[time-nuts] 10MHz LTE-Lite
kb8tq at n1k.org
Thu Nov 20 18:03:11 EST 2014
Probably a question for John Miles (who designed them and is a list member) or Symmetricom (who now sells them for $10K to $15K).
Quick and dirty description - takes the two inputs and digitizes them against an internal clock. The result is fed to a PC via USB. The data is auto-correlation processed on the PC and after a bit of work by the CPU, you get phase noise information.
> On Nov 20, 2014, at 5:34 PM, Alex Pummer <alex at pcscons.com> wrote:
> Hi Said,
> do you have any information about how that "TimePod 5330A works" any principal description?
> On 11/20/2014 2:08 PM, S. Jackson via time-nuts wrote:
>> Hello Mike,
>> attached is a 10MHz DIP-14 TCXO Phase Noise plot from a random LTE-Lite
>> I had sent out a 20MHz typical phase noise plot some weeks ago, and
>> comparing the two they are almost perfectly 6dB apart as would be expected from
>> the 20log(n/m) relationship. There are variations from unit to unit of
>> course, but it does not seem like one version of the board or the other has
>> advantages in terms of phase noise.
>> I had also sent out a superimposed plot of the 20MHz and the divide-by-2
>> 10MHz output of the same board at that time, and again the relationship was
>> almost perfectly 6dB lower at 10MHz versus 20MHz.
>> While phase noise follows theory, it does seem that the DIP14 metal shield
>> has a beneficial effect on the ADEV stability though. The plots we are
>> getting are pretty darn good, and I want to test more boards before I post any
>> ADEV, because its quite a bit better than our specification and I want to
>> make sure its real.
>> The 10MHz DIP-14 boards do not have an isolating buffer like the 20MHz
>> boards do, on these the TCXO drives the output directly, so one must be careful
>> to set the equipment to 1M Ohms input impedance or use a buffer
>> externally, which is what we did to measure the attached PN plot.
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