A remote remodel

March 1, 2007

There are a couple of good reasons why radio stations execute remote broadcasts. First, it's a great way to interact with the local audience; and second, it can often be a nice revenue source for the station.

As the station engineer, you may be charged with determining the best way to execute remotes for the station. For our purposes, let's assume that you're putting together a brand new system without any legacy equipment. We'll focus primarily on 21st century techniques.

Wired vs. unwired

When setting up a system for remotes decide if with the wired route or the unwired route fits the application. This distinction is clouded somewhat with the wide availability of the public Internet, so there is quite a bit of crossover with some of the equipment that is available.

Talk shows on remote are an ideal way to interact with listeners. Chef Jasper Mirabile (seated) talks with guest Chef Gary Puetz while Dennis Eversoll, CPBE CBNT, checks the setup on KCMO-AM Kansas City.

Generally speaking, the wired route is based on older technology. You could totally rely on the local telephone company to provide wire connections back to the station. In the old days you could order an 8kHz or 15kHz audio circuit. While they often worked well (and they often didn't) they always required a test visit before the day of the remote. The tariffs are usually quite high for this type of circuit, so unless you planned on originating multiple remotes from the same location, this type of wired circuit was not economical.

In the early 1990s, ISDN codecs became available and supplanted the dedicated audio circuits. While an ISDN circuit was often less expensive (not only for installation but also on a monthly basis) it had much in common with the older style of lines: the telephone company required a couple of weeks to install it, and it still needed to be tested ahead of the remote date. To a great extent, the quality of the remote broadcast audio depended on the codec itself and not the quality of the telephone company technician that installed the line. On the other hand the complexity of the ISDN codecs sometimes scuttled the remotes.

The unfortunate reality is that ISDN is now also obsolete; some telephone companies balk when the customer wants to place an ISDN order. The reason is pretty simple: There are better ways to get more data over a single copper pair, which means more money for them. Telephone service providers are inclined to spend their capital dollars on equipment that can handle these new methods, forsaking the older.

So what are you left with if you want to make use of wired circuits for remotes? POTS (though also becoming obsolete in its pure form) is ubiquitous so that is an option, and the Internet is readily available in many places because of DSL technology. Still, there are lots of options for wired connections.

Comrex has many years of experience in building equipment used to broadcast remotes over plain old telephone circuits and not surprisingly its current line includes all the features and functionality that you would expect. The Matrix codec field version has one mic-level input, one mic or line level input, a headphone output and a line-level out as well. The studio version is 1RU and does not have the mixer and headphone features. The Matrix uses an on-board POTS codec that can provide 15kHz of duplex audio response depending on the quality of the POTS connection. However, the user can also add modules to the Matrix such as the Portable ISDN module, the Matrix GSM module or the Matrix Telcell module.

Comrex also offers the Access, which takes advantage of the increasingly diverse set of connection possibilities: POTS, DSL, cable DSL (as well as 802.11x (Wi-fi), 3G data networks, high-speed cellular data networks). It uses the Comrex-developed Broadcast Reliable Internet Codec and will perform at several user-selectable quality levels. HE-AAC and AAC low-delay are also available for use over robust networks.

Tieline offers the I-mix G3, which is a complete remote broadcast package (mixer and headphone amp built-in). The basic unit is a POTS codec, but it has an expansion slot to plug in other types of codec modules. For example, a second POTS codec module can be added, giving the I-mix the capability of bonding two POTS lines together, providing mono, stereo or even dual-mono feeds of as much as 15kHz in audio bandwidth. Alternatively, the expansion slot can be loaded with Tieline's IP software module, allowing the unit to connect to wired LAN. (ISDN and GSM plug-in modules are available for the I-mix 3 as well.)

Musicam has its own codec that will work via IP: the Netstar. This device can send and receive audio, contact closures and ancillary data via TCP/IP, ISDN or dedicated data lines. It contains not only the standard algorithms such as G.711, G.722, MPEG Layer 2 and MPEG Layer 3, but also MPEG AAC and MPEG Layer 4 AAC-low delay. This unit can deliver uncompressed 20kHz audio with near-zero delay if the IP connection supports it.

Audio TX sells a software package called Communicator that allows the user to create a remote session via TCP/IP through physical connections such as a LAN, Wi-fi or DSL. The PC or laptop on which Communicator runs can also be turned in to an ISDN codec. The Windows software includes algorithms for MPEG Layer 2, Layer 3, G.722 and G.711, and can connect with other manufacturers' codecs.

The APT Tokyo is another full-featured, multiple algorithm codec that can be used over a LAN by way of Ethernet, or via its USB connector. In addition to MPEG Layers 2 and 3, G.711, G.722 and MPEG AAC, it also includes the APT proprietary algorithms such as Standard Apt-x and Enhanced 16, 20 and 24-bit Apt-x. This device features a built-in inverse multiplexer that allows it to use four separate ISDN circuits, and hence provide up to a 512kb/s data rate.

The Orban Opticodec 7600 is a duplex audio codec for use via Ethernet, X.21 or V.35 interfaces, or as many as three ISDN interfaces or mixed with POTS interfaces. Configure and operate the codec directly with the front panel keypad and high-resolution graphical display.

A relatively new player is Mayah, and it recently introduced the Centauri II 3300/3301. This is a codec with multi-channel I/O. The bit rate is determined by the application and can be as low as 160kb/s with AAC+SBR (MPEG4 AAC HE) or as high as 6Mb/s with linear audio. Connectivity via IP and ISDN is possible.

Perhaps the best-known manufacturer of ISDN and POTS codecs is Telos Systems. The Zephyr Xport is a POTS codec that, with the inclusion of the field-installable ISDN option, can be made into an ISDN codec as well. The Xport uses AAC Plus audio coding for POTS connections; MPEG AAC low delay for ISDN connections made with an Xstream on the far end; and its G.722 option allows it to communicate with other G.722 codecs as well. The unit offers a built-in mixer with mic and line-level inputs, and independent headphone outputs that can listen to received audio or monitor mixes.

No wires

Perhaps you've decided that the wireless route is the one you would prefer. You could still choose from several of the codecs discussed above.

The Tieline I-mix 3, when equipped with the IP software module, can operate over a Wi-fi connection with the addition of a wireless media adapter connected directly to its LAN port.

Comrex uses the Access in a slightly different manner. The Access plugs into a laptop (or other PC) via an Ethernet crossover cable. Then, using Windows ICS, the Access shares the wireless Internet connection that the laptop makes — irrespective of the network type.

Now wait just a minute here. I'm kind of writing ISDN off, but even though remote pickup (RPU) technology is far older than ISDN I'm bringing it up anyway. With appropriate receive sites built in advance and an effective means by which the RPU audio can get back to the station's HQ RPU is really hard to beat — at the very least — in terms of its timeliness.

TFT offers the 8888 RPU transmitter and the 8889 RPU receiver. The system includes frequency-agility, selectable deviation on the transmitter (with 20W RF out) and selectable bandwidth on the receiver. The receiver can be controlled remotely and DTMF tones change the operating channel and IF bandwidth. The transmitter includes a built-in mixer with three mic- or line-level inputs; a send/return loop for connection to an external audio processor; a built-in peak limiter and a headphone output for monitoring the locally mixed audio.

Not to be outdone, Marti recently introduced a new RPU transmitter: the SRPT-30. This unit comes with two factory selectable frequencies, four front-panel mic level inputs (line level input available on D-connector on the back of the unit) going into its built-in mixer, and as much as 30W RF out. The SR-30 is the current model RPU receiver.

Conquering the delay issue

Whether you use one of the IP codecs or even ISDN, you will have to deal with the delay in the “round trip” time that the remote talent will experience. Unless you want the talent throwing the headphones down on the table (or maybe even at you) you'll have to send mix minus audio back to the remote site in some way. If you are transmitting HD Radio, then you have an additional eight-second delay to deal with. If you're doing a live show then you will be operating with a profanity delay in-line as well. The bottom line is that this is an issue that can't be ignored.

If you choose to go the wired route you will take advantage of the duplex nature of all POTS, TCP/IP (and ISDN) codecs. Develop a mix-minus at the station and feed it back to the remote site. If you choose the wireless Internet option, you can solve the problem in the same manner due to the duplex nature of the connection. If you want to go strictly wireless with RPU, then your problem is a bit more cumbersome.

