[time-nuts] DATUM 9390 comments...

[Burt I. Weiner]

Eugene,

Those DAC numbers should be fine.  My two units are also 
9390-52054.  Having the built-in screen display is a nice feature.  A 
bunch of years ago I was involved in a pager watch system developed 
by Seiko.  The project eventually didn't pan out and they pulled all 
of the equipment from the various radio stations that carried the 
paging signals on their subcarriers.  Equipment that wasn't 
proprietary was sold and I bought four of the 9390-52054 
clocks.  They all had the year 2000 software up-grade.  I gave one to 
a buddy and traded one off to a local metrology lab for a lifetime of 
calibration and service on my Tek 494AP spectrum analyzer.  I 
maintain the remaining two for my standards associated with my 
off-air broadcast frequency measurement service as well as my Ham 
activities in FMTs.

http://www.biwa.cc/freqmeas.htm

http://www.k5cm.com/k6OQK%20FMT%20NEW.htm

During one of my adventures for Seiko I spent a couple of days with a 
field engineer from DATUM back when they were in Anaheim.  I learned 
a lot about these units from him. One of the nice features about the 
9390 series is that rather than being phase locked to the GPS system 
they're phase-steered.  The fellow explained that this made for a 
much smoother transition when switching birds and they are much more 
consistent in stability.  He explained that in the beginning they had 
problems with short and long term stability when they were simply 
phase locking the internal oscillator.  Supposedly the 9390 series 
was their top of the line product for timing and frequency.

Since they are relatively "old" units you may want to consider 
re-capping the power supplies and also replacing any electrolytics on 
the boards.  Replacing these caps can sometimes solve mysterious 
problems.  For sure, take a close look at the electrolytics and see 
if any are bulging or if the magic hair has come out of them.  About 
three years ago I replaced all of the electrolytics in my units on 
general principles.  I run mine on a UPS and about the only 
maintenance I really ever do is to check and set the DAC as necessary.

You will be very happy with your units.  Keep in touch and let me 
know how it goes.

Burt, K6OQK



>From: "W2HX" <w2hx at w2hx.com>
>To: time-nuts at febo.com
>Subject: Re: [time-nuts] DATUM 9390 Question...
>
>
>Hi Burt, thanks for the excellent information and your experiences with this
>model! I have to models, the -52054 and -52117
>The 52054 seems to see the SVs much more easily. The 52117 using the same
>antenna and antenna location sees nothing (I haven't tried moving the
>antenna to a substantially better location yet to see whats what). I wonder
>if they have different receivers in them? I have yet to open them up.
>
>Thanks for relating to me that this disappearing SVs is not uncommon. It is
>counterintuitive, but who knows what they were thinking when it was
>designed.  I did the master reset procedure quite successfully as the LAT
>and LON both reset to the numbers in the manual.
>
>My two dacs (on the two models) are at about 28,000 and 39,000 hopefully
>that is sufficient to stay in range of the DAC.
>
>Bottom line, thanks a lot for the info. Very helpful to know I am not alone!
>
>73 Eugene W2HX
>

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at att.net
www.biwa.cc
K6OQK