10MHz GPSDO by "BH3SAP"

[daddygo]

Anyone tried this little guy?: https://www.sparkfun.com/sparkfun-dualband-l1-l5-gnss-breakout-dan-f10n.html

Hi fredo_

Basically a standard precision type, which is highlighted as an advantage is surface-mounted. But in my opinion, this is a disadvantage if you want to measure, repair, etc...

-plus it has an integrated antenna in its basic configuration and an external one if you want...

The external antenna connection is made by "via" (RF in ext. is on the other side of the PCB because the module is surface-mounted), which is not recommended from an RF perspective, so the question is whether it will perform good with an external antenna. (??)

I think this module has been optimized for integrated antenna., - and mass production.
BTW:  I like SparkFun. I looked at a lot of their stuff because they share their designs.

Otherwise, it looks good inside -here is the block diagram.

PS: must try 


br,
Krisz

[bingo600]

Anyone tried this little guy?: https://www.sparkfun.com/sparkfun-dualband-l1-l5-gnss-breakout-dan-f10n.html

You would have to make sure you have an antenna that supports both L1 & L5 (gnss)
Most cheap does just support L1.

IMHO you'd be better off with a "real" timing gps like this M8T ... Remember to get a SMB (GPS) to SMA pigtail
https://www.ebay.com/itm/134243322249?

[fredo_]

You would have to make sure you have an antenna that supports both L1 & L5 (gnss)
Most cheap does just support L1.

Yeah, that was the advertised dual-band feature that caught my eyes ;-)

[daddygo]

Anyone tried this little guy?: https://www.sparkfun.com/sparkfun-dualband-l1-l5-gnss-breakout-dan-f10n.html

You would have to make sure you have an antenna that supports both L1 & L5 (gnss)
Most cheap does just support L1.

IMHO you'd be better off with a "real" timing gps like this M8T ... Remember to get a SMB (GPS) to SMA pigtail
https://www.ebay.com/itm/134243322249?

Hello for all,

it is a properly RF designed PCB (pict. 1), but the price makes it suspect that it has a fake module, for example, the once "star" NEO 6 was counterfeited by many...

I don't know how can sell a complete PCB for $29 with a GPS module that costs $58 for 100 units, MOUSER data (pict. 2).

-factory RF design guidelines (pict.3)

- by the way, anno I was looking at the LEA-M8T, but because of the price, I don't plan to use it, UBX-M8030 is in the background which is pretty good stuff:
https://www.u-blox.com/en/product/ubx-m8030-series

[bingo600]

it is a properly RF designed PCB (pict. 1), but the price makes it suspect that it has a fake module, for example, the once "star" NEO 6 was counterfeited by many...

I don't know how can sell a complete PCB for $29 with a GPS module that costs $58 for 100 units, MOUSER data (pict. 2).

These boards are "usually" Pull's from decommisioned boxes.
The board is also called the "Huawei board"

I haven't noticed any issues with mine, they can do all the M8T stuff.

I haven't heard about fake Huawei M8T boards as of now.

BUT i bought mine a few years ago...
Who knows what the "Chinese Optimizers" have done now.

Maybe "pulled/used" is good here.
https://www.ebay.com/itm/316914788061?


NOTE : The PIN-Block uses 2mm pitch
And the Antenna plug is SMB


I have BAD experince w. the Huawei LEA-5T board ...
They seem extremely sensitive to surrounding noise , hence not loading the almanac.
Even just adding the uart wires will create issues .... KEEP Away

[daddygo]

You would have to make sure you have an antenna that supports both L1 & L5 (gnss)
Most cheap does just support L1.

Yeah, that was the advertised dual-band feature that caught my eyes ;-)

I am thinking of redesigning the PCB with NEO-M9N module to NEO-F10N, because price/performance ratio would be the best, as the ZED-F9P and NEO-M10T are $100 modules, the F10N is only $40 with dual-band
(true the F10N is not a timing module as the F10T, but dual-band)

it is also true that there will be other plus design things to do with it see pict.4

[bingo600]

Here's my GPSDO output
Measured on my Rigol DS1054z (100Mhz) , as it was just nearby


Coax from GPSDo to BNC-T on CH1
50ohm termination :
BNC T at Scope end - W. 50ohm Radial termination on one of the T's

First one terminated 50R
2'nd unterminated


Waiting for maywat mawyatt, before doing any mods 


Edit: I have a 143' OCXO in mine

[daddygo]

it is a properly RF designed PCB (pict. 1), but the price makes it suspect that it has a fake module, for example, the once "star" NEO 6 was counterfeited by many...

I don't know how can sell a complete PCB for $29 with a GPS module that costs $58 for 100 units, MOUSER data (pict. 2).

These boards are "usually" Pull's from decommisioned boxes.
The board is also called the "Huawei board"

I haven't noticed any issues with mine, they can do all the M8T stuff.

