EMRFD Message Archive 7254

Message Date From Subject
7254 2012-02-15 19:28:42 Daniel Mendes VCO question
I need a (preferentially) cheap circuit to make a VCO with about +-0.5%
pullability. The frequency doesn´t matter as long as it´s between
20-200MHz (I have so many ways to multiply or divide it to generate
exactly what I want). I started testing VCXO circuits but I can only get
about +-300ppm from them, and even that is a stretch.
as a stopgap i´m using a Crystek VCO, but it´s damn expensive. It´s not
to be used for RF purposes, but I think people with RF background could
give me good directions about it, so i´m asking here (I lurke here
trying to improve my RF skills). Any ideas?

Thank you all


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7257 2012-02-16 11:17:08 Daniel Mendes Re: VCO question
Thanks for the idea, seems relatively easy to test. I´m trying a more
complex idea based on the "wide range VXO" by G3ESP, using 2 crystals to
make a wideband VCXO. I will try your idea first.


> Daniel,
> You might try a ceramic resonator substituting for a
> crystal in a conventional oscillator circuit. It would benefit
> from some temperature compensation, but should
> be easily pull-able with a variable-capacitance diode.
> Ceramic resonators cover the lower end of your
> 20 - 200 MHz. range...they don't have the high Q that a
> crystal does, but usually have higher Q than most
> L-C resonators.