Well, you also get ADEV down to <1e-14 at tau = 1 second, and a 13 digit
frequency counter. And as long as you're working in the HF range, the
big advantage over a PLL system is that you only need one reference
oscillator because the reference and DUT frequencies are independent.
As JohnM said, the 5115 is really more of an ADEV box. As I understand
it, it was mainly intended to replace the 5110 which had very limited PN
capabilities.
John
----
Bob Camp said the following on 04/07/2010 08:14 PM:
Hi
So basically what I get when I buy a 5115 is a limited frequency range box that isn't quite as good as (as in 40 db worse than floor) an HP 3048. Of course I'd need to buy a cheap synthesizer to go with the 3048 if I wanted to do the "any frequency" stuff at the 5115 level.
Bob
On Apr 7, 2010, at 7:04 PM, John Ackermann N8UR wrote:
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.
John
----
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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