[hpsdr] Precise receive frequency measurement

[Bruce Beford]

Which is exactly what I do, Phil. Thanks. I asked "in the open", for those
who may not know this. I have dabbled in the FMTs that are run regularly,
and I have used the Mercury/Excalibur with the Trimble Thunderbolt GPSDO.

In the past, I have been able to nail the mystery signal down as close as 9
milliHertz on 20M. Down in that accuracy range, Doppler shift is the biggest
issue, and causes the operator to use a fair amount of "Kentucky windage" to
place the best guess. Knowing your actual RX freq setting to within a couple
milliHertz does not really grant you any better accuracy in the over-the-air
measurement, in my experience.

73,
Bruce
N1RX

-----Original Message-----
From: Phil Harman [mailto:phil at pharman.org] 
Sent: Friday, March 08, 2013 3:07 AM
To: Bruce Beford; hpsdr at lists.openhpsdr.org
Subject: Re: [hpsdr] Precise receive frequency measurement

Yes,  but it will be if you use an external 10MHz reference that has your 
required accuracy.,

73 Phil...VK6APH



-----Original Message----- 
From: Bruce Beford
Sent: Friday, March 08, 2013 10:05 AM
To: hpsdr at lists.openhpsdr.org
Subject: Re: [hpsdr] Precise receive frequency measurement

***** High Performance Software Defined Radio Discussion List *****

Thanks, Phil.
Doesn't the overall accuracy of this formula assume that the 122.88 MHz
clock -is- in fact, exactly correct?

73,
Bruce, N1RX

> 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:

> phase =  frequency * 2^32 / 122880000

> You will be able to calculate the actual frequency from the above.

> 73 Phil...VK6APH





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