[time-nuts] 10811 warmup

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Jan 21 22:33:33 EST 2007


Normand Martel wrote:
> It's bizarre..
>
> The oscillator is some kind of Colpitts but with coils
> instead of capacitors in the feedback path.
>
> (i don't call it a Hartley, bcause Hartley's use a
> SINGLE tapped inductor.)
>
> 73 de Normand VE2UM
>
> --- Dr Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> wrote:
>
>   
>> Hal Murray wrote:
>>     
>>>> Is it okay to power up the main assembly once it
>>>>         
>> is removed from the
>>     
>>>> outer shell / insulation? 
>>>>     
>>>>         
>>> Lots of info here:
>>>  
>>>       
> http://www.hparchive.com/Manuals/HP-10811AB-Manual.pdf
>   
>>> I think I saw a warning about that, but maybe it
>>>       
>> was something else.
>>     
>>>   
>>>       
>> It is OK to power up the oscillator and output
>> amplifier, but the oven 
>> circuit should not be powered up.
>>
>> Bruce
>>
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>   
Normand

It is in fact a Colpitts with unwanted mode suppression.
At the desired oscillation frequency the feedback network is capacitive.
At the undesired overtone frequencies one of the feedback components is 
inductive, and the circuit will not oscillate.
Some form of mode suppression is required in most precision overtone 
oscillators.

Bruce



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