[time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

Magnus Danielson magnus at rubidium.dyndns.org
Sun Sep 18 08:04:25 EDT 2016


Indeed, now I see it. As we expect around +10 dBm, the noise-floor might 
be raised by about 20 dB.

I was more considering what is the reference noise here, is there a 
single oscillator as reference? Can a quieter reference oscillator be 
used? Can a cross-correlation setup be done?

Cheers,
Magnus

On 09/18/2016 01:52 PM, Bruce Griffiths wrote:
> The signal level is also very low.
> Brue
>
>     On Sunday, 18 September 2016 11:47 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
>
>
>  The phase-noise still looks fairly high. How do you measure this?
>
> Cheers,
> Magnus
>
> On 09/18/2016 01:27 PM, David C. Partridge wrote:
>> Now that's interesting I just re-ran the measurement, and got a quite different result which is attached.  The spurs have GONE.
>>
>> My only guess right now is that the E4406A power supply is getting quieter as it has been on for longer (I've only had it powered for short periods before now).
>>
>> Dave
>>
>> -----Original Message-----
>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Magnus Danielson
>> Sent: 18 September 2016 11:56
>> To: time-nuts at febo.com
>> Cc: magnus at rubidium.se
>> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.
>>
>> Hi,
>>
>> On 09/18/2016 12:26 PM, David C. Partridge wrote:
>>> The local power is 50Hz, so I can understand the 100Hz spurs, but I
>>> don't quite "get" where the 200Hz spurs are coming from.  Or is that
>>> just BAU harmonics?
>>
>> Consider full-wave rectification of 50 Hz, the power consumption load on the capacitor after the rectifier creates an inverse sawtooth wave of
>> 100 Hz, and sawtooth waveshape have both even and odd harmonics.
>>
>> While much of this is regulated out in the next step, some of it makes it though.
>>
>> Cheers,
>> Magnus
>>
>>>
>>>
>>> Thanks
>>>
>>> Dave
>>>
>>>
>>>
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