[time-nuts] GPS SDR (was: FE-.5680A trimming resolution)

Magnus Danielson magnus at rubidium.dyndns.org
Sun Feb 5 12:49:24 UTC 2012


On 02/03/2012 05:30 AM, Jim Lux wrote:
> On 2/2/12 12:05 PM, Daniel Schultz wrote:
>> I found this homebrew GPS receiver project recently:
>>
>> http://www.holmea.demon.co.uk/GPS/Main.htm
>>
>> No custom specialized chips that are unavailable in small quantities,
>> or which
>> will go obsolete in a few months. I think the best solution for the open
>> source GPS community is to design open source receivers with commodity
>> parts
>> that won't be discontinued in the near future, or for which another
>> commodity
>> part can be substituted if need be. Maybe somebody can extend this
>> design with
>> a 2-bit ADC on the end (not me, too many projects here already...)
>>
>> Dan Schultz N8FGV
>>
>
> I still think that finding appropriate off the shelf parts to make a
> subharmonic sampler would be a better strategy..
>
> It's all about whether you want IF filters and a mixer+LO or RF filters.
> I think the amps are the same either way.

The problem with the limiter design is that it is captured by CW noise. 
It's in the literature. Using a few bits reduces the need, but the AGC 
control loop needs to be there. With sufficient bits it isn't very 
critical with AGC anymore.

Cheers,
Magnus



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