Waiting on a TNC to N adapter, but I have some more information/observations to add.
CH721 head (system) is not terrible to use, but I glanced over the fact that you can only have 1 mission plan. You need the elusive and expensive CH100 to hold more than 1 mission plan. The HHCH has same features/limitations as the CH721 head.
Programming is through the brick DB9, not the head DB9.
When applying power, read the manual for control head setup. You will get no power/activity if you don't connect the ignition sense wire to power. This is on the head side, if you don't want ignition sense, hardwire the white wire to positive power, otherwise attach it to ignition sense power.