PIC-PIC RF Comms

[Kamikaze47]

Reducing the baud to 1200 improved the range a fair bit. At 5v I now get about 15m line of sight. At 12v, about 30m... Still a fair way short of the 100m these units are supposed to achieve, but not too bad.

[Ron Marcus]

Just for giggles, try increasing the number of $55s you send to..say 8. Next pick a more balanced header character like $AA. You can also put a small character delay using DEFINE (Maybe 1 mS). If this helps, you need more of a preamble to balance the data slicer.
What are you using for antennas? Usually the companies range test their units with twelve element Yagis. Well, maybe not that bad, but the test data is usually taken in an optimum noise free environment with no multipath. These parameters don't exist on our earth, and you should probably halve most manufacturers range estimates. I've had to test most offerings in the OOK market, and upgraded to FSK for my more serious work, and better impulse noise immunity.

Ron

[Kamikaze47]

For antennas Ive tried using 1/2 Wavelength and 1/4 Wavelengh bits of coathanger wire, and found the 1/4 Wavelengh (6.47 inches) to give better range.

The reason I used $66 as a start character is becuase it is fairly balaced (same number of 1's and 0's). I will try $AA though, and will also try adding more $55s and see if it improves the situation.

Thanks for the advice guys.

[Kamikaze47]

making it 8 $55s, and changing the start character to $AA dont seem to have made any difference unfortunately

[Ioannis]

For one thing, I would never try to transmit more then half the maximum baud rate of the specified Tx/Rx pair.

Also, a manchester encoding/decoding scheme is a must for such RF links.

More to this, check if the power supply to the Receiver is very clean. If necessary add extra R's and C's to filter more the power from your sepparate 78xx chip. Large capacitors are good thing to consider.

Ioannis

[Kamikaze47]

If you look at what im sending you will notice that it already in machester format:

$55,$55,$66,$95 = 01010101 01010101 01100110 10010101

[BigWumpus]

Hello,
try more preambel-characters,
Use "DEFINE CHAR_PACING 1000" at the transmitter

We use such simple receivers/transmitters... ;-)

[rhino]

If you look at what im sending you will notice that it already in machester format:

$55,$55,$66,$95 = 01010101 01010101 01100110 10010101

Not sure I agree with this statement. I'm no RF engineer by any means, but I think the manchester equivelent for this would be:

0110011001100110 0110011001100110 0110100101101001 1001011001100110

Melanie explains it HERE very well.