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variable HF oscillator

N

Nelly

Jan 1, 1970
0
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?
 
M

Michael A. Terrell

Jan 1, 1970
0
Nelly said:
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?


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
 
D

Don Bowey

Jan 1, 1970
0
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?

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

Don
 
J

Jamie

Jan 1, 1970
0
Nelly said:
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?
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?
 
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