I am composing a presentation about FM sats, hopefully to be given in a few months at a hamfest. How to remember which way to compensate for doppler: Always adjust the higher frequency. For V/u or U/v sats, this means adjust the 70cm side and leave the 2m side fixed. Which way to move it? Very easy to remember. If 70cm is the UPlink, you'll adjust your transmit frequency UPward through the pass. If 70cm is the DOWNlink, you'll adjust your receive frequency DOWNward through the pass.

I think others have basically explained why.

Dave AD7DB