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WMS 81
UHF Wireless Microphone System
The WMS 81 wireless microphone system comprises a
transmitter (bodypack or handheld), a receiver and optional
accessories. The bodypack and handheld transmitters have
the same transmission characteristics, with a maximum
radiated power of 10 milliwatts. Through signal companding
(compression and expansion), a dynamic range greater than
100 dB is attained at the receiver’s output. Audio bandwidth
extends from 50 Hz to 20 kHz. Through digital diversity
reception, the performance of the system is uniform over a
wide range in typical performance spaces, extending up to
distances of 330 feet (100 meters).
Individual handheld microphone and bodypack transmitters
are factory matched to a given receiver. Fifteen frequencies are
available in each of twelve UHF channels that occupy the range
of 710.2 - 745.6 MHz. Because of some frequency overlap, and
the recommendation that adjacent sub-channels not be used in
a given installation, the user may expect approximately 14
usable channels in a given multiple receiver installation.
The PT 81 bodypack and HT handheld models are
powered by 2 AA batteries, and normal battery life of 8-10
hours can be expected from alkaline 1.5 volt cells. The PT 81
accepts both microphone and line level input signals, and
input sensitivity can be selected for optimum transmission.
The PT 81 accommodates a variety of lavalier and
headworn microphones as well as electronic instruments
such as guitars and keyboards via the MK/GL guitar cable.
The D 880 WL1, D 3800 WL1 and C 535 WL1, three
modular versions of AKG’s most popular handheld vocal
mics, are available as modular heads for the HT 81.
The HT 81 handheld transmitter has the following controls:
power on/off, microphone mute, input sensitivity control, and
selection of the desired transmitting frequency. Powering of
the handheld transmitters is the same as for the bodypack.
The SR 81 receiving unit is one standard rack unit high and
one-half rack unit wide. Thus, two receiving units can be
placed side by side. Each SR 81 comes from the factory with
the chosen UHF bandwidth containing a set of 15 preset
operating frequencies. The SR 81 is a digital diversity
receiver which uses a microprocessor to monitor signal
strength and silently switch between antennae.
The SR 81 receiving unit is one standard rack unit high and
one-half rack unit wide. Thus, two receiving units can be
placed side by side. Each SR 81 comes from the factory with
the chosen UHF bandwidth containing a set of 15 preset
operating frequencies. The SR 81 is a digital diversity
receiver which uses a microprocessor controlled switch. This
provides optimum signal reception.
Controls on the SR 81 include: carrier frequency selection,
and output level control. Indicators on the unit include: RF
mute, audio input level, RF strength, diversity LEDs, and
transmitter battery status. Squelching action is made
automatic by use of AKG’s TCSQTM (tone code squelch)
circuitry. Each SR 81 is provided with two 1/4 wave diversity
antennae; however when a number of receivers are used in a
single installation it is advised to use the optional powered
antenna accessories. Up to ten receivers can be fed by a
single pair of powered antennae.
• Factory matched and optimized
transmitter/receiver frequency sets
• Digital diversity reception
• Dynamic range >100 dB
• Simple, foolproof setup procedure
• Both bodypack and handheld
microphone transmitters available
• 14 intermodulation-free UHF
channels with multiple receivers
SR 81 receiver:
Receiver type:
PT 81 bodypack transmitter:
Antenna inputs:
2 x 50-ohm BNC sockets
Audio bandwidth:
50 Hz to 20 kHz
Modulation type:
Modulation method:
Input sensitivity:
Typical -95 dBm
10 mW
Squelch threshold:
Automatic, using pilot tone (32.678 kHz)
Frequency stability:
±10 ppm
Audio bandwidth:
50 to 20 kHz
flexible, quarter-wave wire
THD at 1 kHz:
<0.4% at rated deviation
Rated deviation:
±30 kHz
Typical 100 dB (A-weighted)
Signal-to-noise ratio:
Typical 50 dB (A weighted)
Audio output:
Input impedance:
220 kohms, 600 pF
Audio input:
3-pin mini XLR; 1400 mV for
rated deviation at 1 kHz
Balanced XLR-M, mic/line
level switchable, typical 30 dB
unbalanced: 1.4” jack: 0 dBm
XLR: 6 dBm
Current consumption: 220 mA typical
Phantom powering:
Pin 3: 6 V/6k8 ohms
Power requirement:
11 to 15 V dc or ac from external power
2 AA 1.5V batteries
8.27 x 6.7 x 1.65 in. (210 x 170 x 42 mm)
Battery life:
8-10 hours
Net weight:
18.8 oz. (470 g)
3.62 x 2.56 x 0.79 in. (92 x 65 x 20 mm)
Included Accessories:
Net weight:
3.04 oz. (76 g) without batteries
Pin out:
Pin 1 = gnd, pin 2 = audio, pin 3 = type
Radiated RF power:
Current consumption: 170 mA/2.4 V
Power requirement:
HT 81 handheld transmitter:
Type, bandwidth and polar pattern:
See individual microphone
specification sheets
Modulation type:
RF radiated power:
10 mW
Rated deviation:
±30 kHz
Signal-to-noise ratio:
Typical 50 dB (A-weighted)
Current consumption: <150 mA/2.4 V
Power requirement:
2 AA size 1.5V batteries
Battery life:
>10 hours
1.4 x 9.4 in. (36 mm dia. x 240 mm)
Net weight:
9.8 oz. (245 g)
12 intermodulation-free frequencies
710.200 MHz (1)
US58 734.400 MHz (1)
710.600 MHz (3)
735.200 MHz (5)
711.200 MHz (6)
737.200 MHz (F)
713.000 MHz (F)
US59 743.000 MHz (2)
719.200 MHz (2)
743.600 MHz (5)
721.800 MHz (F)
745.400 MHz (E)
Rackmount Kit
Miniature screwdriver
Stand Adapter (with HT)
Optional Accessories:
PS 81:
Active, wideband antenna splitter for
connecting up to 4 SR 81 units or
3 SR 81 units and one additional PS.
RA 81:
External receiver antenna with integrated
booster, powered via cable from the
PS81 antenna splitter.
