[time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.
Bob Camp
kb8tq at n1k.org
Sun Sep 18 09:35:14 EDT 2016
Hi
If you are measuring the OCXO, you should be getting around -155 to -160 dbc / Hz at 100 Hz offset.
Depending on the particular board you have, and how it is powered, the numbers out of the TBolt
can be quite a bit worse than this. With a good supply, you should get within 5 db. There are a lot of
spurs, so you do need a pretty good (narrow bandwidth) analyzer to sort them out from the noise floor.
Bob
> On Sep 18, 2016, at 8:42 AM, David C. Partridge <david.partridge at perdrix.co.uk> wrote:
>
> 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
>>>
>>>
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> <Thunderbolt pn3.png>_______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
More information about the time-nuts
mailing list