[time-nuts] GPS SDR

Attila Kinali attila at kinali.ch
Thu Feb 2 09:28:44 UTC 2012

On Wed, 01 Feb 2012 21:53:16 -0800
Jim Lux <jimlux at earthlink.net> wrote:

> You don't need the ADC: you just need a limiter/comparator.

Yes, but this degrades sensitivity quite a lot.

> You don't need insane sampling rates. Think in terms of subharmonic 
> sampling.

This requires that you have an ADC that has the anlog bandwidth of
the signal. And ADCs with a analog BW in the GHz range are damn expensive
and hard to get.

Also a problem is to get the sampling frequency right if you want to
sample more than one band. Downmixing solves both of these problems
at the cost of higher complexity and a bit more noise.
> >> Is there a publically-available antenna design that's easy to
> >> fabricate, has a stable phase center, covers 1100--1600 MHz, and has a
> >> good pattern over this band with low cross-polarization?  Even a large
> >> choke-ring design would be okay if it's fully specified.
> I think there are some crossed dipole designs around.  What about quad 
> helix?

Crossed dipole are narrow band and not easy to build as dual band designs
at least at those frequencies. Quad helix needs quite a precision to get
the right frequency and dual band designs (stacked helixes) get even more

				Attila Kinali

The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin

More information about the time-nuts mailing list