[time-nuts] Rapco 1804M - serial problems?

David J Taylor david-taylor at blueyonder.co.uk
Mon Oct 17 14:45:52 UTC 2011

> The data is nearly all good, so probably not a rs232 rate issue. Looking 
> at the transformations in the above data,
> / => ?
> 1 =>q
> , => <
> CR => =
> m => }
> they are all single/multiple bit flips in the top nibble of the 
> character hex value. Maybe it's a UART that has hickups.
> I couldn't find a schematic, but may be worth looking to see what's 
> connected to the RS232 tranceiver chip..


Many thanks for your investigation.  I can confirm that the device has a 
Z85230 serial chip, and I took a look at the soldering on the topside of 
the board, and it all looked fine.  I had wondered about taking the 
processor board out and checking the underside soldering, but that 
involved disturbing so much that I've ruled that out for the moment.

The box was supplied with a generic GPS puck antenna by the eBay seller, 
and it's not that sensitive so I've ordered a better puck antenna (for the 
moment, I don't want the complexity of an outdoor antenna) and when that 
arrives and I have a better GPS signal I'll visit the box again.  No 
urgency right now.

I have checked the 5 MHz using the RWM calibration of my R8500 receiver, 
and it's spot-on as near as I can tell which is likely good enough for me.

SatSignal software - quality software written to your requirements
Web:  http://www.satsignal.eu
Email:  david-taylor at blueyonder.co.uk 

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