hi all
can any body have idea about electronics used in FSK (frequency shift keying ) that used to transmit digital data

BR

 

I am sure that there are many ideas, what do you want to do?

__________________
see my website: www.geocities.com/russlk

 

The easiest way I can think of to do FSK is to use a varactor diode in the tuneing stage of an oscillator

__________________

 

hi all
I just want to know how to send digital data let's say "1Byte" and how to rescieve it using FSK way any schematic for fsk transmitter and resciever will be helpfull

Thanx alot for ur concern

BR

 

How about using a FSK RF transceiver?

http://secure.oatleyelectronics.com/...roducts_id=388

It costs 33 aussie dollars, and is a great piece of kit. Best of all it allows 2-way data transfer

__________________
Spency.

PIC Micro's - Your mind is the limit

PIC's and interfacing with other devices - a PIC Basic Guide @ digital-diy.net

 

For more info on the device, have a read of the datasheet, it sums it up quite well

__________________
Spency.

PIC Micro's - Your mind is the limit

PIC's and interfacing with other devices - a PIC Basic Guide @ digital-diy.net

 

hi again
thank u very much every one , actually ur links & info are very helpfull

But i have remote car switch , iam trying to understand the way it operates, It uses HT12E as digital data Encoder & one transistor as transmitter
is that FSK technique , if so how the transmitted data rescieved & decoded.
any help will be appreciated

Thanx in advance
BR

 

Click here too have a look on Wiki

Frequency-shift keying is a form of frequency modulation in which the modulating signal shifts the output frequency between predetermined values.

This is how the data is encoded;

__________________
Spency.

PIC Micro's - Your mind is the limit

PIC's and interfacing with other devices - a PIC Basic Guide @ digital-diy.net

 

Its hard to say from your description. My first guess is that your remote uses PPM (pulse position modulation) which is a simple form of AM where the encoding chip output is turning the transistor oscillator on and off according to a serial string of bits. This is quite common in North America for garage door opening remotes, for example. If the device uses FM, then the single transistor would still be an oscillator but its frequency may be easily shifted using a varactor diode on its tank circuit fed from a digital serial string of bits from the encoder. Hard to know unless you can spot a varactor diode near the transistor.

__________________
RadioRon

 

Remember using a modem on a telephone line to access the internet?
An old modem used FSK between two or more audio frequencies.
My first modem was 14.4kB/sec and I could hear it alternate between two frequencies. A 56k modem sounds like a lot of noise.

__________________
Uncle $crooge

 

Hi all
here is arough schematic for that small transmitter

BR

Attached Images

transmitter.gif (4.0 KB, 25 views)

 

That's about the roughest schematic I've ever seen here on the boards, but damned if it isn't good enough. I would say that based on this, you have a pulse transmitter which is where the RF carrier is turned on and off according to a sequence from the encoder chip. The fact that the encoder controls the DC flow throught the transistor emitter is the best clue showing the encoder is turning the oscillator on and off.

__________________
RadioRon

 

My first modem was using the old Bell103 tone standard at 300 baud. At about that same time, I learned about RTTY on HF radio using audio FSK. A different signalling standard, but the same general idea.

If you think about it, the 56K modem has to be very spectrum efficient to send so much data on a land line. What you hear is indeed very spectrum efficient since it sounds as if it is filling the entire "audio" spectrum with an equal distribution of energy, which is the definition of white noise.

__________________
RadioRon