[time-nuts] Trak 8810 Station Clock

[Bob kb8tq]

Hi

It’s a pretty good guess that a device from that era ran a “downconverter” head end.
They had a full RF front end out at the antenna and fed some sort of IF frequency 
back to the unit. Various outfits had approaches to how to do it. The net result is that
the head end is pretty specific to this or that box (or at least series of boxes). 

Since it’s an entirely different approach to getting things done, directly replacing the 
head end with a modern module is going to be tough. The normal alternative is to 
build up a downconverter. Some do it from scratch, others find a similar unit 
somewhere and modify it to do the job. The big trick is to find out exactly what the
main box is looking for ….

Bob

> On Jul 20, 2019, at 12:30 PM, Chris Quayle <syseng at gfsys.co.uk> wrote:
> 
> Hi,
> 
> Bought one of the above gps clocks at a radio rally last
> Sunday. Looked ok on the outside, but severe corrosion
> from a leaked backup battery inside. Cleaned all that up,
> replaced some caps and a few other parts on the psu board
> and now at least partially working. All the menus seem to
> work, no signal or power failures, leds blinking 1pps on
> the main board and all rear panel outputs seem ok.
> 
> Problem is that the gps engine fails to initialise in post.
> Can't find any reference for this model on the web.
> Did find an 8820 manual, but that has a different mainboard
> and the serial port command set doesn't work on the 8810,
> though characters are echo'd.
> 
> This looks like very early gps module and no info on the
> web for it. Read one page that suggests that this module
> might be similar to the Magnavox MX4200 and perhaps a
> connection to Truetime ?, but no other info found.
> 
> The board says "Magnavox GPS Engine", with a part number
> label 900578-803-3. Data codes on the devices are 1990-1992,
> so must be a very early model. Question is, are there any
> later gps modules compatable with this device in terms of
> command set, or perhaps a known working board for sale, or
> a manual somewhere ?. There's a neat output board that takes
> a 10 Mz input, to provide 4 of each 1, 5  and 10Mhz sine
> wave outputs on the back panel, useful in itself, but it
> would be good to have this working, to add to the collection.
> 
> Thanks,
> 
> Chris
> 
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