Re: ProgRock not working #progrock

Robin Midgett
 

Hello Sid & the group,
Sid, you're not alone. I can't seem to get my ProgRock to be stable with GPS discipline. It is far more stable & accurate without GPS discipline; I have the standard issue crystal, the die cast aluminum housing (Bud 234) for the project & a 5 volt TO-220 regulator thermally bonded together in close proximity. The indoor room temperature is stable within 5°F. When operated in this mode (no GPS discipline), I find the ProgRock to run within 5-10 Hz. of desired frequency. Like your set up, my power supplies are clean.

Presently, I have a solid, clean 11.7mS wide 1PPS at 4.15V going into the 1PPS input of the ProgRock. This is after having level shifted it up from the 3.3V 1PPS output of the Trimble Resolution T GPS, which is noted for it's accurate 1PPS output. The native output pulse width of the GPS is 1mS. Not being able to achieve results even close to expectations, and based on info from Hans, I stretched the 1PPS pulse width from 1mS to 11mS and shifted the level up. Perhaps worth noting is that the unloaded output voltage from the level shifter stage is a solid 5 volts, but when connected to the ProgRock it falls to 4.15V. I don't know if that is proper or not, but I noted from Sid's post that the QLG1 output is a full 5 volts, and his GPSD ProgRock isn't working as expected.

Querying the registers under GPS discipline I find Reg. 2 to be updating, but still the oscillator behaves like a wayward soul on an Australian walkabout; as much as 9kHz off frequency over 8 hours. By comparison, without GPS, the oscillator is usually less than 10 Hz. from the target over a similar time span. Clearly, some of these boards aren't quite ripe for use under GPS discipline. 
I have a second kit presently unbuilt; I'm curious to see if there will be a difference. I also have the QLG1 & OCXO on the way from QRPLabs; perhaps those changes will put this kit on the right track.
My desire for this oscillator is a base for a set of propagation beacons, so frequency accuracy & stability are of high interest & desire.

Thanks,
Robin Midgett K4IDC


On Fri, Jul 12, 2019 at 7:21 AM Alan de G1FXB via Groups.Io <g1fxb=yahoo.co.uk@groups.io> wrote:
??my thoughts.....

It would be useful to know What settings other than the defaults have you entered?
for instance the default settings allows for +/- 5Hz inaccuracy before discipline is applied.
Beyond that:-

Perhaps don't loose sight of your statement " If I place the ProgRock in a small cardboard box, the same freq errors occur, just slowed down. "
By the sound of it,you perhaps see?? atleast some drift caused bt temperature variations. You are not using the OCXO version of the synth PCB(?),
any reason not to in applications needing stability
? (an uncased xtal will be sensitive to environmental changes.
Much has already being discussed over the requirements of frequency stability for the synth modules both here & in the Notes & FAQ's
ones that differ from the median spec would be most noticeable in freq standard use such as your desire,
if you still have persistence tendency for drift perhaps substitute the xtal for another and note the affect if any?
(The Xtals used are nothing special, they come from the same bag that are supplied with the other kit's, The OCXO benefit is that it and the accompanying osc components are heated to well above (hopefully) ambient temperature circa 45 degC to achieve greatest stability. It also has an additional buffer stage that further isolates the xtal from loading changes within the Si5351 IC.)


the minute changes in the 27MHz ref measurements are scaled according to the choice of output freq, there was a good discussion thread months back demonstrating this while putting the U3S on VHF....
(If considering one of the many of the "cheaper" self contained TCXO modules exhibit caution as staircase shaped steps to their control and don't necessary play nice with a second level of correction in this application if the ProgRock GPS calibration is also enabled, choose one or the other but not both? )

" So, I am wondering, is there anyone, anywhere who has built one of these that actually stay on 10 MHz within a few tenths of a Hz? "
Regarding your measurements,
How does the Progrock perform when compared against WWV to produce a beat note and measurement using for instance ARGO Or Spectrum Lab App?

In a past thread about "how good" Hans has quoted:-
" The ProgRock when it is properly set up and working properly, should be within +/- 0.5Hz of the desired 10,000,000 Hz. That is, 0.05ppm (50 parts per billion). The frequency "steps" as the algorithm hunts around making corrections, are NOT several Hz, they will be a fraction of a Hz. Theoretically the steps will be sized 0 to 0.3Hz at this output frequency. They depend on the arithmetic with the particular reference clock measurement that is made by the 1pps."

Alan

On 12/07/2019 02:20, w7qjq wrote:

ProgRock not working.
I have trying for weeks to get my ProgRock to function properly.?? It simply refuses to dicipline the Si5351 clock generator to stay on 10 MHz.
Typical example: From a cold start (power-on), after a few minutes the GPS receiver acquires enough sats to begin the 1PPS.?? At that point the (10 MHz) CLK0 freq error will be several KHz. The ATtiny84 controller will begin pulling the freq towards 10 MHz.?? The Si5351 Reg 2 can be seen changing the 27,004,xxx MHz as expected.?? After another few minutes the Reg 2?? value settles and the CLK0 freq will be 10MHz +/-???? 2 or 3 Hz .?? But the CLK0 freq will not remain at any freq for very long...just a degree or two temperature change will start it moving and the Reg 2 value will not change as necessary to correct the error.?? The only times that the error is zero (+/-?? 0.1Hz) is?? when the Reg 2 value and the changing temperature
just by chance allow it.?? As I type this, the freq is 9,999,9976.

My 10 MHz standard is a Trimble ICM-SMT GPSDO spec'ed at +/- 0.3 x 10-8 but in reality is better as determined by zero-beat with WWV.?? The Trimble 10 MHz provides the reference clock for a HP5302A counter and one channel of a 2-channel scope whose second channel is looking at the Si5351 CLK0.

I have attached some photos that illustrate the setup and results.

Photo 1 shows the setup.?? I have one pc running Hyperterm to talk to the QRPLabs terminal program.
A?? second pc is running u-center.exe to monitor the QLG1 receiver.

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Photo 2?? shows the CLK0 freq as a fn of the Reg 2 value (with 1PPS disabled only for this test...obviously connected for all other testing/operation).

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Photo 3 shows how I compare the two 10 MHz freqs.?? The slightly lumpy ProgRock waveform is an artifact of some cable impedance mis-match.?? The HP counter (with 10 Sec timebase)?? is also measuring the CLK0 signal with a resolution of 0.1 Hz.

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Photo 4 shows what the QLG1 is seeing...the excellent?? S/N values are a result of the amplified antenna ( $3 USD).

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Photo 5 shows the 1PPS

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Photo 6 shows the Si5351 27 MHz xtal divided by 8.


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Some additional details...
1)?? Room temperature varies only a few degrees (F) during the day/night cycle.?? If I place the ProgRock in a small cardboard box, the same freq errors occur, just slowed down.
2)?? 5 Volt supply is clean.
3)?? When I load Reg 2 with a value that stops the drift for the temperature at that moment (freq error zero), within several minutes the freq will have wandered off several tenths but the ATtiny84 controller will not have changed the?? Reg 2 value to correct the error.?? After 15 minutes or so, the error might reach 2 or 3 KHz, Reg 2 may or may not be updated but even if the Reg 2 value has changed, it is still not a value that will bring the freq to zero error (+/-?? 0.1 or 0.2 Hz).
4)?? I have tried different values for Reg 5 with no observable difference. It is otherwise set to 0.
So, I am wondering, is there anyone, anywhere who has built one of these that actually stay on 10 MHz within a few tenths of a Hz?
73,?? Sid???? W7QJQ
Radio Welling


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