[hpsdr] Precise receive frequency measurement

[Brian Lloyd]

On Thu, Mar 7, 2013 at 2:28 AM, John Marvin <jm-hpsdr at themarvins.org> wrote:

> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi,
>
> Someone previously mentioned (I think it was Joe) that Hermes/Mercury does
> not always use the exact frequency that is programmed into the receiver,
> due to the down conversion / decimation algorithms used in the FPGA. Is
> there any documentation on this? For example is there a formula for
> determining which frequencies will be exact? If not, will frequencies that
> are exact multiples of the sampling rate be exact (for example 7.056 Mhz in
> the 40m band is an exact multiple of 48 Khz, assuming 48 Khz was being used
> for the sample rate).
>

Ditto this request. I plan to use my Hermes board in the frequency
measurement tests and knowing the truncation and/or round-off errors would
be really useful since I am shooting for something close to 1e-10 accuracy.

-- 
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian at lloyd.com
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
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