[time-nuts] Wenzel oscillator - L1 value?

Philip Pemberton lists at philpem.me.uk
Thu Apr 24 20:07:45 UTC 2014


I was under the impression it was a relatively low phase noise design...

In any case, my 10MHz crystals are parallel-resonant. Are there any
alternative oscillator designs you'd suggest I look into?

Thanks,
Phil.



On 24/04/14 02:38, Bob Camp wrote:
> HI
> 
> The circuit they show is not very low phase noise, so adding stuff is not going to degrade it much. It will lower Q, but again, it’s not really Q limited over most of the range. 
> 
> The real issue with the circuit is that it has lousy load isolation. 
> 
> Bob
> 
> On Apr 23, 2014, at 9:06 PM, Tom Knox <actast at hotmail.com> wrote:
> 
>> Does adding these filter elements lower Q or affect Phase Noise?
>> Thanks;
>>
>> Thomas Knox
>>
>>
>>
>>> From: lists at rtty.us
>>> Date: Wed, 23 Apr 2014 17:47:26 -0400
>>> To: time-nuts at febo.com
>>> Subject: Re: [time-nuts] Wenzel oscillator - L1 value?
>>>
>>> Hi
>>>
>>> Roughly (very roughly) speaking, the series combination of C1, C2, C3 and L1 should equal the load capacitance of the crystal. If there is a varicap, it’s likely in series as well. If the crystal is cut for series, then L1 resonates with the caps in series. 
>>>
>>> You can put it on a Spice program and get more accurate results. 
>>>
>>> Bob
>>>
>>> On Apr 23, 2014, at 10:23 AM, lists at philpem.me.uk wrote:
>>>
>>>> Hi,
>>>> I'm currently playing around with crystal oscillators (specifically a homebrew OCXO) and came across the Wenzel low-distortion crystal oscillator:
>>>> http://www.wenzel.com/pdffiles1/pdfs/xtalosc.pdf
>>>>
>>>> This uses an inductor (L1) to trim the crystal frequency, with the note that a varactor/varicap could be added to allow the frequency to be trimmed electronically.
>>>>
>>>> Has anyone built one of these oscillators?
>>>>
>>>> How would you pick a value for L1? I've been reading up on other crystal oscillator types (Colpitts, Clapp,...) and have yet to find anything which uses this style of frequency trimming.
>>>>
>>>> Where would I add the varactor if I wanted to add EFC? Across C3?
>>>>
>>>> Thanks.
>>>> -- 
>>>> Phil.
>>>> philpem at philpem.me.uk
>>>> http://www.philpem.me.uk/
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-- 
Phil.
lists at philpem.me.uk
http://www.philpem.me.uk/



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