[hpsdr] New clock oscillator for OpenHPSDR?

[Brian Lloyd]

On Fri, Dec 13, 2013 at 10:52 AM, Helmut, DC6NY <dc6ny at gmx.de> wrote:

> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Kjell.
>
> Thanks for information, but I see no direct chance for any substitution in
> this 5V sine wave application. On the 10 MHz level phase noise hasn't been
> an issue and concerning to the sampling frequency 122,88 Mhz I'm not sure
> that the approx. 10 dB better phase noise can improve SFDR dramatically.
> But
> it's interesting that a lot of suppliers meanwhile  discover phase noise a
> determining factor of total system's performance.
>

Please correct me if I am wrong, but the loop filter at the output of the
phase comparator prior to the control input at the 122.88MHz master
oscillator effectively attenuates the phase noise from the 10MHz reference
thus preventing it from affecting system performance. I would expect the
native phase noise of the 122.88MHz master oscillator to dominate the phase
noise performance of the system. This would mean that a low-phase-noise
reference (GPSDO or Rb) is not that necessary.

Am I correct?

-- 
Brian Lloyd, WB6RQN/J79BPL
706 Flightline Drive
Spring Branch, TX 78070
brian at lloyd.com
+1.916.877.5067
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