No RTK fix with LR radio

Q&A forumNo RTK fix with LR radio
Kaupoi asked 8 months ago

I’ve been using LR radio for transmitting corrections from my base to my NTRIP Server with success now ovar a year. Now I came up to a situation I need to put receiver LR xbee module on one of my rovers. I updated firmware to 1.13 and uploaded the latest configuration file (simpleRTK2B_FW113_Rover_1Hz-00.txt) to the rove successfully. 
Leds show:
GPS->XBEE off
XBEE->GPS blinking 3 pulses/s
GPS FIX blinking 1/s
RTK FIX on
 
My antenna is at the window at the moment, but I can get instant FLOAT with NTRIP but with xbee LR only 3D. 
What could be the reason I can’t get FLOAT (and with better view of sky FIX mode) with LR radio?

4 Answers
clive1 answered 8 months ago

Perhaps the radio isn’t configured properly?
Check the ZED gets RTCM3 messages via UBX-RXM-RTCM, if it is not getting messages properly it will stay in 3D forever..

Kaupoi answered 8 months ago

UBX-RXM-RTCM was empty. But it seems that indoor radio antenna can’t handle finnish weather outdoor very well. I changed the antenna of the base, and now I see messages coming in at rover UBX-RXM-RTCM. But fix mode is still 3D.

Kaupoi answered 8 months ago

Using 1005,1074, 1097 and 1230 I get a FIX now. Adding 1084 or 1087 no FIX. 

paulo answered 8 months ago

The problem is the lack of bandwidth of the radios. In the release 1.13 the RTCM receiving part rejects the complete packet of messages if one of them is missing.
Therefore when you try sending additional messages you loose the FIX.
A reasonable configuration for the use of all constelations is sending 1005 and 1230 every 9 or 11 secconds and 1074 1084 1094 1124 every seccond. It will not work with the MSM7 messages because they are larger and you do not have ennough bandwidth with the radios in the configuration they are delivered by ardusimple.

PPascal replied 8 months ago

Thanks, your answer helped a lot. Please @Ardusimple update config files accordingly, I met the same problem as topic subject.

Ardusimple Staff replied 7 months ago

Hi paulo, we can’t reproduce the problem here. can you confirm that you are using our configuration files for both base and rover?

G. Thalmann replied 1 month ago

You can further improve success of communication using only 2 GNSS systems: GPS and GLONASS (MSM4 and 1230 message).