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<DIV>Hi Brian,</DIV>
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<DIV>The frequency is sent to Hermes/Mercury as a 32 bit value in Hz. This
is converted to a 32 bit phase word as follows:</DIV>
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<DIV>phase = frequency * 2^32 / 122880000</DIV>
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<DIV>You will be able to calculate the actual frequency from the above. </DIV>
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<DIV>73 Phil...VK6APH </DIV>
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<DIV style="font-color: black"><B>From:</B> <A title=brian@lloyd.com
href="mailto:brian@lloyd.com">Brian Lloyd</A> </DIV>
<DIV><B>Sent:</B> Friday, March 08, 2013 12:03 AM</DIV>
<DIV><B>To:</B> <A title=jm-hpsdr@themarvins.org
href="mailto:jm-hpsdr@themarvins.org">John Marvin</A> </DIV>
<DIV><B>Cc:</B> <A title=hpsdr@lists.openhpsdr.org
href="mailto:hpsdr@lists.openhpsdr.org">hpsdr@lists.openhpsdr.org</A> </DIV>
<DIV><B>Subject:</B> Re: [hpsdr] Precise receive frequency
measurement</DIV></DIV></DIV>
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<DIV
style="FONT-STYLE: normal; DISPLAY: inline; FONT-FAMILY: 'Calibri'; COLOR: #000000; FONT-SIZE: small; FONT-WEIGHT: normal; TEXT-DECORATION: none">*****
High Performance Software Defined Radio Discussion List *****<BR><BR>
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<DIV class=gmail_quote>On Thu, Mar 7, 2013 at 2:28 AM, John Marvin <SPAN
dir=ltr><<A href="mailto:jm-hpsdr@themarvins.org"
target=_blank>jm-hpsdr@themarvins.org</A>></SPAN> wrote:<BR>
<BLOCKQUOTE
style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote>***** High Performance Software Defined Radio Discussion
List *****<BR><BR>Hi,<BR><BR>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).<BR></BLOCKQUOTE>
<DIV> </DIV>
<DIV>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. </DIV>
<DIV> </DIV></DIV>-- <BR>Brian Lloyd, WB6RQN/J79BPL<BR>3191 Western
Dr.<BR>Cameron Park, CA 95682<BR><A href="mailto:brian@lloyd.com"
target=_blank>brian@lloyd.com</A><BR>+1.767.617.1365
(Dominica)<BR>+1.916.877.5067 (USA)<BR>
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