dBm measurement with alpha station

Hi everyone,

I found out, that it is possible to measure the signal strength using Alpha-Station. The results measured are between 50 dBm and 115 dBm. Is it possible, that someone explains me what I am measuring exactly ?

Because I was not able to find an explanation in the tutorial.

Best regards,
Patrick

Hi Patrick,

Here is a definition for RSSI:

  • RSSI

Received Signal Strength Indicator – A specification of the quality of a receiver. RSSI measures the amount signal strength required by a receiver to be able to decode the information in the signal. The lower the number (in negative values), the better the RSSI.

Now it should be noted that Alpha Station is for some reason removing the - sign from the value so a value of 50 is actually -50 and a value of 115 is actually -115.

Digi(the manufacturer of the wireless modules) does not actually provide anything like a chart to convert RSSI to a signal strength percentage unfortunately. But this is mainly due to the fact that there is no perfect solution to converting dBm values to a percentage. There are many differing opinions as to how this should be done.

In conclusion -50dBm would be a very strong signal and -115dBm would be extremely week as the module only as a receive sensitivity of about 110dBm so that is actually 5 points below the rated connection strength.

There is a good article on dBm as it relates to WiFi here:

Sorry for the long answer.

Hi Travis,

Thank you for your answer. I understand now better how the signal strength is measured. However, there is one thing which I would like to explain:

  • I measured 115dBm with two sensors power level 1 and 4 directly next to the Modem.
  • I measured 58 dBm when the sensors were far away from the Modem.

In my opinion, this means that the minus sign is not forgotten but the measured value is shifted by approximative 170dBm. What do you think about that ?

Best
Patrick

Hi Patrick,

That’s possible. I did not develop the Alpha Station software and the engineer who did is no longer with the company so you may be correct in that assumption.

Hi Travis,

Is there a possibility to find out more about the signal strength with another software ? Or by analyzing the source code of Alpha Station?

Best
Patrick