HD Radio in 2017: What’s New And What You Need to Know

We regularly take stock of the state of HD Radio in the US August 11, 2017

We regularly take stock of the state of HD Radio.

The NAB Show is likely still fresh in your mind, so let’s start with what we learned in Las Vegas.

DRIVING THE COST DOWN

One of the criticisms I have heard from other radio engineers, and read in various publications, is that HD Radio is too expensive for smaller operations. I can’t dispute this because, of course, what is too expensive for one station or group might be doable for another.

However, there is an understanding in the HD Radio group within Xperi (which purchased DTS, the company that had previously purchased HD Radio parent company iBiquity) that in order to get smaller stations (and smaller markets) to add HD that the cost of implementation needs to come down. As the various generations of HD Radio technology have come out, the cost has substantially decreased.

GOOD OPPORTUNITY TO ADD HD

When I first installed HD Radio in the mid-2000s, installing an additional transmitter was really the only practical way to go, and naturally, this made the cost fairly high.

The other piece of the puzzle was getting the RF out there — you could either make use of a separate antenna or an injector, which would allow a small fraction of the IBOC RF generated by that new transmitter to reach the main antenna.

Needless to say, this was an inefficient way to accomplish the goal.

Fortunately, over the last decade, transmitter technology has come a long way, and use of a combined amplifier is now common practice. This eliminates any need for an injector or a separate antenna. It also saves you space, and eliminates the need for more AC power and more air conditioning. The combined amplifiers, while not providing as good efficiency as an FM-only transmitter, are still efficient, especially when comparing them to the older tube-type rigs.

Each radio engineer has his or her favorite brand, so let’s take a look at what is offered by several well-known transmitter manufacturers.

Nautel NVLT transmitters can now be fieldupgraded to support HD Radio transmission with an add-on exciter.

Nautel introduced the NVLT series of transmitters in 2012 and 2013, in the power range 3.5 kW to 40 kW. At that time, it was designed to handle analog FM only; however, during the NAB Show, the company announced that the NVLT line can now be upgraded to support HD Radio transmission.

The company also introduced a new HD MultiCast+ Importer/Exporter, which combines an HD Radio Importer and Exporter in one unit. This 2-RU device makes use of Xperi’s Gen 4 HD code and includes a built-in multi-channel audio card, GPS receiver, Nautel Reliable HD Transport, software and station logo support. Operation of the HD MultiCast+ platform is versatile, in that it can be used as an all-in-one product or separately as an importer or exporter. The importer codes the secondary program services of an IBOC transmission, which can include digital channels, two, three, four and multiple data channels. The exporter combines the digital version of the main audio stream with the secondary audio and data services from the importer.

Nautel also announced reduced pricing for its Exporter+.

The company also introduced its new solution for Single Frequency Networks for HD Radio, which includes two key elements: A hybrid FM+IBOC booster installation that minimizes on-channel interference, and a method to achieve precise input-to-output time synchronization for both FM and IBOC across multiple HD Radio transmitters. An implementation of the HD SFN at KUSC in Los Angeles was the subject of an article in the October 2016 issue: http://www.radiomagonline.com/gallery/0006/this-hd-radio-sfn-is-kuscs-booster/38264.

The GatesAir Flexiva FLX with PowerSmart 3D compact design allows for a smaller footprint, and liquid cooling either negates or drastically reduces the need for air conditioning in the transmitter plant.

GatesAir has an extensive line of VHF FM transmitters. Let’s look at their Flexiva FLX with PowerSmart 3D. It’s a liquid-cooled FM solid-state transmitter family that, when operating as a combined amplifier, supports transmission of HD along with analog FM.

Flexiva FLX utilizes modern 50 volt LDMOS amplifier devices, high-efficiency power supplies, variable speed cooling and the Flexiva FAX exciter with real-time adaptive correction. Its compact design allows for a smaller footprint, and its use of liquid cooling either negates or drastically reduces the need for air conditioning in the transmitter plant, which increases the overall efficiency and lowers the cost of operation.

The Flexiva High Power Transmitter line features identical power blocks for scalability, with power levels from 10 to 80 kW. (The 10 kW power block uses 16 rack units.) The use common dual power amplifiers and IPA modules for all power levels simplifies the spares requirements; RF amp modules and power supply modules are hot-swappable. The transmitter will operate from single-phase or three-phase power, Delta or Wye configurations, from 190 to 464 VAC.

