[GreenKeys] Dovetron Tempest MPC-1000T II

[Roy Morgan]

On Apr 23, 2010, at 11:19 AM, Michael O'Day wrote:

> I found a Dovetron Tempest  MPC-1000T II on ePay, but the  
> description I found online says the "T" means it is for "secure"  
> operations with power & optical filters to prevent radiation, and is  
> not for casual or business use.


Michael,

The not for casual or business use is baloney.  The parts about power  
and optical filters is right.  The Dovetron Tempest units work just  
FINE for casual or business use, as a couple of list members have  
posted.

> My question is: can this work for me at home ( I also see it has no  
> high-level power supply ) or is it too specialised for the average  
> ham application.

Yes, it can work for you at home.

The "T" stands for "Tempest", which in turn stands for "... a U.S.  
government code word that identifies a classified set of standards for  
limiting electric or electromagnetic radiation emanations from  
electronic equipment."
(See: http://www.eskimo.com/~joelm/tempestintro.html )
...  Bruce Gabrielson, who has been in the TEMPEST biz for ages, has a  
nice unclassified general description of TEMPEST  (at http://206.102.92.130/ses/papers/TEMPEST/Whatis.html 
  - this link does not work for me at the time I'm writing.)

Basically is is a collection of methods to keep signals from inside  
the equipment from being detected at some distance. A normal teletype  
setup with non-tempest equipment might be eaves-dropped upon from  
perhaps a few hundred feet away, or even much more if conditions are  
right. (that's an uninformed guess, NOT based on any experience)

The basic differences between a Tempest Dovetron and a normal one are  
that the Tempest unit has:
- no loop supply ("high level": 120 volts at 60 ma or so)  (BUT, I  
understand that the winding on the transformer that would supply the  
loop current IS there, just unused.)
- low level signals in and out
- BNC connectors for most or all signal connections
- An effective power line filter
- A screen over the cross pattern tuning indicator to keep signals  
inside
- (I think) certain small differences in the way frequencies are set  
or selected, or in the range of tone frequencies themselves.

So, you'd need BNC connectors to hook the thing up.
IF you have Model 15 or Model 28 type equipment that runs on and sends  
out high level loop signals, you'd need a way to convert the low  
voltage signals to high level signals and vice versa and a loop  
supply. Many quite simple circuits are available, you can build the  
gadgets yourself.  More complicated interfaces are available and have  
been described, and have had circuit boards available with parts  
lists, software and such for the teensey computer used.  If you are  
going to use a computer, you don't need anything special at all.

Roy


Roy Morgan
k1lky at earthlink.net
529 Cobb St.
Groton NY, 13073
Home: 607-898-3607
Cell: 301-928-7794