First is the use of a phone coupler. Because the remote site isn't tethered, you'll likely use a cell phone to call this coupler, steal the receive audio from it somehow and mix that into the talent headphones. Sounds easy, right? There are a few challenges. Usually the connections aren't that reliable. You need to be within range of a cell, then you need to get a circuit, then it needs to remain connected. As anyone who has used a cell phone can tell you, none of those things are guaranteed. Oh yes, then there is the cost of the call itself.

Secondly, you can make use of an RPU channel to transmit the IFB audio outbound to the remote site. This is convenient if you have the channel and the equipment and the site — all of which can be problematic. If the IFB transmitter is at the same location as the RPU receiver, then use the same RPU antenna with a duplexer to receive and transmit.

Thirdly, use some spectrum in the upper part of the FM baseband to transmit audio to the remote site. This obviously requires spare capacity on the studio-transmitter link to carry the IFB audio. This also requires the available subcarrier spectrum. A station that already has one or two SCAs could have some challenges. All this also assumes that there is an FM signal in the station group.

There are at least two manufacturers offering SCA generators; one is Broadcast Electronics. BE offers the FC-30, a 1RU device that lives at the transmitter site or back at the studio if carried on a 950MHz composite STL and operates between 33kHz and 95kHz. A 150 microsecond pre-emphasis setting is standard, but it can be set internally for 75 microseconds, which allows use of a legacy FM audio processor to drive its audio input.

Mounting equipment in rack cases simplifies setup and protects the equipment.

Modulation Sciences offers the SCA-186, a 2RU device that includes the subcarrier generator, a built-in audio processor, a deviation meter and a transmitter tuning aid.

Now if someone just made an SSB SCA generator. This would eliminate the need to turn the SCA carrier off after the remote is done.

The last mile

Any one of these three methods requires some type of receiver at the remote setup location, whether it is a table top or the inside of a remote truck. How do you get the IFB audio to a talent roaming with a wireless mic? There are several wireless mic manufacturers that make IFB systems as well.

Lectrosonics offers the T4, a frequency-agile (operating on one of 256 UHF channels, in 100kHz steps) that transmits a 250mW signal. The receiver is the R1a and its receive frequency range complements the T4. It comes in the belt-pack form with a housing of machined aluminum, and sports as much as eight hours of battery life with an alkaline cell.

Shure offers several systems known as personal monitors that can be used for IFB service. The PSM 700 system is made up of the P7T transmitter and the P7R beltpack receiver. The transmitter occupies a half-width rack unit, even with its built-in power supply. The unit has an antenna connector, so the transmit antenna can be located away from the unit. The belt-pack receiver features LED indicators for power, low battery and RF reception. The system can operate in stereo mode.

Sennheiser also makes several systems that can be used as IFBs. The EW300IEMG2 operates on any one of 1,440 channels spread over five blocks in the UHF TV band. The transmitter can be rack mounted, includes audio input metering and radiates 30mW. The beltpack receiver uses an autoscan function to find the transmitter. The system can operate in stereo mode.

One little hint I will give is this: when building a remote truck, put the wireless mic receive antenna and the IFB transmit antenna on top of the mast. Make sure the coil running up the mast has the appropriate number of coaxial cables installed ahead of time.

Executing remote broadcasts has always been in the province of the engineering department. When building a new system, find the correct balance between functionality and ease of use. Having a nicely engineered and constructed remote system is a great way to make a good impression on air staff, programmers and clients — and goes a long way in getting them all to recognize you as the hero you know you are.

Resource Guide

Manufacturers of remote broadcast equipment


Mayah Communications
+49 811 55 16 0

Allen Osborne Assoc.

+44 121 256 0200

APT (Audio Processing Technology)

Medical Coaches

ATA Audio

Mobilized Systems




Neural Audio

Barix Technology

Nicral Ltd./Sonifex
+44 1933 650700

Bickford Broadcast


Broadcast Products

Phoenix E.N.G.

Calumet Coach Co.



Sennheiser Electronic

Creative Studio Solutions


Custom Mobile Products

Software Authority


Sony Electronics


Studio Technologies

E-N-G Mobile Systems

Telex Communications


Telos Systems

Frontline Communications



Tieline Technology

407-688 2806



Wolf Coach

Marti Electronics

+31 15 262 5955

Irwin is the chief engineer of WKTU-FM, New York City.

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