[time-nuts] Symmetricom 5115

Bob Camp lists at rtty.us
Thu Apr 8 12:18:42 EDT 2010


Hi

True, the 3048 is not much of a frequency counter. It's also pretty limited
as an Adev box.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of John Ackermann N8UR
Sent: Thursday, April 08, 2010 8:25 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Symmetricom 5115

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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> 
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