[time-nuts] pulling oscillators

Rix Seacord eseacord at verizon.net
Sat Mar 5 20:07:47 UTC 2011


Don
If you search the web, someone used inductive coupling to the inductor 
in the oscillator ckt of a 706. I don't recall if it had the high 
precision osc in it. they were using the rig for satellite work.
good luck

Rix Seacord K2AVP
eseacord at verizon.net

845-628-0892
914-262-9186


On 3/5/2011 2:52 PM, Don Latham wrote:
> The crystal oscillators are reference oscillators in 2 meter ham radios. I
> wanted to make the least perturbation in the radio, hence pulling instead
> of simply introducing the correct reference. I will be using a reference
> of the nominal frequency the radio should have, so really should not need
> to pull more than a few ppm if that? also not woried about the phase
> noise, either. Will derive the driving signal from my gps 10 mhz or from
> one of my FEI Rb devices. I need the accurate frequencies, or at least I
> think I do, because the 2 meter radio will drive a transverter to 2.4 GHz
> moonbounce.
> Sorry about not knowing how far I need to pull, or the specs of what's
> there. I suspect there has been some drift since the radio was made.
> Putting in a vcxo or varactor simply puts off the problem, as then I have
> to monitor<that>  frequency and control it. I could cobble in a little
> tuning cap, but still would be left with a pretty temp sensitive
> reference.
> Hope the question is clearer, and thanks to all who replied!
> Don
>
> Adrian
>> Don,
>>
>> if you have a reference oscillator of the right frequency, what's the
>> the purpose of trying to pull a CMOS oscillator to the same frequency,
>> rather than just using the reference frequency?
>> Please be more specific on whant your requirements are.
>>
>> Adrian
>>
>> Don Latham schrieb:
>>> Hello all:
>>> I've developed a need for pulling crystal oscillators built in to pll
>>> circuits. These are cmos, and have the common style oscillator circuit
>>> built in. The crystal is across an inverter in the chip, and there is a
>>> small cap between each end of the crystal and ground.
>>> The chips are pll's in radio transceivers, early at that.
>>> I could carefully remove the crystals and caps, simply driving the
>>> non-inverting input on the chip with the reference, but I would rather
>>> simply tack on a very small cap and "pull" the crystal oscillator with
>>> an
>>> external reference signal of the right frequency.
>>> Anyone out there tried this?
>>> Thanks
>>> Don
>>>
>>>
>>>
>>>
>>
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