As far as classification goes, that is all there is, but that does leave some questions unanswered.
Class A amplifiers are known as channelized, and Class B are referred to as wideband. Most Class A amplifiers can be programmed for 32 individual channels, with some models offering more depending on the frequency band. Class B can be programmed for two channels per frequency band, depending on filter bandwidth.
Both Class A and B can come in variants from ½-watt up to a maximum of five (5) watts. While they both provide the same level of total amplification, Class A boosters dedicate most of that power to the individual channels used by the public safety network.
Class B, on the other hand, allocates equal power to all signals within the filter’s bandwidth. This leaves Class B amplifiers susceptible to inefficiencies due to the amplification of these unwanted signals.
These unwanted signals, also called spurious, can make booster output fluctuate in heavily used radio frequency (RF) environments, such as urban areas, making optimization and output power management difficult. The saving grace of a Class B amplifier is that these large bandwidths accommodate a considerable number of channels. So, if there are more channels than a Class A unit can handle, Class B offers the most cost-effective solution when the channels are in close alignment, and there are no unwanted strong interfering signals in the range of the filter’s bandwidth.
The other primary consideration between Class A and Class B is the noise generated. Class A can only transmit when the amplifier detects a signal and then mutes the channel. Class B does not have this capability and must be in an always-on state. This has a greater potential of generating noise for the public safety network or any other networks used in the filter’s bandwidth.
Since Class B boosters are more likely to cause noise to surrounding sites, they must be registered with the FCC upon installation and before turn-up. This adds another step to the process, but the upcoming standards will require this for both Class A and B boosters.
Pricewise, Class A amplifiers tend to cost more than Class B due to the filters used in construction. However, Class B ERCES configurations may require more power in a like-for-like comparison to compensate for the inefficiency caused by amplifying spurious or unaffiliated signals.
In summary, there is no “one-size-fits-all solution” when it comes to the best choice for a public safety bi-directional amplifier. The decision should be made based on the AHJ’s requirements, the number of channels needing amplification, and specifics of the local network environment to ensure the best functionality.
Pierson Wireless is an industry leader in ERCES and Public Safety DAS solution design, implementation, and system monitoring. To learn more about our expertise in the space or to schedule a consultation, visit our Public Safety resource page.