MINNESOTA REPEATER COUNCIL (MRC)

                        Member of Mid America Coordination Council (MACC)

       

                    Technical Standards and Design Goals

                  for Amateur Radio FM Voice repeaters.

 

                            With revisions through 09/23/95

       

                                   Table of Contents

       

        I. Repeater Transmitter                                Page 3 thru 5

              Frequency Accuracy and Stability

              Power Output

              Spurious Radiations

              Peak Deviation

              CTCSS or Digital PL Tones

              CW ID or other tones

              Hum and Noise

              Modulation Linearity

       

        II. Repeater Receiver                                  Page 5

              Frequency Accuracy and Stability

              Selectivity

              Sensitivity

              Frequency Response and Distortion

              Squelch types

       

        III. Repeater System                                   Page 6& 7

              Audio Input/Output ratio

              Use of CTCSS, Digital PL or anti-PL

              Station Antenna

              Duplexer

              Ferrite Isolators

       

        IV. Glossary of terms used in these standards          Page7 & 8

 

        I. REPEATER TRANSMITTER

       

        1.1  Transmitter center frequency accuracy and stability

       

Repeater station transmitters must operate within .0005% of the coordinated  and  assigned transmit frequency over the operating  temperature range of 0 to 50 degrees centigrade. This is the minimum design  standard. The ultimate design goal for transmitter stability over the  range of  -30 to +60 degrees centigrade temperature range should be  .00025%.  This  tolerance can be expressed in the following  allowable  frequency tolerance from the assigned transmitter frequency:

       

        Freq Range               Design Goal      Minimum Requirement

           29 Mhz                        75 Hz              150 Hz

           52 Mhz                      130 Hz              250 Hz

          146 Mhz                     365 Hz              725 Hz

          222 Mhz                     560 Hz             1000 Hz

          444 Mhz                   1100 Hz             2200 Hz

         1296 Mhz                     3.2 Khz             6.4 Khz

       

        1.2  Transmitter power output level

       

Repeater transmitter RF output power shall be consistent with the minimum effective radiated power (ERP) required for the coordinated repeater  coverage  area. The following ERPs are the maximum allowed  by  MRC Frequency Coordination Policies:

       

        Repeater frequencies from 29.5 to 420 Mhz

                Antenna HAAT 100 ft and below - 800 watts ERP

                Antenna HAAT 101 to 525 feet  - 400 watts ERP

                Antenna HAAT 526 to 1050 feet - 200 watts ERP

                Antenna HAAT above 1050 feet -  100 watts ERP

       

        Repeater frequencies above 420 Mhz

                Antenna HAAT 100 ft and below - 800 watts ERP

                Antenna HAAT 101 to 525 feet  - 800 watts ERP

                Antenna HAAT 526 to 1050 feet - 800 watts ERP

                Antenna HAAT above 1050 feet -  400 watts ERP

       

        (Antenna  HAAT  is  the mounting Height Above Average  Terrain  of  the

        transmit  antenna. This might not be the same as the  antenna  mounting

        height  above the ground, depending on where your repeater  station  is

        located. See HAAT in definition of terms for description).

       

        1.3  Transmitter spurious radiation

       

Spurious  in-band and out-of-band emissions developed by  the  repeater transmitter  shall be at least 60 Db below  transmitter  power  output. This is necessary to conform to FCC part 97 rules.

 

        1.4  Transmitter peak deviation

       

The  maximum repeater transmitter FM peak deviation must be no  greater than 4.5 Khz and should be symmetrically centered about the transmitter assigned center frequency. This peak deviation includes the sum of  all voice, CTCSS, digital PL, ID and Touchtone signals in any combination.

       

        1.5  Transmitted CTCSS or Digital PL tones

       

If Continuous Tone Coded Squelch (CTCSS) is transmitted by your repeater transmitter the level should be set at 600 Hz maximum peak transmitter  deviation. The minimum deviation is recommended to be 250 Hz.  Use of EIA standard CTCSS tones below 300 Hz is required.

