which type of modulation has high stability in frequency .... reactance modulation or the varicap modulation!
because i made a FM TX of reactance modulation,but it had lot of frequency drift ,so next i am going to make a varicap modulation,so please suggest me!

 

which type of modulation has high stability in frequency .... reactance modulation or the varicap modulation!
because i made a FM TX of reactance modulation,but it had lot of frequency drift ,so next i am going to make a varicap modulation,so please suggest me!

Long term frequency drift is almost always temperature related.

I don't know what frequency range you're working with, but if it's FM, you need to have a crystal controlled oscillator or a synthesizer.

The reactance modulator is probably SIMPLER to make stable, since you modulate the PHASE after the fact. Direct Varactor frequency modulation usually requires some sort of long time constant feedback loop, like a PLL.

A few more details would be nice.

Eric

 

the frequency is from 80-90Mhz,so as u say a crystal controlled oscillator has a good stability! is the frequency of the crystal oscillator is fixed or can it be variable.please explain me!