One of the key components of a directional antenna system, which involves an aerial receiving or transmitting device that converts electrical energy into radio waves and vice versa, is phase equipment (also known as a phasor cabinet). This system is widely used in directional AM stations and in the medium wave frequency band (AM), since it allows the strengthening of the signal in a particular direction and reduces interference to stations located in other directions that are not desired. In fact, it is possible to set the degree of directivity of the antenna radiation pattern, which is controlled by the amplitude and phase weights of each individual element.
To ensure maximum precision and stability, phase equipment is used. The phasor manages the energy that is sent to each antenna tower in a system. The phasor cabinet contains tuning coils, fused / vacuum mica capacitors, inductors, RF contactors, and variable junctions of circuits connected to the other components; it’s all housed in the cabinet where someone can make most of the adjustments (on the front panel control knobs) to increase coverage area or achieve the best antenna gain (beamwidth) and path, or nullify interference .
A phasor can even help fix small transmission problems. It is not uncommon to find a slight change in the directivity or performance of the antennas. However, a simple solution can be applied by controlling the cabinet knobs. Through this radio component, you can adjust the phase and the power that goes to each antenna.
On the face of the phasor cabinet, it is possible to check the current levels of the base without opening the cabinet doors or removing its panels, as there are indicators that show the mode of operation. However, a technician may need to use the back doors of the cabinets for easy access to parts, to gain access to all housed components. Sometimes an engineer may need to check the equipment inside the cabinet, when he needs to inspect the system after finding a fault in the system. From the inside, the person can insert a measuring instrument, for example, to troubleshoot and fix what may not be working properly.
A good example of the phasor malfunctioning is when the owner’s antenna monitor readings change dramatically or there is no shorting bar (J-plug) that may have fallen out of its plug / connector. Every now and then the cabinet requires a radio engineer to discover the problem (s) and make sure the phasor is being powered by the transmitter (s).
In addition to changing the phase or increasing the amplitude of the signal, for example, to obtain the necessary direction of the antenna system, the phasor unit is also crucial for the operation of other devices, such as the antenna tuning unit (ATU), line termination unit (LTU) and antenna coupling unit (ACU), whose feeder lines are also mapped to each tower. To obtain sufficient signal strength and correct phasing and matching of matrix parameters, it is critical that each unit work side by side to obtain the desired directional pattern and achieve the desired measurements.
In short, the phasor, its power splitting and matching equipment for directional AM operation, housed in the cabinet, is intentionally used as a unit phase controller ensuring that power is being applied to each antenna. It is commonly used as a monitoring system to verify pattern changes, of which can be customized to suit user needs.
Common characteristics of a good cabinet include:
• Easy access from front and rear panel through hinged doors
• The ability to check current levels without even opening the front doors
• Digital front controls including aluminum handles or knobs for precise adjustments
• Dual AC receptacle in each bay
• Clear identification of each component through engraved labels
• J-plugs positioned for easy access, including grounding posts from adjacent bridges
• Interior panels that divide the bays, so that RF isolation to day and night networks can be guaranteed
• A variety of fixed and variable capacitors
• An input current meter that allows remote output.
Fabrication and Placement: Directional antenna phase units are typically constructed in weather resistant, non-corrosive aluminum housings (when placed outdoors) or placed in metal cabinets (when used indoors) or on stands of medium; they may also have an open panel and an ATU-type shelf for wall mounting.