RSSI and other questions

[hydrolocked]

1) I am playing with the RSSI values - maybe UPman can help - what is this calibrated to? there must be some dBuV reference and approximate value per RSSI point... just trying to build a better looking pseudo accurate interface.

2) what are the approximate (3 dB) bandwidths of the different receive modes? (there's FM, NFM, WFM, FMB, and AM)

3) what is the rationale behind blocking (or not including) 512 - 764 MHz? I didn't think these were "forced" blocks, like the cell band is.... I know there's not a LOT out there, but there are a few things in there that might be interesting... any chance these might be "brought back", or will the hardware (filters, etc.) not support it?

thanks....

 

[hydrolocked]

OK, here's at least one answer:

the RSSI is totally relative to some internal reference, and varies (slightly) with frequency.

Using a Rohde & Schwarz signal generator (SML01) set with a 1 kHz deviation modulation:

at 150 MHz

-20 dBuV corresponds to an RSSI of ~100 (this is in the noise floor, but the tone was discernable only because i knew it was there)
-17 dBuV = minimum discernable signal
-15 dBuV = 113
-10 dBuV = 141
0 dBuV = 230
+30 dBuV = 407
+40 dBuV = 432
+50 dBuV = 456
+60 dBuV = 462
+75 dBuV = 489

at 450 MHz, the numbers are slightly lower (I only gatherd 0 dBuV and above), and it's not a consistant value, but it's typically 5 - 15 RSSI points

the RSSI LOOKS to be somewhat logrythmic, but it doesn't track with dBuV, uV/mV, or dBm.

overall:

0 dBuV RSSI points:

850 MHz - 225
450 MHZ - 227
150 MHZ - 230
30 MHz - 235

If i get some more time with the sig gen, i might try to find some more noise floor measurements.

I'm testing this on a 996T with firmware 3.0.

 

[hydrolocked]

here's a plot on how the RSSI relates to real world values.

 

[brscanning]

Thanks for the post. I have attempted to make some sense of the RSSI levels for ID Tracker II. I ended up just scaling the signal meter to what appeared to be the top value. It was no where near the expected 0 - 1023.

 

[hydrolocked]

with my maximum value less than 600, and my program sweepign the signal generator up to +10 dBm (10 mW, or 117 dBuV), i think their scale is a bit whacked - in order to hit 1000, it would see you need almost a full watt (+30 dBm or +137 dBuV) induced into the receiver... unless you're parking under a high powered transmitter location, it doesn't seem realistic!