       

The  following standard CTCSS tones are suggested to be used  in  these defined areas of the State of Minnesota:

       

        Zone        Primary CTCSS tone   Secondary CTCSS tone      Area

         1                151.4                103.5                NE

         2                123.0                127.3                NW

         3                141.3                156.8                SW

         4                136.5                100.0                SE

         5                114.8             118.8/162.2          Metro Area

         6                146.2                167.9                CEN

       

These tone frequencies are suggestions, not requirements. The intent is to have a common CTCSS tone frequency for all local activity.  Use  one of these tone frequencies if you have not already picked another.

       

        1.6  Transmitted CW ID and other tones

       

These  tones  should be low-distortion sine-wave generated  tones  that have  passed thru a low pass filter prior to entering  the  transmitter modulator. Peak deviation of these tones shall not be greater than  2.0 Khz. A minimum peak deviation of 1.0 Khz is also suggested.

       

        1.7  Transmitter hum and noise

       

Hum  and  noise  from the repeater transmitter (excluding  PL,  ID  and touchtones) should be at least 50 Db below peak deviation.

       

        1.8  Transmitter modulation linearity

       

Linearity  of transmitter modulation should be 5 % or  less  (straight-line  method).   This reduces adjacent channel splatter  and  recovered audio distortion.

 

 

        II. REPEATER RECEIVER

       

        2.1  Receiver center Frequency Accuracy and Stability

       

The  Frequency  Accuracy and Stability requirements  for  the  repeater receiver should be the same as the repeater transmitter specifications.  The  receiver  operating  frequency shall be fixed  with  no  Automatic Frequency Control (AFC) used on 450 Mhz and below.

       

        2.2  Receiver selectivity

       

Overall  receiver performance based on RF and IF filtering should  have at a minimum the following characteristics:

       

        Bandwidth at - 6 Db              13 Khz ( + or - 6.5 Khz)

        Bandwidth at -100 Db             30 Khz (+ or - 15 Khz)

        In-band ripple                   1.5 Db max

       

        2.3  Receiver sensitivity

       

Repeater  receiver sensitivity should be less than .5 microvolt and  be consistent with coverage area and transmitter ERP to provide a balanced repeater system.

       

        2.4  Receiver audio frequency response & distortion

       

The  receiver audio frequency response shall be flat (within + or  -  3 Db) from 100 to 3000 Hz with less than 5 % distortion.

   

        2.5  Receiver squelch types

       

Repeater  receivers shall use noise, sub-audible (CTCSS) or digital  PL type receiver squelch circuitry only.

 


      

        III. Repeater system

       

        3.1  System audio input/output ratio

       

The repeater system (receiver to transmitter) shall be adjusted to give a  1  to 1 ratio between the deviation of the input signal  versus  the deviation  of  the  repeated output signal. This means  that  an  input signal  to the repeater receiver with a maximum audio deviation of  4.0 Khz  would  have a repeater transmitter output signal  with  a  maximum audio deviation of no greater than 4.0 Khz.

       

        NOTE:  This does not mean that circuitry cannot be incorporated in  the

        repeater  system  to boost low deviation signals, but that  in  systems

        where this technique is not used the audio input/output ratio should be

        kept at 1 to 1.

 

        3.2  Systems using CTCSS (PL), Digital PL or anti-PL

       

Protection of the repeater system input by use of CTCSS or other  means should  be considered for all repeater systems and is  recommended  for all  systems  for best spectrum utilization on  the  heavily  congested repeater  bands and frequency pairs.  If the use of CTCSS (or  anti-PL) has  been  specified  as part of the frequency  coordination  for  your repeater station, IT MUST BE USED.

       

        3.3  Access systems using CTCSS or Digital PL tone

       

If  Continuous Tone Coded Squelch (CTCSS) access has been specified  as part  of  your repeater station frequency coordination, or is  used  by your  repeater  station  to protect your receiver,  the  CTCSS  decoder should  be adjusted to decode CTCSS tone levels with a 600  Hz  maximum peak transmitter deviation. The minimum deviation is recommended to  be 250  Hz. Use of EIA standard CTCSS tones below 300 Hz is required.

