[time-nuts] Realistic Tbolt phase noise

Bob Camp lists at rtty.us
Tue Mar 9 17:21:00 UTC 2010


Hi

How are you multiplying it to 1 GHz and checking it? 

I've seen multipliers that have issues beyond about -130 at 100 Hz. It's not
common, but it can happen.

------------------

The supply provided by TAPR is a pretty basic unit. It would not surprise me
if some were better than others. They also may work better on US mains
voltage than they do on international voltages. I would rig up another
supply and see what happens. That would at least rule out the supply as an
issue. 

In a previous post the idea of putting a 7805 and 7812 regulator on the
TBolt came up. If you have +14 available that seems like the best thing to
try.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Christophe Huygens
Sent: Tuesday, March 09, 2010 7:50 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Realistic Tbolt phase noise

This is with the power supply as provided by TAPR so should be ok.

Xtof.


On 09/03/10 13:44, Bob Camp wrote:
> Hi
>
> Power supply noise would be the first thought.
>
> Next up would be grounding inside the Thunderbolt (card to case,
connectors to case).
>
> Bob
>
>
> On Mar 9, 2010, at 7:32 AM, Christophe Huygens wrote:
>
>    
>> Hi,
>>
>> I noticed several vendors on Ebay have the t-bolt on sale.
>>
>> However, the once showing their own PN plots seem to get only
>> -115, -120 dBc/Hz at 100Hz. Yet,
>> http://www.leapsecond.com/pages/tbolt/noise.htm seems
>> to have mucht better results: up to -150 depending on
>> power supply.
>>
>> By multiplying to 1GHz I also seem to be getting something
>> like -75 or - 80 rather than -110.
>>
>> Any thoughts?
>>
>> Christophe
>> on4iy
>>
>>
>>
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