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Frequency Selection (72-76 MHz)

The M-175 transmitter can operate on one of 88 available channels
between 72-76 MHz.  COMTEK channel designations indicate both
standard non-companded channels and high-fidelity companded channels.
Channels 1-88 are to be used only with receivers having 2:1 audio
companding processing.  Channel position 91-00 is to be used only with
receivers having linear non-companded audio processing.  COMTEK
transmitters automatically transmit the proper modulation when set to
either number channels 1-88 or channels 91-00 (A-J).

After you have determined the channel on which
you are going to operate,  position the two rotary
switches to indicate the channel.  The left
rotary switch is for 

tens

 and the right rotary

switch is for 

ones,

 e.g. to select channel 41

(72.92 MHz),  position the left rotary switch
to point to 4 (X10), and position the right
rotary switch to point to 1 (X1).  

Refer to frequency charts

on pages 9 and 10 for selectable frequencies.

Multiple Channel Operation

When multiple transmitters are broadcasting in the same immediate area
(within 100 feet), the RF signals will “mix” together generating additional
signals.  If these product frequencies are too close to a frequency which you are
using, you will experience intermodulation interference.  This condition is
common to all radio receivers to some extent.

Simultaneous operation of more than three channels requires frequency
coordination to avoid intermodulation interference which could result in
poor or unusable performance.

To avoid this type of interference, you should select frequencies from one of
the standard groups (see group frequency charts on pages 9 and 10), or use
COMTEK’s frequency selection software available at www.comtek.com to
determine appropriate frequencies or contact COMTEK to obtain a free copy.

M-175 FREQUENCY SELECTION

Summary of Contents for M-175

Page 1: ...M 175 OPERATOR S MANUAL 357 West 2700 South Salt Lake City Utah 84115 Phone 800 496 3463 Fax 801 484 6906 http www comtek com M 175 Personal Communication Transmitter ...

Page 2: ...oduction Setup Controls Battery Removal Replacement Battery Charging Auxiliary Audio Input Operation Snap On Belt Clip Frequency Selection Frequency Information P 7 Option Optional Accessories Trouble Shooting Specifications Warranty and Service 1 2 3 4 5 6 7 7 8 9 10 11 12 13 14 15 16 ...

Page 3: ...s transmitter incorporates the latest digital and analog technologies to produce high quality sound with low residual noise wide dynamic range and extended frequency response The audio processing circuit allows a choice of companded 2 1 audio processing when used with Comtek full fidelity receivers or non companded 1 1 audio processing on prescribed channels with Comtek and other lower cost popula...

Page 4: ...by inserting the microphone plug into the receptacle on the top of the transmitter The transmitter is operating when the transmitter power switch is turned on and the battery status on indicator illuminates NOTE The 48 inch microphone cord also functions as part of the transmitter s antenna system For optimum performance this cord should be fully extended Coiling or bunching the microphone cord ma...

Page 5: ...cepts an electret type microphone having a 48 long cord with a micro mini 2 5 mm mono plug The microphone cord functions as part of the transmitter s antenna system and must be in place for auxiliary audio input operation If microphone function is not necessary the optional microphone switch should not be on for this operation s POWER BATTERY STATUS INDICATOR This LED indicator will illuminate con...

Page 6: ... Replace a low battery immediately M 175 BATTERY REMOVAL REPLACEMENT Pull back battery door latch and allow battery cover door to spring open To remove battery simply manipulate the bottom of battery out of thecompartment and remove To insert battery face battery with negative terminal in line with large hole in battery compartment press battery into compartment and close battery door until it sna...

Page 7: ...e battery to charge for 14 hours for a full charge Unit must then be unplugged When using the NBC 9 3 1 digital fast charger the charger will automatically end the charge cycle and the red LED will change to green With the NBC 9 3 1 charger the unit may be left in the charger until the unit is used 5 Periodically open the battery compartment on stored COMTEK units to check for battery leakage If a...

Page 8: ...ug 1 4 audio phone plug and XLR connectors are available from COMTEK Setup a Connect the microphone to the transmitter by inserting the microphone plug into the receptacle on the top of the transmitter Note The microphone cord functions as part of the transmitter s antenna system and must be in place for auxiliary audio input operation If microphone function is not necessary the optional microphon...

