Now widely used for wireless microphone VHF (very high frequency) and UHF (ultra high frequency) two transmission bands.
VHF band range is 30MHz - 300MHz, a wavelength of 10m - 1m, often referred to as “UHF.”
UHF-band frequency range is 300MHz - 3000MHz, a wavelength of 1m - 0.1m, often referred to as “UHF.”
The two radio bands are widely used in TV, FM radio, mobile phones, pagers, stock information machine, microwave communications and radar.
A variety of radio wave propagation in free space, has the time and geographical constraints, the frequency overlap cross, without the constraints and regulations, will inevitably generate interaction, so the use of radio waves in the world to have a uniform requirement, so that the interaction between them minimized. Permit the use of wireless microphone frequency range is defined as:
VHF band for the 169MHz - 230MHz, 61MHz frequency range were occupied. In the 61MHz frequency range is subdivided into A, B, C three sections, namely: VHF (A) to 169MHz - 185MHz, VHF (B) for the 185MHz - 200MHz, VHF © to 200MHz.
UHF band for the 690MHz - 960MHz, 270MHz frequency range were occupied, can be set hundreds of wireless microphone channels. Required frequency range can be extended up to set more wireless radiation channel.
VHF and UHF two-band radio wave propagation characteristics:
VHF advantage of the smaller metal objects small reflection, diffraction, and penetration strong, low feeder loss, longer battery life time, lower cost; defects is subject to VHF TV channel, paging, letters, and industrial machines pollution, such as welding, electrical interference such as big, you can use a narrow frequency range, Duo Maike use frequency congestion, less compatible with the frequency, small signal dynamic range.
UHF advantage is less high-frequency interference; can use the frequency range of 270MHZ, scalable range, can Duo Maike use, may form a larger system, the signal dynamic range. Drawback is the small metal object more reflective, multi-channel transmission can interfere with;
on the human body and other non-metallic objects blocking attenuation; feeder big loss, the receiver should be as close to the microphone; needs more transmit power, the battery used short time and higher cost.
In general, VHF appropriate for hotels, convention centers, sports fields (Hall), multi-function hall and education system; UHF appropriate for broadcast television, theater performances and demanding, multi-channel wireless microphone systems work simultaneously.
I belong to VHF band wireless microphone models are: MR-8000, MR-8200, SF-225, SF-325, UK-300, etc.;
UHF band are: USF-128, USF-228, UK-532, UB-210, UB-220, SF-318, US610, US800D so.