[Milsurplus] Yet more on the TCM....

[Kenneth G. Gordon]

On 6 Jul 2017 at 7:37, David Stinson wrote:

> From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
> Subject: [Milsurplus] Yet more on the TCM....
> 
> >I wonder how many of these transmitters are "out there" and even 
> >more, how many are being
> > used on the air?
> 
> An "educated guess," based on what
> we've seen of the fate of mil rigs heavier
> than a TCS:  Probably less than a couple of dozen
> are "out there,"  meaning they could be found by
> a collector and acquired.

Yes. That is about what I figured too... too bad, in my opinion, but on the other hand, who 
today would want a 70+ year old transmitter which is much bigger than a shoe-box? Only 
fools like me, I guess. Some of us appreciate the technological history and the efforts of the 
OT. Most don't.

>  A fortunate few are in garages
> or storage buildings.  The others are rotting in wet
> basements or leaking barns.  All are awaiting the
> "around tuit" that will likely never come.

Yes.

> That makes your project to ressurect that fine
> transmitter all the more important.

I agree.
 
> > The more I read from the manual about this
> > transmitter (thanks a HEAP, Nick!!!), the more
> > impressed I am with the design.
> Amen.  In the light of today's tech, these folks were
> working with "stone knives and bear skins."  But
> they accomplished marvels with them.

Yes. No computers, not much more than a "slip-stick" and lots of imagination.

Well, I have "blown up" the schematic. Mine is now 11" wide and around 2 feet long. As I 
mentioned yesterday, I found and corrected what I consider to be a really egregious error. I 
am hoping there aren't any more subtle ones hidden in there, but in any case, I can get 
around any there may be.

I am also going to "blow up" the wiring diagram. That one will also be 11" wide, but from the 
looks of it, it will be more than 4 feet long. It is rather "dense".

Also, I was wrong when I said it used blocked-grid keying: in point of fact, the keying circuit is 
cathode keying of the VFO and at least one of the buffer/multipliers, while the finals use fixed 
bias. And it is keyed by the relay. There are very detailed instructions on adjusting that relay 
in the manual. Yet, using that relay (which is also an antenna-change-over relay) the system 
would be a full-QSK system. Nice!

Also, according to the manual, the antenna impedances it matches are from 5 to 50 ohms. 
The manual even recommends a short end-fed wire antenna, resonant at 1350 kHz. (!!)

The transmitter is not really much bigger than a Globe King 500, and actually weighs less 
than that rig.

I do wish I had the outer cabinet for it. Maybe someone here knows where there is one? If I 
can't find one, I'll cover the sides and back with sheet aluminum painted with black wrinkle. I 
had thought about building a wooden "cabinet" for it, but that would look strange, so I'll have 
to think about that a bit more.

I am going to contact the local club today and tell them that I am going to buy it. I hardly think 
anyone else would want to "waste" the effort to get it in operation.

I am really looking forward to putting it in shape.

What fun!!!! :-)

Ken W7EKB


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