Hello,

I need for FSK modulation scheme with a Hartley oscillator and varicap diode.
Does anyone have such a scheme?

Thanks!!!

 

Hello,

Do you want the modulate the RF?
At what frequencies should this oscillator work?
Normaly the FSK is done in audio range and modulated on th RF.

Bertus

 

I need coherent binary FSK modem with Hartley oscillator, modulator and demodulator for my graduate work. I think that This oscillator should work to 1200Hz for "0" and 2200Hz for "1".

 

Hello,

Take a look at the following PDF for the theory of FSK:
Tutorial 17 - Frequency Modulation (FM) , FSK, MSK and more

From page 9 the PDF starts with FSK.

This tutorial comes from this page:
http://www.complextoreal.com/tutorial.htm

Bertus

 

Thanks Bertus, but I need a elektric scheme of FSK modulation with Hartley oscillator and varactor diode.......

 

Hello,

You will not manage the 1200 vs 2200 Hz using a varactor diode.
The capacity change would be to large.

Better make two oscillators and switch between them.

Bertus

 

Hm, Then I could use a nearer frequency.

 

I think that the frequency range is not as important. It is important that to work at a high frequencies (>1kHz).

 

Does anyone have such a scheme?

 

There are a scheme of Hartley oscillator and Hartley oscillator with varicap diode. Frequency of "1" and "0" are almost identical (f1=2.212MHz, f0=2.201MHz). Does anyone know how to set the difference frequency is about 200-400kHz?


Sorry for my bad English.

 

Hello,

When you make C5 larger, the influence of the BB112 will be larger.
Now you have a VERY small value for C5.

Bertus

 

I have a scheme for modulator. frequencies that were obtained from the simulator for "1"=(680hKz - 691kHz), "0"=(669kHz - 675kHz). Frequencies are variable over the time. Now I need scheme for FSK demodulator, which worked for this frequencies. Is it a good solution IC NE564? Scheme for modulator and datasheet for IC NE564 are attached.

http://www.datasheetcatalog.org/datasheet/philips/NE564.pdf