KB405: UR91 Simplex Radio Receiver Frequently Asked Questions

This article was last updated on Sept. 18, 2011, 4:38 p.m. | Print Article | Leave Feedback

Simplex Radio Coverage

One UR91 should provide full coverage for a typical model railroad under most circumstances. Simplex Radio reception is affected by metal objects between the throttle and UR91 simplex receiver, or large metal objects adjacent to the receiver; a furnace is one example of such an object.

Such objects cause a second reflected signal, impairing the radio throttle signal's ability to reach the UR91. In this case, the receiver gets the signal directly from the throttle, then another signal right on top of it from the reflection.

Moving the UR91 to another location may solve this problem, or you can add an additional receiver to LocoNet.

The UR91 also has an Infrared receiver built in so it can receive signals from infrared throttles

How many simplex throttles can I operate with a UR91?

The UR91 will allow the use of about ten simplex radio throttles at the same time.

There is a certain amount of variability to this rule, depending upon air time for simplex signals being received and processed. Your operation will determine just how many will be usable at one time.

If you have a lot of mainline traffic running where there are few 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.

: You can add as many UR91s to your railroad's LocoNet as you need to eliminate any dead spots which you may have. But, adding more UR91s of the same frequency will not allow you to have more than ten radio throttles.

To increase the number of throttles you can run 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.

Extended Operation Periods
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, you allow other radio throttles to run tetherlessly.

LocoNet Polarity or Phasing?

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. LocoNet operates best when the polarity, or phasing of LocoNet cables is the same all around the layout. 

Powering UR91?

The UR91 comes with a wall-plug power supply that must be used to power the UR91.

Without this power supply, the UR91 will draw power from LocoNet. Since the LocoNet provides limited power, the UR91 is likely to not have enough power to provide adequate radio coverage causing problems with plug-in throttles.

Also with the power supply 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.

UR91 Simplex Radio Receiver Antenna?

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 use.

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