Solutions by Industry

Verifying Signal Strength

Raveon wireless modems have a number of ways an installer can verify that the system is working properly.  This application note describes how to verify signal strength on Raveon’s VHF and UHF data radio modems.  

Read The Last Recption’s Signal Strength

The command ATRSreturns the signal strength (in dBm) of the last message that the radio modem you issue it to received. 

The wireless data radio modem must be in the “Command Mode”.  To put the radio modem into the Command Mode, connect to the radio modem using a terminal program such as HyperTerminal or TeraTerm.   If the data radio modem has Ethernet capability, log into it as administrator.  Issue the +++ sequence.  this is three plus signs, with nothing before or after them.  The radio modem will respond with its model number and an OK: prompt when it enters the command mode. 

When you are in the command mode, type ATRS followed by the Enter key.  The  radio will return the signal strength of the last packet it received, followed by an OK prompt as shown below:

OK
ATRS
-92
OK

This indicates the last packet of data that the radio received over-the-air had a signal strength of -92dBm. 

Read the Reception History

There is a short history buffer in the radio that keeps track of the signal strengh and time of the last few packets.  The ATHS command will display a table of the historical packet signal strength and times. 

OK aths ROM RSSI TIME 0000 0 0 0000 0 0 0000 0 0 0000 0 0 1000 -110 33 0002 -75 45 08EA -99 122 0002 -74 131 OK

The most recent reception is on the bottom of the list.

Ping Another Data Radio Modem

The above two processes rely upon having received something from another radio.  There are cases when a newly installed radio has not yet received any data over the air.    In these cases it may be better to ping a remote radio.  You can send a “PING” message out one data radio modem to another.  A PING will cause the remote radio to respond with a short PING BACK message that the originating radio modem will receive.  Embedded in the PING BACK message is the received signal strength that the remote radio modem received the PING message at. 

When the originating radio modem receives the PING BACKmessage from the remote radio, it outputs the ID of the remote radio, and the Received Signal Strength (RSSI) that the remote radio read when it received the PING message.

Note, for PING to work the “Remote Access” must be enable on the remote radio.  By default it is enabled.  The command ATRV 0 enables remote access and ATRV 1 disables it.

Shown below is an example of how a PING command will look, when a radio modem pings unit 0002.

ok ping 0002 <RPR> FROM=0002 -74</RPR> ok

Read the Instantaneous Signal Strength

There is a command within the Raveon data radio modem that allows you to read the current RF level on the radio channel.  It is the ATRQ command.  The moment you issue the ATRQ command, it reads the RF level of any signal on the channel, and reports it back. 

To be useful, you will probably have to have some other radio transmit continuously or put a signal generator on the radio channel at the moment you issue this command. 

It is useful for determining if there is a lot of RF interference on the radio channel.  A clear interference-free channel will have a noise-floor below -120dBm. 

 

Filed under: Installation Information | Posted on December 22nd, 2011 by John Sonnenberg

Leave a Reply

You must be logged in to post a comment.