Crystal based Hartley oscillator

Hi,

I want to construct one AM transmitter which can transmit high frequency(High bit rate) signals.. For example,DTMF signals..


First step i want to build one oscillator which will provide good wave form out put(Clear wave form).. I am planning to go for Hartley.. It seems if we design it using crystal,it will yeild better reslut.. So can u suggest what modifications i can do in basic hartley oscillator to make it into a crystal based one..

Take a look in the ARRL Handbook for Radio Amateurs - not the only source but a good source.

DTMF signals are not digital rather audio tones used to represent a value and as when used as a digital system are very slow. The interdigital spacing, the length of time the audio has to sent all slow it down for data. With the tone duration and interdigital pause both 40mS then a 4bit value canbe sent every 80mS or a symbol rate of 12.5 baud(or with the the 4bits-50baud), if a 8 bit value is required then the baud rate will be halved or 25baud, not what any one would describe as a fast data system.

FYI: look up Colpitts oscillator, the Hartley is the one with a tapped inductor. Another type that you might want to consider is the Pierce Oscillator circuit.

I'm still working on this Hartley to be a VXO but does run at exactly the crystal frequency.

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