CAM-D
Encyclopedia
Compatible Amplitude Modulation - Digital or CAM-D is a proposed hybrid
digital radio
format for AM broadcasting
, put forth by well-known broadcast engineer Leonard R. Kahn.
The system is an in-band on-channel
technology
that uses the sideband
s of any AM radio station
. Analog
information is still used up to a bandpass of about 7.5kHz, with standard amplitude modulation
. The missing treble
information that AM normally lacks is then transmitted digital
ly beyond this. Audio mixing in the receiver
then blends them back together.
Unlike other IBOC technologies like iBiquity
's HD Radio
, Kahn's apparently does not provide a direct path to all-digital transmissions
, nor any multichannel
capability
. The advantage however is that it takes up far less of the sidebands, thereby causing far less interference
to adjacent channel
s, hence the "Compatible" in the name. The interference problem has plagued HD Radio on AM, along with the fact that it, like CAM-D, is proprietary
.
Digital Radio Mondiale
, commonly used in shortwave broadcasting, can use less, the same, or more bandwidth as AM, to provide high quality audio. Digital Radio Mondiale requires digital detection circuitry not present in conventional AM radios to decode programming. Special CAM-D receivers provide the benefit of better frequency response and a slow auxiliary data channel for display of station ID, programming titles, etc.
s are not directly upgradeable to transmit HD Radio. It is true that older transmitters may lack the transmission purity needed to support HD Radio's digital transmission standard, but more recent transmitters are more likely to be capable of upgrading to transmit HD Radio. CAM-D is said to work with a wider variety of existing transmitters, which is a selling point for smaller broadcasters with limited budgets. The price of the CAM-D hardware is $65,600 as of July 1, 2007.
program. This provides enhanced fidelity
that under adequate analog signal conditions may allow AM stations to transmit music and other program content with a more life-like sound.
A significant disparity between Ibiquity
's AM HD Radio and CAM-D is that of time diversity
. Namely, HD Radio's AM broadcast scheme broadcasts two copies of the program offset by a few seconds, allowing signal to be briefly lost and maintain uninterrupted program audio (for example, driving under an overpass, multipath in urban areas, lightning, switching transients, etc.). . However, in the field, HD Radio, at a distance from the transmitter, is still not immune to the aspects of the AM dial such as those below.
A substantial problem of analog AM transmission is that it is subject to poor signal to noise ratio due to radio frequency noise from man made and natural sources, such as fluorescent lamps, motors, switches and lightning. Simply adding high frequency information does not produce high fidelity
. HD Radio
signals on AM, however, use more bandwidth signal wise and often create "hash" on surrounding frequencies, up to 30 kHz from the center frequency. This interference, which is audible mainly on analog radios, was one of the reasons Citadel Communications
pulled night broadcasts of their AM HD station's signals. CAM-D does not produce interference on any channels 10 kHz or more from the center frequency.
CAM-D is a system that is applicable to medium wave and possibly shortwave transmission. Since receivers are designed for multiple bands, a receiver that requires a substantially different architecture for CAM-D will require special circuitry that will increase its cost. This is similar to HD Radio
and other digital radio services. Since they all require new circuitry, inevitably, the price of manufacture will increase. This price will likely begin to decrease once the technology becomes proven. Since all new broadcast radios are moving to full digital formats that decode with nearly identical hardware (XM, Sirius, HD Radio
(in digital mode), Digital Audio Broadcasting
, Digital Radio Mondiale
) in the long term, the overhead of analog circuitry will cause a cost penalty to implement the technology in future radios.
In-band on-channel
In-band on-channel is a hybrid method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency....
digital radio
Digital radio
Digital radio has several meanings:1. Today the most common meaning is digital radio broadcasting technologies, such as the digital audio broadcasting system, also known as Eureka 147. In these systems, the analog audio signal is digitized into zeros and ones, compressed using formats such as...
format for AM broadcasting
AM broadcasting
AM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public AM broadcasting is carried out in the medium wave band world wide, and on long wave and short wave...
, put forth by well-known broadcast engineer Leonard R. Kahn.
The system is an in-band on-channel
In-band on-channel
In-band on-channel is a hybrid method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency....
technology
Technology
Technology is the making, usage, and knowledge of tools, machines, techniques, crafts, systems or methods of organization in order to solve a problem or perform a specific function. It can also refer to the collection of such tools, machinery, and procedures. The word technology comes ;...
that uses the sideband
Sideband
In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, containing power as a result of the modulation process. The sidebands consist of all the Fourier components of the modulated signal except the carrier...
s of any AM radio station
Radio station
Radio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both...
. Analog
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
information is still used up to a bandpass of about 7.5kHz, with standard amplitude modulation
Amplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
. The missing treble
Treble (sound)
Treble refers to tones of high frequency or range. In music this corresponds to high notes, and for this reason the treble clef is often used for instruments with higher pitch. Examples of treble sounds are guitar tones, female voice , young boy voice, etc. They have frequencies above 9 KHz. Treble...
information that AM normally lacks is then transmitted digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
ly beyond this. Audio mixing in the receiver
Receiver (radio)
A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
then blends them back together.
Unlike other IBOC technologies like iBiquity
IBiquity
iBiquity Digital Corporation is a company formed by the merger of USA Digital Radio and Lucent Digital Radio, with the goal of creating an in-band on-channel digital radio system for the United States and around the world...
's HD Radio
HD Radio
HD Radio, which originally stood for "Hybrid Digital", is the trademark for iBiquity's in-band on-channel digital radio technology used by AM and FM radio stations to transmit audio and data via a digital signal in conjunction with their analog signals...
, Kahn's apparently does not provide a direct path to all-digital transmissions
Transmission (telecommunications)
Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...
, nor any multichannel
Multichannel
Multichannel may refer to:*Multichannel audio, i.e.**Stereophonic sound, namely two channel audio**Surround sound, more than two channels though still technically stereo**Ambisonics, a studio or live way of recording with many channels...
capability
Capability
Capability is the ability to perform actions.As it applies to human capital, capability is the sum of expertise and capacity.It is a component within the theories of:* Capability-based security and Capability-based addressing in computing...
. The advantage however is that it takes up far less of the sidebands, thereby causing far less interference
Interference (communication)
In communications and electronics, especially in telecommunications, interference is anything which alters, modifies, or disrupts a signal as it travels along a channel between a source and a receiver. The term typically refers to the addition of unwanted signals to a useful signal...
to adjacent channel
Adjacent channel
In broadcasting an adjacent channel is an AM, FM, or TV channel that is next to another channel. First-adjacent is immediately next to another channel, second-adjacent is two channels away, and so forth. Information on adjacent channels is used in keeping stations from interfering with one...
s, hence the "Compatible" in the name. The interference problem has plagued HD Radio on AM, along with the fact that it, like CAM-D, is proprietary
Proprietary protocol
In telecommunications, a proprietary protocol is a communications protocol owned by a single organization or individual.-Enforcement:Proprietors may enforce restrictions through patents and by keeping the protocol specification a trade secret...
.
Digital Radio Mondiale
Digital Radio Mondiale
Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave...
, commonly used in shortwave broadcasting, can use less, the same, or more bandwidth as AM, to provide high quality audio. Digital Radio Mondiale requires digital detection circuitry not present in conventional AM radios to decode programming. Special CAM-D receivers provide the benefit of better frequency response and a slow auxiliary data channel for display of station ID, programming titles, etc.
Availability of Receivers
At present, there are a limited amount of special receivers capable of receiving CAM-D. According to Leonard Kahn however, the system has seen potential growth within the past year (2007).Upgradeability of existing transmitters
KCI (Kahn Communications, Inc., the company that invented CAM-D) uses as one of its main selling points that some older transmitterTransmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
s are not directly upgradeable to transmit HD Radio. It is true that older transmitters may lack the transmission purity needed to support HD Radio's digital transmission standard, but more recent transmitters are more likely to be capable of upgrading to transmit HD Radio. CAM-D is said to work with a wider variety of existing transmitters, which is a selling point for smaller broadcasters with limited budgets. The price of the CAM-D hardware is $65,600 as of July 1, 2007.
