v5 GPS Discussion

[cadenhillis]

Hello,
In our fork of the v5 mainboard, I kept all the GPS circuitry the same, but the manufacturer of the S1216V8 indicated that for getting an unlocked version for flight, we would have to go with something like one of their Orion B16-01. Since these are the same footprint, are still part of the L1 band, and don't need an external LNA, they seem to be acceptable substitutes. For consistency, our ground testing model instead also has the PX1120S module as it appears to have the exact same functionality.

My question is:
With the RF splitter installed, and the J5 unused summation port terminated to 50ohms, and using an active antenna on J6, I still cannot seem to get a lock-on under clear sky to read data. I know the devices are different, but is there a different way to terminate unused input on the EP2W+ for better reception?

I've used a NanoVNA v2 to view the network of J6 to the testing antenna I'm using, and that looks fine, so *presumably with J5 terminated, the path from the GPS module to U13 is fine also. Additionally, I've verified that the module is sending and I am receiving packets, but it just can't grab a lock on.

I guess I'm just asking if there is anything obviously incorrect before I go nuclear and hunt down a scope that can get a 1575MHz reading and buy a few more GPS antennas if the antenna is malfunctioning.

Thanks everybody :)
bad quality board pic:

[polygnomial]

Have you tried with two GPS antennas pointing at different parts of the sky? What brand and model of GPS antenna are you using?

[ijohndoe]

It has a nice gps feature and a very easy application

[mlyle]

@cadenhillis Did you ever figure this out? Deciding what GPS to source...

If that's a 50 ohm terminator at DC, the issue isn't that it sapped the active antenna power, is it?

[DogZapper]

I've been reviewing the PyCubed V5 hardware myself over the past few days. From what I've read the S1216V8 is not a good choice for a new design. The PX1120S is a footprint compatible newer part and would be more appropriate for new designs. It is my understanding, that the PX1120S receives & can power an external antenna indirectly from it's 3V3 supply. My suggestion is that maybe your issue is caused by the RF SPLITTER (EP2W+). Can you try bypassing around the splitter and see if you get a GPS lock then?