I just recieved my new 7c radio. My Nexstar was on ch 38. My new transmitter is on 39. The reason for switching channels is because a guy has a scanner at my club and said 38 showed to be a bad channel because of some kinda of interference. Now he tells me after 2 months of flying. Not wanting to take a chance though. So I did not want to put my new reciever in my Nexstar, just wanted to use the transmitter. So I pulled out the 38 crystal from the nexstars reciever and replaced it with the 39 from my new setup. It works fine just want to know is there like a positive and a negative on crystals? Just wanting to know if there is a wrong way to put it in.