Where did you purchase the ZED-F9P for $78?
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On taobao. Not sure this was the exact same I used for the reference but something like this. I didn’t get the ZED, just the other three. Was curious about the stats once I knew enough to read the data sheet properly.
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I just ordered the LC29H(BS) GPS/RTK HAT for my Pi 5. I’ll feed RTK data to rtk2go.com as an NTRIP server.
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Nice! Curious to hear your experience.
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First shipment of GPS stuff arrived: ATGM336H-f8n76, UBLOX NEO-M9N-00B, and various multiple frequency antennas.
I bought the wrong SMA connector type for the widest frequency antenna (GPS+BD+GLONASS). I’ll be tearing that open to see what’s inside.
ATGM336H-F8N76
This seems to be ZHONGKEWEI’s top of the line GPS module. Highly capable, more so than the NEO-M9N, and slightly over $5. I’m most interested in this one so I wired it up first.
- I’m surprised how small the module is
- 115200 baud default speed
- It uses significantly more current than an older ATGM module (60mA vs 20mA). This seems to be the result of tracking 4 networks at once, and can be selectively reduced.
- This might be a tough board to find
Simultaneously tracking GPS, GLONASS, BeiDuo and Galileo.
NEO-M9N
The Swiss designed Ublox might surprise, but I think the ATGM is more fully featured. Attached it to the same antenna in the same position as the previous test.
- Even more current, up to 100mA while acquiring a fix.
- 38400 baud default
Currently only tracking GPS and Galileo networks, Eventually some GLONASS satellites did show up, but BeiDuo only blipped a few times.
Interestingly, we get SBAS (geo sync orbit supplemental position data) from GAGAN (india) and EGNOS (EU). the ATGM didn’t pick up either of these.
First Impressions
It seems like the ATGM module is better at tracking multiple networks. BeiDuo reception is very good, while the N9M barely picks it up at all. We also see a few satellites on frequencies not supported by the N9M.
M9N however picks up SBAS satellites. The ATGM is supposed to support SBAS, though the supported networks are not listed in the datasheet.
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My latest are also U-blox, and I’m a bit disappointed at current consumption. I need to tune update rates, etc to try to get it down.
My plan is for the GPS and an ESP32 to work together either USB or battery powered.
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Well, I have my LC29H(BS) up and sending RTK data to RTK2Go. We will see how it goes from here. I need to buy a rover device to connect to this.
http://rtk2go.com:2101/SNIP::STATUS#single
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Nice! RTK2go really makes it easy to get an RTK base station online.
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The LG290P arrived, the most expensive board I’ve tested (~$40). It has a built in UART to USB converter, which is handy.
Unfortunately we don’t get to test it 
Even after an hour it doesn’t find a single satellite. To double check I connected a different module to the same antenna and it got a fix within seconds.
[14:47:57.099 Uart Tx:0015 B] $PQTMVERNO*58
[14:47:57.104 Uart Rx:0054 B] $PQTMVERNO,LG290P03AANR01A04S,2025/01/02,17:20:51*1A
This is the firmware that shipped.
[15:02:39.989 Uart Tx:0015 B] $PQTMVERNO*58
[15:02:39.995 Uart Rx:0067 B] $PQTMVERNO,LG290P03AANR01A06S_PPP_TEMP0829,2025/08/29,17:08:39*43
Managed to update it to the latest beta firmware from SparkFun’s git repo. Still no connection.
It acknowledges but fails to change the update rate from 20Hz to 1Hz. Looking for debug output in the fire hose of NMEA is mildly maddening.
Also notable:
- Some users report getting boards from Aliexpress that have an identical module that uses different commands, different firmware, and different bootloader. (This is not the case with our module)
- Quectel seems to list lots of features as fully supported now that aren’t supported yet. This year there were promises of a firmware update every month with an advertised feature, only for it to slip. They did eventually release the beta firmware I loaded for evaluation only.
Given that this was a $40 module and the only alternative on Taobao appears to be the weird mutant people got from aliexpress, this might be the end of the road for the Quectel adventure.
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