[TMC] TMC SBE-6 exciter

[Chris Kepus]

Duncan,
What a great acquisition for the AWA!  TMC ads from the 50s and 60s always
looked so cool with all their wonderful equipment, racks, and consoles, etc
etc. 
As a result of TMC's effective advertising and the GPR 90's great looks, I
now have a GPR-90 and have become interested in general GPR lore.

Not being familiar with the GPR 92, I have a lot of questions and I hope you
will find the time to answer them. :-)
How do you like using the GPR-92 (general operating impressions)?  How do
you rate the sensitivity, selectivity, and stability?  How do they compare
with the 90 (from an operator's viewpoint)?  Do you find the AGC for SSB
effective?  Any comments about the product detector and audio quality of AM
and SSB?  
TIA for any and all comments.
73 es HNY,
Chris
W7JPG 

-----Original Message-----
From: tmc-bounces at mailman.qth.net [mailto:tmc-bounces at mailman.qth.net] On
Behalf Of Duncan M. Brown
Sent: Thursday, January 01, 2009 8:11 PM
To: tmc at mailman.qth.net
Subject: [TMC] TMC SBE-6 exciter


Hello to the group!  I just discovered this list.  My first REAL SW
receiver (after a couple of Knight-kits) forty five years ago was the TMC
GPR-90 and I thought it was a great radio (wish I had kept it!)

I am now volunteering at the Antique Wireless Assoc. Museum.  A couple of
years ago we acquired a complete TMC station from an underground bunker of
the New York State Emergency Management Office. The station consisted of a
console with a GPR-92, MSR, FFR, & TIS-3; and a SBT-1KV transmitter.  All
the equipment had to be disconnected and brought up two flights of stairs
to get it out of the bunker. We reassembled everything at the AWA Museum
Annex and checked out the receivers, but are just now getting a chance (and
space) to work on the SBT-1KV.  I have the SBE exciter at home and have
been checking it out with the help of the SBE-8/9/10 manual (thanks John
Poulton !!).  I have it aligned and working now after fixing one bad coax,
intermittent switch contacts in the oven, and intermittent grounds on some
coils.

My question is that our SBE exciter is stamped with a model number "6".   I
have been told that there is no such thing as a SBE-6 and I was beginning
to think that maybe whoever stamped the model number on the unit just got
his stamp upside-down and it really is a SBE-9.  It does have the same SB
filters (FX-158 & FX-160) as a SBE-9 and looks like a SBE-9 (according to
manual IN-2008A).  But as I have been getting more intimate with the unit,
I have noticed some differences from the manual:
	1. This unit has no V128 (USB/LSB meter preamp). Under our chassis
there
are a couple of power resistors where V128 is in the manual.

	2. In the manual alignment instructions (p5-10) & schematic, there
are
listed 14 trimmer capacitors for the eight HF mixer crystals selected by
the "BAND, MCS" switch.  This chassis has 8 trimmer capacitors located next
to the 8 HF crystals and the silkscreened reference designators do not
aggree with the manual (though they are in the same number range).

	3. On the back of the chassis there are two BNC connectors marked
"USB
OUT" & "LSB OUT".  These are shown in the manual rear panel picture of Fig
2-5, but there is no other mention of them in the manual instructions,
parts list or schematic.

	4.  The manual says to adjust a variable capacitor (and it is shown
on the
schematic) on balanced modulator Z-107, but there is no (accessable)
variable capacitor on Z-107 of this unit (just a variable resistor).

I've notice many errors in the the manual, so possibly these are just
changes that weren't covered/corrected in the manual. Or maybe I have SBE-9
that is earlier or later than the manual.  The serial number on the "SBE-6"
plate is 17582.  The FX-158 LSB filter has a date code of "May 26 '64" and
the FX-159 carrier notch filter has a date code of "Aug 5 '64".  This is
the  only SBE that I have seen, so I don't have anything to judge by.  Can
anyone tell me if these are normal variations for production SBE-9s, or do
I have an oddball unit??

Thanks & 73,

Duncan Brown, K2OEQ
AWA Electronic Communication Museum
http://www.antiquewireless.org/


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