Re: ProgRock not working #progrock
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Hi Robin, Graham, Sid, all
There have been a lot of posts on this topic and being on vacation at the moment I kind of lost track of where this got to.
ProgRock should work as advertised on the web page and documentation. If it doesn't, something is wrong.
A GPS disciplined ProgRock should be accurate well within 0.05ppm (note that this parts-per-million specification means that the absolute precision in Hz, scales with frequency). This is what I have seen in all my tests and has been verified by other constructors too. To get the system working does require:
1. GPS correction threshold register must he understood properly. To get maximum precision requires setting the GPS correction threshold register to zero (default is 5Hz).
2. The 1pps signal needs to be at 5V logic level. Many GPS units have 2.8V logic level outputs and need level conversion. This can be done with pull-up resistors with some care and some inevitable degradation in noise immunity. Or with proper level conversion.
3. The GPS pulse needs to be long enough for the processor to handle it properly. I'm not actually sure what the minimum is. Many common modern GPS modules have 0.1 second positive pulses, these work fine. Some modules with very short pulses e.g. 1 microsecond wouldn't work.
Note that the QRP Labs QLG1 GPS kit http://qrp-labs.com/qlg1 was used in all my testing and works very well. It has 0.1 second positive pulse and it has proper logic level conversion. The QLG1 has a very accurate 1pps specified with max 11 nanosecond r.m.s error.
If the ProgRock isn't performing as expected then something is wrong. That could be an electrical problem (soldering problem, dead component etc); or some issue with the characteristics of the 1 pulse-per-second signal input.
If there's any question I haven't covered here, please let me know.
73 Hans G0UPL
On Mon, Jul 15, 2019, 16:31 Robin Midgett <K4IDC@...> wrote: