AM BROADCASTINGPRESENTED BY:MICHAEL ANGELO M. DIMAON

INTRODUCTION TO AM BROADCASTING

-AM broadcasting is radio broadcasting using Amplitude Modulation.-a dominant method of broadcasting during the first two thirds of the 20th century.-Central Intelligence Agency World Factbook lists approximately 16, 265 AM stations worldwide.

Frequency bands of AM Broadcasting

1. Long Wave(153 kHz-279 kHz)- generally uses a 9 kHz channel spacing.-not available into the Western Hemisphere and European.

2. Medium Wave(520 kHZ-1,610 kHz)- in the Americas(ITU region 2) 10 kHz spacing is used, elsewhere it is 9 kHz.

3. Short Wave(2,300 kHz-26,100 kHz)- generally use a narrow 5 kHz

AM is better suited to talk radio and news programming because of its susceptibility to atmospheric interference and generally low-fidelity sound.

Medium wave and Short wave radio signal act differently during daytime and nighttime.During the day, AM signal travel by ground wave, diffracting around the curve of the earth up to a few hundred miles.After sunset, changes in the ionosphere cause AM signals to travel by sky wave, enabling AM radio station to be heard much farther than during the day.

KBP Technical Standards And Operating Requirements for

Medium Frequency Broadcast Stations

INTRODUCTION

In the formulation of Technical Standards for domestic broadcasting, the more important considerations must include:1. The prevention of harmful signal

interferences;2. The provision for better signal quality, so that

the listener may enjoy a clear and more realistic sound reproduction, and

3. The proper utilization of broadcast spectrum.

Definition of Terms1. Medium Frequency Broadcast Station

An AM Broadcast Station licensed for aural or sound transmissions intended for direct reception by the general public and operated on a channel in a medium frequency band.2. Medium Frequency Broadcast Band

The band of frequencies from 526.5 to 1705 kHz.3. Medium Frequency Broadcast Channel

The band of frequencies that occupied by the carrier and two (2) sidebands of an AM Broadcast signal with the carrier frequency at the center. Channels shall be designated by the assigned carrier frequencies starting from 531 kHz in increments of 9 kHz.

4. Carrier WaveA sinusoidal voltage or current generated in

a transmitter and subsequently modulated by a modulating wave.5. Carrier Frequency

The frequency of the carrier wave.6. Operating Frequency

The carrier frequency at any particular time.7. Authorized frequency

The carrier frequency authorized by the Authority.

8. Hertzthe term “hertz” abbreviated “Hz”, is used

as a unit of frequency, supplanting the term “cycle per second”(cps).9. Percentage Modulation (Amplitude)

In a positive direction:M=(MAX-C)100C

In a negative direction:M=(MIN-C)100C

Where:M-modulation level in percent

MAX- instantaneous maximum level of the modulated radio frequency envelopeMIN- Instantaneous minimum level of the modulated radio frequency envelope10. Maximum Percentage of Modulation

“Maximum percentage of modulation” means the greatest percentage of modulation that may be obtained by a transmitter without producing, in its output, harmonics of the modulating frequency in excess of those permitted by these regulations.11. High-Level Modulation

“High level modulation “ is modulation produced in the last radio stage of the system.

12. Low- Level Modulation“Low-level modulation” is modulation produced in

an earlier stage than the final13. Operating Power

“Operating power” is the transmitter output power.14. Maximum Rated Carrier Power

“Maximum rated carrier power” is the maximum rated power at which the transmitter can be operated satisfactorily and is determined by the design of the transmitter.15. Authorized Operating Power

“Authorized operating power” is the power authorized by the authority.

16. Input Power“Input power “ is the product of the voltage

and current at the output of the last radio stage, measured without modulation.17. Antenna Input Power

“Antenna input power” is the product of the square of the antenna current and the antenna resistance at the point where the current is measured.18. Antenna Current

“Antenna Current” is the radio-frequency current in the antenna with no modulation.

19. Antenna Resistance“Antenna resistance” means the total resistance of the

transmitting antenna system at the operating frequency and at the point at which the antenna current is measured.20. Modulator Stage

“Modulator stage” means the last audio amplifier stage of the modulating wave which modulates a radio-frequency stage.21. Modulated Stage

“Modulated stage” means the radio-frequency stage to which the modulator is coupled and in which the continuous wave (carrier wave) is modulated in accordance with the system of modulation and the characteristics of the modulating wave.

