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Unknown GPSDO but BG7TBL logo on the circuit board and OCXO !

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hector.pascal:
Hi,
I'm not really sure what the battery is for - maybe it's not needed with this OCXO or the V.Kel GPS module. But certainly no battery is fitted in this version, and no date or "BG7TBL" text exists anywhere on the pcb.
The GPS module seems to be a 7M equivalent as the part number says it has a UBX G-7020 engine.  But note that there is no UBlox logo on the label!
Thanks for the datasheet - a pity I can't read Chinese!
Photo as requested.
H-P

Diabolo:
Thanks for the circuit photo.
----
The BT1 battery is used to keep the latest information received on the satellites to facilitate / accelerate the locking of the GPS. On pin 22 (BCKP) of VK1612U7M3L, the datsheet indicates:
- "It’s recommended to connect a backup battery to V_BCKP in order to enable Warm and Hot Start features on the receivers. Otherwise connect to GND".

All GPSDOs BG7TBL have a battery connected BT1, 3-volt LIR MS621FE-FL11E.


Diabolo

Hans_18T:
I got my GPSDO-PLL this week, the (circuit)board is Labeled as "PLL GPSDO BC7TBL 2018-02-10. GPS receiver has no label, The OCXO indicates: 1042/0394C - Fo=10MHZ - TOC0713A (includes a battery)
Front panel green (no indication BC7TBL)

Ohm_My:

--- Quote from: jpb on February 24, 2018, 07:59:20 pm ---
--- Quote from: charly724 on February 24, 2018, 09:34:41 am ---- frequency accuracy is higher than my measuring accuracy

--- End quote ---
If you use the TF930's computer interface  then you can extend the gate time to get more precision though with longer gate times the two GPSDOs will agree with each other more anyway so you might not gain a lot. The counter keeps the counts going continuously so if there is a frequency difference and the phase difference reaches 20 nanosecs then the frequency value will change at that point and you could estimate how long it took for a 20nsec shift.

--- End quote ---

This is interesting. What is the command to measure beyond the 100s gate time (M4)? I just recently purchased this unit and came across your post.

jpb:

--- Quote from: Ohm_My on June 21, 2018, 02:46:57 am ---
--- Quote from: jpb on February 24, 2018, 07:59:20 pm ---
--- Quote from: charly724 on February 24, 2018, 09:34:41 am ---- frequency accuracy is higher than my measuring accuracy

--- End quote ---
If you use the TF930's computer interface  then you can extend the gate time to get more precision though with longer gate times the two GPSDOs will agree with each other more anyway so you might not gain a lot. The counter keeps the counts going continuously so if there is a frequency difference and the phase difference reaches 20 nanosecs then the frequency value will change at that point and you could estimate how long it took for a 20nsec shift.

--- End quote ---

This is interesting. What is the command to measure beyond the 100s gate time (M4)? I just recently purchased this unit and came across your post.

--- End quote ---
Sorry, I was a little lax in my statement. There isn't a specific command to extend the gate time but if you measure continuously then it doesn't reset between gates. I was measuring longish time periods (for testing 10MHz oscillators which I had mixed with a reference) and what I did was measure period and in software recover the count of the 50MHz clock. Then you can treat n gates as one super gate n times as big and use the total count.

The key point is that the counter, though it doesn't interpolate, it doesn't reset either.

Unfortunately they don't give the count readings directly so you have to recover it from the floating point number that is returned.

Though you're trying to get two numbers from one it is not impossible. Say you're measuring a period and using a gate of 1 second. The counter will return the ratio of the change in the internal 50MHz clocked counter and the nearest integral number of periods of the frequency being measured. You know the average number of periods from the measured period and the gate time, call this m periods.

Then what I did was assume that the true number was m-1, m or m+1 and for each I would calculate what the 50MHz clock count must be to give the measured period. This should be an integer so I'd choose the case m-1, m, m+1 that gave the closest to integer answer.

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