The fire crackles through a high-rise building as first responders rush inside. Their radios must work – not just well, but perfectly. In these critical moments, emergency response radio communication systems (ERRCS) reliability isn’t just about meeting code requirements – it’s about saving lives.
RF wattmeters are devices that measure power (watts) into a circuit or system such as a transmission tower. Bi-directional wattmeters allow the user to take data on a system while it is operating. In addition to delivered power, they also measure reflected power.
Antenna gain indicates how strong a signal an antenna can send or receive in a specified direction. Gain is calculated by comparing the measured power transmitted or received by the antenna in a specific direction to the power transmitted or received by a hypothetical ideal antenna in the same situation.
Wattmeters are used in a variety of electrical circuit measurement and debugging applications. For example, they can check the power consumption of electrical appliances. RF wattmeters are devices that measures power (watts) into a circuit or system such as a transmission tower.
A power divider divides an incoming signal into two (or more) output signals. In the ideal case, a power divider can be considered loss-less, but in practice there is always some power dissipation.
An isolator is a type of non-reciprocal passive network that allows designers the freedom to construct networks where the transmission coefficient in one direction does not necessarily have the same loss as in the reverse direction. In an isolator, ideally, RF energy can be made to flow through it in only one direction.
TX and RX filters select a specific portion of the RF or microwave signal based on the desired frequency, and reject the rest of the signal being transmitted or received. The range of frequencies that are passed by a filter are called the pass-band, the ranges of frequencies that need to be rejected are called stop-bands. Unless otherwise specified, filters reflect energy in the stopbands, rather than absorb it.
A crossband coupler is a three-port network that allows transmitters and receivers of different frequency bands to share a single feedline to an antenna. It does this by using low-pass, high-pass, or band-pass filters to isolate the desired signals from each other, with very low loss in both paths to the antenna.
Any time there are RF or any electrical equipment out in the field, it’s going to be subject to a wide range of environmental factors. Extremes of temperature, wind-blown debris, and moisture from rain or snow even dew can all interfere with signals you’re trying to transmit or receive.
A coaxial termination is a device that can be placed on one end of a coaxial transmission line to absorb the transmitted signals without impacting other system components. A termination presents a “matched load” to the system impedance (usually 50 or 75 ohms), so that a terminated transmission line will behave like an infinitely long line where the signal never has a chance to reflect back to the signal source.
Cavity filters are one of many types of Radio Frequency (RF) filters, and are one of the fundamental building blocks of modern communications systems. This paper describes the basics of cavity filters. For additional information about specific Telewave cavity filters and solutions that employ the filters, please visit our web site at www.telewave.com.
Cavity filters are a type of resonant filter used for either passing desired RF signals within a specified frequency range or rejecting RF signals within a range of frequencies. The resonant cavity within these filters can be constructed from durable materials, such as highly conductive and dimensionally stable metals, to reliably perform for years in harsh environments.
Why New Narrowband Channel Assignments Impact Channel Isolation Requirements
Narrowbanding has been a congestion mitigation challenge since the early 1990’s, and in 2013 the FCC required all current licensees to be fully operational with 12.5 kHz equipment.
It is common for multiple radio and wireless providers to share communications sites and cell towers, and this proximity often results in spectrum congestion.Radio frequency interference can originate from a wide number of sources, from natural phenomena such as lightning and sun spots to high power broadcast systems like AM/FM radio and TV transmitters, 2-way radio, paging, cell phones, and emergency and public safety communications systems, power lines, transformers, medical equipment, as well as any device that produces RF energy.
An ideal telecommunications tower site would have every band in critical industrial, commercial, and public safety spectrum fitted with a dedicated antenna and receive unit for optimum sensitivity. However, the large size of 30 MHz to 960 MHz antennas and radio equipment, and the congestion of many tower sites, often requires the receive antennas to pull double-, or multi-, duty.
The term duplexer refers to an electronic device that enables forward and reverse (transmit and receive) signals to travel in a single signal path. For telecommunication applications with densely populated towers and expensive premiums on leasing antenna space, duplexers can allow a single antenna to operate as a transmit and receive antenna. As not all duplexers are created equal, there are several key aspects to consider when evaluating duplexers for a specific application.
An antenna is a mechanical structure by which electromagnetic waves are sent out or received.
An antenna accomplishes this by being made so that its structure will be resonant at the frequency or frequencies of interest. At the heart of most common antennas is what is known as a dipole. In the simplest form this can be two metal rods, typically one pointed up and the other pointed down with the feed point being between them.
Intermodulation is a term that everyone in the LMR (Land Mobile Radio) industry has known for many years. We all have seen and/or used some sort of intermodulation tool that is used to pick system transmit and receive frequencies so that the sums and differences of the transmit frequencies will not equal any of the receive frequencies. We do this just in case, there is some non-linear item in the local transmitter or receiver environment that might take the transmitter energy and re-radiate it as a mix, landing on one of the receive frequencies.
Certain RF products, such as cavities, duplexers, and filters, rely on specific RX frequencies for optimal performance. Understanding factory input criteria—whether for transmitter or receiver use—is crucial for proper function and integration. Duplexers allow simultaneous transmission and reception on a common antenna, while intermodulation suppression panels prevent unwanted interference. Explore our article to learn more about product-specific requirements to optimize your RF system.
Tower top amplifiers (TTAs) and preselectors are crucial in optimizing radio communication systems, particularly in environments where tower space is limited and interference is a concern. Telewave.io offers a range of high-quality tower top preamps and preselectors designed to improve receiver sensitivity, reduce interference, and enhance overall system performance.
