@Crichton I actually did sign up for the SoftRF forum and tried to sign up at Lilygo, but they never sent me a validation email.
I found this forum first, because I googled, “TBeam Supreme” and this was Google’s first response. I am presuming that the T-Beam Supreme portion is the same between Meshtastic and SoftRF, but, obviously I don’t know that. I’m attributing this to a hardware issue, not software. I wouldn’t think software would affect how quickly it gets an initial fix. But I really do appreciate people’s willingness to help out when they can.
@b8b8 I live in a one floor (with attic) wooden house. Roof is asphalt shingles. I live in a rural area, there are trees around, but definitely no skyscrapers and I’m relatively speaking at the top of a hill.
I agree, completely unfair to compare the fix time on the GPS to that of a cellphone because the cellphone uses cell tower assist. I think it is fair to compare this to the GPS mouse that I have. Despite not being powered in at least several months, it achieved a first fix in about 50 seconds. Subsequent fixes were achieved in a couple seconds. Unfortunately, I don’t know what’s inside the “mouse”, it could have some sort of keep-alive memory or it could dump data to a non-volatile memory, I just have no way of knowing. That GPS about 1.3" square or so, so it’s possible it’s a bigger antenna. Again, I just don’t know. I did compare them side by side outdoors, and the GPS mouse outperformed significantly. But maybe it had some stored information that helped it.
I guess what bothers me is that the uBlox M10 claims to cold start in about 30 seconds. I presume cold start means… cold start. No stored information whatsoever. I would expect, that outdoors, this should be able to get first fix in 30 seconds with no battery in it, etc.
I bought the antenna you mentioned (wish the cable were a bit longer). It does seem to do better, it’s hard for me to tell exactly how much because the behavior isn’t consistent. I was able to see a time to first fix over a bit over a minute at one point outdoors. I also loaded the “GNSS Access” firmware which directly transfers the Ublox output (and input) to the USB so that I can talk to it with u-Center. I’ve seen as many as 25 satellites locked in. I think the SoftRF software may be limiting you to a max of 12 reported satellites for some reason, and this may not reflect reality. Overall, I think the GPS mouse is still outperforming this.
The other thing that bothers me (and this may well be lack of recent experience with GPS) but with so many parallel correlators I don’t understand why even after the fix, it seems like it’s so slowly adding additional satellites. The reality of the situation is there should be processing gain that is increasing with the square root of the length of capture. So, 120k C/A codes which is only 2 minutes should give you 25dB of gain. That’s more than the quoted difference beween acquisition and tracking, so I don’t see why it should ever take 5, 10, 15, or 20 minutes to acquire a satellite. Of course, it’s quite possible they don’t look at that much data so they never get that much processing gain, and it’s just random whether or not they get low enough noise for a time period to acquire the signal.