       

The  following standard CTCSS tones are suggested to be used  in  these defined areas of the State of Minnesota:

       

        Zone        Primary CTCSS tone   Secondary CTCSS tone      Area

         1                151.4                103.5                NE

         2                123.0                127.3                NW

         3                141.3                156.8                SW

         4                136.5                100.0                SE

         5                114.8             118.8/162.2          Metro Area

         6                146.2                167.9                CEN

       

These tone frequencies are suggestions, not requirements. The intent is to have a common CTCSS tone frequency for all local activity.  Use  one of these tone frequencies if you have not already picked another.

       

       

        3.4  Repeater Station antenna

       

Repeater  station antennas should be commercial grade and built to  EIA standards. The repeater system antenna should have a VSWR of 1.25:1  or better  on transmit and receive frequencies at a site where a  duplexer is used in order to properly terminate the duplexer.

       

Repeater stations with transmitter antennas that will be located on  an antenna tower greater than 200 feet above the ground should submit  FCC form  854  to the Federal Communications Commission  (FCC)  before  the antenna is installed. This form might modify your Amateur Radio station license  to include tower lighting and painting, the same  as  required for the other radio services that might be on this same tower.

 

        3.5  Repeater Station Duplexers

       

Repeater  stations  should use duplexers with "band-pass"  rather  than "band-reject"  characteristics.  Band-pass duplexers  better  attenuate frequencies on both sides of their pass-band.

       

        3.6  Repeater Station Ferrite Isolators

       

It  is recommended that ferrite Isolators (Circulators) be  used  after the repeater transmitter final output stages and the duplexer, in order to  reduce intermod products, spurious emissions and to improve the  RF stability  of the repeater transmitter. Many commercial  two-way  radio sites  will have the use of a isolator as a requirement  for  operating from these sites.

       

        IV. Glossary of terms used in these technical standards

       

        4.1   Anti-PL  - A method of allowing multiple repeaters to  share  the

        same  frequency  pair  by  having one system use  CTCSS  (PL)  and  the

        other(s) installing CTCSS decoders to not allow the repeater station to

        be keyed up when a CTCSS tone is heard on the input frequency.

       

        4.2  CTCSS - Continuous Tone Coded Squelch System is a method of adding

        a continuous low frequency tone to the transmitter to allow  protection

        from  unwanted key-ups of a repeater system. Known by the  trade  names

        Private  Line (PL) from Motorola, Channel Guard (CG) by  General  Elec-

        tric, Quiet Channel by RCA and many other manufacturers.

       

        4.3 Digital PL - A method of protecting the input of a repeater receiv-

        er by looking for a coded digital burst of data that will identify  the

        users transmitter as matching the stored digital data at the receiver.

       

        4.4  HAAT - Height Above Average Terrain is the calculated  height  the

        antenna  is mounted above a flat average of the height above sea  level

        of  the  ground  at the 40 points within a 10 mile  circle  around  the

        antenna mounting location. HAAT might be a positive or negative number.

       

 

        4.5  ERP - Effective Radiated Power is a calculated power output  which

        combines the power out of the transmitter with the gain of the  antenna

        less the loss of the duplexer and coax feedline to the antenna.

       

        4.6  Ferrite  Isolators  and Circulators - A Ferrite  Circulator  is  a

        device that passes RF with low loss in one direction (ie from Port 1 to

        Port 2) while reflected power is routed to a different output (ie  from

        Port 2 to Port 3). This prevents reflected power from your antenna  and

        strong   signals   from   nearby  transmitters   from   entering   your

        transmitter's  final  output stage. A Circulator normally has  a  dummy

        load attached to Port 3. An Isolator has the dummy load built-in.

       

                                                            Put into Microsoft Word format   12/01   P.E