I am confused over your question...but I'll try.....postive and negative shift......well there is a frequency, say 72.810, there is an upper and lower side band to that freq...the upper sine wave and the lower sine wave....or positive shift for the upper and negative shift for the lower......It is my understanding that not only do you have to be on the same freq but on the same sideband...(positive and negative shift).....The good news is that some receivers are shift selectable with a little jumper wire on the side of the receiver and some receivers will work with either postive or negative shift.
The channels 51, 52, etc are different frequencies.....in your picture of the chrystals one is channel 36, 72.510. the other is channel 52, 72.830...these 2 chrystals won't work together....not only do the chrystals have to be the same freq one has to be for the transmitter the other for the receiver....
Hope this helps...Good flyin