So would you need RemoteCommand on all Kerbin-orbiting sattelites? Or where else do you control ships from?
You need any "Pod" element that has "RemoteTech" in its description. These are the new RT pods/disks or - if you use the RT compatibility mod (
http://kerbalspaceport.com/remotetech-probe-compatability/) - all stock probes as well. This is required to process remote commands as well as relay them to other satellites.
To contact a remote probe you need a powered antenna on the remote probe that has enough range to reach back to KSC or to a relay satellite, and you need a pod with the remotetech command/control components. If the antenna is a dish, then it has to be targeted specifically through the context menu. Omni-directional antenna don't need to be targeted and they automatically form links.
The KSC tracking station is a 5Mm omni-directional antenna. For your first step I'd suggest putting a geosynchronous sat in orbit directly above KSC, or do as I did and place a mesh of sats in half-geosynch orbit to cover the surface. Each of my commsats has a RemoteTech Command part and a 9Mm omni-directional antenna. My munar commsat has two 50Mm dishes, one pointed at the Mun and one pointed at Minmus.
Interplanetary probes will require a satellite link for most of their travel time. As SatDishes are disabled by default, you'll immediately lose contact to the vessel right on the launchpad if no antenna is mounted. Tip: Attach the antenna to your first launcher stage. Before launch, enable your satdishes and link them up properly, then you can safely discard the antenna during ascent and don't have useless weight to carry around.
I'm planning to put a munar relay sat in a polar orbit around the mun with a dish pointing back at Kerbin.
More pics as I go:
The 4/5th pictures say 'out of contact' because the small omni-directional antenna aren't deployed yet. When undeployed they have a 2km range. I also hadn't targeted the dishes at any of the available relays, so the craft was cut off entirely and flown by the kerbonaut instead.