A very very very strange problem-Urgent help needed please!

[Melanie]

And the PT encoders/decoders do what exactly?... they take a carrier and MODULATE it with a PWM ENCODED signal at one end, and then decode it at the other end. They DON'T try to send RAW DATA. Actually the PT encoders DON'T modulate the carrier themselves, they provide the Tx Module with an equivallent 'AUDIO' signal which is then modulated within the AM or FM Transmitter Module. At the receiver end, the receiver, after demodulation, sends this 'Audio' component to the PT Decoder which then decodes the signal.

The usual junk Tx/Rx Modules are NOT the wireless equivallents of a piece of wire linking two ends of a Serial Link (like RS232).

Any Radio Ham will tell you (and there are quite a few on this forum) that you can't send high-speed RTTY (eg your Serial Data) using CW (A1A class modulation). If it was Audio (tone) Modulated (A2A) you'd have a better chance (because you obviously have either an AM or an FM Tx/Rx pair) and at least you'd be using the integral modulator - the way the designers of the modules intended them to be used. If you want range AND reliability, then for example you would pick say an F1 or F2 Modulation type.

Some Tx/Rx Modules have integral DATA MODULATORS with integral ENCODERS/DECODERS and can guarantee DATA-IN/DATA-OUT. Most modules haven't! They rely on YOU providing a signal (usually an AUDIO Tone or Tones) which are then modulated onto a carrier by either AM or FM (with FM having superior noise rejection - which is why you pay more for those). Now the PT encoders usually provide a 1kHz signal (give or take) which then varies depending on what information it conveys... note that 1kHz signal being the equivallent of your Audio Tone which is then MODULATED onto your carrier.

If you are just keying a carrier (which is what you are doing), all you are doing at the receiver end is the equivallent of switching your squelch control (a crude anomaly but will suffice for this explaination). Great. It works. But in doing this you have just sacrificed 95% of your range.

[Bruce]

If you're up for a test, try the two .hex files attached. One for an encoder, and one for a
decoder.

Both files have been compiled for a 12F635. Schematics for connections are in the screen
captures. If your RF modules can handle 4800bps, connect the baud pins to Vcc.

For 2400bps connect the baud pins to ground.

D0-D3 on the decoder are momentary, and should stay high for as long as a button on the
encoder is held at Vcc. Let me know what kind of range you get.

[FromTheCockpit]

If you're up for a test, try the two .hex files attached. One for an encoder, and one for a decoder.

........... Let me know what kind of range you get.

Sure Bruce, I will let you know as soon as possible. Thanks.

[FromTheCockpit]

Hi, Bruce. The PICs with these hex files are not working. So I put my setup on a breadboard and by using a piece of wire between GP.5 of both. I do see a voltage pulse on GP.5(Tx) of the Transmitter but no response from the receiver. I used 2400 Baud. I await your feedback.

[Bruce]

Can you post photos of what you have assembled & indicate which RF modules, power supply, etc you're using?

[FromTheCockpit]

Here is the photo of my bread-board setup. The LED to right of the 1uF Cap is for power indication.
I don't have any technical details about these modules apart from that they are ASK based and are for short range RF applications. I have tested other simpler codes with them and PT enc/dec as well, everything works perfectly. They don't have any sort of marking on them as well so I can search the internet.

My power supply if from 7805. Power supply is ok as I keep testing small projects every other day.

[Bruce]

Made a slight adjustment. These should work on pretty much any RF modules.
Let me know if this version works for you.