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Old March 14th 07, 09:56 AM posted to rec.radio.amateur.homebrew,sci.electronics.basics,sci.electronics.design
Anthony Fremont Anthony Fremont is offline
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First recorded activity by RadioBanter: Mar 2007
Posts: 34
Default VCXO frequency isn't high enough

Jamie wrote:
Anthony Fremont wrote:


Thanks, I took it out and the frequency increased by only about
70Hz, but it did increase. :-) Do you know of anything else I can
do to increase the frequency by about another couple of kcs?


try a different Xstyle, it sounds like your at the limits..
it's possible the chip has too much capacitance on the
osc legs, i suppose you could try a stand alone osc with a
high freq transistor to lower the cap. use a buffer on the
stage to drive the chip .
Also, have you considered the board mounting? you could
have to much cap via your board construction.


Looks like you are quite likely correct. Without the inductor and with a
10pF cap in place of the variable cap, I can get the frequency up to just
over 3580kHz. I did some looking around and it appears that if I were to
parallel another crystal, I could get a bigger spread on frequency. Or I
could just try a different crystal too. I think I will tinker on a
breadboard to see how high in frequency I can get the crystal to vibrate.