RTK Base station radio coverage in hills


I am new to agopengps and am thinking about setting up a system in time for next spring. I farm organic in a rather hilly part of the country. I would be installing autosteer on various IH tractors such as the 756 826, and maybe a case IH 7130. I would like to use a hydraulic steering block so as to keep the operator station nice and uncluttered.

My main question now is as to an rtk base station. I would like to use an rtk base station with a radio link to the tractors. being as my ground is quite hilly, i forsee difficulty in getting a good radio link over all the hills and down in the valleys, and would like to not rely on cellular internet for the rtk fix. with that background, here are my questions.

can i put multiple base station towers around the farm (¼-½ mile apart) and will the tractor system use eithier or both as needed, or will the multiple radios interfere with each other? I suppose i would be using an xbee radio or whatever else was working for other people in this example.

can i use some other radio link that was better? (such as a a TNC and some FM 2 way radios?) can i run the xbees or similar radio through some repeaters and get good coverage that way?

basically the questions boil down to; what can i do so that i have a good radio link to my rtk base station on a farm that is RF challenged.




Lower frequencies will work better but seeing as your bases would be close together, you could run a mesh network with Digi SX (Ardusimple LR but with different settings/firmware).

Do you know what you local regulations are for frequency and power output?

Do you have a central hill that might cover everything?

Honestly the easiest way is to use NTRIP, RTK over cell internet connection. Several free NTRIP caster PC programs are out there. We published one a few years ago (Back40Precision), there is also SNIP free caster and BKG free caster. Both ours and SNIP will run on a plain old Windows PC. But to use NTRIP you need to have a fixed IP address for your house/farmstead where the PC is located or use a web server which means paying an access fee to google or some other server space rental company.
Then you use your cell phone as the in tractor “client” end of the system. Either a Blue Tooth link to the tractor receiver or shared hotspot. As long as you have cell data coverage this works well.

Otherwise, you can use repeater radios. You have to setup each radio to listen to the master radio located at the base station. These then can repeat the data transmission. Each needs to be where they can pick up the master radio or the one before it in the link. This way the tractor can have access to at least one repeater or the master in every field. You must place the repeaters high enough to clear the hills before it. Freewave radios are the easiest to setup to me anyway. Freewave 900Mhz for NA or 800something Mhz for most EU countries don’t require licenses most of the time.

Many xbee radios are capable of operating as a mesh network. If the rover and base can’t communicate directly, they will automatically find a path through other radios on the network.

Kind of like a repeater, but more advanced and different terminology.

You could setup an xbee with a USB battery bank and set it on hill tops as necessary. Or if you get in an unforeseen scenario you could even use a spare tractor to create a mesh.

I would not think about creating multiple bases. It’d be quite an additional cost, quite a bit of additional work, and getting the lines to match up between bases will be an extra headache. Thinking about mounting weatherproof boxes on multiple tall things and running power to them all already stresses me out!

I would still try to connect the base to the internet if possible, then you could always hotspot your phone for NTRIP if you go to the neighbours place or something.

My base uses internet and I’m looking into radios as well. Internet in Canada is too expensive and not reliable enough. Setting up a reliable internet connection in the cab is harder than it sounds. The tablet with a SIM card doesn’t get great signal, the phone hotspots aren’t stable. Getting dad or part timers to setup a hotspot is just not possible. If I have to buy a cellular router device then I’d rather buy radios. I just want it to work when I turn on the key. My current base is a pi, RTKbase, micro F9P, and a custom PCB for POE. I think I’m going to modify the PCB with an XBEE slot and have all the options.

We’ve found some free workarounds for a static IP or servers.

Instead of using a fixed IP you can use a free dynamic DNS service like DuckDNS. Or you can use a free VPN like TailScale running on a home device (pi).

Or there are free NTRIP web servers like rtk2go.

thanks for all the replies! I currently dont have a cell phone that i carry with me, so while i could buy one, radio sounds like the best option. Glad to know that the freewave and/or xbee radios can operate in repeater/mesh configuration. I have some experience with radios, (the commercial 2 way kind), and have helped build a couple of remotely powered radio links, so i could reliably handle the power and tower side of multiple small towers. i agree with the lower frequencies working better, i would much rather get into the uhf or high vhf frequencies, but it is hard to find legal frequency space in the best spectrum, unless i ran it over a commercial business radio link. i have hopes of access to a 140’ tower, but that still might not cover all my valleys at 900 mhz or similar, and may cause problems with tower sway in wind if my gps is up anywhere near that high.

are there any good threads here on the forum for a good rtk base build with a radio link and/or a good thread on radios in mesh/repeater configuration for me to read up on?


Really you only need the radio or antenna on the tower. Mount your base antenna closer to the ground on a fixed point. We have ours on a bucket on the end of our house roof at the peak. Just have the bracket mounted slightly to the side. The same could be done on a fixed post like 6 ft up from the ground and run cable to the receiver. Then mount the RS232 radio either on the tower or at the base and run coax up to an antenna.
Many former Deere comparable Comnav base stations were setup like that. So long as your gnss antenna is fixed then tower sway on the radio antenna won’t matter at all.

It’s hard to beat freewave 900mhz radios on power output and range. Deere even used freewave inside their radios.

As far as a base. I just found Sparkfun electronics is selling a base complete using the Ublox F9P. They have USB and Ethernet output. They also have a connector with serial outputs but it appears to be at the 5 volt TTL level so would need an added rs232 converter to hook it up to most radios.

Depending on your cell service, most companies have wifi hotspot devices. Like Verizon Jetpack. You can always use that sharing the family data. Then whoever drives the tractor just needs to turn it on. Just one way to get different drivers and use cell service. For whatever reason tablets with SIM cards don’t have the best reliability with cell service. Seems the phones and hotspots work much more reliably but all depends on the cell provider network coverage.

My base is on the house roof, connected via ethernet, and the radio is on my tower, also connected via ethernet. It’s all very custom but no long coax cables.

Could you share how you did that radio setup? What does the hardware look like on the radio end?

My base (Piksi Multi dev kit) has ethernet built in. So at the radio end I used an ethernet serial server device with TTL serial connected to the Xbee serial. Currently I run strsrv in-between to control the message rate but my radio’s TCP client could connect directly to my base’s TCP server.

Thanks Matt. I’ll have to look into that, that’d be a nice way to get the radio somewhere else on the property and get the antenna up much higher. RTKBase can host a local TCP server, an ESP on the radio end could connect and do the serial serving.