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NEWS BULLETIN
FOR IMMEDIATE RELEASE
Welcome to the world of AMAX™ AM high fidelity and meduci AM stereo wideband sound, day and night. The future of radio is now. AMAX is here. AMAX is "AM Radio at its MAXimum Potential" in the 21st century. Better reception. Better sound. Please visit Wikipedia and AMAX for further detail.
We have adopted Motorola's C-QuAM™ technology, and are proud to offer their latest integrated circuit decoder technology available for C-QUAM™ stereo tuners, to provide optimum AM stereo performance. We are giving C-QuAM™ a second chance in the marketplace.
Introducing the new 2008-model second generation meduci AMX-2000 stereo tuner. This new AM stereo broadband tuner offers many specially tuned AMAX circuits for excellent AM performance. Tuned RF stage for excellent sensitivity. Four IF tuned bandpass circuits on AM provide optimum selectivity. Full wave balanced envelope detector achieves low distortion audio. Precision "noise immune" pilot tone detector virtually eliminates "falsing" stereo pilot identification in the field. Class-A biased audio output amplifiers do not colorize the sound.
These AM stereo products cannot economically be purchased anywhere else. There are many stations broadcasting wideband full fidelity sound. When received using an appropriate wideband AM stereo receiver or tuner, the recovered noise-free high definition sound is virtually indistinguishable from FM stereo broadcasts. Hearing is believing. Sample one of our AMAX high definition products, and judge the enhanced fidelity for yourself.
| History of AM Stereo |
Analog AM stereo technology has claimed its roots almost since the beginning of conventional monaural AM broadcasting within the United States. Later, four different competing AM stereo systems were placed on the air in the early 1980's, including systems from Motorola (C-QuAM™), Magnavox (PMX), Kahn-Hazeltine (ISB), and Harris Broadcast (Variable Angle Compatible Phase Multiplex, or V-CPM). Eventually in 1993, Motorola's C-QuAM technology achieved the exclusive standard for AM stereo broadcasting within the U.S.A. During this time period, Australia, Japan, and other countries were also exclusively using the Motorola C-QuAM system, making C-QuAM the essential de facto world standard for hearing AM stereo broadcasts.
All of the AM stereo systems share in common the addition of a stereo exciter to the existing monaural AM transmitter. This exciter typically has two outputs: the monaural L+R audio, which is fed to the transmitter's normal audio input; the second output is the R.F carrier, which replaces the signal from the transmitter's normal quartz crystal oscillator stage. This signal also contains the necessary phase modulated (quadrature) information. Because these exciters are retrofitted onto transmitters which were never designed for AM stereo operation, they also must contain corrective equalizers and adjustable delay networks, to insure that all of the phase relationships are correct through the modulated stage of the transmitter, power amplifier, and ATU/antenna system. Decoded stereo separation suffers if the timing and phase relationships are not correct.
Motorola's C-QuAM system is covered in several U.S. patents written by Frank H. Hilbert and the late Norman W. Parker of Illinois. Norman Parker invented the C-QuAM system, per written correspondence from his wife, Margaret Parker. Margaret also wrote all of the patents. Patent number 4,218,586 was applicable to the basic system. Other patents included 4,406,922 and 4,192,968. Delco Electronics Corporation (now known as Delphi) later introduced many new C-QuAM inventions, covered under various U.S patents.
| About iBiquity HD Radio |
There is a new technology called HD Radio from iBiquity. The letters HD do NOT stand for High Definition audio. Some would say that the two letters stand for Hybrid Digital. This is a hybrid digital / analog mode, until there are sufficient HD radios available in the marketplace, to allow stations to discontinue analog broadcasting (which may take two lifetimes). In the hybrid mode, this HD invention allows FM stations to stream additional programming (HD1, HD2, and HD3) to consumers with HD radios (up to eight streams in the full digital mode). This provides potential new revenue streams, as well as a better footing to compete against satellite radio, MP3 players, CD, and other newer consumer technologies. Program information is also available in text format on the HD Radio, to display song title, traffic alerts, music format, or other specific content. HD Radio has legs for the FM broadcast medium. This cannot be said for the AM broadcast band.
AM stations use iBiquity's digital techniques to transmit a low bit-rate signal to specialized HD radios designed to receive this narrow-band signal. Each AM station is allowed to transmit one stereo digital channel, and cannot stream multiple channels, as in the case of FM HD Radio.
Currently, there are inherent flaws that make it extremely difficult to reliably and continuously receive a 50kW AM station's HD signal more than approximately 20 miles from the transmitter site. In comparison, a full-power non-directional 50kW AM station can be received in C-QuAM stereo, where available, more than 200 miles from the transmitter site. Later generation HD Radio receivers should provide better usable sensitivity figures, to better receive the HD radio signals, under widely varying reception conditions encountered in the field.
