I will probably get a survey antenna to start with but i will probably buy and end up testing a bunch of gps antennas to find the cheapest one that works. I dont care how it looks so even a bare antenna with a wire coming out of it will do as long as its cheap enough and does the job, il probably test a few regular GPS antennas plus a few random antennas like these.
That cheap helical one seems promising. The expensive versions are very good. If that one has reasonable sensitivity, it’s a great budget option.
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I ordered this antenna to get started. il probably get a helical next and stick it on the boat.
I have been doing some digging and im not the first person to test this GPS module with ardupilot, there have been a couple of people that have tested versions of it over the years and got it working but I think just a lack of documentation has stopped it being more popular.
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Tested the 1120R and 1122R modules briefly and can confirm they are just as good as the F9P. And they are in stock 
. Tested with RTk as well - all works.
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My receiver has arrived! Its not as big as I thought it was, Will be a couple of weeks probably before i get the antenna.
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I have been looking at public NTRIP streams to get the RTK working but it occurred to me that im not sure if mission planner NTRIP client can be used since the skytraq requires its corrections via a different serial port, I have only done RTK using a M8P GPS with a single serial port before so is there anyway to set this up in ardupilot or will I need a second serial link and another way to send corrections, im really hoping to avoid buying another RTK GPS to act as a base.
I was looking at this pinout for the gps, does anyone see anything wrong with connecting TX1 and RX2 to the same serial port on the flight controller and enabling RTCM injection?
I suspect you could wire the “RTCM input” serial port to a second GPS port on the flight controller.
Even if you don’t get a GPS input to the flight controller, you should be able to route the RTCM out to that serial port to satisfy your input needs for the GPS.
I’m curious about the difference of the Skytraq being L1/L5 vs the F9P being L1/L2 and what that might mean for speed to fix and final fidelity - and under what conditions is one better than the other?
Is there a L5 Glonass signal?
I started doing RTK with some old LEA-5T modules and GPS only using a Raspberry Pi running RTKLib.
It was agonizing waiting for a fix and it wouldn’t stay.
I moved up to M8Ts which were a little better, but still spotty.
The F9P with L1/L2 GPS & GLONASS made a big difference - and I was able to let the F9P do the RTK calculations onboard.
I can use the F9P with a regional NTRIP service, but it’s GPS-only and while it gets a fix, it isn’t as reliable and takes longer than when I use the F9P base I installed on the chimney, I believe at least part of the improvement is adding GLONASS into the mix and coming close to doubling the number of satellites.
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I think that’s a fine idea. Neither ArduPilot nor the GPS will “know” the difference.
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I have been trying it with public NTRIP but I think there is an issue with the GNSS viewer software that comes with the GPS module, I have tried it with NTRIP servers using the NTRIP client built into the software but it’s not sending anything into the GPS module, next plan is to test with a separate usb serial adapter and NTRIP client and see if it can get RTK fix.
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The SkyTraq can receive corrections over the standard RX/TX pins. You can test this in Mission Planner directly (their GNSS viewer is kinda sucky to be honest).
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Also, the make an L1/L2 module, not just L1/L5. PX1120R or PX1122R is for L1/L2.
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@jedilord I plan on testing injection via mission planner next. I will probably get it wired up tomorrow, I just wanted to make sure it was actually working first.
I have looked at their other modules and the NS-HP-GN2 PX1122R was only 99usd compared to the 50usd for this one, but I wanted to see if the cheapest one they sold was actually usable for ardurover, if It’s not then the 99usd l1/l2 module will be the next one I test.
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Thank you.
If nothing else, this might be a cheaper fixed base implementation than using an F9P.
I’m using GPS for Yaw so I have two F9Ps on the rover, and currently a third for the fixed base - it seemed a waste at the time, but it was the cheapest L1/L2 receiver I could find that did RAW (or actually calculates the RTCM messages from a provided fixed position)
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I have been looking at mounting options for the antenna, I need to be able to move it to the side to clear the solar panel. Turns out gopro mounts are ideal for mounting gps antennas, you just need a thread adapter to change the 5/8 to a 1/4 thread to use the big antennas or just glue a smaller one to a GoPro thread adapter with the insert removed.
The plastic arm is quite flexible so if your going offroad the carbon or aluminium arms would be better. This GPS doesnt have a compass so im going to get a double gopro adapter and mount both to the arm.
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Hey @geofrancis,
I’m also interested in testing out these cheap SkyTraq RTK receivers. Quick question since you have one on hand, Is the SMA connection on the PCB normal or reverse polarity and is it male or female?
Thanks
Its an SMA connector, without the pin.
