Connection RS2+ to external UHF radio to communicate with Cat D6T Dozer running Trimble Gear

I’m looking for information on which Radio I need to connect to my Cat Dozer which is running Trimble equipment at 900Mhz .

I want to connect an external radio through the RS232 port and brodcast corrections to the dozer.

You won’t be able to broadcast corrections to the dozer via radio like you would with an on -site base but if you have a SIM in the machine you can do NTRIP. That would require data access at the base as well so you would need something on site or you could set it up at a location within 40-50km of the site. I setup a base at my house and broadcast through my home Wifi.

What I have been told by SItech which is my local Trimble Machine control supplier is that there should be a radio that I can connect to that would broadcast to the dozer, not directly from the RS2 but through a Trimble radio that would connect to the RS2 via the RS232 port. If that’s not the case then what modem part number do I need on the dozer to NTRIP it?

I know you can connect an external antenna but i’m not familiar with that method. I used Topcon but somebody else on here might be more familiar.

For NTRIP on the dozer it depends on the screen you have. Most of the newer ones already have a modem so you would just need a SIM card and service, but if it’s an older screen you might have to get a modem as well.

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What specific model numbers of trimble equipment are you using. Trimble is very picky to connect to and they change the rules depending on the generation or use of equipment you have. For example an agricultural receiver or modem is locked from connecting to construction equipment,

Your connection options will be outlined in the owners manual for the GPS guidance system that you have equipped.

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Update on this topic,

We have the NTRIP working but still trying to get the external radio to broadcast. I’m being told that I need an older RTCM message to do this. I need RTCM 3.1 and not the RTCM 3.3 that is in the current version. Any help on this would be great

Hi Jason,

At the moment, apart from outputting standard RTCM3.3 messages from Reach, you can additionally output the following ones:

  • 1004 GPS
  • 1008 Antenna Descriptor and Serial number
  • 1012 GLONASS
  • 1033 Receiver and Antenna Descriptors

To choose them, go to Base settingsRTCM3 messagesShow legacy messages. You will need to check the ones you need and choose the frequency. I recommend sticking to the default one, though.

Let us know if it helps.

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Tried switching to legacy messages and still no output on the Trimble TDL 450H uhf radio connected via serial port.

Any help on this would greatly be appreciated.

Hi Jason,

We can check the connection from the Reach’s side to ensure that everything is working fine. I can’t really help you with the settings on the radio so hopefully the users who made it work will chime in here.

Please double-check that:

  1. You connected the proper pins of the radio and the external port. It should go like this:
  • RX ↔ TX
  • TX ↔ RX
  • GND ↔ GND

The pinout of the RS232 port is available in our docs.

  1. Your radio has a stable external power supply. According to the specs, you need to supply the radio with 11.0 V DC to 16.0 V DC, 15 Amp maximum. The RS232 port can provide 5 V only. The overall setup would look close to this setup with PC ADL Vantage:
  1. The output from the Reach is set to Serial. The baud rate matches the one you’ve set on the radio.

If none of this helps, you can double-check that RS2 outputs the data directly from RS232. For that, you will need to remove the radio and check if you see any data on your PC, for example. This will help us to see where the issue starts.

OK so for some context here we started trying to connect to this dozer VIA NTRIP which caused us some problem because the Trimble gear in the dozer is older DCS900 and had to be upgraded to the latest firmware in order to receive the RTCM3.3 msg’s from Emlid Caster. We got that working and running fine. The next step was making sure that in non-cell covered projects we would have corrections going to the dozer so we got the radio that was on the dozer upgraded to a FRU - Radio SNR430 On-Machine 403-473 MHZ Cat. Once that was done we got a TDL 450Hx - 35W Radio System Kit; 430-450 MHz external radio so that we can connect the RS232 port of the EMLID RS2+ an send corrections to the dozer.

After we got the radio and had it installed on the dozer and had the external radio programmed we had to build a patch cord to connect from the Reach RS2+ to the TDL 450 radio. We found the pinout for Trimble in the manual that came with the radio and were able to match it up to the Emlid with the pinout available in the EMLID Documents at []

After we had the proper cable we had to test out the baud rate of transfer which we ended up on 38400 bauds for transmission on Trimble Talk V1. We had to turn on the legacy msg’s in the RS2+ and turn off all of the new mesages in the RTCM 3.3 to turn it into basicly RTCM 3.1 which the DCS900 can read.

Once that was done the transfer rate was verified and everything is working great we are getting 3cm accuracy which at this point we will continue to hope for better once the RCS900 Firware updates allow the newer RTCM 3.3 messages to come through.

If anyone has a bette way to do this connection or has insight on how o get more accuracy out of the base please feel free to comment.


Jason, thanks for sharing your solution! Hope it will help the users who are only starting up with this :slight_smile:

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