Scan-Select PCM Receiver help.

[andyrauc]

Hi
I have a JR R790UL scanselect receiver and have never been able to get it to work. My transmitter is a JR XP8103 and it is set to PPM to fly my Raptor and my Mini Titan. I recently sent my transmtter to the US to have it serviced and send the receiver along asking that they check it. My radio was returned repaired and a note saying the receiver was working fine. I press the button the solid light goes out. I then hit the button again and the light flashes rapidly for a few seconds then slows to a steady blink. The transmitter is on but I am unable to get the receiver to bind to the radio. My module in the radio is FM 72.390 so I can see no reason why the two do not want to communicate. Am I doing something wrong?

[unwind-protect]

It's not clear from your post, but if it's a PCM receiver, it won't recognize your radio if it's set to PPM. JR also has a couple of variations of PCM; you almost certainly want SPCM selected.

If you've done all that I'm afraid I'm lost for ideas.

[andyrauc]

this is the receiver:
http://www.jrradios.com/Products/Def...odID=JRPR790UL

My setup on my radio is PPM which is what is required. I did try set it to SPCM but it did not seem to make a difference. Could you tell me what is the difference between PPM and SPCM?

[Gav]

this is the receiver:
http://www.jrradios.com/Products/Def...odID=JRPR790UL

My setup on my radio is PPM which is what is required. I did try set it to SPCM but it did not seem to make a difference. Could you tell me what is the difference between PPM and SPCM?

pcm pulse code modulation receiver wont work at all if your transmitter is in ppm pulse position modulation mode. I dont know how your tx works exactly but would you need to select PCM on the tx then switch off and back on again like i have to on my futaba tx before the internals swith over to pcm mode?

[unwind-protect]

Could you tell me what is the difference between PPM and SPCM?

They're the over-the-air protocol used.

Basically, PPM looks like this to the receiver:
11111111111111100000111111110000000000001111111111 1100000000000000
Where the number of ones in a group set the position of a servo, and the number of ones in the next group set the position of the next servo, and so on.

PCM looks like this:
11001101010010111010011110010100011010101110100001 1011101111011101
With the servo positions encoded in binary. Clearly each is incomprehensible to a receiver expecting the other. Different forms of PCM use different binary encodings and so are incompatible.