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ANTENNA COMBINING

The converse of antenna distribution, antenna 

combining, can be employed in one of two ways. With 
wireless microphone systems, multiple antennas can be
combined together to feed a single receiver (or multiple 
receivers with antenna distribution) to provide coverage
across multiple rooms or in extremely large spaces. For
wireless personal monitor systems, which usually consist of
rack-mounted transmitters, antenna combining is used to
reduce the number of transmitting antennas, i.e. the 
antenna combiner allows all the transmitters to share a
common antenna.

Multi-room Antenna Setups

For multiple room coverage, use passive combiners.

Since they do not require power and are typically compact,
they can be located wherever necessary. A passive 
combiner will typically result in at least 3 dB of loss, so be
sure to include this figure when calculating cable loss. 
Multiple combiners can be used in series, if more than 
two locations need to be covered, so long as enough 
amplification is provided to make up for whatever additional
losses are incurred. For situations where more antenna 
amplifiers are needed than can be effectively powered by
the receiver or antenna distribution system, additional bias
“Tee” power adapters must be used. These adapters allow
a bias voltage to be “injected” into the antenna cable.

It is important to keep multiple antennas feeding a

common receiver input as isolated from each other as 
possible in order to minimize potential phase cancellation
that could result in signal dropout. Certain receiver designs
will be better equipped to deal with this situation than 
others, but it is a worthwhile precaution nonetheless.

Antenna Combining for
Personal Monitor Transmitters

Antenna combining is crucial to obtaining optimal 

RF performance from personal monitor transmitters. 
Several closely-spaced, high-power transmitters suffer from 
excessive intermodulation (a transmitter interaction that 
produces additional frequencies) problems. In this case, a
passive combiner should be used for combining two 
transmitters. For more than two, though, an active combiner
is recommended. An active antenna combiner will typically
accept between 4 to 8 transmitters. Unlike active antenna 
distribution systems, which can be cascaded together for
larger setups, active antenna combiners should never be 
“actively” cascaded. If
more than one combiner
is needed to combine all
the transmitters together,
a passive combiner
should be used to 
connect two active 
combiners together. As
always, be aware of any
extra losses incurred with
the passive combiners.

Similar to active 

antenna distribution 
systems, active combin-
ers also have a specified
frequency bandwidth.
Be sure to select the
proper bandwidth for
the given transmitter 
frequencies.

= UA221 

(passive combiner)

= UA820 

(1/2 wave antenna)

10

ANTENNA SETUP

Wireless Systems Guide for

Multi-room coverage: 3 separate rooms – 6 antennas 

UA830WB (RF amplifier)

UA221 (passive combiner)

Equipment 

Rack

DC

supply

Room C

Room B

Room A

bias T (necessary for more than two amplifiers per line)

Multi-room coverage: 1 room divided by airwalls – 4 antennas

Room C

Room A

Room B

Airwalls

Equipment 

Rack

= UA830WB 

(RF amplifier)

Active antenna combining

Summary of Contents for ANTENNA SETUP

Page 1: ...A Shure Educational Publication ANTENNA SETUP WIRELESS SYSTEMS GUIDE By Gino Sigismondi and Crispin Tapia...

Page 2: ......

Page 3: ...bution 3 or more receivers 8 Antenna Remoting 8 Antenna Combining 10 Multi room Antenna Setups 10 Antenna Combining for Personal Monitor Transmitters 10 Quick Tips 11 Suggested Reading 11 Section Two...

Page 4: ...hen attached to an audio input As with any transducer following certain guidelines helps ensure maximum performance When dealing with radio frequencies in particular considerations such as antenna siz...

Page 5: ...an be mounted directly to the wireless receiver or antenna distribution system this also includes front mounted antennas on the rack ears These antennas require a ground plane for proper reception whi...

Page 6: ...the front When deciding where to mount antennas always try to maintain line of sight between the receiving and transmitting antennas For example if the back of the rack faces the performance area the...

Page 7: ...sulting in erratic coverage Additionally closely spaced antennas can aggravate local oscillator bleed which is a potential source of interference between closely spaced receivers Finally for remote an...

Page 8: ...ncies over a large range typically several hundred Megahertz Narrowband devices may be limited to no more than 20 or 30 MHz Since these are active devices frequencies outside the bandwidth of the dist...

Page 9: ...ntenna amplifiers are also band specific available as both narrow or wideband Each connection between two sections of cable may result in some additional signal loss depending on the connector To incr...

Page 10: ...at could result in signal dropout Certain receiver designs will be better equipped to deal with this situation than others but it is a worthwhile precaution nonetheless Antenna Combining for Personal...

Page 11: ...account Antennas are designed to be sensitive to particular frequencies Be sure to use the proper antenna for the frequency of your wireless system Antenna efficiency degrades somewhat outside of the...

Page 12: ...a 3 4 receivers 1 active antenna distribution system w 4 outputs 2 receivers 2 passive splitters A antenna B antenna SLX4 SLX4 SLX4 SLX4 UA844 POWER UHF ANTENNA POWER DISTRIBUTION SYSTEM SLX4 SLX4 SLX...

Page 13: ...w 4 outputs each A antenna B antenna SLX4 SLX4 SLX4 SLX4 UA844 POWER UHF ANTENNA POWER DISTRIBUTION SYSTEM SLX4 SLX4 SLX4 SLX4 UA844 POWER UHF ANTENNA POWER DISTRIBUTION SYSTEM SLX4 SLX4 SLX4 SLX4 UA8...

Page 14: ...tenna combining 2 4 systems 1 4 to 1 antenna combiner 1 2 3 4 5 6 7 8 PA821 PSM Antenna Combiner 470 870 MHz 50 OHMS ACTIVE COMBINER MAIN OUT INPUT SIGNAL A IN B IN A B OUT POWER Shown Shure PA821 wit...

Page 15: ...2 3 4 5 6 7 8 PA821 PSM Antenna Combiner 470 870 MHz 50 OHMS ACTIVE COMBINER MAIN OUT INPUT SIGNAL A IN B IN A B OUT POWER Shown Shure PA821 with built in 2 to 1 passive combiner 1 2 3 4 5 6 7 8 PA821...

Page 16: ...enna 0 dB Amplifier 10 dB 100 RG213 Cable 7 dB Net Gain 3 dB Net Gain Calculation Antenna 0 dB Amplifier 1 3 dB Amplifier 2 10 dB 75 RG8X Cable 10 dB Net Gain 3 dB Net Gain Calculation Antenna 0 dB Am...

Page 17: ...a 30 feet Net Gain Calculation Antenna 0 dB Amplifier 3 dB 25 RG8X Cable 3 dB Net Gain 0 dB Net Gain Calculation Antenna 0 dB 6 RG58 Cable 1 dB Net Gain 1 dB 30 ft 10 m RG8X 6 ft 2 m RG8X 10 m Many mo...

Page 18: ...nd recording engineer Gino s experience includes performing and composing and sound design for modern dance and church sound Crispin Tapia Crispin Tapia is an Applications Engineer at Shure Incorporat...

Page 19: ...e of charge To obtain your complimentary copies call one of the phone numbers listed below or visit www shure com Microphone Techniques for Studio Recording Microphone Techniques for Live Sound Reinfo...

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