Ladyflyer

My Feedback: (2)

It is because the decoder reads the shift and translates it to the individual servos . There is high limit deviation and low limit deviation about the center ,carrier freq . The pulse can drive either high limit or low limit with it's on/off state . One type may go plus 5 kHZ when ON and minus 5 kHZ when OFF ,and vice-versa . The deviation as far as I know is symmetrical about the carrier, The deviation is plus AND minus not plus OR minus. It is just a matter of which direction the on/off state drives the frequency shift.

Lynx

RC is either carrier, or carrier +5khz that's it there are no alterations of that basic operating principle. Positive and negative shift are ONLY references to what those shifts are considered. +VE means when the carrier changes to the shift frequency it's considered the positive going pulse of the PPM signal. with -VE it means that the shifted frequency going to the carrier is the positive going pulse. +ve and -ve are simply logic terms that describe what state change are considered what binary states.

tknobby

Great thread.

I am using Multiplex equipment now but I do have a Multiplex 9ch. IPD uni receiver that I had changed from + shift to - shift in order to use w/ my 8U transmitter. Ernie from Payson AZ did the mod. Looks like he just swapped out a crystal to make the change. I have the original crystal.

My question - can I just take the receiver apart and swap the crystals out have have the receiver back to + shift or will I need to set this up on a scope to perform any final adjustments?

Thanks in advance.

Tom...

strato911

A simple crystal change won't alter the whether the receiver is configured for +ve or -ve shift. The internal electronics need to be modified for that, unless the receiver is designed for both. In that case, there is a small switch, or jumper wire to make the change. I don't think the Multiplex Uni has that feature.

Ladyflyer

My Feedback: (2)

An inverter ahead of the decoder chip will do it . Some receivers have the provision on board .