RCDD · Question #234
As a wireless designer, you have been tasked with designing a DAS which supports UHF public safety radios. You have determined that if you increase the power of the base station antenna, you can…
The correct answer is D. The legal limits of the transmitter. FCC regulations set a legal maximum on transmitter output power for UHF public safety frequencies, making that limit the primary restrictive constraint when considering a power increase in a DAS.
Question
As a wireless designer, you have been tasked with designing a DAS which supports UHF public safety radios. You have determined that if you increase the power of the base station antenna, you can solve coverage problems in the basement. One of the restrictive items that you should consider is:
Options
- AA single antenna may not provide the total power multiple antennas may provide
- BThe proper launch amplifier has to be chosen to provide the proper power
- CThe building's wall types may still affect the coverage
- DThe legal limits of the transmitter
How the community answered
(40 responses)- A3% (1)
- B10% (4)
- C3% (1)
- D85% (34)
Why each option
FCC regulations set a legal maximum on transmitter output power for UHF public safety frequencies, making that limit the primary restrictive constraint when considering a power increase in a DAS.
The power distribution difference between a single antenna and multiple antennas is an engineering trade-off, not a legal restriction on how much power may be transmitted.
Choosing the correct launch amplifier affects system performance but is a hardware selection consideration, not a regulatory constraint that limits the permissible power level.
Building wall attenuation is a propagation factor that influences coverage prediction but does not legally restrict the transmitter power level that may be used.
Regulatory bodies such as the FCC establish maximum allowable transmitter output power and EIRP for each licensed frequency band, including UHF public safety channels governed under 47 CFR Part 90. Exceeding these limits constitutes an illegal operation that can cause interference to other public safety users and result in enforcement action regardless of the coverage benefit achieved. A DAS designer must verify any proposed power level falls within the legally permitted threshold before implementation.
Concept tested: FCC regulatory power limits for public safety DAS transmitters
Source: https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-90
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