For what you are doing, PPM or FM will do fine. If you want a PCM later, like stated, switch it in the trans and get a PCM rec. Tower now has a PCM rec for about $100. Thats not bad. Seems I was paying about $169 when I bought the other 4 I have. I also aquired a few FM and use those as well. Works great. Get them all on the same freq that not a lot of people at the field use and you will be fine. You don't need to be able to change it. In over 25 years of flying, I have never needed to change freqs.