| What does UHF Mean? |
Ultra High Frequency (UHF) designates a range of electromagnetic waves with frequencies between 300 MHz and 3 GHz (3,000 MHz). ITU allocation 9. The wavelengths range from one to ten decimetres (10 to 100 cm). As an example, the Global Positioning System uses UHF. UHF proceeds VHF and follows SHF (Super High Frequency), EHF (Extremely High Frequency) and THz (Terahertz) bands of the microwave frequency range.
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| What does VHF Mean? |
Very High Frequency (VHF) designates a range of electromagnetic waves with frequencies between 30 MHz to 300 MHz. ITU allocation 8. The wavelengths range from 1 to 10 metres. Currently VHF is at the low-end of practical frequency usage, new systems tending to use frequencies in SHF and EHF above the UHF range. VHF proceeds HF and follows UHF, SHF (Super High Frequency), EHF (Extremely High Frequency) and THz (Terahertz) bands of the microwave frequency range.
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| What does HF Mean? |
High Frequency (HF) designates a range of electromagnetic waves with frequencies between 3 and 30 MHz. ITU allocation 7. The wavelengths range from 10 to 100 metres. HF follows VHF, UHF, SHF (Super High Frequency), EHF (Extremely High Frequency) and THz (Terahertz) bands of the microwave frequency range.
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| What is the difference between UHF and VHF? |
There are pro's and con's for VHF and UHF in two-way radio systems. Both UHF and VHF radios are mainly prone to line of sight factors. VHF systems are considered less reliable than UHF in situations where there will be interference such as inside buildings with people, walls and other electronic devices or outside where there are lots of trees. This is due to the frequency range at which it operates. UHF however is designed to alleviate the signal interference problems that VHF face as mentioned above, thanks to its shorter frequency range. Although, if you do plan to use your wireless microphone system outside where there will be no interference, VHF offers approximately double the broadcast / operating range over UHF, due to the longer frequency range (i.e. If a VHF wave and a UHF wave were transmitted over an area without barriers, the VHF wave would travel almost twice as far). VHF wireless radio offers an increased battery life over UHF units. For handheld radios this is a plus. VHF equipment is usually lower cost for those on a budget.
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| What does Wireless Mean? |
In two way radio systems, a wireless system means there is no physical wiring between the transmitter and receiver (i.e. transmitting signals over invisible radio waves instead of wires). The receiver is not exempt from being plugged into the mixing unit. It simply provides wireless communication for the transmitter such as microphone, lapel or headset to the receiver.
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| What does Wired Mean? |
In two way communication systems, a wired system means there is physical wiring between microphone and mixing unit. Generally, a microphone will feature an XLR connector if the cable is detachable. In comparison to wireless systems, you are restricted to where you walk with a wired system as you are restricted by the length of the cable.
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| What is a Lapel Microphone? |
A lapel microphone is a small electret (type of condenser microphone) or dynamic microphone designed to clip to collars, ties, or other clothing to allow for hands-free operation. The cord may be hidden by clothes and either run to a radio frequency transmitter in a pocket or clipped to a belt (for mobile operation), or directly to the mixer (for stationary applications).
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| What is a Condenser Microphone? |
The name condenser microphone actually refers to a capacitor system, in which two plates with voltage between them are used to create sound. The outer plate (diaphragm), is typically made of a thin material that vibrates when sound waves strike it. The vibration changes the distance between the two plates, thereby changing the capacitance. Condenser microphones are the most common types of microphones you'll find in studios. They have a much greater frequency response and transient response. This is the ability to reproduce the 'speed' of an instrument or voice. They also generally have a louder output, but are much more sensitive to loud sounds. Condenser microphones are generally much more expensive than dynamic microphones. They require the use of a power supply, generally 48 volt 'phantom power' on most mixers, represented by 'P 48' or '48V' or even by a self-contained battery. Condenser microphones are generally used only in studios because of their sensitivity to loud sounds and the fact that they're quite a bit more fragile than their dynamic counterparts. That being said, you'll find them onstage at live music venues for use as drum overheads or for use in orchestral or choral sound reinforcement. With condenser microphones, you'll find two different types: small diaphragm, and large diaphragm.
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| What is a Dynamic Microphone? |
Compared to condenser microphones, dynamic microphones are much more rugged. They're also especially resistant to moisture and other forms of abuse, which makes them the perfect choice onstage. Dynamic microphones are legendary for not only their good sound quality, but the amount of abuse they can withstand. Any good rock club probably has at least 5 of each of these microphones in various states of aesthetic ruin; however, they still turn on and more than likely sound just as they did the day they came out of the package. Dynamic microphones don't require their own power supply like condenser microphones. Their sound quality is generally not as accurate, however. Most dynamic microphones have a limited frequency response, which makes them well-suited, along with their ability to withstand high sound pressure levels, for loud guitar amps, live vocals, and drums.
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| What is Feedback? |
Audio feedback is the ringing noise (often described as squealing, screeching, etc) sometimes present in sound systems. It is caused by a 'looped signal', which is a signal that travels in a continuous loop. In technical terms, feedback occurs when the gain in the signal loop reaches 'unity' (0dB gain). One of the most common feedback situations is when you stand too close to the speaker whilst using a microphone - the microphone feeds a signal into a sound system, which then amplifies and outputs the signal from the speaker, which is picked up again by the microphone.
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| How do I Prevent Feedback? |
To eliminate feedback, you must interrupt the feedback loop. You could invest in a digital feedback eliminator. There are various models available with varying levels of effectiveness. Alternatively, here are a few suggestions for controlling feedback:
* Change the position of the microphone and/or speaker so that the speaker output isn't feeding directly into the mic.
* Keep speakers further forward (i.e. closer to the audience) than microphones.
* Use a more directional microphone.
* Speak (or sing) close to the microphone.
* Turn the microphone off when not in use.
* Equalise the signal, lowering the frequencies which are causing the feedback.
* Use a noise gate (automatically shuts off a signal when it gets below a certain threshold) or filter.
* Lower the speaker output, so the mic doesn't pick it up.
* Avoid aiming speakers directly at reflective surfaces such as walls.
* Use direct injection feeds instead of microphones for musical instruments.
* Use headset or in-ear monitors instead of speaker monitors.
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