Page 9: ...put with the microphone plugged into the transmitter priority should be given to the microphone gain adjustment The mixing balance between the auxiliary audio and the microphone should be made with the volume control of the auxiliary audio source Note The optional microphone switch only affects the microphone It does not affect the auxiliary audio input M 175 AUX OPERATION Cont SNAP ON BELT CLIP S...

Page 10: ... rotary switch to point to 4 X10 and position the right rotary switch to point to 1 X1 Refer to frequency charts on pages 9 and 10 for selectable frequencies Multiple Channel Operation When multiple transmitters are broadcasting in the same immediate area within 100 feet the RF signals will mix together generating additional signals If these product frequencies are too close to a frequency which y...

Page 11: ...2 38 MHz 72 40 MHz 72 42 MHz 72 46 MHz 72 50 MHz 72 54 MHz 72 58 MHz 72 62 MHz 72 64 MHz 72 66 MHz 72 68 MHz 72 70 MHz 72 72 MHz 72 74 MHz 72 76 MHz 72 78 MHz 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 CHAN FREQ 72 80 MHz 72 82 MHz 72 84 MHz 72 86 MHz 72 88 MHz 72 90 MHz 72 92 MHz 72 94 MHz 72 96 MHz 72 98 MHz 74 61 MHz 74 63 MHz 74 65 MHz...

Page 12: ...ith companded receivers In order to accommodate a greater variety of receivers the M 175 transmitter incorporates the option to operate with receivers that have companded or non companded audio processing However the M 175 transmitter must operate non companded with non companded receivers and companded only with receivers that incorporate companding processing A mismatch will result in unacceptab...

Page 13: ...ded belt clip Auxiliary audio input jack BNC type connector FWA 72TL short top loaded whip antenna M 175 P 7 OPTION Page 11 FWA 72TL Antenna This short top loaded omnidirectional antenna minimizes the size of the antenna required to operate in the VHF frequency range of 72 76 MHz In order to maintain good propagational efficiency this type of antenna has limited bandwidth Two separate antennas mus...

Page 14: ...p on belt clip supplied with M 175 6 P1 Universal pouch 7 SM 185 Unidirectional electret condenser microphone 8 PSC HM Headworn unidirectional electret microphone Auxiliary Audio Input Cords 9 CB 36 STM Stereo mini 3 5 mm supplied with M 175 10 CB 36 RCA Phono plug optional 11 CB 36 ST1 4 Stereo 1 4 optional 12 CB 36 XLR XLR F 3 pin connector optional M 175 OPTIONAL ACCESSORIES ...

Page 15: ...not illuminate when new alkaline batteries are used Transmitter Audio Problem If There is no visual indication on the voice modulation level indicator when speaking into the microphone of the M 175 transmitter Then Turn up the microphone gain setting clockwise until the voice modulation indicator illuminates with speech level Make sure the optional muting switch is in the mic on position Check the...

Page 16: ...smitter is tuned to If interference noise is heard a new clear channel must be selected 5 Transmitter Power and Receiver Sensitivity Check the M 175 transmitter with the PR 75 or PR 216 72MHz receiver for normal R F sensitivity This can easily be done by range checking the receiver and transmitter with the microphone cord antenna removed from the transmitter Tune the receiver and transmitter to a ...

Page 17: ...linear overload protection attack time less than 1 ms recovery time 10 ms Frequency Modulation 10 kHz deviation companded Operating Radio Frequency ity 88 synthesized channels in the 72 76 MHz band Out of Band Emissions Better than 50 dB below carrier R F Stability 20 ppm XTL controlled Digitally synthesized RF Power Output 40 mW to antenna system FCC Compliance Type Accepted under FCC Part 90 Ant...

Page 18: ...ed COMTEK shall bear no responsibility or obligation with respect to the manner of use of any equipment sold by it COMTEK SPECIFICALLY DISCLAIMS AND NEGATES ANY WARRANTY OF MERCHANTABILITY OR FITNESS OF THE PRODUCT FOR A PARTICULAR PURPOSE INCLUDING WITHOUT LIMITATION ANY WARRANTY THAT THE USE OF SUCH EQUIPMENT FOR ANY PURPOSE WILL COMPLY WITH APPLICABLE LAWS AND REGULATIONS Service Policy Warrant...

Page 19: ...357 West 2700 South Salt Lake City Utah 84115 Phone 800 496 3463 Fax 801 484 6906 http www comtek com ...

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