Causes of Poor Transmission Rates

for ST-MOD, while preforming test mission

 It might be related to low solar energy input under the test conditions?

What you can look at is the advance of the Argos transmission serial number and then relate it to the average solar panel voltage. Assuming a transmission every 2 minutes and 8 hours of good sunlight per day (cutting off the first two hours after sunrise in the morning and last two hours before sunset in the evening and/or allowing for some cloudy skies),the nominal transmissions should be 240 per day. As far as a non-shaded tag at the surface with 12 hours from sunrise to sunset and about 3.6V solar panel voltage at day and 0V at night,we should see about 1.8V.

Things to consider if transmission rates of the ST-MOD are low or non existent when performing a test mission.

  • Do the tags have an unobstructed view of the sky?

  • Is the container the tag is in transparent enough to allow the tag to charge properly so it can successfully transmit.

  • Cloudy weather

These three things could greatly affect the transmission performance of the tag during its test mission.

Problem still persists?

  • Check configuration logs for parameters listed below.

    • Argos Transmission Days above zero

    • Start and Stop voltages are correct at 3550mV and 3150mV

    • transmit delay set to 45 seconds

    • CESR is 395 mOhm

    • transmit power of 230


  • Monitoring the transmissions using a radio scanner tuned to 401.650 MHz, while the tag is connected to the computer and SeaDock open

    • Type this command in the white command field, replacing the ### with the serial number of the tag: $###,0,SP,1776,AVTXS,3150

    • Hit the 'Send' command to issue the command

    • Then, verify by getting a calibration report and making sure that 'TX Volt High Threshold' now shows up as 3150mV

    • Next, hit the 'Monitor Mode' button and wait. The tag will exit dock mode after 30 seconds. It will then run in the normal operating mode, including Argos transmissions.


You will see a single digit or character every 16 seconds. This is the 'heart beat' that indicates the tag is operating. The single digit or character corresponds to the tags capacitor volatage with 0-9 corresponding to 2000mV-2900mV and A-G corresponding to 3000mV - 3600mV.

Once the 3150mV minimal transmission voltage has been exceeded (heartbeat 'B' or 'C'), the tag should transmit.

You will now see messages like this:

?BAAB 

ARGOS TX Packet (57/31):FF,FE,2F,F6,3A,4B,AD,04,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,FB,


PA: 225SP 303mA 

?BAAB 

ARGOS TX Packet (57/32):FF,FE,2F,F6,3A,4B,AD,06,00,1F,56,6D,CD,A4,08,86,B8,C3,00,53,AC,00,52,00,0C,FF,E1,03,AB,FE,73,00,36,01,00,00,00,0A,


PA: 225SP 313mA 

?BAAB 

ARGOS TX Packet (57/33):FF,FE,2F,F6,3A,4B,AD,07,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,F8,


Notice the heartbeat messages (BAAB). Next, you see the Argos transmission with the number of transmit days remaining, a transmission serial number and then the byte value of the data packet. For example (57/31) means 57 post pop-up transmission days remaining and this is transmission serial number 31.

Following this, you will see the power amplifier (PA) settings that were used in the transmission. For example 225SP 303mA means that the amplifier power set point was 225,and the transmit current was 303mA. Essentially,the transmit current should be close to the 300mA target commanded in the configuration file. The set point is tag specific, but will generally be around 210-240 units.

Listening to the Scanner

If all of the above checks out, it is useful to listen on the scanner for the characteristic sound of the transmission. Attached find an audio file that includes two such transmissions and their characteristic sound. If for example the modulation settings got cleared,you might here only a slight hissing. Or,if the transmitter does not transmit,then nothing at all.