[time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812...

[Bob Camp]

Hi

I would pretty much ignore any 60 / 120 / 180 Hz spurs in a US phase noise plot. The same thing would be true of 50 / 100 / 150 Hz spurs from a country that uses 50 Hz power. Unless everything is running in the middle of a corn field on batteries, there is no way to be *sure* that they are not part of the measurement setup. 

If you happen to be on a circuit with heavy rotary machinery, you can see artifacts at 1/2 or 1/3 or 1/4 the power line frequency. I doubt that in that case the bearings on the equipment are going to last very long. They rarely are strong enough to bother a phase noise plot, but I have had it happen. 

Bob

> On Nov 17, 2014, at 3:01 PM, Tom Miller <tmiller11147 at verizon.net> wrote:
> 
> That first spike falls right at 60 Hz. I wonder if your test setup is picking up some hum?
> 
> Tom
> 
> ----- Original Message ----- From: "S. Jackson via time-nuts" <time-nuts at febo.com>
> To: <kb8tq at n1k.org>; <time-nuts at febo.com>
> Sent: Monday, November 17, 2014 2:26 PM
> Subject: Re: [time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A,Z3811A, Z3812...
> 
> 
> Hi Bob,
> 
> yes, the 10MHz plot is rotten, no doubt. The 15MHz plot is quite good till
> about 40Hz offset, then it becomes pretty rotten too.
> 
> Here is one of my 58503A units (using the 10811 OCXO) as a comparison..
> measured against our DROR-IIA (this plot was actually done to show the
> DROR-IIA PN, but since that unit actually has less noise and spurs than the
> 58503A we can simply use it as the reference for this purpose).
> 
> The good news is that getting the close-in phase noise to be good is very
> hard to do and the unit delivers that out-of-the box already. Filtering out
> the  noise and spurs above 40Hz offset is pretty easy to do. It should be
> fairly  straight forward to cobble up a small PN filter for those units to get
> rid of  the noise and spurs above 40Hz offset.
> 
> bye,
> Said
> 
> 
> In a message dated 11/17/2014 09:31:46 Pacific Standard Time, kb8tq at n1k.org
> writes:
> 
> Hi
> 
> Here’s the phase noise on the 15 MHz. There are a few  spurs, and an very
> real hump out at the likely frequency of the Lucent  switcher.  The 15 MHz is
> pretty clean compared to most /all of the other  units I’ve seen on the
> surplus market.
> 
> I would not multiply this up to  40 GHz with a broadband multiplier. I
> would be quite happy to run it into a  PLL with a rational bandwidth. You will
> beat the noise on the output with a  fairly simple VHF VCXO past 100 Hz. No
> reason to have a bandwidth outside the  20 to 80 Hz range.
> 
> Math:
> 
> 15 MHz to 150 MHz -> 20 log (N)  -> 20 db.
> 
> -140 dbc / Hz shown below at 100 Hz offset -> -120  dbc/Hz
> 
> You can get numbers better than -120 dbc/Hz at 100 Hz offset out  of a
> number of pretty simple VHF VCXO circuits. Bert has one that seems to  work fine
> for him.
> 
> Bob
> 
> 
> 
> 
> 
> --------------------------------------------------------------------------------
> 
> 
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