The Advantages and Disadvantages of UHF Radios
What Are UHF Radios?
UHF stands for ultra-high frequency. UHF radios pick up radio signals with very short waves.
For example, the 430 MHz frequency equates to a 70 centimeter radio wave. UHF waves are smaller than VHF or very high frequency radio waves. The 144 MHz frequency has a two meter radio wave. The UHF radio spectrum goes up to 1 Gigahertz.
The frequency that UHF radios cover has expanded from 400-470 MHz. First UHF radios showed up in the 512 MHz band, then 800-960 MHz. As radios have become better at reducing cross-talk and interference, you now see UHF radios in the 700-800 MHz frequency range.
UHF radios generally have four to five watts of transmitting power. They are commonly used by first responders like police officers and paramedics.
Advantages of Hand Held UHF Radios
One of the greatest advantages of handheld UHF radios is their portability. Furthermore, their signal can be boosted with an external antenna. However, handheld radios don’t do as well in handling interference on the same frequency band.
Mobile radios that could fit on someone’s dashboard will have similar frequency scanning capability as a hand-held radio. UHF radios are not affected by solar activity. They work in almost any weather conditions.
UHF radios are popular because they can be built around a single loop antenna from several inches to several feet across. When coupled with bouncing signals off the moon or ionosphere, someone with a UHF radio could talk to someone else on the other side of the planet. This is why UHF radios are popular with ham radio operators.
The lower end of the UHF bands are less prone to electronic noise than other frequencies; for example, the lower UHF bands are not as prone to interference from power lines or nearby microwave ovens.
Because of the short wavelength, UHF performs better in hilly and mountainous areas. In Roanoke, Virginia, 800 MHz trunking repeaters are far superior to their 470 mhz counterparts. The same can be said for television transmission in mountainous areas.
Disadvantages of UHF Handheld Radios
According to “Electronic Access Control” by Thomas L. Norman, UHF radios require licensing in most of the world. This makes it hard for many businesses to be able to use UHF radios unless they were already licensed the frequencies.
UHF frequencies are assigned to various governmental agencies and groups. In the U.S., many cities have already assigned the entire UHF frequency range except for a few bands set aside for amateur radio.
Another limitation for UHF frequencies is that they are often line of sight. If someone is in a canyon, their handheld UHF radio may not work until they get out of the canyon. However, UHF signals can reach further if signals are bounced off of the ionosphere.
UHF radios suffer from interference from nearby TV stations that also rely on UHF and RFID that uses UHF as well as other frequencies. For example, UHF radios use the 400-470 MHz frequency range, but 433 MHz is specific to RFID applications. According to "RFID Design Principles" by Harvey Lehpamer, the problem is compounded by the fact that countries have allocated different UHF frequency ranges to cell phones, radios, RFID and alarms.
The Evolution of UHF Radios
UHF handheld radios are gradually being replaced by VHF radios in the public safety field as technology improves. However, many police departments and fire departments still have UHF radios in the field.
The Federal Communications Commission has tried to ease up demand for these frequencies by “re-banding” or reallocation of frequency bands. As radios have become digitized, the FCC has been allocating smaller frequency ranges to various groups. Radio manufacturers have gone from 100 kHz channels, to 50 kHz to 25 kHz to 12.5 kHz and now 6.25 kHz channel spacing. The FCC is enforcing this “narrow banding” by refusing to license new systems that did not meet the narrow band requirements.
In January 2011, the FCC refused to accept applications for new systems or transmitters that couldn’t operate within a 12.5 kHz bandwidth. According to the U.S. Department of Homeland Security, in January 2013, the narrow-band requirements became mandatory across the country. Any handheld radios, repeaters or base stations that did not meet this narrow-band requirement lost their license to operation; the only solution is to redesign them or replace them with compliant hardware.
- "Mike Meyers' CompTIA RFID+ Certification Passport" by Mike Meyers, Mark Brown, Sam Patadia and Sanjiv Dua
- "RFID Design Principles" by Harvey Lehpamer
- “Electronic Access Control” by Thomas L. Norman
- “Voice Radio Communications Guide for the Fire Service” by the U. S. Department of Homeland Security