For HD Radio applications, use of the FAX exciter means that the fourth-generation HD Radio Crest Factor Reduction and Adaptive Pre-Correction technology will be in use, serving to maximize transmitter efficiency, while allowing for a higher amount of IBOC output for a given amplifier size.

The transmitter front panel allows for configuration and diagnostics, and the embedded web server allows for control and monitoring from anywhere IP access is available. The transmitter also supports SNMP for monitoring and control.

Broadcast Electronics refers to their approach to the peak-to-average power problem as Vector Power Enhancement, and it’s a standard feature in both of their STXe exciters, the STXe 60 and the STXe 500. The STXe exciters can operate in HD Radio (or DRM+) applications and would be used to drive a transmitter using a combined amplifier (that is, amplifying both the analog FM and the IBOC carriers). The STXe 60 tops out at 60 W and is the standard for the S and T series transmitters; the STXe 500 is the standard for the T series.

The T-series comes in three power levels: The FMi-17T, the FMi-21T, and the FMi-25T.

The FMi series is a linearized version of the classic FM-T series of BE single-tube transmitters.

The Continental Electronics 816HD line has three power levels: 816HD-20 for power up to 20 kW, 816HD-25 up to 25 kW of power and liquid-cooled 816HD-28L for applications up to 30 kW of analog power.

If you are starting from scratch with your HD Radio implementation, then you’ll need to outfit yourself with the importer and exporter as well; BE offers its XPi 10 Embedded Exporter, along with the IDi 40 Importer.

Continental Electronics continues to offer the 816HD and 816-HDR lines (HDR meaning “HD-ready”) family of transmitters based on three different analog FM + HD power levels: the 816HD-20 for power up to 20 kW; the 816HD-25 up to 25 kW of power, and finally, the liquid-cooled 816HD-28L for applications up to 30 kW of analog power.

Common features of the Continental line of FM transmitters are the single-tube design; solid-state IPA; SCR “Soft-Start;” automatic power output control; use of the quarter-wave cavity in the output amplifier; use of the grounded screen grid circuit using screen neutralization; automatic filament voltage regulation; automatic power interrupt recycle; two independent VSWR protection circuits; and a positive-pressure cabinet, which helps to keep the inside of the transmitter clean.

Inside view of Rohde & Schwarz THR-9 shows multiple stacked amplfiers along with integrated cooling system. Front view of Rohde & Schwarz THR-9 liquid-cooled VHF transmitter.

Those of you who visited the spring show within the past two years may have seen Rohde and Schwarz’s entry in to the U.S. FM and FM+HD transmitters market, the THR9.

It’s compact — up to 40 KW from one rack and 80 KW from two. And it uses a completely redundant (and highly efficient, according to their literature) liquid cooling system. This either negates or substantially reduces the need for air conditioning in the transmitter plant, thus increasing its overall efficiency and lowering on-going energy costs.

An Ethernet connector allows the transmitter to be operated locally or via the LAN interface; it can operated remotely via its embedded web interface or integrated into a network management system via SNMP.

The THR9 makes use of HD Radio Generation 4, achieving substantially better crest factor reduction than third-generation IBOC transmitters, serving to maximize its efficiency while allowing for a higher amount of IBOC output for a given amplifier size.

OFF-AIR RECEPTION AND TIME ALIGNMENT

Clearly, if you are going to transmit HD Radio, you’ll need a way of monitoring it at your studio headquarters. Time alignment of the analog signal and the simulcast HD is of extreme importance as well. (We have covered precise time alignment previously. Check out http://tinyurl.com/ya8mttbz.)

Inovonics recently introduced their Aaron 655, a new HD Radio receiver in their line of rebroadcast (translator) products. The Aaron 655 employs a sensitive FM / HD Radio SDR-based receiver that will return to the programmed frequency and reception mode following a power interruption. In addition to FM and HD1 through HD8 program sources for rebroadcast, the 655 accepts analog, AES-digital and streaming program inputs with fallback-priority selection; its outputs are composite, analog, AES digital and streaming. IP connectivity with a Web-browser interface permits total remote control of the unit from any PC or mobile device, along with remote audio monitoring. Local GPIO failure alarms are augmented with email notifications, alarm logs, and full support of SNMP.

In addition to FM and HD1 through HD8 sources for rebroadcast, the Inovonics Aaron 655 accepts analog, AES-digital and streaming program inputs with fallback-priority selection.