PSU 10:
Central power supply unit for support of
up to 10 SR 61 and up to 3 PS 61 units.
External directional antenna
Color code set for easy channel
CH 60:
Hard Case for carrying a single
complete system
MKA 20:
20 meter cable for PS 81 and RA 81 B
UAM 1:
Universal antenna mount for moving
antennas to front of rack
Guitar cable for PT 60, PT 61,
PT 80, PT81
BNC connecting cable used to connect
PS 81 (antenna splitter) to SR 81
(receiver) - 2 required per receiver
( ) = channel setting on front of SR81
Architects and Engineers Specifications
The wireless microphone system shall operate selectively over
the UHF frequency range from 710.2 to 745.6 MHz, providing at
least 15 selectable channels channels with transmitter power not
exceeding 10 milliwatts. Both handheld and bodypack type
transmitters shall be provided. The transmitters shall operate with a
companding system that is complemented by the receiver,
providing an A-weighted system dynamic range in excess of
100 dB. The transmitters shall provide the following switchable
functions: input sensitivity, power on/off, and microphone mute.
Handheld transmitters shall have a maximum diameter of
1.4 inches and a length no greater than 9.4 inches.
The receiver shall operate on the diversity principle, and that
action shall be inaudible as such. Total harmonic distortion at 1
kHz for rated deviation shall be no greater than 0.4%. The receiver
shall provide automatic squelch adjustment (TCSQTM) for
optimum system operation. An output mic/line level adjustment
shall be provided, and there shall be both balanced XLR-M output
and unbalanced 0.25 in. jack. A rackmounting kit shall be included
as a standard accessory and the wireless microphone system shall
be the AKG Acoustics Model WMS 81.
Graphical Data
Figure 5
4-Channel System with Powersplitter and Power Supply Unit:
10-Channel System (Maximum Copnfiguration) with Power
Supply Unit and 3 Powersplitter:
AKG is constantly improving and modifying its products, therefore, specifications are subject to change without notice.
Figure 3
4-Channel System with Powersplitter without
Power Supply Unit:
HT 81
9.45” (240 mm)
HT 81
(52.5 mm)
9.45” (240 mm)
HT 81 with D 880 Head
(36 mm)
Graphical Data
AKG is constantly improving and modifying its products, therefore, specifications are subject to change without notice.
SR 81
PT 81
Limited Warranty
Valid only in the United States. AKG Acoustics warrants AKG products against defects in material
or workmanship for a period of two years from the date of original purchase for use, and agrees to
repair or, at our option, replace any defective unit without charge for either parts or labor. Important:
This warranty does not cover damage resulting from accident, misuse or abuse, lack of reasonable
care, the affixing of any attachment not provided with the product, loss of parts or connecting the
product to any but the specified receptacles. This warranty is void unless service or repairs are
performed by an authorized service center. No responsibility is assumed for any special, incidental
or consequential damages. However, the limitation of any right or remedy shall not be effective
where such is prohibited or restricted by law. Simply take or ship your AKG product prepaid to our
service department. Be sure to include your sales slip as proof of purchase date. (We will not repair
transit damage under the no-charge terms of this warranty.) Note: No other warranty, written or oral
is authorized by AKG Acoustics, Inc. This warranty gives you specific legal rights, and you may also
have other rights which vary from state to state. Some states do not allow the exclusion or
limitation of incidental or consequential damages or limitation on how long an implied warranty
lasts, so the above exclusions and limitation may not apply to you..
Microphones · Headphones · Wireless Microphones · Wireless Headphones · Headsets · Electroacoustical Components
AKG Acoustics GmbH
Lemböckgasse 21–25, P.O.B. 158, A-1230
Tel: (43 1) 86 654-0*, Fax: (43 1) 86 654-516
Internet: http://www.akg-acoustics.com
AKG Acoustics; A Division of Harman Pro Germany
Bodenseestraße 228, D-81243 München/GERMANY
Tel: (089) 87 16-0, Fax: (089) 87 16-200
Arbiter Pro Audio
Wilberforce Road, London NW9 6AX/ENGLAND
Tel: (0181) 202 1199, Fax: (0181) 202 7076
Specifications subject to change without notice.
914 Airpark Center Drive
Nashville, TN 37217, U.S.A.
Tel: (615) 620-3800, Fax: (615) 620-3875
Studer Japan Ltd.
2-43-7, Uehara, Shibuya-ku, Tokyo 151-0064/JAPAN
Tel: (813) 3465-2211, Fax: (813) 3465-2214
Erikson Pro Audio
620 McCaffrey, St-Laurent, Quebec, H4T 1N1, CANADA
Tel: (514) 738-3000, Fax: (514) 737-5069
Internet: www.jam-ind.com/eriksonpro
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