First adopters have stated that their HD radios will move back and forth, at their own will, from analog to digital modes. This is due to the received signal strength, and the need for each HD radio to use an outdoor antenna. When reverting back to analog, AM sound is lower fidelity monaural, comparable to fidelity from a landline telephone connection. There have also been consumer reports, and personally verifiable evidence, that the HD signal eliminates reception of weaker first and second adjacent analog AM stations.
Critics have stated that the current HD Radio madness is a combination of low power, destructive interference, with artifact-filled audio, deaf receivers, and half-hearted programing. This is not exactly the best environment for radio stations and group owners to compete with the other consumer technologies for listeners.
Since there is a low bit-rate compressor / decompressor (codec) used in the HD Radio system, there are not two independent stereo audio channels, compared to C-QuAM stereo. There is steering logic that the receiver uses to move the sound between the left and right speakers. Also, all of the audio bits are not transmitted (compared to WAV files, or compact disk digital media). HD Radio's digital bit stream is compressed (turned into low digital bit-rates) prior to transmission. This reduces the delivery overhead and also conserves transmitted bandwidth.
New advances in transmitter design make HD Radio possible. Spectral re-growth is minimized, due to using better linear power amplifier transmitter stages. This also reduces the incidental carrier phase modulation, which also makes better C-QuAM stereo sound possible, with wider stereo separation. Unfortunately, since HD radio uses phase modulation to deliver part of their digital signal, it infringes on the real estate of C-QuAM analog stereo. Therefore, HD Radio and C-QuAM technologies cannot co-exist on the same AM broadcast station.
From Thomas R. Ray III, Vice President/Corporate Director of Engineering, Buckley Broadcasting/WOR Radio, New York:
"The AM signal is composed of three parts, or blocks, of OFDM
carriers. The first block is -45dB down from carrier, and is
located from 0-5kHz, in quadrature with the carrier. The second
block is located from 5-10kHz, is -43dB, and is also in quadrature
with carrier. The third block is located from 10-15kHz, is -28dB
down, and amplitude modulates the carrier.
"The block under the audio carries station ID information, timing
information, text information and such. The block from 10-15K
carries the "primary audio", which is the mono audio. The block
from 5-10K carries the stereo information.
"Obviously, if the AM carrier goes away, so does the entire signal.
"That is HD transmission in a nutshell. ...
"In the all digital AM waveform, the primary carriers will occupy from
5kHz on the lower sideband to 5kHz on the upper sideband. The
secondary carriers move to the upper sideband at 5-10kHz. The
tertiary carriers move to the lower sideband at 5-10kHz. Level of the
primary is -15dBc (presently -28dBc). The level of the secondary
carriers becomes -30dBc (presently -43dBc). The level of the tertiary
carriers becomes -30dBc (presently -45dBc)."
As noted in the description by Thomas Ray above, in the hybrid AM digital/analog mode, the new OFDM carriers are significantly reduced in amplitude (and voltage) from the main analog carrier, hence the sensitivity issues encountered in the field.
Large media companies (such as CBS Radio and Clear Channel) own and operate many AM signals in many medium-size and large markets. As a suggestion, any under-performing AM radio format should be discontinued in a given market. Then the AM station should be converted to an all-digital HD Radio mode, and simulcast one of the remaining AM music-formatted stations. This may largely resolve the AM receiver sensitivity issues in the field. This experiment would also determine if listeners are really interested in the new HD Radio technology, and thus be motivated to purchase a new radio. ABC's Radio Disney AM station outlets should also convert to full-time HD Radio digital mode.
meduci has inquired into licensing iBiquity's HD Radio technology. However, we will not introduce new products until the receiver sensitivity issues are resolved. This should occur when stations suspend the analog/digital hybrid mode, and begin iBiquity's "all-digital, all-the-time" broadcasting mode.
Cox Broadcasting is making a conscious decision not to allow self-induced interference on their AM stations, when these same stations are already competing to be heard over other increased man-made and natural noise sources.
What has been positive about the launch of HD Radio?
Stations have been allowed to upgrade their entire transmission chain, in many cases. Equipment that was used for decades has been discarded and retired, including very old analog playback devices, analog consoles, turntables, cart machines, cassette machines, DAT machines, CD players, MD players, analog processors, analog exciters, legacy analog-only transmitters, analog studio-to-transmitter-links, et cetera. Stations that upgraded to HD Radio have put considerable expense in implementing digital transmission and storage. Digital has been used in the audio chain after the microphone all the way to their new transmitters. Have listeners noticed? Do they care?
Equipment manufacturers have also greatly benefited by the HD Radio migration path. Stations probably will not institute another grand scale upgrade of this magnitude for another 40 years.
