[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.
> 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. 

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

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


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