I ordered a similar one that came from Aliexpress but it's rather disappointing. On the display it just says 10.000 Mhz GPSDO for a while then changes to say PPB -2.3 and PWM31077 but there are no instructions at all so I have no idea what that means. Pushing in the knob gets into a menu where I can select Contrast, Offset, PWM Set and Exit but that's all. It never displays the time like they show in some photos and there's no way to even tell if it's picking up any satellites or working at all! I opened it up and inside it has an Arduino STM32 and NEO-6M module plugged into the main board with just it's 5 pins holding it. The main board also has a 10.000 Mhz OSCO on it and outputs on the back for 1PPM and 10 Mhz.. With the top off I can at least see the LED blinking on the NEO-6M so I guess it's working to some extent but they should have put the LED on the front. Since there are no instructions can you tell me what PPB -2.3 and PWM31077 mean and how to use the settings for Offset, PWM Set?
@@uni-byte Mine just has an Arduino, GPS, 10 Mhz osc with a 5 volt regulator and LCD, there's no VCO. After it runs for a while the PPB number goes down to just a fraction like 0.6 or something so I think that's some amount of error?
@@stevec5000 Honestly I have no idea. I'd either need the instruction manual or the code for the Arduino to be able to tell what is being reported and why. Sorry. Keep searching and if you find something drop a note here to help out the next person.
I'm guessing they're running a custom PID / FLL on the Altera to sync the ocxo into the 1 pps, that's quite a ways to go for one of the cheaper units! You could do everything from just a microcontroller if you wanted to. How warm does the box get after an hour then?
That's correct. If it follows BG7TBL's original design paradigm that's exactly what it does. The CPLD feeds data to the MCU which controls the OCXO who's output is then fed back into the CPLD. You could certainly do it all in an MCU, but it would need to be a bit better than the ATmega8. It gets warm in about 2 minutes and (by touch) seems to stay close to that.
@@uni-byte Yep. It's neat that GPS not only solves 'Location', but as a side benefit it distributes precise 'Time' and 'Frequency' to everyone. One could imagine a 'Time & Frequency' Go-Box with battery. One might be outside for 30 or 45 minutes waiting for the Green LEDs (including rubidium module) indicating phase lock to GPS, and then go inside to the basement (no GPS) carrying a just-locked atomic standard good for an hour or two.
@@JxH Sounds like a cool project. Yes, a good rubidium module could last hours as a timing standard and even years as a frequency standard once properly calibrated to the GPS signal.
You're welcome. After a power failure it goes through a multi-step process. Firs, after about 3 minutes the OCXO will come up to temperature. When that happens the accuracy is better than 1 part per million. In about 30 minutes it will have acquired enough satellites to begin disciplining the OCXO and teh accuracy increase to less than 1 part in 100 million. To get to around 1 part in 10 billion supposedly takes it less than 24 hours but since this is the most accurate device I have I don't have any way to ascertain that.
