The power supply is for the radio. I have been able to connect with my UR91 two rooms away. The key is making sure the battery in your throttle is strong and that you're using radio not IR for transmission(this is displayed when connecting). The throttle will default to radio if that is available.
Richard
The power is to run the radio on the UR91.
The reason you put power to anywhere on the Loconet is that the power to operate throttles that get plugged in, or the radio curcuits in the UR91 and UR92, comes fromt he Railsync lines in the Loconet cable. That's a thin phone wire. Same principle applies here as it does for the track bus - thing wire, too much current = voltage drop. One or two throttles isn;t an issue, unless you happen to have panels very far fromt he command station. Add more, and add in the load of the radio panels, and the voltage can easily fall below the minimum required to keep everything working. And when it gets marginal - things get flakey and don;t work as expected. The way the panels are designed, if you plug in a power supply, they will use whichever is higher of the multiple ways to supply power.
I've never been a fan of the option in the manual to run ONE wire between panels to power multiple ones fromt he same power supply - that still puts one side of the circuit in the thin phone wire of the Loconet. Again, all well and good for a few throttles. The better way is to run a pair of wires like a bus and make drops with the proper 2.1mm plugs and plug each one in that way.You don;t want to go nuts and use say a 3 amp power supply to power every panel on the layout - a short with 14V at 3 amps can cause some damage, you should either use multiple smaller supplies or make seperately fused runs, each covering part fo the layout, or use a fuse/breaker on each drop.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Don
Digitrax supplies a PS14 with every UR91 to power it.
As for coverage - I have found that you almost have to be able to see the UR91 as full height backdrops and walls seem to really cut the signal strength!
BOB H - Clarion, PA