Here at AmpliVox we sell both UHF and VHF wireless systems. A lot of our customers ask which is best for their setup. Here are some factors to consider when purchasing a wireless sound system and spending your dollar wisely. Factors to include are: where the systems will be used, how they will be used, and for what purpose or application. Other factors, such as whether the equipment will be used in many different cities, may also be important.
UHF wireless systems always cost more than similar VHF wireless systems. The extra cost of UHF equipment is due to the necessity of using more expensive ultra-high-frequency parts, the greater total number of parts required and the need for more expensive construction techniques. Other manufacturing costs are also higher, especially the amount of time required to adjust the equipment and verify its performance. While the cost difference between UHF and VHF equipment has been declining, it is unlikely to disappear.
If the wireless equipment will be used in different cities, VHF systems operating on the special frequencies in the 169-172 MHz range will be a good economical choice (applicable in U.S. and Canada). However, these frequencies, which are sometimes referred to as "traveling frequencies," are very popular, and are not a good choice for situations where large numbers of wireless systems are likely to be present, such as at trade shows and expositions. In such situations, frequency-agile UHF systems will be a better choice.
If the wireless equipment will be used in situations where several other wireless systems are likely to be present, UHF systems are recommended. This is because more frequencies are available, reducing the chances of interference. Such as a trade show or conference.
Wireless mic systems generally operate in several bands from 150MHz to 216MHz, which includes the VHF TV channels 7 through 13, or in the 470MHz to 806MHz UHF band (TV channels 14 through 69). TV channels 60 to 69 (746 to 806MHz) are being re-allocated, as of the date of this writing, for other applications. In addition, the band from 470 to about 516MHz is also being re-allocated for public safety applications. The demand for more spectrum usage is increasing while the available spectrum for wireless microphones is decreasing. Above the TV band is another part of the UHF spectrum from 902 to 928MHz. This upper UHF band is a "general purpose" band being used by a multitude of different applications ranging from garage door openers and amateur radio, to home-use cordless telephones. Generally speaking, the 902 to 928Mhz band is not a good choice for wireless microphone systems, especially for professional use in traveling applications. Interference is virtually guaranteed in this band. So again, it is unreasonable to assume that UHF is better by default.
Simply put, UHF systems do not hold any large technical advantage over otherwise similar VHF systems. The primary advantage of UHF operation is that there is less chance of interference because of more available frequency spectrum.
Information from: Audio Technica, Sweetwater, Wikipedia