The Justin 808 is Inovonics’ single-RU device designed to maintain the time alignment between the analog FM and HD1 channel to within 23 microseconds (±1 sample). The Justin 808 can be added to the HD simulcast air chain only, making its time-alignment adjustments to the HD1 audio stream, leaving the analog FM air chain untouched.

The Inovonics Justin 808 can be added to the HD simulcast air chain only, making its time-alignment adjustments to the HD1 audio stream, leaving the analog FM air chain untouched.

In addition to continually checking the time alignment, it also matches the levels between the air chains and corrects out-of-phase conditions between the two. The entire synchronization process is 100-percent automatic. Justin’s web interface features SNMP support and can be configured to send email or SMS alarm messages.

The Belar FMHD-1 features a 640x240 color LCD display and rotary encoder for its local user interface.

The Belar FMHD-1 is their HD Radio monitor receiver, used to simultaneously decode the HD Radio signal and analog FM signal, while displaying HD Radio status, data, time alignment, and configuration information, as well as total, pilot, L, R, L+R and L−R metering and RF spectrums. The 2RU device features a 640x240 color LCD display and rotary encoder for its local user interface. The FMHD-1 supports the monitoring multiple audio streams and simultaneous monitoring of two streams with an optional second plug in HD decoder. It has eight user-assignable analog audio outputs and three assignable AES-3ID outputs; other features include frequency-agility, antenna and high RF level inputs, RF spectrum analysis including NRSC mask and sideband power measurements, a time alignment graphic display analysis (±16384 samples, ±375 ms to ±256 samples, ±5.8 ms), audio polarity, level alignment graphic display analysis (±20.0 dB), HD control and status information, HD SIS and PAD Data and bit error rate measurements. The ADC is the optional automatic delay correction module for the FMHD-1.

The DaySequerra M4-FM front panel LCD display allows for monitoring of demodulated audio, carrier, pilot, composite and SCA level measurements with better than 1.0 percent accuracy, as well as RBDS and HD Radio PAD/SIS.

DaySequerra recently introduced its new M4FM-HD, a single-RU monitor receiver for FM and HD. It allows for monitoring of analog FM, the HD simulcast, and the multicast channels HD-2 through HD-8. It will stay tuned to FM analog, HD-1 or the selected multicast stream during power or I2E interruptions. The user can monitor the station’s HD Radio HD-1/MPS diversity delay using the built-in Split-Mode feature. The front panel LCD display allows for monitoring of demodulated audio, carrier, pilot, composite and SCA level measurements with better than 1-percent accuracy, as well as RBDS and HD Radio PAD/SIS, along with network and alarm conditions, audio level, digital audio quality and carrier quality indications.

Rear panel balanced analog outputs provide +4 dBm @ 100-percent modulation and the front panel headphone output can deliver more than 1W into 8 ohm. Full-time AES3 digital audio output is also available. The M4FM-HD also provides a password protected embedded web server, allowing for full remote control and monitoring.

DaySequerra’s M4.2Si broadcast allows for the monitoring of AM, FM, the HD simulcast, and the HD2 through HD8 streams.

The M4.2Si Broadcast is another of DaySequerra’s monitor receivers. It allows for the monitoring of AM, FM, the HD simulcast and the HD-2 through HD-8 streams. Like the M4FM-HD, the M4.2Si will return to its previous setting following a power interruption. The front panel LCD allows for the checking of all RBDS and HD Radio PAD and SIS, artist experience, analog audio levels, digital audio quality and carrier quality indications.

With the optional TimeLock feature, the M4.2Si can be used to continually measure the time delay between the analog FM and the HD simulcast to an accuracy of one sample. Alignment issues can be reported through a rear-panel alarm or via email alerts.

FINAL STEPS

There is another important piece of gear that you may need to upgrade if you are adding HD Radio to your system: the audio processor.

While it may seem like an easy to way to save on implementation cost, it’s proven unwise to use separate processors for analog FM and simulcast HD.

The reason is simple: Even if the time alignment is exact, the blend between analog and digital audio will not sound good. This technique was used commonly ten years ago, but it is not considered good engineering practice today.

The big audio processor manufacturers, including Wheatstone, Omnia and Orban, all make audio processors with parallel processing chains, one optimized for analog FM, and the other for the simulcast HD stream.

While installing a new transmitter is a good opportunity to add HD Radio, it also makes for a good opportunity to upgrade your on-air processing.

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