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

David C. Partridge david.partridge at perdrix.co.uk
Sun Sep 18 08:42:55 EDT 2016


I've just redone the measurement without the external attenuator and with 10dB attenuation set internally to the analyser.

The results are attached.

Dave

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Bruce Griffiths
Sent: 18 September 2016 12:52
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

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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