Community Forum

Reach RS+ tests with external UHF radio (450 MHz)

(Dmitriy Ershov) #1

To collect cm-accurate data in the real-time, you need a reliable correction link between base and rover. With a set of Reach RS+, you can use built-in LoRa radio for RTK communication. This will work well for most applications on distances up to 8km (sometimes even up to 19km).

In some cases, you might want to use other connectivity options of Reach RS to set up RTK link. For instance, if you send/receive RTCM3 corrections from RTK GNSS receiver of another manufacturer.

With the good Internet coverage, the easiest way to configure RTK communication between Reach RS and third-party receiver would be to use NTRIP caster.

If you don’t have Internet access (i.e.you work in the remote area) you can use Reach RS with an external radio to connect it to the third-party receiver. Another typical use case scenario for Reach RS with an external radio would be the agricultural correction service that supplies RTK corrections over radio using industry standard protocols.

Reach RS base and rover communicating over UHF radios.

To demonstrate how Reach RS works with an external radio, we took two 450 MHz UHF radios equipped with RS-232 and Bluetooth and did a quick outdoor test.

Any external radio can be connected to Reach RS/RS+ over USB, RS-232 or Bluetooth. To test different connectivity options, we used RS-232 to connect the radio to the base station and Bluetooth to pair another radio with the rover.

To connect the radio module to the bottom connector of Reach RS you can use DB9 cables for Reach RS/RS+.

Base station. Radios are connected via RS-232.

After placing the base, you can start streaming RTCM3 corrections via Serial port.

The rover was paired with another radio module via Bluetooth (read how to connect Reach with another device via Bluetooth).

Reach RS rover. Radio is connected via Bluetooth.

To start receiving the corrections on rover go to Correction input tab and select BT. If your radios are configured correctly, you’ll see grey bars in the Status tab of ReachView.

Radio modems used for the tests:

− AW435BT

− HPT404BT

If you use Reach with an external radio, please share with us what radio you are using and tell us what your application is!

(Dmitriy Ershov) pinned #2

(Timd1971) #3

Brrrrrrrrr…… : /

(Jake Harders) #4

Hey Dmitriy,

I thought this was topical.

I developed a radio and housing that attaches directly to the Reach RS. It uses the battery of the Reach for power, attaches to the existing 1/4-20 hole and also uses the antenna that comes with the Reach.

I would really like to use this with the ublox NEO M8P but need the industry standard MSM7 1077(GPS) and 1087 (GLONASS) protocols to make this work.

(l3technologycambodia) #5

What is the maximum baseline distance with this radio system? How much does it cost?

(Jake Harders) #6

This is a prototype and I am currently doing range testing. Standard tests are done at a little more than half a mile with no problems not exactly line of sight. As soon as I have a day off in a nice flat field I will post here with real data. Price is something I haven’t looked into. This is just something I wanted but I’ll let you know.

(l3technologycambodia) #7

I was also asking dmitriy.ershov too.

(Dmitriy Ershov) #8

Hey there,

In my post I’ve specified the models we tested:

You can check the manufacturer’s website to see the specs and the price. We didn’t test range.

(l3technologycambodia) #9

List prices:

AW435BT: $2,590.00
HPT404BT: $1,720.00

(l3technologycambodia) #10

Anyone has successfully integrated RFD 900+ radio with Emlid RS+ for Base and Rover? Did it improve the range of baseline?


I have the RFD900+ but haven’t used it lately. From memory, I think you would be able to get much further with Emlid’s LoRa than the RFD900+.

Of course the results will depend heavily on how you configure the settings.

(Carl Schaefer) #12

Does anyone know if you can simply amplify the existing LoRa transmitter to increase distance and penetration for a Base Emlid RS+? I would envision an external amplifier and antenna for the Base with separate power source much like is discussed here but keeping the frequency the same so the Rover units can continue to use the internal LoRa receiver. This would eliminate the need to carry a separate radio receiver on the rover units.

I need to increase distance to about 5-8 miles in some mountainous terrain and while using a 400mHz UHF radio system would definitely help over the standard internal LoRa, having to change frequencies just adds more weight/devices to the rover unit for the surveyors.

Regardless, it is good to know the external UHF radio system works and is an option. Thanks for posting dmitriy


(l3technologycambodia) #14

Yes, I think we are able to just amplify the built-in LoRa radio of Base, it would be great. RS+ is easy to use and light with its built-in LoRa. I am not sure if it is possible or not with this idea.

(Jake Harders) #15

You would just need to find a 400 MHz amplifier that takes 100mW in and spits out something higher yet legal in your country. I haven’t found one.

(Sylvain Poulain) #16

Or type your frequency in Google or eBay or others with boosters …

(l3technologycambodia) #17

but this amplifier has different frequency than RS+ built in radio?

(Sylvain Poulain) #18

Yes you will need 868 or 915MHz ! Please note that you could have lot of interference with this kind of boosters (need to shield it and cable with copper tape). And remember depending where you living : it could be illegal ! It’s widely use in long range UAV FPV world …

(l3technologycambodia) #19

Thank you so much for this. Did you test and see if it works with RS+ LoRa radio? We want to test this but I was told it could break the LoRa radio if the product is not compatible.

(Tatiana Andreeva) #20

Hey there,

It’s hardly possible to use an amplifier with LoRa radio. LoRa radio is more complicated than other radios, so an amplifier more likely will affect only transmitting power, not the receiving.

(l3technologycambodia) #21

We haved used RS and RS+ for over a year now and our clients also, but we could not reach 2km Baseline. Should Emlid introduce external radio system that work longer like other L1 L2 models?