[time-nuts] Symmetricom 5115

John Ackermann N8UR jra at febo.com
Wed Apr 7 19:04:18 EDT 2010

I just took a look at the datasheets for the 5115, 5120, and 5125.  .

The 5115 is the "base" model covering through 30 MHz and without a 
cross-correlation capability.  At 10 MHz input frequency, its spec is 
-133 dBc/Hz at 1 Hz offset, and -147 dBc/Hz at >100 Hz offset (not 
spec'd at greater offsets, so presumably that's the floor).

The 5120 adds correlation to lower the noise floor.  At 10 MHz input 
frequency, it is spec'd at <-145 dBc/Hz at 1 Hz, and <-175 dBc/Hz at 10 kHz.

The 5125 extends the 5120 frequency range to 400 MHz.  At 10 MHz its 
"typical" performance is -145 dBc/Hz at 1 Hz offset and -170 dBc/Hz at 
10 kHz (specified performance is about 5 dB worse; the other two 
datasheets only specify spec, not typical).  The floor increases with 
frequency, with the close-in noise going up more rapidly than the floor 
further out.

All three are spec'd at 1 dB accuracy, and can measure at offsets down 
to 1 milliHertz.  One thing that's nice about the TSC boxes compared to 
traditional PN measurement systems is that the reference doesn't need to 
be at the same frequency as the DUT.


Jeffrey Pawlan said the following on 04/07/2010 05:52 PM:
> Dear Nicholas,
> Thank you for getting this discussion back to technical aspects related 
> our real quest for technical information.
> Please look in your actual documentation for the current model 5125 and 
> confirm its actual specs. I had read some specs on the Symmetricom 
> website but I do not know for which model. Although automated and easy 
> to use, I remember that the phase noise floor was lackluster and makes 
> me think that this may be fine for very close-in measurments but not for 
> the usual 100Hz to 100KHz offset measurments. Please let us know what 
> you find with this equipment.
> Regards,
> Jeffrey Pawlan
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