[time-nuts] HP 58540A Phase Noise Improvements

John Day johnday at wordsnimages.com
Fri Jul 7 14:41:45 EDT 2006


You're right Matt. The basic PN performance of the LO chain in the 
IC-7800 is not too good. Measurememnts of the IMDR confirm this. So I 
personally think looking for a lower phase noise OCXO would be a 
fruitless exercise. It would be far more valuable to figure out what 
features of the design of the 7800 contribute to the problem. The 
IC7800 is a 'strong' receiver in terms of IP3 and IP2 - one of the 
best in ham terms, but I am not sure that without drastic internal 
surgery you are going to do any better.

Of course, if someone would like to send me an IC7800 I would be 
happy to experiment on it!

John


At 01:19 PM 7/7/2006, Matt Ettus wrote:
> >
> > Does anyone have any suggestions as a replacement OCXO with excellent phase
> > noise approaching -160 dBc @ 1 kHz?  Are there any special precautions or
> > other alignments required when dropping in a replacement OCXO?  Thanks!
> >
>
>Paul,
>
>It is very likely that the close-in phase noise of the ICOM is
>determined more by the dividers in the PLL than by the phase noise of
>the reference oscillator, especially at such low levels.  Assuming
>that the ICOM divides the 10 MHz down to at least 100 kHz, the phase
>noise of the OCXO would be divided down to -200 dBc, which is well
>below the internal divider noise of the PLL.  Thus even an OCXO with
>absolutely no phase noise would not improve things.
>
>Matt
>
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