What is the modulation technique used?
Rather than use a spectrum analyzer you might be best to use a receiver that can stay locked on the 218.025MHz carrier. One cheap option that works well at that frequency is a USB TV tuner capable of being used by SDR (software defined radio) software. For example see the RTL-SDR page.

There are quite a few software options listed at the bottom of the page but personally I've found the SDR# software to be good if you're running Windows. In the case of a periodic signal you'll also be able to capture it to a wave file for later analysis. Having said that I agree with the comment by markt that it’s likely to just be CW.