Or you can search ebay for a high end 72mhz transmitter that has selectable frequency box. That is what I did and after turning two dials it was tuned to my receiver. I found it easier than trying to score crystals. BTW I paid only $30 for the TX and it basically has all the features the modern 2.4ghz systems have for a small fraction of the price a new system would cost you. Just an idea.