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.

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