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

[Dana Whitlow]

Mark,

When you refer to "30 dBc", what is that?   Is it the eb/n0 value?  If so,
with the XLi's
behavior as you report it, your scheme would fail over most of the useful
signal range.
And, it will probably differ from setup to setup of the HW, depending on
all the parameters
that have already been discussed.

Dana



On Fri, Jun 14, 2019 at 9:00 PM Mark Sims <holrum at hotmail.com> wrote:

> 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,
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