May 22, 2018

Choosing the Right Wireless Intercom System: System Coverage (Part 7 of 9)

When trying to decide what Clear-Com wireless is right for you, knowing the coverage areas of your wireless system's antennas may effect which wireless is right for you. Today, we will discuss the system coverage section of the Choosing the Right Wireless Infographic. 


Download the full Infographic HERE.




Just as with any other product communicating via radio waves, the effective distance between the beltpack and the antenna will differ depending on the environment in which it is being used. Radio waves can be attenuated by walls, floors, ceilings, trees, the human body (such as the audience), and numerous other objects. They can be reflected and/or stopped by metallic objects, such as structural beams, safety doors, lighting equipment and truss, bodies of water and so on.

FREESPEAK II

Under ideal conditions, the maximum range between a FreeSpeak II beltpack and the antenna is 500 m (1640 ft). Typical distances are between approximately 50 m (160 ft) and 150 m (485 ft), depending on the environment. 

As the antenna requirements for an installation are being determined, keep in mind both the number of beltpack users who will be working in an area (based on the beltpack capacity of the antenna), and the layout and potential RF attenuating and reflecting items in the location. Be conservative in distance estimates to make sure that enough antennas are included to provide the necessary coverage for the installation. Remember that additional antennas may be added. 

General rules and tips for antenna placement:

  • Keep antennas high and in line-of-sight (lower placements away from interfering objects can, at times, be beneficial. It depends on the environment)
  • Keep antennas away from larger metallic objects and surfaces
  • Antenna coverage is circular, so put the antennas in the center of the area in which the coverage is required
  • When overlapping the coverage zones in order to create a larger continuous coverage area, test the inbetween areas with a beltpack for potential areas of low RF signal and adjust the positioning of the antennas as needed
  • Because of potential body shielding during movement, it is useful to place two antennas in different locations within larger working areas to minimize low-level signals and potential signal dropouts
DX SERIES

The common antenna type used in the DX Series systems is an external Dual Diversity 1/2 ave dipole omni-directional antenna. The DX Series base stations use two of these antennas. The base electronics switch between these antennas to obtain the best signal quality. Both antennas act as a transmit and receive, so one antenna could be removed and the system would still operate. The purpose of having two antennas is to overcome multipath dropouts. If one antenna is remoted, the base will still select the antenna that gives the best signal.

Some installations require that the antennas be removed from the base station chassis and placed in another location to ensure better line-of-sight operation. Antennas can be placed outside of equipment racks and microphone stands, wall brackets, or any other suitable mounting device. To do this, the DX Series has an optional remote antenna kit, consisting of a bracket, coax cable and screws. Adding addition coax cable to the antenna connection will reduce the range to that antenna because of signal loss, but it will fill in a bad coverage spot. Therefore, it is best to keep antenna cabling down to a minimum whenever possible.

General rules and tips for antenna/base station placement:
  • The base station should be located so that you maximize the line-of-sight operation - even if this requires operating through a glass window
  • Metal equipment racks will block RF from reaching the antennas mounted to the base station inside - rear-mounted antennas may not work inside a metal rack
  • Minimize the number of walls between the base station and area where the beltpacks will be operating
  • If necessary, the base station can always be moved closer to the area of highest beltpack usage for more thorough coverage
  • Always do a walk test before making the decision of where to place the base station



May 21, 2018

Choosing the Right Wireless Intercom System: Regional Approvals (Part 6 of 9)

When trying to decide what Clear-Com wireless is right for you, the frequency band regulations may effect which wireless you are allowed to use. Today, we will discuss the regional approvals section of the Choosing the Right Wireless Infographic. 


Download the full Infographic HERE.




One of the first things you need to know about frequency bands is that the use of radio equipment is subject to regulations in each country. A given device may not be allowed to cause harmful interference to other authorized users. The device must accept any interference caused by other users. RF equipment must be installed by qualified professional personnel. It is the responsibility of the installer to ensure that only approved equipment and/or systems are deployed and that effective radiated power does not exceed permissible limits established by the country's regulatory agency in which it is used. 

Wireless partyline systems have been analog for many years and can still be found, although use of the radio spectrum they occupy is in a state of change. These analog wireless systems use the UHF frequencies of 470 - 698 MHz, part of which has been selected by the FCC in the US, to be auctioned off, banning the use of wireless microphones, transmitters, intercom systems or other wireless devices on a licensed and unlicensed basis. Despite the efficiency of the lower UHF band, long-term use may be in decline because of these regulation changes. But not all is lost.

