variable HF oscillator

Jun 01, 2007 3 Replies
N

I need to vary the frequency of operation of a transceiver IC from



7MHz to 9MHz. The oscillator needs to feed into the crystal oscillator input and crystal oscillator output pins of the IC (the current design does not have a variable oscillator and is just using a crystal). Ideally I would like to control the frequency of the oscillator using the PWM of a micro controller (unfortunately the current micro does not have a DAC). Any ideas on the best way to do this?
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M

rec.radio.amateur.homebrew would be a better place to ask for this help.

Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
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D

Many xtal oscillator circuits work well by just replacing the xtal with a series LC network.

Don

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J

You can emulate PWM output with the processor. all you need is to use a timer (IRQ) driven to generate the output pulse on the pin of your selection.

Normally the IRQ rate is put at multiples of the shortest PWM pulse you may generate. With this, you simply use a scalar counter to adjust the output duty cycle.

As far as the OSC goes, you can replace the Xstyle with an LC and Variac tuning diode assembly how ever, I don't know what you have planned to monitor the freq for stability?

"I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
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