[time-nuts] Truetime XLi sat signal levels (dBW to dBc/SNR conversion question)

[Mark Sims]

I have figured out an empirical formula for mapping between the TrueTime dBW values and the more traditionally reported signal level values.   

I ran a Ublox F9T and the TrueTime in parallel off the same antenna.  By comparing the TrueTime and Ublox sig levels a rather trivial mapping function popped out.   Basically you divide the dBW level by the (max dBW)(=145) -min dBW(=196) values) to get a value in the range of 0..1   Multiply that by 50 and add a 3dB fudge factor).   The two values match within 1 dB.

My XLi uses a Motorola M12 GPS receiver.  The XLi reports signal levels less that around 30 dBc as -196 dBW,