Is it Time for a New Transmitter?

October 4, 2013


October is the time of the year we need to think about capital purchases for the following year. Transmitters are one of the most expensive of capital items, so I'll outline the new and updated products available now.

transmitters

Harris Broadcast is offering its Flexiva Compact Class line of FM transmitters, which come in 50W, 150W, 300W, 500W, 1kW, 2kW, 3kW and 3.5kW (analog) versions, and they are very compact - the largest requires four rack units. They're frequency-agile, with broadband amplification, so there's no need for tuning of course. The unit has an integral direct-to-carrier digital exciter, stereo generator, and RDS generator as well. Flexiva can operate at full rated power with up to a 1.5:1 VSWR and will reduce power proportionally up to 3:1 VSWR before shutting down. Fast analog VSWR protection circuits mute the transmitter instantly in the event of a shorted or open antenna or line to protect the transmitter. The lower power versions of this transmitter (up to 550W) operate on line voltages from 100 to 250Vac; the higher power versions, 208 to 250Vac (single phase, and between 47 and 63Hz).

Harris Flexiva

Harris Flexiva


It looks to me like Harris designed this transmitter line to handle less-than-ideal transmitter sites. What if you wanted to build an N+1 site to backup an entire cluster? This transmitter could be the way to go for such a plan. Some of its features could make that idea fairly easy to implement and manage; for example, it has a Web-based HTML GUI and SNMP support, so (assuming you have IP access to the transmitter site) it would be easy to bring it up on the air from just about anywhere. It has five different program source inputs: two AES, two composite and one analog. Each input is monitored for valid program content and can be programmed to switch to a valid backup source should the main source drop below a predetermined threshold and time interval. Upon restoration, the program can automatically switch back to the main source.

You can buy this transmitter for analog FM now and be able to upgrade it to a combined amplifier for analog and digital after December 2013 when the new Flexiva G4 Exgine is released. New features will then include hybrid crest factor reduction, real-time adaptive correction, a built-in spectrum analyzer, and host audio extraction. (If that becomes your plan, make sure you size the amplifier correctly; for example, the largest version of this transmitter (FAX 3.5K) will provide 1.7kW of analog FM at the -10dBc IBOC level.)

A few final optional features to mention: Add an Orban 5500 to it for built-in audio processing; or add a GPS receiver for Single Frequency Network synchronization.

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Going one more

Let's take this N+1 idea a little farther and see what is available in terms of broadband antennas. Shively makes the model 6832, which is broad-banded (VSWR 1.35:1 or less across the entire FM band) and will handle up to 2.5kW per bay. Another possibility for a low power N+1 application could be the Jampro JCPB. Its VSWR spec is 1.25:1 or better across the entire FM band, and it's also rated at 2.5kW per bay.

Harris HPX

Harris HPX


On the opposite end of the power scale for Harris Broadcast is the HPX, which is its high-power, vacuum-tube PA line of transmitters. According to Harris, the HPX system "provides the highest operating efficiency of any transmitter in its class" thanks to its 1/4-wave cavity and grounded cathode design. Its basic on-board controller provides critical life support, control, automatic exciter switching and fault diagnostic functions without reliance on a microprocessor. The enhanced transmitter control unit option combines the basic controller functionality with a microprocessor and 1/4 VGA touch-screen GUI for increased control and diagnostics, including TCP/IP connectivity, Web remote control/monitoring and SNMP support.

The HPX can also be used as a combined amplifier for HD Radio purposes. As an example, in conjunction with the Flexstar exciter, and using the real-time adaptive correction feature, the HPX-40 can make 31.5kW FM and digital at the -20dBc level, or 17kW at the -10dBc level.

For nearly my entire career I've been connecting a stereo generator output to an exciter input via a piece of coax, although there was that time, in the 1990s, where I experimented with running AES straight in to an exciter. The results were mixed - I was soon back to the coax runs. The Nautel Omnia Direct interface makes an AES connection from an Omnia 11 directly to a Nautel NV series exciter. Wheatstone has also unveiled its application of this technology, which is called Baseband192. Nautel and Wheatstone have both produced videos on this topic.

The operational specifics are pretty simple in concept. Think for a moment about the workings inside a typical audio processor/stereo generator combo: After all the audio processing is finished, the stereo generator, still in the digital domain, converts this audio to the familiar composite MPX format, and a final digital to analog conversion takes place. If that signal is routed via coax to the composite input of (for example) the integrated digital exciter in an transmitter, a subsequent analog to digital conversion takes place at the input of the modulator. Wouldn't it be great to eliminate that D/A and A/D conversion set? Well, by scaling the AES sample rate up to 192kHz (giving 96kHz of audio bandwidth) the intermediate steps along the way can be eliminated. The coax is replaced by an XLR cable to transport the AES data stream.

