[time-nuts] 5 x 2 x 3 = 30 MHz

Magnus Danielson magnus at rubidium.dyndns.org
Sun Jul 19 11:09:20 EDT 2015


Good afternoon,

It comes as no big surprise that ultrastable oscillators has 
double-isolation both on thermal and power-supply sides. Both being 
important environmental noise injection paths for any oscillator, moving 
the operating points of transistors about.

Long-term systematics is indeed something to look at. We've had long 
discussions on thermal stability before.

Cheers,
Magnus

On 07/19/2015 02:19 PM, KA2WEU--- via time-nuts wrote:
> Good morning,
>
> That is too close for my taste. For long term stability, 1 Hz and less the
> transistor has more influence then considered  . It is a pity that this
> group does not address this topic.More to come. I am supervising a PhD
> dissertation and it became clear that that is an issue
>
> Ulrich  N1UL
>
>
> In a message dated 7/19/2015 8:12:44 A.M. Eastern Daylight Time,
> radio.n9xr at gmail.com writes:
>
> I am  attaching a file showing the schematic for the trap used in a
> Colpitts
> oscillator which will look like 58pF at 5MHz and will be inductive  at
> 5.5MHz.  So something like this can be used in place of a pair of  one of
> the split capacitors at ~56pF loading the crystal.
>
> Jerry  N9XR
>
> On Sat, Jul 18, 2015 at 11:59 AM, Magnus Danielson  <
> magnus at rubidium.dyndns.org> wrote:
>
>> Dear  Ulrich,
>>
>> Now you taught me something useful, that the SC-cut  has inherent less
>> noise than AT-cut. Many thanks.
>>
>>   Indeed, measuring below 1 Hz starts to be challenging as environmental
>>   aspects chimes in. I assume you ovenize your crystals, to make use of
> the
>> turn-over point.
>>
>> Even for ovens, (wind)shielding  to reduce thermal stress turns out to be
>> helpful. Some toss their  oscillators into thermal flasks too. As always,
> a
>> myriad off issues  creep up as you push the noise down and want to verify
>> it. Thermal  mass has proven useful in many ways. There was a nice paper
>> from NIST  where they used water-bottles to stabilize WWVB.
>>
>>   Cheers,
>> Magnus
>>
>> On 07/18/2015 11:52 AM, KA2WEU--- via  time-nuts wrote:
>>
>>> Good morning,
>>>
>>> the  AT Cut is inherently noisier then the SC cut but the SC has some
>>>   spurious resonances  modes. Measurements below 1 Hz are very tricky as
> the
>>> oscillator must be (more or less) insulated from hum, infrared  (heater)
>>> .  Here I
>>> am still struggling  .
>>>
>>> Ulrich N1UL
>>>
>>>
>>> In a  message dated 7/17/2015 9:59:55 P.M. Eastern Daylight Time,
>>>   n1hac at dartmouth.edu writes:
>>>
>>> He  doesn't mention  that that crystal is used in New Horizons:
>>>
> http://www.bliley.com/products/crystals-precision-standard/vacuum-sealed/
>>>
>>>   Nice.   I have a similar crystal from Valpey-Fischer, 5 MHz 5th
> overtone
>>> AT-cut  (as opposed to your 3rd overtone  SC-cut).  I would be interested
>>> in  what you would use  for an oscillator circuit.
>>>
>>> David  N1HAC
>>>
>>>
>>> On  7/17/15 4:27 PM, paul swed  wrote:
>>>
>>>> Ulrich,
>>>> Nice picture.  What  are you doing with the crystal? I have several
> older
>>>> crystals that are  nice but have never done  anything with them.
>>>> Regards
>>>>     Paul
>>>> WB8TSL
>>>>
>>>> On Thu, Jul 16,  2015 at 6:02 PM, KA2WEU---  via time-nuts
>>>>
>>>   <time-nuts at febo.com
>>>
>>>>     wrote:
>>>>>
>>>>> I am working with this ......  amazing device,  Ulrich N1UL
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