Wireless Reception Tweaking

Diagram for RB02 Reception


The ProCab seems to propogate the radio signal better to the sides of the cab than to the front or rear. Turning the cab sideways to the base station will sometimes result in better communications. The cab works much better with the antenna vertical. In crowded layout rooms we’ve had good luck attaching the base station to the ceiling with the antenna pointing down. Others report good results with tipping the base station on it's side.

About your wireless Procab:The Procab-R is designed to eliminate the need for tethered operation of an NCE ProCab. All present and planned features of the cab are usable while untethered from the cab bus. The adapter is battery powered and will supply power for both cab operation and the adapter itself. Although the installed wireless adapter is designed to operate at any voltage from 2 to 16 volts we recommend the use of 4 AAA cells. The ProCab has a built in battery chamber for 4 AAA battery cells. The transmitter power of the Procab is .00025 Watts. By comparison your cell phone can put out 3 Watts or about 12,000 times the power of the ProCab. For this reason a general discussion of wireless communications follows.

Wireless communications: We are continuously asked about the operating distance of the wireless cab. There are many factors governing the useful range of wireless products. The Procab-R operates in the ISM (Industrial, Scientific and Medical) radio band at 916.5 MegaHertz (Mhz). Many cordless phones,wireless computer networks, home automation systems, and wireless security devices also operate in this portion of the radio band and all contribute to radio interference. In any radio system, propagation of the radio signal will suffer in the presence of ‘in band’ intererence. When devices operate in the same frequency band they may contribute interference to the point where your cab may not work at all. On the other hand your wireless cab may interfere with the operation of the other devices you already own. Radio waves are like one big telephone ‘party line’ where everyone is talking at once. A device using these radio waves must attempt to sort out what ‘voices’ are relevant to its operation and which ones are ‘noise’. If there is too much noise it can’t do this successfully and will operate poorly or not at all. This is especially prevalent in Arenas and convention Centers due to multiple cell phone repeaters and security devices. Indoor radio propagation is an issue for special consideration. The human body readily absorbs RF energy in the frequency band used by the cab radio. Placement of the base station can mitigate blocking of the radio signal due to human body absorption. In most indoor situations ‘dead spots’ can be found where reception is very difficult. These can occur even if there appears to be a direct line of sight between the transmitter and receiver. These dead spots, or ‘nulls’, are the result of multiple radio transmission paths between two points caused by reflections off metal objects such as steel beams, screen wire, concrete rebar, metal door and window frames, ceiling tile frames, model railroad track, etc. Nulls occur where the path lengths differ by an odd ½ wavelength (about 6 inches at 900 MHz). Deep nulls are usually very localized and can be avoided by moving slightly, usually only a few inches. When performing complex tasks involving many messages displayed on the ProCab, communications between the cab and command station may take longer than expected thus slowing down your programming. In these instances you may find it more expedient to plug in the cab while doing extensive programming or system setup.

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