22. Daytimethe term “daytime” refers to that period of time between 2200

Universal Time Coordinates(UTC) to 1000 Universal Time Coordinates(UTC) (6:00 AM-6:00 PM local standard time).23. Nighttime

The term “nnighttime” refers to that period of time between 1000 Universal Time Coordinates(UTC) to 2200 Universal Time Coordinates(UTC) (6:00 PM-6:00 AM local standard time).24. Experimental Period

The term “experimental period” means that time between 12 midnight to 5 AM local standad time (1600-2100 Universal Time Coordinates)(UTC). This period may be used for experimental purposes in testing and maintaining apparatuses by the licensee of any medium frequency broadcast station on its assigned frequency and with its authorized power, provided no interference is caused to other stations maintaining a regular operating schedule within such period.

25. Field StrengthThe root-mean-square (RMS) value of the voltage

stress produced in space by the electric field or a radio wave, and is expressed in volts per meter or in decibels(dB) relative to it.period of time between 2200 Universal Time Coordinates(UTC) to 1000 Universal Time Coordinates(UTC) (6:00 AM-6:00 PM local standard time).26. Effective Field

The term “effective field” or “effective field intensity” is the root-mean-square (RMS) value of the inverse distance field at 1.6 km. from the antenna in all directions in the horizontal plane.

27. Service Areasa. the term “primary service area” of a broadcast

station means the area in which the groundwave field of 1 mV/m (60dBu) is not subject to objectionable interference or objectionable fading.

b. The term “secondary service area” of a broadcast station means the area served by the save and not subject to objectionable interference. The signal is subject to intermittent variations in intensity.

c. The term “intermittent service area” of a broadcast station means the area receiving service from the groundwave but beyond the primary service area and subject to some interference and fading.

28. Audio-Frequency (af) signal-to-interference Ratio Is the ratio (expressed in dB) between the values of

the voltage of the wanted signal and the voltage of the interference, measured under specified conditions, at the audio-frequency output of the receiver.29. Audio-Frequency (af) Protection Ratio

Is the agreed minimum value of the audio-frequency signal-to-interference ratio considered necessary to achieve a subjectively defined reception quality.30. Radio-Frequency (rf) Wanted-to-Interference Signal Ratio

Is the ratio (expressed in dB), between the values of the radio frequency voltage of the wanted signal and the interfering signal, measured at the input of the receiver under specified conditions.

31. Radio-Frequency (rf) Protection RatioIs the value of the radio-frequency wanted-to-

interference signal ratio that enables, under specified conditions, the audio-frequency protection ratio to be obtained at the output of the receiver.32. Attended Transmitter

Attended transmitter means a transmitter where a qualified technician is in attendance during all periods of its operation.33. Carrier Shift

The variation of the mean carrier amplitude resulting to the process of amplitude modulation; carrier shift is expressed as the percentage modulation by a sinusoidal test signal, the variation being expressed as a percentage of the unmodulated carrier amplitude.

34. Total Harmonic DistortionThe effective value of the harmonic voltages present in the

audio frequency output of the equipment under test. It is expressed as a percentage of the effective value of the fundamental audio frequency voltage and the harmonic voltages present in the output.35. Noise Level

a. “Noise level” means the root-mean-square (RMS) value of the voltage of spurious origin present in the audio frequency output of the equipment under test, expressed in decibels relative to a specified root-mean-square (RMS) value of sinusoidal audio frequency voltages.

b. “Unweighted noise level” in a specified band means the noise level in that band measured by an instrument, the frequency response of which is uniform over that band.

36. Frequency ResponseThe variation, over a specified audio frequency range of

the transmission efficiency of the equipment under test; the variation is expressed in decibels relative to the transmission efficiency at a specific frequency, such as 1,000 Hertz.37. Gain of an Audio Frequency Amplifier

The gain of an Audio-frequency amplifier or a chain of auio-frequency equipment incorporating one or more such amplifiers, means the ratio, expressed in decibels of the power delivers to the load at a specific frequency (usually 1,000 Hertz) to the power which would be delivered to the same load if the amplifier or chain of equipment were replaced by an ideal transformer matching the nominal load and source impedances.

38. Spurious EmissionThe emission on any frequency outside of the Assigned

channel or authorized band of frequencies and tolerances allowed by these regulations. Emissions outside of the assigned channel, as a result of the modulation process, is not considered spurious, unless it is due to over modulation.39. Authority

the National Telecommunication Commission.40. Licensee

The holder of a license for a broadcasting station issued by the authority.41. Qualified Technician

A person who is a holder of a radio operator’s license or its equivalent, as required by these regulations, issued by the authority.