One of the biggest innovations incorporated in wireless intercom is the all-digital radio. A significant feature of some digital wireless systems operating in 1.9 GHz and 2.4 GHz is that they use transceivers that require no end user licenses for operation in some countries. These systems never need frequency coordination and do not suffer from the interference that analog radio signals incur regularly. In addition, the wireless systems allow for many more simultaneous users than ever possible in the lower UHF systems.

A common transmission scheme used for digital wireless intercom is frequency hopping spread spectrum (FHSS), a technology originally developed for military guidance systems to make them insensitive to frequency jamming. FHSS-based wireless intercom systems transmit digitized audio samples for all intercom channels and beltpack return talk paths in a single transmission burst serially on a narrow band RF carrier. This is then repeated on carious frequencies in a defined pattern known by the base station and the beltpack. Depending on the implementation, FHSS may be used in conjunction with redundant transmission where a second transmission pattern is utilized in parallel, or redundant, transmission of the digitized audio on the same carrier after the primary transmission. the most recent versions also include a mechanism that validates the next frequency in the FHSS pattern before using it for transmission or moving onwards to the next frequency. Frequency bands that are commonly used for FHSS include 2400 - 2480 MHz range. 

Another common digital transmission scheme is DECT (digital enhanced cordless telecommunications) standard. Originally developed for cordless telephones, the DECT multi-carrier TDMA (time-division multiple access) technology allows for very efficient spectrum utilization over 2 to 10 common carriers in the 1800 - 1930 MHz range, depending on regional allotments. The DECT protocol automatically assigns time slots and carriers to individual devices.

Because of these differing transmission schemes and frequency band regulations per country, the FreeSpeak II 1.9 GHz system is only allowed to be used within the United States, Canada, EU countries, Australia, New Zealand, Hong Kong, Singapore, Japan, Argentina, and Brazil. There are no current regulation restrictions for the FSII 2.4 GHz, DX410, DX300ES, DX210, or DX100 wireless systems. 

May 18, 2018

Choosing the Right Wireless Intercom System: Number of Users (Part 5 of 9)

When trying to decide what Clear-Com wireless is right for you, the number of users you have and how they need to talk and listen to each other may be the determining factor of what system you need. Today, we will discuss the number of channels section of the Choosing the Right Wireless Infographic. 


Download the full Infographic HERE.



Before we get into the details of what system will work for you, we need to explain the three different types of communication channels. 

SIMPLEX COMMUNICATION

A simplex communication channel only sends information in one direction - from the sending device to the receiving device. Simplex is used only when the sending device does not require a response from the receiving device. For example, a radio station usually sends signals to the audience, but never receives signals from them; therefore, a radio station is a simplex channel. Another example is a microphone to a loudspeaker.




HALF-DUPLEX COMMUNICATION

In half-duplex mode, data can be transmitted in both directions, just not at the same time. At a certain point, it is a simplex channel whose transmission direction can be switched. Two-way radios are typical half-duplex devices. It has a push-to-talk (PTT) button, which can be used to turn on the transmitter, but turn off the receiver. Therefore, once you push the button, you cannot hear the person you are talking to but your partner can hear you.



FULL-DUPLEX COMMUNICATION

A full-duplex communication channel transmits data in both directions at the same time. It is constructed as a pair of simplex links that allows bi-directional simultaneous transmission. Take the telephone as an example. People at both ends of a call can speak and be heard by each other at the same time because there are two communication paths between them. Thus, using the full-duplex mode can greatly increase the efficiency of communication.



Ok, now that you understand what kind of communication you need to have, simplex, half-duplex or full-duplex, you're now ready to compare wireless systems based on this requirement. 

DX100: Supports up to 4 full-duplex users or 15 half-duplex users

DX210: Supports up to 4 full-duplex users or 15 half-duplex users. Able to connect up to 4 base stations together for up to 16 full-duplex users or 44 half-duplex users.

DX300ES: Supports up to 3 full-duplex users or 15 half-duplex users. Able to connect up to 4 base stations together for up to 12 full-duplex or 60 half-duplex users. 

DX410: Supports up to 4 full-duplex users in single-channel mode or 15 half-duplex users. Able to connect up to 4 base stations together for up to 16 full-duplex users or 44 half-duplex users.

FSII 1.9 GHz: Supports up to 5 full-duplex users per transceiver or a total of 25 full-duplex users with up to 10 transceivers. Able to connect base stations together for up to 65 full-duplex users when mixed with FSII 2.4 GHz transceivers on a system.

FSII 2.4 GHzSupports up to 5 full-duplex users per transceiver or a total of 40 full-duplex users with up to 10 transceivers. Able to connect base stations together for up to 65 full-duplex users when mixed with FSII 1.9 GHz transceivers on a system.