[time-nuts] Thunderbolt reception problems

Magnus Danielson magnus at rubidium.dyndns.org
Sun Nov 22 23:39:58 UTC 2009


GandalfG8 at aol.com wrote:
>  
> In a message dated 22/11/2009 21:23:49 GMT Standard Time, bg at lysator.liu.se 
>  writes:
> 
> AMU and  SNR are two different scales. I do not have a translation. A
> Kepler award  recepient once explained Trimbles AMU as "a meaningless
> unit". That said,  SNR or C/N0 values cannot be directly compared between
> different receivers  since the measures might be taken at different points
> in the  receiver.
> 
> The Trimble monitor program can be made to switch between AMU  and SNR in
> one of the configuration menues. I think you might have switched  to SNR.
> 
> 
> ----------------------
> Ah, that explains it, I wasn't aware there were two options but you're  
> quite right.
>  
> I don't recall switching it, and Thunderbolt Monitor doesn't seem to have  
> the option to switch it anyway, but I found the option in GPSMon 1v05  and 
> 1v6 and it can indeed be toggled.

The Thunderbolt Monitor does have it, I just ticked the box and had my 
C/N measures instead. In the "Setup" menu, select "Packet Masks and 
Options..." where you in the "Packer 35 Options" frame, the "Auxiliary 
(Byte 3)" sub-frame find a tick-box for "Output dBc/Hz". Tick the 
tick-box and press the "Set Options" button and you get dBc/Hz values 
rather than AMU values.

> Whereas GPSMon changes the label of the field to suit it doesn't help that  
> Thunderbolt Monitor leaves it described as AMU regardless of the  setting:-)

A bit confusing indeed, but the values should never really overlap, so 
values should be a good hint on what to expect.

Bottom line, use C/N values whenever you can.

Cheers,
Magnus



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