMR
_____
See photos. This auction is for FOUR AM/CW Rack transmitters as
described below. These are pick-up only in Pittsburgh, PA.

The transmitter shown in the first 3 pictures is a “Globe King
500B”-based Homebrew Transmitter. This is a homebrew transmitter in a 5
foot tall rack. It has 5 decks in the rack: Original WRL 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 rest of the WRL Globe King 500B transmitter. The
modulation transformer is a Thordarson 300W Multi-match. It uses 3B28’s
in the power supplies. The 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.
Actually, 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.

The next picture shows the "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. The AC power wiring is kind of kludgy and would probably benefit
from changing over to a 3-conductor grounded line. It could also use new
HV connectors for safety, though it is working fine as-it-is. It was all
built by N3GWE. 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, as is Ed's modified Eico 722 VFO (shown in the next
pciture). The mods to the VFO are 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.

The next 4 pictures show a 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 if you want to use it. 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. 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.

Finally, the last picture shows GWE II. This is an AM-only TX in a
six-foot tall black wrinkle rack. It is bandswitching 80M and 40M only.
The final is a single 250TH driven and modulated by 6146s. This has a
good signal on 80 meters today. I have not tested 40 meters on it and 40
may need a little work. With N3GWE's handwritten documentation. This
uses an RCA mod transformer and I have a spare one that goes with it,
though the spare may not be any good.





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