2 Pack GPS+BDS Dual-Mode Module Flight Control Satellite Positioning Navigator, ATGM336H Replacement NEO-M8N NEO-6M for Arduino

Small and works great. I'm using it as a reference for a raspberry pi time server and it needs no external components. Hook up to +3.3 volts, ground and it lights up. Connect Tx and Rx data lines to one of the Raspberry Pi 5's UARTs (I used UART4 on GPIO pins 12 and 13) and then hook the PPS (Pulse Per Second) interface to GPIO pin 8 which can generate a hardware an interrupt to discipline the clock and the rest is just software configuration! I did have two issues. The first was because the external active antenna connector is on the bottom of the board I had to mount it on a 5 pin socket which leaves it standing a bit high above the proto-board, but not really an issue in my application. The second was I had a Bluetooth keyboard dongle plugged into the Raspberry Pi. Because the included antenna has a very short cable the two were very close to each other. The much stronger transmit signal from the Bluetooth dongle overwhelmed and desensitized the GPS receiver and made it nearly impossible to acquire satellites indoors. Simple fix, I removed the Bluetooth dongle and was immediately able to sync to multiple satellites. If I need to use the dongle again I can just be connected via a USB extension able to get is away from the GPS antenna. For bonus points add a ML2032 3V rechargeable battery for the Pi 5's real time clock and configure a couple of Internet time sources as backup and you have a rock solid stratum 1 time source accurate to within a few nanoseconds

Good little units. but they are CASIC modules not anything Ublox related. This will probably not matter to most. They default to GPS + BeiDou But you can change it. GPS $PCAS04,1*18 GPS + BeiDou $PCAS04,3*1A GPS + GLONASS $PCAS04,5*1C

Was not able to cold start indoors, even after several minutes, though it somehow eventually picked up time-of-week. Better than I would have expected. Initial cold start outside was a little bit disappointing (about 2 minutes) but that could have been RF noise from the microcontroller a few centimeters away. After maintaining a 3d fix for 15 minutes to allow the full GPS navigation message to be received, power was briefly removed to restart. Within 5 seconds, valid fixes were being produced again, even without having a completely unobstructed skyview. Going inside with a valid fix often maintains that fix. For the last hour the receiver has maintained lock on 8-11 PRNs with SNRs between 12 and 26dB, including acquiring new PRNs as various SVs dropped below the horizon. Of course, that's how it's supposed to work: having an accurate almanac and a properly disciplined clock makes acquisition and tracking efficient. Even indoors, a hot start worked well, producing 3d solutions within 10 seconds.

I've been looking for a stamp-size GPS rvcr with a tiny antenna of very low gram weight -and price. The GPS module is almost same size as an ExpressLRS EP1 or 2. This is it, and I can get a 3D lock in around 15 seconds from energize (due to warm start) once the onboard battery maintains sufficient charge. 5 to 7+ birds outdoors without reflector. The update rate could be better, but one thing at a time. Better yet, I remove its rechargeable cell and replace (external wire) it to an LIR2450 (120mAh) to power it and a piggybacked Vifly beacon. [the original micro LiPo batteries poop after a year] Bundled together, I get a more or less continous, longer lived power source for these two crucial finder location devices, and the charging function managed by the vifly. Tricky to solder in, but well worth it. For no fear flights just remember to record OSD with GPS coordinate telemetry so you capture last known location, then get out the Garmin and geotrack within sonic/visual range.

Before you buy these modules I found a fatal design flaw in them. The antenna connector has 360 degrees of free movement, also happens to be a 3.3v component right next to it, what ends up happening is these two components can touch. Shorting 3.3v straight to ground, causing the component to overheat and potentially burn the surrounding material, I personally fixed this with some electrical tape. Overall these modules work great for GPS, and I had great accuracy with them.

Works on my toy project. Boot up can take time to acquire satellites but after that, seems to work well.