[time-nuts] DIY Loran-C frequency receiver update

Remco den Besten besten at gmail.com
Mon Sep 29 02:37:18 EDT 2008


Hello Paul and all,

With much interest I read your 'pioneering postings' concerning your 'poor 
mans' LORAN-C-project.

> My current darling is the Analog.com ADUC7026, which seems to have the
> best analog section, but which needs a 42 MHz clock input to sample
> the antenna signal exactly 1 million times per second.
>
> A close second is the www.st.com STM32F103RBT6 which needs a 56 MHz
> clock to run the ADC at 1MSPS, getting 33% more CPU power at the
> same time.

> In both cases, an external PLL (the TAPR Clock-Block ?) will be necessary
> from the atomic frequency to the clock input.

Perhaps it would be an idea to use an Rb-standard with an integrated DDS, 
such
as the FE-5680A. It is capable of producing frequencies up to 20 MHz (and a 
bit higher).

Let it run on 1/3 of the necessary clock frequency and multiply by 3 with a 
transistor
in class C with subsequent filtering and clamping (after all, there are a 
lot of HAMs here ;;-).
Perhaps with the ADUC7026 21 MHz might be possible, in that case 
multiplication by 2
can be achieved with EXORs.
You loose, of course,  a bit of precision, but the 'hazzle' is less.
FE-5680A's can be obtained relatively cheaply on Ebay.

Hope this speeds up your project?

Remco






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