RS2 Radio communication with other GNSS?

Hello to all,

I am attempting to send corrections out from my RS2 base to a Hemisphere S631 rover using radio.

The RS2 of course uses LoRa radio and accepts specific frequencies, with a decimal point. For example, 915.0 MHz. The S631 appears to use instead frequency bands and different radio modes such as TrimTalk, etc. I chose Freewave 900 M as that matches the frequencies of the Reach RS2 (902.0-928.0 MHz). For the S631 there is also an option for different hop tables and the possibility of importing a radio configuration file and advanced settings. Both the config file and advanced settings appear to be only available with dealer intervention.

Despite trying different settings on both the RS2 and the 631, I’m unable to get corrections into the S631.

Can anyone help me sort this out?


LoRa from Emlid is propetairy, so only other Emlid units can understand.
You can however attach an external 3rd party radio to the serial output, and that way send out corrections.


Do you have Internet connection in your area?
You can set the RS2 to transmit the corrections to the emlid caster and connect the rover to the mountpoint with ntrip.
I also have hemisphere rover along with reach M2 as base station.
It works but I have some problems with M2 stopping sending the corrections but I am interested to see if RS2 works properly as base station with 3rd party rovers.

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Depending on the distance you are wanting to transmit and a couple other considerations there are two other radio options that can be used.

RFD900 radios are 1W and average between $80-100 each, 3DR radios are normally either .5W or .1W and average between $20-40

I actually did a combination of both as they work on the same SiK technology. I use a RFD900 on my base for the 1W output and a 3DR on my rover. I also found software for the RFD00 and 3DR that enables multi-point so if I am using more than one rover multiple units can receive the base.

Here is the link for cabling

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Hi Christian @wizprod and knowledgeable others- Do you have experience or recommendations on external radios I can use in the 900-928 MHz range that are more or less turnkey, using the RS2 serial port or maybe its USB? By turnkey, I’d like not too much difficulty with cables and will certainly need some interface to configure the radio settings easily.

I can’t use the serial port on my rover (the Hemisphere S631) and connect e.g., a LoRa radio there because I need that serial port for position output.

In terms of the radio protocol of the external 900 MHz I seek, the 900 MHz of the S631 uses Freewave 900 M.


What is your Hemisphere connected to via serial cable?

On your Hemisphere with the serial port, can you configure the input for RTCM? The serial port has 3 pins used (normally) ground, RX (receive) and a TX (transmit), one serial connection can be connected to two devices. Serial out would most likely be NMEA connected to whatever device or monitor (TX from the hemisphere to RX of the device/monitor) Serial in would be RTCM connected to a radio (RX of the Hemisphere to TX of the radio). Baud rate etc. would have to be the same for everything.

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That sounds potentially promising, thanks. My Hemisphere needs to connect via serial port to a ground penetrating radar (GPR). The GPR needs positions in NMEA GGA. I guess that sort of setup does raise the question of how I would go about configuring the radio settings…

Hi Brian,

Please keep us posted on your progress!

I can comment on the radio settings that should be used from Reach’s side only. If you connect an external radio to the Reach RS2 USB port, you will need to choose the Serial USB option in the ReachView 3 Correction output tab.

Hi @vgo195,

May I ask you to elaborate on the issue with the Reach M2 base that stops sending corrections? In which situations does it happen?

I have reported the problem in other post so you can check it there.

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How deep does your GPR go, accurately? I have always wanted to try one to locate existing farm drainage tile.

Depth depends on antenna frequency and on soil conditions and moisture. With my setup, worst case is about 1 m depth-- that would be in pure wet clay. Best case is dry sand, then 10+ meters. Normal range I see where there’s some clay but not too much is 2-4 m. GPR doesn’t work in areas of salty or brackish groundwater.

so in our heavy clay, not so good

I always think it’s worth a try. Technically speaking, there are two uses of the word “clay”-- one is a size description, and clay-size material is not the issue for GPR. Clay mineralogy is the problem. Clay minerals like illite, montmorillonite, and similar are electrically conductive and that’s the problem.

If you are in the US, there are a series of GPR suitability maps that may help

GPR index very low in our area see attached from your attached map.GPR

Yes, lots of glacial drift there in Ohio… map shows low or very low where you are. That’s doesn’t mean it’s not worth a try, as I find that modern GPRs often perform better than I would expect by the USDA suitability maps. Feel free to message me for further info and tips.

Problem is, they do not have a “loaner” unit to give it a try.

Remember with 232, RX and TX lines are completely separate other than configuration.

So if everything is set to 57600 8 N 1 for example, the radar gets the hemisphere tx out position, and the corrections come in on the hemisphere rx line, grounds are common.

Used this on the m2 to get corrections in and position out the s1 port at the same time after i think @kseniia.suzdaltseva told me it would work.

I can confirm that the S1 port can be used for both Correction input and Position output. However, a custom cable is needed for this purpose.

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