[time-nuts] Secondary phase noise standard & FE405

Bob Camp kb8tq at n1k.org
Sun Nov 13 08:10:54 EST 2016


> On Nov 13, 2016, at 2:55 AM, Gerhard Hoffmann <dk4xp at arcor.de> wrote:
> Am 12.11.2016 um 23:52 schrieb Bob Camp:
>> Hi
>> Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS spurs come
>> straight through. Since the FE-405 compensates for all sorts of things, the DDS moves
>> around a lot. Even a one bit change on a DDS will move spurs around. With an ever changing
>> DDS, you have an ever changing forest of “stuff” on the output.
> I would not expect a lot of dynamics after a month of cont. power up. And the spurs
> do not move and they don't average away, at least not within my limits of boredom.
> The PLL bandwidth seems to be 50 Hz, so the forest from 100KHz to 5MHz is
> far out. That seems somewhat weird and raised doubt together
> with the power level being out of spec.

The spurs you need to watch are under 50Hz. They are the ones from the DDS. The higher
stuff is from the microprocessor. 


>> Not the best thing for a “standard” …..
> I've tried to kill 2 birds with one stone. The FE405 had collected dust for
> months and still was mostly untested.
> The oscillator is not part of the "standard"; I could have used a BVA or
> a maser by just plugging in. I just needed a centre frequency with a
> few dBm for the E5052B to lock on.
> All I want is some known phase noise reference reference lines
> for my private phase detector experiments. Recalibating the
> phase detector by modulating oscillators on different frequencies
> is no fun if you change the Schottkies every 2 minutes.
> regards, Gerhard
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