We understand the reasons why stations upgrade to HD Radio. We are living in a world where this is not your grandfather's radio. Today's listeners have many diverse choices competing for their attention. American radio stations feel compelled not to sit on their collective laurels, and not to be sleepy and complacent. They want to provide increased benefits to their listeners. They wish to fiercely compete in this new multimedia environment. Otherwise the future for terrestrial radio may be very grim, as stations would face declining ratings (and revenue).
However, is HD Radio the saving grace for terrestrial radio? Or will it go the way of FMX, quad records, 8-track tapes, and Dolby FM? Only the future will tell.
Consumers have not widely embraced HD Radio to date. Many reasons persist:
* There are only (up to) two new channels available for each FM station transmitting HD Radio simultaneously with traditional analog.
* Audio quality deteriorates for all services as the iBiquity FM bit stream is split (further divided from one to two, then from two to three streams).
* Radios do not properly "fall back" to FM analog when the HD multi-cast disappears during signal fade. As a result, consumers are required to press a button on their radio in order for the station's audio to return.
* There is not any tangible benefit for AM broadcasters. Even the 50kW flame-thrower power-houses are relegated to digital service up to (approximately) 20 miles from their transmitter site location.
* There are zero additional new channels available for each AM station transmitting HD Radio.
* Wideband AM HD Radio fidelity does not exist. True HD audio passband is up to 4 kHz. Audio frequencies above 4kHz are synthesized by the HD Radio codec. This conserves transmitted bandwidth. Ambience and high frequency stereo separation are lost. This results in artificial sound reproduction, that still cannot overcome external interference. And do not forget that the AM analog monaural sound channel needs to be cut back to 5 kHz (maximum top end) in order not to interfere with the new binary OFDM digital-generated AM HD Radio subcarriers.
* AM HD Radio critics have hailed how the AM HD carriers do not fit within the NRSC-2 passband and permissible FCC emission mask. If true, this would be illegal. However, iBiquity was careful to design these carriers to fit within the NRSC-2 mask. However, they took advantage of a "legal loophole," in that the NRSC-2 mask was never designed for continuous energy to be contained within the two outer (lower and upper) sidebands of any given AM radio station. Regular analog audio does not continuously splatter. There are momentary peaks encountered, as the modulation hits 100%, where the audio may invade the first adjacent frequency. AM HD carriers are continuous in this spectrum. Analog AM radios interpret this continuous energy as a legitimate part of the analog transmission. Automatic Gain Control circuits amplify this continuous energy several fold, and the result is a very loud and distinctive "hissing sound" present on first and second adjacent frequencies to an AM HD radio station. This is why the vocal AM HD Radio opponents are objecting. This "hissing sound" steps onto the station's first and second adjacent neighbors.
* People are voting with their wallets. MP3 players (iPods and such), and satellite radio sales are up. HD radio sales are down. Also, 70 percent of new cars sold now offer an auxiliary audio input jack on their radios, ready for connection to MP3 players and other external devices.
* Radio stations are not generally promoting their HD services very well, except at the top-of-hour legal ID. When HD is being promoted, consumers are still confused. When consumers hear HD, they asume that the station upgraded their facility, so that their current analog radio will sound better. Many do not know that their existing radio needs to be upgraded (at their own cost). It seems that this additional expense is being downplayed by the media companies.
* It seems that there is a general "who cares" attitude among listeners, when they are given the choice of hearing multiple FM HD Radio streams. Their perception is that existing analog radio sounds fine to them. Why make the financial upgrade to digital? And we will not discuss what listeners perceive of AM HD Radio.
Since consumers largely feel that analog FM stereo fidelity is acceptable, we suggest that FM stations discontinue the simulcast of their analog signals on FM HD-1. Instead, use this HD-1 channel at each FM station with HD-2 and HD-3 to create three independent additional sources of programing (and hopefully, additional revenue streams) to complement the terrestrial analog signal. This may require a field firmware upgrade to the HD Radios to receive analog broadcasting, independent of the digital HD channels.
meduci, LLC specializes in custom freelance engineering, design and production of electronic products in prototype quantities to full scale manufacturing. We also design low frequency (class A, class AB, class D) audio power amplifiers, class C power R.F amplifiers, and R.F front-end (amplifier, mixer, oscillator), using Motorola, National Semiconductor, and other custom ASIC chipsets and discrete components. We strive for quality and excellence in workmanship. Our products are designed for faithful sonic reproduction of the on-air source material. For customers with specific requirements, you could always count on us to produce innovative solutions. Our customers are benefited by better pricing, quality warranty, and excellent technical support. Contact us for a free quotation -- we appreciate your business. Our goal is to meet the needs of our buyers, distributors and dealers, and we can work on an ad hoc basis.