I haven't heard about fake Huawei M8T boards as of now.

BUT i bought mine a few years ago...
Who knows what the "Chinese Optimizers" have done now.

Maybe "pulled/used" is good here.
https://www.ebay.com/itm/316914788061?


NOTE : The PIN-Block uses 2mm pitch
And the Antenna plug is SMB


I have BAD experince w. the Huawei LEA-5T board ...
They seem extremely sensitive to surrounding noise , hence not loading the almanac.
Even just adding the uart wires will create issues .... KEEP Away

Yup, that might be correct, -Huawei back-stock units, I used to work with Huawei routers (AR series) and switchs at Vodafone,
but I didn't remember the S5750 switch type and I can't find anything about it, even though I still have Huawei enterprise access to their doc. system.

-the RF section is incomplete (YES) missing a cap and a resistor, see my design with NEO-M9N,
but it is much better than the SparkFun module design linked by @fredo_, where only "via" can be used to place the external ant. RF part to the other side of the PCB, it is not good(!) bacause make serious capacitance and resistance between the layers, which varies with frequency and layer temperature and is poorly compensible.

[bingo600]

-the RF section is incomplete (YES) missing a cap and a resistor, see my design with NEO-M9N,
but it is much better than the SparkFun module design linked by @fredo_, where only "via" can be used to place the external ant. RF part to the other side of the PCB, it is not good(!) bacause make serious capacitance and resistance between the layers, which varies with frequency and layer temperature and is poorly compensible.

To me it seems like the sensitivity of the "china gps" is fine enough.
One has to remember it's a FLL by design.

If i were to improve on the BH3SAP, it would be adding a Timing GPS ...
Especially for TRAIM and the ability to keep 1PPS lock w. just one bird in view

[Kurt_!]

Same to me " Done "

[daddygo]

-the RF section is incomplete (YES) missing a cap and a resistor, see my design with NEO-M9N,
but it is much better than the SparkFun module design linked by @fredo_, where only "via" can be used to place the external ant. RF part to the other side of the PCB, it is not good(!) bacause make serious capacitance and resistance between the layers, which varies with frequency and layer temperature and is poorly compensible.

If i were to improve on the BH3SAP, it would be adding a Timing GPS ...
Especially for TRAIM and the ability to keep 1PPS lock w. just one bird in view

Yeah, I've thought about this a lot, but a decent timing module costs cca. $100 or above....
(I don't like solutions derived from existing units, I prefer my own designs.)

But yes, everything speaks in favor of it when we think about its right way dev.
It could be exciting because the basic PCB is there and, let's say, the NEO-F10T is the same size (12.2 x 16.0 x 2.4) as the NEO-M9N, but I haven't checked the PIN layout yet.

I will look into this further, for sure.

https://www.u-blox.com/en/time

+++edit:

It could be easily solved with a little redesign. -see PIN assignment picts

[bingo600]

Same to me " Done "

Do you have a 3.3v USB-->TTL Uart converter ?
Then you can look at the received GPS RX/TX at these pins
https://github.com/fredzo/gpsdo-fw?tab=readme-ov-file#gps-uart-passthrough

[mawyatt]

Here's my GPSDO output
Measured on my Rigol DS1054z (100Mhz) , as it was just nearby


Coax from GPSDo to BNC-T on CH1
50ohm termination :
BNC T at Scope end - W. 50ohm Radial termination on one of the T's

First one terminated 50R
2'nd unterminated


Waiting for maywat, before doing any mods 

Those don't look too bad!! The loaded waveform looks nice with equal Rise and Fall times, however with the unloaded output showing ~3.5VPP which indicates U5 output might be saturating according the the data sheet, take a look at this. Recall U5 Pin6 is the output, also look at the input Pin 3 and VCC Pin 8 and 7, use a 10X scope probe of course!!

Recall the units we had (both returned as one couldn't lock on sats and the OCXO required an input control voltage beyond what the PWM control could deliver, the other you had to reset {remove cover} every time powered up). The U5 waveforms on these looked bad, VCC was ringing as was shown and unloaded and loaded waveforms were not "clean". We'll see how the replacement looks whenever it arrives!! 

Best

[Kurt_!]

Reinstalled the original firmware...
What I noticed is that it's much faster on the frequency?
Max. 20 minutes....

[bingo600]

Yeah, I've thought about this a lot, but a decent timing module costs cca. $100 or above....
(I don't like solutions derived from existing units, I prefer my own designs.)

These were $15 back when the modules just came out  (Well not fancy desolder , but gps cut out from pcb)
https://www.ebay.com/itm/364757958454?

Or this ... Desolder whatever you need, and reuse
https://www.ebay.com/itm/375759146797?

I doubt i would be especially interested in a DIY GPS module ...
I don't have a drawer full of RF components, and shipping, handling & customs from Digikey. Would prob cost the same as an ebay board.

