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Differential corrections troubleshooting - Radios

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Haroon Haider
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Intro

When you are not able to get into a differential position mode (RTK integer, RTK float, Differential), you may want to troubleshoot whether the radios are actually communicating. This article is intended to ensure there is communication at the hardware level.

Radios that are mentioned in this article: 

  • SATEL
    • Satelline EASy (manual attached)
  • Freewave
    • FGR2
    • I2
There is a glossary at the end for some technical terms.
 
 
 

Step 1 - Frequency

The first priority is to ensure that the radios are in the same frequency and that this frequency is viable. On the back of the radio should be a sticker describing the possible frequency range, which should be checked with the number that periodically flashes on the radio display.
 
This frequency must be a multiple of 25 kHz (i.e. 0.025 MHz). It is possible that other radio users at OxTS may be on the same, or similar frequencies so you may want to ask around in your building to check for interference.
 

Step 2 - Baud Rate

There is a chain of four items which must all have the same baud rate - the base station, the sending radio, the receiving radio and the mobile station.
 
OxTS devices (RT3003 etc.) 9600 bps by default
NovAtel devices (PwrPak7 etc.) 19200 bps by default

 

Step 3 - Operating Mode

The next step is to check that each radio is in the correct mode - RX for the receiver and TX for the transmitter. For the Satel radio this can be found in:
  • Setup (Right button)
    • -> Additional (Use up/down buttons to find)
      •   -> Priority (Check that it says RX/TX) 
When correctly set up, the RD or TD LED lights should be flashing on the front of the device, as well as the CD light. 
 

Step 4 - Serial Connectors

The link between radio and receiver is a serial connection, which has many possible configurations. It is important to find the user manual and check that the pins on all cables match up with what you need. 

Radios
Satel EASy radio DB15 female (in)
FreeWave FGR2 radio DB9 female (in)
GNSS Receivers / INS Devices
RT3003G INS DB15 male (out)
GPS-Base Receiver

DB9 male (out)

Communicates to radio through COM2 port
PwrPak 7 Receiver

DB26 male (out)

N.B. - supplied with COM1 only cable with a DB9 female ending (can be tricky)
 
Depending on your radio, receiver and supplied cables, you may be using a type of serial converter or genderchanger:
 
Unit Likely use case Check for
PwrPak7 direct connection to RT3003G 14C0097A cable in between Power provision and data pins 2 and 3 
PwrPak7 connection to Satel radio Genderchanger to fix the female end connector Mirroring the pins (2 and 3) rather than being carried through
 
 
 

Step 5 - Error Correction Settings

Make sure that the error correction settings are not drowning out any desired signals - if in doubt, turn this feature off on both radios to see if the problem is fixed.

Step 6 - Sanity Check

If the radio still isn't working, try using a third radio to check for shorted or otherwise damaged serial connectors. It is recommended to cut the power before removing serial connectors to prevent any electrical faults, so this may have occurred before you acquired the radio.

 
 
 

Satel Radio LED Definitions

RTS CTS TD RD CD Descriptions
Request To Send Clear To Send Transmitting Data Receiving Data Carrier Detect  
Off Red Off Off Off Idle - No data transmission at all
Off Red Off Off Red (constant) RSSI threshold possibly set too low
Off Red Red Off

Red

 Transmitting a data packet
Off Red Off Off Orange Noise or other transmission on this frequency
Off Red Off Green Green Receiving a packet

 

Freewave Radio LED definitions

Base CD Base TX Base CTS Mobile CD Mobile TX Mobile CTS Descriptions
Red Red Red Red Off Red flash Power no link
Green Slow red flash Slow red flash Green Slow red flash Slow red flash Linked
Green Green Green Green Green Green Setup mode

 

 

 

 

Glossary

Carrier Detect Line

The "Carrier Detect" (CD) LED refers to a signal from the radio modem to the DTE (Data Terminal Equipment). It indicates whether there is activity on the radio channel - it's active whenever a signal exceeding the level required for reception exists on the radio channel, or when the radio modem itself is transmitting.

It doesn’t make any difference if the signal is an actual data transmission, a signal of a radio transmitter not belonging to the system, or even an interference signal.

RSSI Level

RSSI, or “Received Signal Strength Indicator,” is a measurement of how well your device can hear a signal from an access point or router.

Because an RSSI value is pulled from the client device’s WiFi card (hence “received” signal strength), it is not the same as transmit power from a router or AP.

 

 

 

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