General Technical Requirements

1. Adequacy of components2. Compliance with Electrical Wiring Rules3. Regulation of Supply voltage4. Protection

a. Protection of Personsb. Protective device and safety rules are observedc. Protection of equipment

TRANSMITTING EQUIPMENT

Location of Antenna Site

The main considerations in the selection of an antenna site are:a) Location in relation to the population to be served

and to other communication installations and airports.

b) Conductivity of the soil at and immediately adjacent to the site;

c) Conductivity of the path between the site and the target area.

Antenna Design

The transmitting antenna system shall be vertically polarized and shall radiate an effective field of not less than that of a 60-degree vertical radiator

Transmitting Equipment

The transmitting equipment and facilities shall be laid out in accordance with good engineering practice, thereby providing ease of maintenance and operation, and safety to personnel.

Location and LayoutThe building shall be of a design and type of construction suitable to the area in which it is located and it shall comply with relevant building regulations.1. Adequate space shall be provided in the building to facilitate

access to all equipment for operation and maintenance purposes. Adequate space for staff facilities shall also be provided.

2. Adequate ventilation and, where necessary, air-conditioning shall be provided to ensure satisfactory working conditions for staff and equipment.

3. Adequate lighting shall be provided in all equipment rooms to facilitate operation and maintenance of the equipment.

BROADCAST AUXILIARY SERVICES

Broadcast transmission auxiliary services fall under these three categories:1. Studio-to-Transmitter Link (STL)2. Remote pick-up broadcast station3. Communications, coordination and

control link

The frequency band allocation for STUDIO-TO-TRANSMITTER LINK/REMOTE CONTROL SYSTEM shall be:Band A 300-315 MHzBand B 734-752 MHzBand C 942-956 MHz

The maximum power allowable for STL’s shall be 15 watts.

The frequency band allocation for REMOTE PICK-UP STATION shall be:Band A 300-315 MHzBand B 734-752 MHzBand C 942-952 MHz

The maximum power allowable for remote pick-up stations shall be 35 watts.

The frequency band allocation for communications, coordination and control link shall be:Band A 412 MHz (non-exclusive)Band B 25.67-26.1 MHzBand C 12.235-162.615 MHz and 166.250-170.150 MHzBand D 432.5-433 MHz and 437.5-438 MHz

the maximum power allowable for communications, coordination and control link shall be:Band A-100 watts (SBS) , B-160 watts (ERP), C-160 watts (ERP), D-200 watts (for repeaters).

OPERATING REQUIREMENTS

Hours of Operation

Minimum Operating ScheduleThe licensee of each medium-frequency broadcast

station shall maintain a minimum operating schedule of two-thirds of the total hours that it is authorized to operate except that in emergencies when, due to causes beyond the control of the licensee, it becomes impossible to continue operating, the station may cease operations for a period not exceeding 10 days.

Broadcast(s) outside of the authorized regular operating schedules (as before regular sign-on schedules and/or beyond regular sign-off schedules) may be aired without prior authorization from the Authority provided the program falls under an emergency category or of very important relevance to the station’s existence. The information shall be entered in the program and operating logs at the time the broadcast was aired.

If a permanent discontinuance of operations is being contemplated, then the licensee shall notify in writing the Authority or regional office where the station is located at least two (2) days before the actual discontinuance is effected.

Other Operating Practices

The percentage of modulation shall be maintained as high as possible, consistent with good quality transmission and, in no case, more than 125 percent on positive peaks nor more than 100 percent on negative peaks of frequent recurrence during any selection which is transmitted at a highest level of the program under consideration.

ALLOCATION RULES AND REGULATION

Maximum Power AllocationArea Maximum Power in KWMetro Manila 50 KWAll other areas 10 KW

AM STRERIOPHONIC STANDARD

The AM stereophonic standard is the C-QUAM AM stereophonic system.

PUBLIC INFORMATION FILEAn updated public information File at each broadcast station shall be made available to the NTC inspector or to any interested party. The public information file shall contain the ff:a. A copy of the station license.b. Documents as to mode of ownership whether partnerships,

corporation or single proprietorship including trade name as registered in the Department of Trade.

c. A list of changes in transmitting facilities arranged chronologically. Annex to this list, the corresponding licenses and permits supporting the changes.

d. Copies of the Program standards, the Technical Standands , the NTC compilation of laws, regulations, circulars and memoranda.

e. Evidence of membership in the KBP.