[daddygo]

Same to me " Done "

Do you have a 3.3v USB-->TTL Uart converter ?

YES.

I have already integrated this into the 1pps impedance matching daughter card.

CH340K USB - TTL + 50 ohm matching & PPS signal selector

This PCB fits into the original GPS module slot, and the GPS PCB (any) is placed on top of it, while it takes out the TTL for USB conversion and forwards it to the MCU as well.

[bingo600]

Recall the units we had (both returned as one couldn't lock on sats and the OCXO required an input control voltage beyond what the PWM control could deliver, the other you had to reset {remove cover} every time powered up). The U5 waveforms on these looked bad, VCC was ringing as was shown and unloaded and loaded waveforms were not "clean". We'll see how the replacement looks whenever it arrives!! 

How (where) are they taking the STM32 clock ?
If it's directly from (unloaded) OCXO output - Wouldn't that be too high a voltage for a 3v3 MCU ?
Maybe even worse on a "Square OCXO"

[mawyatt]

How (where) are they taking the STM32 clock ?
If it's directly from (unloaded) OCXO output - Wouldn't that be too high a voltage for a 3v3 MCU ?
Maybe even worse on a "Square OCXO"

Don't remember other than the first unit had a OCXO that was out of range from the control voltage input to achieve a frequency lock @ 10.000MHz.

Didn't look into how the OCXO output was delivered to the STM, or how any of that was connected. We were considering replacing the OCXO but when then GPS couldn't acquire any sats, just decided to return the unit and get a replacement (which ended up having to reset at power up).

Short term memory is failing, so sorry can't remember all the exact details.

Best

[bingo600]

Same to me " Done "

Do you have a 3.3v USB-->TTL Uart converter ?

YES.

That was for Kurt 

[daddygo]

Yeah, I've thought about this a lot, but a decent timing module costs cca. $100 or above....
(I don't like solutions derived from existing units, I prefer my own designs.)

These were $15 back when the modules just came out  (Well not fancy desolder , but gps cut out from pcb)
https://www.ebay.com/itm/364757958454?

Or this ... Desolder whatever you need, and reuse
https://www.ebay.com/itm/375759146797?

I doubt i would be especially interested in a DIY GPS module ...
I don't have a drawer full of RF components, and shipping, handling & customs from Digikey. Would prob cost the same as an ebay board.

This first eBay link is thought-provoking 

But I have a huge library of components at JLCPCB that I've been collecting for 10 years, and look at the production of 5 complete 1pps daughter cards, including components, which cost only about $60.

So even for small-batch prototypes, it's still worth the price.

[bingo600]

How (where) are they taking the STM32 clock ?
If it's directly from (unloaded) OCXO output - Wouldn't that be too high a voltage for a 3v3 MCU ?
Maybe even worse on a "Square OCXO"

Don't remember other than the first unit had a OCXO that was out of range from the control voltage input to achieve a frequency lock @ 10.000MHz.

Didn't look into how the OCXO output was delivered to the STM, or how any of that was connected. We were considering replacing the OCXO but when then GPS couldn't acquire any sats, just decided to return the unit and get a replacement (which ended up having to reset at power up).

Short term memory is failing, so sorry can't remember all the exact details.

Best

From Daddygo's PCB picts



I assume this is the OCXO output.
Seems like they have a resistor (r4) & cap (c10) before the STM "clock wire"

[mawyatt]

How (where) are they taking the STM32 clock ?
If it's directly from (unloaded) OCXO output - Wouldn't that be too high a voltage for a 3v3 MCU ?
Maybe even worse on a "Square OCXO"

Don't remember other than the first unit had a OCXO that was out of range from the control voltage input to achieve a frequency lock @ 10.000MHz.

Didn't look into how the OCXO output was delivered to the STM, or how any of that was connected. We were considering replacing the OCXO but when then GPS couldn't acquire any sats, just decided to return the unit and get a replacement (which ended up having to reset at power up).

Short term memory is failing, so sorry can't remember all the exact details.

Best

From Daddygo's PCB picts



I assume this is the OCXO output.
Seems like they have a resistor (r4) & cap (c10) before the STM "clock wire"

Agree, looks like it's the OCXO Output. R4 would keep/limit the voltage peaks at the STM within the STM VDD and Ground range, C10 is just for DC isolation.

Best

[bingo600]

Agree, looks like it's the OCXO Output. R4 would keep/limit the voltage peaks at the STM within the STM VDD and Ground range, C10 is just for DC isolation.

Best

I think R4 is 1500Ohm

[daddygo]

Agree, looks like it's the OCXO Output. R4 would keep/limit the voltage peaks at the STM within the STM VDD and Ground range, C10 is just for DC isolation.

Best

I think R4 is 1500Ohm

exactly R4 = 1501

[Kurt_!]

I'm still getting the TTL-to-USB converter. I've already ordered it.
Should the two software programs (u-center and VisualGPS...) work then?