Orban's version follows the system developed by Nautel and Omnia, but samples at 384kHz and uses both left and right channels in the AES3 stream to multiplex the samples in an even-odd sequence between the left and right channels of a 192kHz AES3 link. Using only the left channel it is compatible with the Omnia method. The hardware can be retrofitted into an Optimod-FM 8600 on a rear-panel chassis cut-out.

Broadcast Electronics and Harris Broadcast offer a similar feature on at least one exciter in each of their respective lines. The feature is generically known as MPX over AES in these cases.

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Nautel NVlt

Nautel NVlt


Many are familiar with the Nautel NV and VS series of transmitters. A fairly recent addition is the NVLT series (NV light), which, while based on the NV design, is missing one major feature: It will not operate as a combined amplifier for HD Radio. It's strictly an analog FM transmitter. Still, it has many (if not all) of the features of the NV. Nominal power levels range from 3.5 to 40kW.

versions: 1, 2, 3 or 5kW, with an integral exciter and low-pass filter. (One of the options available is an external exciter kit, which you would use should you want to broadcast with HD Radio). The exciter has a composite input, and three additional inputs -- two for SCAs and one for RDS. Optionally you can add a stereo generator module with AES and analog inputs. Local control is done via the front panel LCD interface, but the unit has Ethernet support, so if your site has IP connectivity, then you can gain access to the transmitter remotely by that means. BE's RGUI (Remote Graphical User Interface) allows for the control and monitoring of up to eight different STX LP transmitters. RGUI also provides for complete diagnostics of the transmitter, as well as event logging.

Broadcast Electronics STX LP

Broadcast Electronics STX LP


Another new BE product is the STXe exciter, which is basically a stand-alone version of the integral exciter for the STX LP series. This exciter has a built-in controller with an updated GUI. Ethernet support allows for http access from anywhere assuming your site has IP connectivity (using a PC, laptop, tablet or smartphone). Additionally, the STXe supports SNMP. With the addition of BE's VPe (Vector Power Enhancement, which is their peak-to-average power reduction technology) the STXe can also operate in the IBOC mode, allowing for the transmission of HD Radio. (DRM+ is an option for stations outside of the U.S. where it is used for DAB in the VHF spectrum.)

Continental Electronics 816R

Continental Electronics 816R


Continental Electronics has been maintaining its familiar line of high-power FM transmitters: the 816R series. Power levels range from 11kW to 21.5kW (using the 816R-2C) up to 40kW (the 816R-7C). A single tube is deployed as the final amplifier (4CX15000A, 4CX20000E, or 4CX25000C depending on the power level). All of the series are self-contained, except the 816R-7C, which uses a separate power supply cabinet and external harmonic filter.

The 816R-HDR (HD Radio-ready) is a high-power combined amplifier for IBOC applications. You can buy it up front as an FM-only transmitter, while planning to add the IBOC components (the Exgine-enabled 802Ex digital FM exciter, along with an exporter) later on. Continental's D816HD series transmitters range in combined TPO from 18kW to 56kW at digital power levels of -20dBc to -10dBc. These combined transmitters use only one tube each, the final power amplifier tube. The D816HD series transmitters are also completely self-contained, including the harmonic filter. (The 70 kW has two high voltage rectifiers and plate transformers located in two separate chassis.) D816HD transmitter systems work with Continental's 802Ex digital FM/HD exciter to provide forward looking fully adaptive pre-correction, system and HD Radio performance monitoring and on-channel spectral analysis.

These combined transmitters may be set up in several configurations: single exciter to drive both transmitters; dual exciters; or, dual exciters and automatic coaxial switcher/combiner. The D816HD-20 will go up to 25.2kW of analog with an IBOC level of -10dBc; the D816HD-25 tops out at 34kW of analog with at -10dBc; and the D816HD-28L will reach 38kW of analog FM with an IBOC level of -10dBc.

It will soon be 2014 and I hope that you will take some time to look in to new features that are available from many of the transmitter manufacturers. Remote access and control, and IBOC capability, are the prominent features that have appeared in the last 10 years. It's not 1980 anymore and many of the features found today are put there to make your life easier.


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Not Just HD Radio

If HD Radio isn't part of your station plans, there are many manufacturers able to provide hardware.

