Re: ProgRock not working #progrock

Hans Summers
 

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:
Hi Graham & the group,
The issue Sid & I and possibly others who aren't reading the mail on this subject isn't about stability with the TCXO or OCXO. The stability with those optional oscillators is well documented and not in question, and for a broad range of applications, mine included, well more than sufficient.
The issue here is making the ProgRock work reliably with GPS discipline, and why that isn't happening reliably.
Diatribes about the NEED for GPS discipline in anyone's application are irrelevant simply because the fact is the product doesn't perform reliably as advertised with GPS discipline, and, very importantly, within the context of kit building and the price of the kit, this is not a deal breaker or terribly surprising. This is part of the value of kit building; the builder has the opportunity to improve the kit as they see fit, or not.
What is perhaps more interesting and worth studying is why the GPS discipline isn't as reliable as it should be, and what's to be done to mitigate that deficiency. Based on the current responses to our (Sid & my) posts, Hans may be the only person qualified to really answer the questions regarding the apparent deficiency.
Further, personal attacks are not helpful, Andy Brilleaux. Let's leave those for the elementary school playground. Let's approach this issue scientifically and see if a successful solution can be had. I suspect it can and will.
Thanks,
Robin Midgett K4IDC


On Sun, Jul 14, 2019 at 3:15 PM Graham W <gram.warrington@...> wrote:
I have built a few prog rocks. I did not use the 27 mhz crystal as supplied, but installed a TCXO as suggested in the manual. I find ,even without GPS control that it is very stable. The pads are already there for the TCXO.
Graham VE3WGW

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