[time-nuts] Low SNR GPS reception and cheap LNAs

nuts nuts at lazygranch.com
Sat Apr 26 04:47:46 EDT 2014


On Fri, 25 Apr 2014 20:19:42 +0200
"Björn Gabrielsson" <bg at lysator.liu.se> wrote:

> > On Fri, 25 Apr 2014 12:21:04 -0400 (EDT)
> > GandalfG8 at aol.com wrote:
> >
> >> Coincidentally, I came across this earlier today when looking for
> >> some MMIC data, perhaps it might be worth a look?...........
> >>
> >> http://lna4all.blogspot.co.uk/
> >
> > Now that's almost perfect! Only two modifications and it does what
> > i need it to do! Thanks a lot!
> 
> Next time I will try a ZX60-P162LN+ from Mini-Circuits.
> 
>  http://217.34.103.131/pages/s-params/ZX60-P162LN+_GRAPHS.pdf
> 
> only $54 for a boxed unit. Bias-T needed to.
> 
> --
> 
>     Björn
> 

Aren't these DC to daylight low noise amps fiction? I was told it is
really hard to design a LNA that is optimal for more than an octave
or so. 

http://www.datasheets360.com/pdf/-5223408218466592358
That minicircuits looks like a good match for 1090 mode-s. Probably
good enough at GPS frequencies too. The input VSWR is good at GPS
frequencies and the output VSWR is OK, maybe a little higher than you
would like. It looks they tuned it for 1GHz.

And yes, amplified noise is amplified noise. But it is a matter of the
noise figure of your receiver. If you are using a crappy DVB-T which
has a noise figure around 5db, you would appreciate the 0.5dB of the
minicircuits. The front end determines the overall noise figure in a
good design. With a gain of 20dB, the noise of the DVB-T is not the
determining factor. But antenna gain is always better than amplifier
gain. 

Regarding the GPS application, you would need to know the noise figure
off the receiver. 

All this said, I think an amplified GPS antenna is cheaper in the long
run.





 



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