Bext offers two compact transmitters: the XL1000 and XL2000. All inside a 2RU package (23" depth and 33lbs in weight) you get the integrated exciter, power amplifier, output filter and power supply. Output standard is a 7/16 DIN. Specify a 7/8 EIA flange if that's your preferred connection.

The integrated exciter uses direct-to-channel modulation and has a single composite input and two other inputs that can be used for SCA and RDS. Additionally, it has its own built-in stereo generator, supporting left/right analog inputs. (An AES input is optional.)

The integrated exciter uses direct-to-channel modulation and has a single composite input and two other inputs that can be used for SCA and RDS. Additionally, it has its own built-in stereo generator, supporting left/right analog inputs. (An AES input is optional.)

Other GPIO access is done via DB9 connectors on the rear panel. RS-232 and RS-485 access are available. If you are looking for a transmitter that can make a good translator, keep in mind that one option for the XL1000/XL2000 is an FSK keyer for ID purposes.

BW Broadcast offers the V2 line, which covers a power range from 5W to 1.5kW. They have a built-in DSP-X processor, 14 factory presets and a built-in FSK and Morse identifier. Gold-clamp transistor technology allows quick in-the-field transistor changes. Ethernet control SNMP and other connections simplify control and monitoring. Power supplies slide in and out.

Ecreso, a division of Worldcast Systems, has the Helios 2000W, a 2kW unit (the entire line covers the 350W to 2kW level), which needs 3RU and weighs about 45lbs. Its integrated exciter uses a direct-to-channel modulator with a built-in stereo generator, accepting analog or AES up to 192kHz sample rate at 16-, 24- or 32-bit word length. Additionally it has two BNC inputs that will accommodate external composite or SCA/RDS signals.

Aside from local GPIO connections for control, Helios supports HTTP using an internal Web browser and Ecreso's AMI (Advanced Measurement Interface) via Ethernet. It also supports SNMP, and has an interesting feature known as Expert Maintenance Reporting. EMR is an optional service, which pushes regular reports on the status of key parameters such as temperatures, currents and voltages, plus information on the performance and lifespan of components such as the fan and power supply, via an IP connection, to Worldcast Systems, where the data is monitored. With trend analysis, EMR can identify problems and issue warnings in advance to allow for corrective action to be taken. A map-based display of current statuses and detailed reports and graphs are available at any time on the EMR user page. Clearly this is a potentially useful feature if you have a widespread network of transmitters.

Ptek has a line of transmitters that includes the Gamma HE series. It comes in six different versions, at power levels of 2, 2.5, 3, 3.5, 4 and 5kW with a 7/8" flange output connector. All but the 4 and 5kW versions use 4RU; the two largest need 6RU. The integrated exciter makes of use Direct Digital Synthesis; the amplifiers are made of up LDMOS, resulting in higher efficiency (and reduced cooling requirements). Aside from front panel metering and control, the transmitters have complete remote control: GPIO and an RS-232 interface that allows access to all major transmitter parameters. An embedded Web-server is optional. The power supply accepts voltages between 208 and 264Vac.

Armstrong has a line of transmitters (that includes the FM Series B) which are completely solid-state and come in power levels of 5, 7.5, 10, and 12.5kW. The amplifiers are self-contained and include three power supplies per amplifier. The IPA for the lower power levels is the FX-150B, and for the larger levels, the FM650B. The output connector is a 1-5/8" flange. AC power input can be single or three-phase, 208-240Vac. The exciter is optional with the purchase, and obviously Armstrong offers those as well; you could certainly consider the FMX-30B.

OMB has a line of products that includes the FMA 2000 HE. This is a 2kW transmitter (3RU) with two 1kW amps with individual switch-mode power supplies; the output connector can be EIA 7/16" or 7/8". Local control is via the front-panel TFT screen and touch keyboard. VSWR protection against line mismatches is included along with an integral low-pass filter. Remote control is provided by GPIO and RS-232. You would need an exciter as well; for example the EM 25 DIG PLUS. This is a frequency-agile exciter, with analong, composite, and SCA inputs. Maximum power out is 25W.

Finally, let's look at the Elenos line. The Medium Power ETG series includes models in the 2.5, 3.5 and 5kW power levels. You can get this transmitter as an amplifier with integrated exciter (in 4RU) or as a 2RU exciter and 4RU amplifier. The Indium series in 10 different versions, from 100 up to 2kW, and the Elenos Eco-Saving line has models from 5 to 30kW.


Irwin is RF engineer/project manager for Clear Channel Los Angeles. Contact him at doug@dougirwin.net.



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