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

Lars Walenius lars.walenius at hotmail.com
Sun Sep 18 08:52:21 EDT 2016


What is the specification for the Spectrum analyzer? They don´t tend to be useful for OCXO measurments so is this especially good? Or is it only the Analyzer phase noise we see?



Lars



Från: David C. Partridge<mailto:david.partridge at perdrix.co.uk>
Skickat: den 18 september 2016 14:43
Till: 'Bruce Griffiths'<mailto:bruce.griffiths at xtra.co.nz>; 'Discussion of precise time and frequency measurement'<mailto:time-nuts at febo.com>
Ämne: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.



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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