10MHz GPSDO by "pulaza"

[KungFuJosh]

I recently tried another 10MHz GPSDO. This one says "v1.1.1 by pulaza" when it starts up.

It has sine, square, and PPS. I bought it for the sinewave output and to see how it is in general.

Well, it's interesting. The output quality is trash, but that's because of the crappy OCXO.

This unit also had trouble getting a lock, so I returned it and ordered another from a different seller to see how that performs.

It looks like it has a MISO/MOSI header, so that could be interesting.

Anybody else have experience with this unit, or know of any better firmware...or any useful tricks? The buttons on the panel don't seem to do anything useful during normal operation.

Thanks,
Josh

[KungFuJosh]

Aaand this is how I know the OCXO was the primary problem with the output.

[KungFuJosh]

I thought I took more gut photos than this. I'll post them if I find them, or take more when I get the new one.

[KungFuJosh]

I received another GPSDO today, from a different seller. This one actually works. Sat lock is fine so far, and the OCXO is much better despite it also being CTI.

CH1 is the new pulaza GPSDO. CH2 is SDG6000X. SDG and Magnova both using old GPSDO as clock source.

Voltage is too high on this GPSDO output for my distro amp. I'll either have to modify it, or use an attenuator on the input.

Thanks,
Josh

[Kurt_!]

I like the rectangular signal.
...and also the zoom function of Magnova.

[KungFuJosh]

I like the rectangular signal.

I like that it has both. It's easier to use a distro amp with a sinewave though, so that's why I went for it.

...and also the zoom function of Magnova.

It is a wonderful scope.

[bingo600]

The HW (Chips) used above , smells somewhat of modified "LARS GPSDO"
Does the HC04 have an own separate LDO , and drives the PWM output (ocxo control voltage) , or is it just buffering the OCXO 10MHz out ?

What is the MCU ? ... Hard to see


/Bingo

[KungFuJosh]

I would guess from the M328P that's an ATmega328P. I'm sure you know this stuff better than I do.

[TylerPeppy]

I received another GPSDO today, from a different seller. This one actually works. Sat lock is fine so far, and the OCXO is much better despite it also being CTI.

Thanks,
Josh

I built a couple of OCXO boards based around the OSC5A2B02 last year, and they seem a bit hit or miss. I ordered 5 and I think 3/5 were actually working. The ones that weren't working I *think* had some issue with their buffers when I cut them open (re: https://www.eevblog.com/forum/projects/teardown-and-re-of-a-cheap-ocxo/). They had a bunch of sideband noise. The ISOTEMP ones are much better it seems.

I got my hands on a couple of Rakon 10MHz OCXOs as well, and those had the best phase noise performance from what I remember.

- Tyler

[bingo600]

I would guess from the M328P that's an ATmega328P. I'm sure you know this stuff better than I do.

I'd say my money are on a slightly "Modified LARS GPSDO".
Guess ... The (PCF)8574T seems to be controlling the display.

Is the HC04 on the backside ?

[KungFuJosh]

I built a couple of OCXO boards based around the OSC5A2B02 last year, and they seem a bit hit or miss. I ordered 5 and I think 3/5 were actually working. The ones that weren't working I *think* had some issue with their buffers when I cut them open (re: https://www.eevblog.com/forum/projects/teardown-and-re-of-a-cheap-ocxo/). They had a bunch of sideband noise. The ISOTEMP ones are much better it seems.

100%. The ISOTEMPs have been consistently better IME. However, this new one wasn't bad enough to warrant swapping it out yet. If it looked like the first one, I would have.

The other thing is, I'm concerned about modifying this one as I don't have any resources yet for restoring it if it needs to be reconfigured.

[KungFuJosh]

I would guess from the M328P that's an ATmega328P. I'm sure you know this stuff better than I do.

I'd say my money are on a slightly "Modified LARS GPSDO".
Guess ... The (PCF)8574T seems to be controlling the display.

Is the HC04 on the backside ?

I can check if I open it up again, but I don't recall anything being bottom mounted.

[bingo600]

Is the HC04 on the backside ?


I can check if I open it up again, but I don't recall anything being bottom mounted.

Really not important , i just couldn't see it on the "Large pcb photos"