[time-nuts] PTS 250

John Ackermann N8UR jra at febo.com
Fri Dec 15 08:50:20 EST 2006

I have pinouts of the BCD connector at 

Note the big red warning sign -- the first 250 I had was in some way 
goofy and that led me down an erroneous path for the pinout.  The pinout 
described for the 160 is correct for all the units (at least the ones 
below 500MHz).

Dunno about the OCXO; I don't think any of the units I have came with an 
internal oscillator.

Note that there's an interesting variant of the 250 -- option "SX51" 
which provides very low phase noise from 0.1 to 25 MHz; basically, it 
adds a divide-by-ten on the output.  You select the low noise mode by 
selecting (I think) the 0.8Hz line and dividing the rest of the 
frequency you entered by 10.  So, entering 100.000 000 0 gives you 
100MHz output; entering 100.000 000 8 gives you 10MHz output.  The 
divided output is a square wave, so might require filtering depending on 
the application.

Manuals are available from PTS, though they don't necessarily have a lot 
of useful information.  PTS doesn't seem to be too interested in having 
anyone but them work on the units, so there's not a lot of circuit-level 

Hope this helps.


Rex wrote:
> Does anyone have information on the PTS 250 Synthesizer?
> I bought one on eBay. Seems to work pretty well, except the OCXO is not
> great. I have a hard time even setting it below about 5x10^-9, but
> output seems accurate and functional if I use external 10 MHz.
> Do cal and service manuals exist for these things? My searches haven't
> found any.
> Does anyone have the pin-out for the external BCD 50-pin connector? I
> found a document for a PTS 160 and the programming pins seem to match as
> far as the 10 MHz digit, but the PTS 250 must have more pins that are
> used for the 100 MHz digit. Anyone know how the high order is programmed
> through the 50-pin connector?
> Thanks for any information you can share.
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