QUESTION

Question

Dear support,

On the same outdoor conditions (fully open sky, no building, no jamming source), on the evaluation board, sometimes cold start take more than 20mn, sometimes less than 2mn.
We think that we may have a bad init sequence on special NMEA sentence. So could you send to us a standard NMEA init sequence to check it please ?

Best regards

François

Answer 1

Hi François,

If you purchased through an authorised supplier, you should have a USB stick with our evaluation software on it, have you tried the same test with this?

Many Thanks

Steve

Answer 2

This is an exemple of  too fast COLD start...

Answer 3

Hi Steve,

Yes, we did it. In fact, we started by do it! But it's manual, so wze wrote a python script to automatically run some test.  Antenna was also  tuned, inside the plastic enclosure, with a VNA. We had checked also that in normal case, we have enought sensibility.

But, it seems that sometimes, we have more than 3 or 4 SV in tracking, and after more than few minutes, we don't have a fix;
It's strange, because with 3 SV (C/N>25), we should get a the 2D fix, and with 4, a 3D fix.

Another strange things, it's that when I send a COLD start ($PMTK103*30\r\n) (with Init frame sent, sometimes I get the fix in 2s, that it's very strange for COLD start, it seems be more an HOT start, isn't it? I can have like a cold start only I send the FULL COLD START command ($PMTK104*37\r\n). Is it normal ?

We think that perhaps, we didn't have the right init sequence: we found only few documenations about some advanced functionnality, like for the predictivity, we the description is very short. I think that perhaps theses functions are not initialized on the right way...

Do you have any idea of what could happen ?

Thanks to you

Comments

Hi François,

The CN level is quite low, even if matched/tuned there may be other issues with your layout or noise. I'd like to review your gerber/layout if possible. Please contact techsupport@antenova.com to get in touch with your regional representative who can help you with a design review.

Many Thanks

Steve