One UR91 should provide 100% coverage under most normal circumstances. Things that will affect it are metal objects between the throttle and UR91 receiver, or large metal objects on an opposite wall from the receiver. Obviously, radio transmissions will be blocked by metal objects, such as furnaces in the basement. The solution for this is to move the UR91 to a location where the metal object will not affect operation, or to add another UR91 to the LocoNet. Large metal objects on the opposite wall can reflect the signal to the receiver causing ghosting. That is, the receiver gets the signal directly from the throttle, then another signal right on top of it from the reflection. The problem is, this second signal mixes with the first signal to make it unintelligible. Again, the solution is to move the UR91 to a better location, or to add another UR91 to the LocoNet.

The UR91 also has an Infrared receiver on it. Refer to the UR90 page for information about Infrared operation.

The UR91 will allow the use of about ten radio throttles at the same time. This, however, is not set in stone. There is a certain amount of air time for radio signals to be received and processed. So, your operation will determine just how many will be usable at one time. If you have a lot of mainline running where there is very little throttle changes, you can probably use more than ten. However, if your crew is one that is constantly throttling up and down, and operating functions, then the limit may be less than ten.

NOTE: you can add as many UR91s on the LocoNet as you need to eliminate any dead spots you may have. But, adding more UR91s of the same frequency will not allow you to have more than ten radio throttles. To have more than ten throttles requires an additional UR91 with a different frequency, and Radio throttles to match that frequency. This equipment is special order, and it is recommended you don't opt for it unless absolutely necessary.

It is recommended that you plug Radio throttles in to operate trains when you'll be at the same location for a prolonged period, such as switching at a yard or industrial area. While Radio operation is quite efficient, there's nothing like a direct connection for the absolute best control - especially at slow switching speeds. By plugging in, it relieves the air-waves of this traffic, thereby allowing other radio throttles to have more band-width.

The UR91 connects to the system via LocoNet. A short cable comes with the UR91 to plug it into the command station/booster or other LocoNet device. While the polarity of LocoNet cables usually is not of importance, this is one device where it matters. The cable that comes with the UR90 is made correctly to plug directly into the command station. However, if you're plugging it into another LocoNet device, you must insure that that device is connected with a correctly made cable. Refer to the LT-1 page for more information.

The UR91 comes with a wall-plug transformer that should be used to power the UR91. Without this transformer, the UR91 will have to get its power from the LocoNet. Since the LocoNet is limited in power, the UR91 is likely to not have enough power to provide adequate radio coverage, and is likely to sap all the LocoNet power - causing problems with plug-in throttles. Also with the transformer plugged in and left turned on when the system is turned off, and the throttle left plugged into the UR91, it will keep the throttle battery alive.

The UR91 has two green antenna wires. These wires should be positioned sticking up in a "V" formation. Do not cut them shorter, or attach additional wire to them to make them longer. They are the exact length needed to tune them in precisely to the 916 MHz frequency that they work on.