Technical aspects and differences with other digital radio methods
CAM-D is said to add high-frequency program information digitally transmitted and then overlaid onto the existing low- to mid-frequency analogAnalog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
program. This provides enhanced fidelity
Fidelity
"Fidelity" is the quality of being faithful or loyal. Its original meaning regarded duty to a lord or a king, in a broader sense than the related concept of fealty. Both derive from the Latin word fidēlis, meaning "faithful or loyal"....
that under adequate analog signal conditions may allow AM stations to transmit music and other program content with a more life-like sound.
A significant disparity between Ibiquity
IBiquity
iBiquity Digital Corporation is a company formed by the merger of USA Digital Radio and Lucent Digital Radio, with the goal of creating an in-band on-channel digital radio system for the United States and around the world...
's AM HD Radio and CAM-D is that of time diversity
Time diversity
Time Diversity is used in digital communication systems to combat that the transmissions channel may suffer from error bursts due to time-varying channel conditions...
. Namely, HD Radio's AM broadcast scheme broadcasts two copies of the program offset by a few seconds, allowing signal to be briefly lost and maintain uninterrupted program audio (for example, driving under an overpass, multipath in urban areas, lightning, switching transients, etc.). . However, in the field, HD Radio, at a distance from the transmitter, is still not immune to the aspects of the AM dial such as those below.
A substantial problem of analog AM transmission is that it is subject to poor signal to noise ratio due to radio frequency noise from man made and natural sources, such as fluorescent lamps, motors, switches and lightning. Simply adding high frequency information does not produce high fidelity
High fidelity
High fidelity—or hi-fi—reproduction is a term used by home stereo listeners and home audio enthusiasts to refer to high-quality reproduction of sound or images, to distinguish it from the poorer quality sound produced by inexpensive audio equipment...
. HD Radio
HD Radio
HD Radio, which originally stood for "Hybrid Digital", is the trademark for iBiquity's in-band on-channel digital radio technology used by AM and FM radio stations to transmit audio and data via a digital signal in conjunction with their analog signals...
signals on AM, however, use more bandwidth signal wise and often create "hash" on surrounding frequencies, up to 30 kHz from the center frequency. This interference, which is audible mainly on analog radios, was one of the reasons Citadel Communications
Citadel Communications
Citadel Communications Ltd. is a Bronxville, NY-based private broadcasting company that operates 5 full-power television stations and 1 low-power station...
pulled night broadcasts of their AM HD station's signals. CAM-D does not produce interference on any channels 10 kHz or more from the center frequency.
CAM-D is a system that is applicable to medium wave and possibly shortwave transmission. Since receivers are designed for multiple bands, a receiver that requires a substantially different architecture for CAM-D will require special circuitry that will increase its cost. This is similar to HD Radio
HD Radio
HD Radio, which originally stood for "Hybrid Digital", is the trademark for iBiquity's in-band on-channel digital radio technology used by AM and FM radio stations to transmit audio and data via a digital signal in conjunction with their analog signals...
and other digital radio services. Since they all require new circuitry, inevitably, the price of manufacture will increase. This price will likely begin to decrease once the technology becomes proven. Since all new broadcast radios are moving to full digital formats that decode with nearly identical hardware (XM, Sirius, HD Radio
HD Radio
HD Radio, which originally stood for "Hybrid Digital", is the trademark for iBiquity's in-band on-channel digital radio technology used by AM and FM radio stations to transmit audio and data via a digital signal in conjunction with their analog signals...
(in digital mode), Digital Audio Broadcasting
Digital audio broadcasting
Digital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....
, Digital Radio Mondiale
Digital Radio Mondiale
Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave...
) in the long term, the overhead of analog circuitry will cause a cost penalty to implement the technology in future radios.
Stations broadcasting in CAM-D
- KDYL, 1060 AM, South Salt Lake, Utah
- WSRF, 1580 AM, Fort Lauderdale, Florida
- WKBFWKBF (AM)WKBF is a radio station licensed to Rock Island, Illinois, and carries a Spanish Regional Music format. The station's frequency is 1270 kHz, and broadcasts at a power of 5 kW...
, 1270 AM, Rock Island, Illinois - KPNPKPNPKPNP is a radio station broadcasting a World Ethnic format. Licensed to Watertown, Minnesota, USA, the station is currently owned by Self Retire, Inc.-History:The station went on the air as KWOM on July 5, 1989...
, 1600 AM, Minneapolis, Minnesota