X-CTU's RSSI Test units

Hi there! I would really like to know in what units are X-CTU’s RSSI (inside the range test sub menu) numbers that are on top of the colored bar.

For example here I have a -60


I would like to know in what units those numbers are. I can’t seem to find anything in the X-CTU and XTend manuals.

I know that through an AT command you are able to get the values of the RSSI (you need to convert them from Hex to Dec I think) but what about that number (the one on top of the colored bar)


The units are in dB. The scale will range between -40 (the strongest the software will report), and the receiver sensitivity of the radio you are testing.

thanks gworle!

According to the XTend manual, the receiver sensitivity is -100 dBm.

So just to confirm: The RSSI can only go from -40 dBm (ideal signal) to -100 dBm (the weakest signal that can be picked), right?


The XTend’s RSSI will be -100dB when the radio is operating at 115200bps (BR = 1), on the RF data rate. When the RF data rate is dropped to 9600 baud (BR = 0), then the receiver sensitivity is -110dB.

well I’m getting -60 dBm (RSSI) in a 1.8 Km link (1.11 miles). Radios are configured to use 1 W of power at 115200 bps… this isn’t very good, right?

apparently -60dBm’s are equal to 0.000001 milliwatts :S

I don’t know much about antennas and appropriate power levels but isn’t that like not much? xD

-60dB isn’t bad at all. This means that you still have 40 more dB of fade margin.

If the environment were to change, that can get eaten up pretty quickly, but in the same LOS, this can mean plenty of distance.

In a line of sight situation, it requires 6dB to double the transmission distance. So, for example, if you get 1 mile and have 40 dB left over, than you would get 2 miles at -66db, 4 miles at -72dB, 8 miles at -78dB, 16 miles at -84, 32 miles at -90

The problem that now I’m seeing is that the cables that I’m using to bring the signal to the antenna are eating around -10dB of the signal strength. Is that a lot? or is this normal?

To the left is the RSSI test with the whip antennas (included in the kit) directly connected to the radios being like 4 m away from each other. To the right is the same test but using the same cables and yagi antennas that I’ve been using for the long range links, but in this case just 4 m away from each other.

Just to let you know, I’m done with the research and we managed to establish a link of 12.35 miles with the Xtend9 modules and high gain antennas.

We didn’t have LOS between them since there was a light obstruction.

Considering that where I live humidity and heat are very high I think that this proves the good performance that those radios can offer.

Thanks for all your help :slight_smile: cheers!