[time-nuts] Thunderbolt reception problems

Magnus Danielson magnus at rubidium.dyndns.org
Sun Nov 22 15:05:26 UTC 2009


bg at lysator.liu.se wrote:
> Hi Said,
> 
> With your background, I assumed you would know better...
> 
> What is your antenna gain? What is your antenna cable loss? Does the Tbolt
> work correctly connected directly to the GPS antenna? Do you have an
> inline LNA to add close to the antenna? Do you have a higher gain antenna
> available?
> 
> If 10dB is a lot or nost... that DO depend on the circumstances.

If you already moved the signal towards the lower end of the input 
sensitivity range, then adding additional loss is an issue. GPS 
receivers degrade their performance gracefully with lower input signal 
to the point where it degrades more and more ungracefully. It's one of 
the tests that one should do.

I have come to realize that my rig suffers severly from cable-loss and 
the lack of antenna gain to be followed by a passive splitter before it 
hits an active splitter. I had to build a gain-rig to overcome part of 
that, but it doesn't feel right to use two LNAs in series. It's just 
darkness before my eyes but it works.

The first fix to this is an inline amplifier to be inserted at the 
antenna. Another fix would be to use a better antenna cable.

Cheers,
Magnus



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