Using Vantage with Shure® Wireless Workbench®

This brief video shows how Vantage, RF Venue’s OS X software for RF Explorer spectrum analyzers, can be used with Shure® Wireless Workbench® in a professional live production scenario to do some very useful things.

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We worked closely with Richard Stockton, a freelancer on a corporate gig with FOH Productions, to get screen recordings of Richard’s computer while he was setting up wireless at the show, switching back and forth between Vantage and Wireless Workbench.

This video shows you how to import wideband scans from Vantage into Workbench, how to perform IMD calculations within Workbench using Vantage scan data, and even a trick Richard has been using in conjunction with manual war-gaming.

Equipment used on the show included Shure UHF-R on the main stage, Shure QLX-D in the breakout rooms, and a mix of Radio Active Designs UV-1G and Tempest intercoms for the crew.

If you’re already using Wireless Workbench to network and/or coordinate your Shure brand wireless audio equipment, using Vantage in tandem with Workbench can allow you to do some things you would not be able to do with Workbench alone.

You can scan as wide as you want with Vantage + RF Explorer, and then import that scan into Workbench as you would from any other analyzer. (If you’re using a networked Shure receiver you are limited to the bandwidth of that receiver: J3, G5, H5, etc)
And since the refresh rate and resolution of Vantage’s interpretation of live RF Explorer data is so fine, you can use Vantage to zoom in on small portions of the spectrum to examine them. There may even be a way to tune cavity filters using RF Explorer + Vantage (forthcoming post!)

If you’ve never done any sort of software coordination whatsoever, using an RF Explorer as the spectrum analyzer for Vantage alongside Wireless Workbench is a very economical way to get into the game without losing out on some necessary features. Wireless Workbench is free. Vantage is $99, and RF Explorers, depending on the module, range from $100 to as high as $400.

Take a closer look and download a free 14 day trial for Vantage at the following link:

http://www.rfvenue.com/vantage

Is VHF the Answer to the Spectrum Crunch?

Last week Lectrosonics announced the release of the IFB-VHF, a 174-216 MHz tuned version of their popular IFB-UHF system.

(Which, by the way, has nothing to do with, and does not look like, the vintage marketing image from the old manufacturer Vega, shown above, and plenty more here.)

Of the new product, Lectrosonics President Karl Winkler said: “By adding the IFB system on the VHF frequencies, it allows users and system designers to move these out of the critical UHF band, which should improve the ability to coordinate larger systems even in a crowded RF environment.”

Lectrosonics is one of the first—but certainly not the last— major wireless audio manufacturers to reintroduce products in the VHF (30-300 MHz) band in an effort to ease the RF congestion at every large-scale production in UHF, and get a running start on the incentive auction’s decimation of 40-50% or more of current UHF spectrum available.

So far, these early second wave VHF devices are all non-performance devices—devices that wirelessly transmit some sort of audio or control that is not heard by the audience. (I say second wave because wireless audio began in VHF, and then migrated up to UHF in the mid to late 90s.) The only other major player to go VHF has been Radio Active Designs, with their successful UV-1G intercom system. There are no wireless microphones or monitors yet in VHF, though we might see some drop down to VHF sooner or later.

The announcement from Lectrosonics last week has got us thinking about VHF in general.

How suitable is it to performance and non-performance wireless audio gear?

What are the benefits of VHF over UHF?

And, crucially, if those benefits exist, can we expect them to last?

[NOTE: This discussion is mostly relevant to the United States and VHF spectrum in the US. Other regions may have different VHF allocations.

What is VHF?

“VHF” is defined by the ITU as radio waves between 30 MHz to 300 MHz. Go ahead and get yourself oriented with this supersized spectrum map.

Wireless audio users are not allowed free range across all 270 MHz that VHF theoretically offers. We are confined to empty VHF broadcast band DTV channels.

In a location where there are no VHF DTV channels, there are 76 MHz of spectrum available.

I want to repeat that. In the best case scenario VHF offers only 76 MHz of spectrum. By comparison, UHF currently offers 220 MHz, and 2.4 GHz around 86 MHz.

The VHF TV broadcast band is also non-contiguous; it is split into three bands (the highlighted blue bars in the chart above) containing 16 DTV channels separated by other services. “Low band” VHF, “mid band” VHF, and “high band” VHF. Low band extends from 54-72 MHz, mid band from 76-88, and high band from 174-216 MHz. Because the separation between low and mid band is so small (only 4 MHz) some lump both low and mid band VHF into simply “low band VHF” and call it 54-88 MHz.

The Pros of VHF

• Lower Traffic
  At the moment, VHF has fewer devices and fewer TV stations in it than UHF. During the DTV transition, many TV stations migrated up to UHF, abandoning VHF due to concerns over interference. Every major wireless audio manufacturer abandoned VHF by the mid 90s, so aside from RAD, Lectrosonics, and a few other products you might encounter on a production, like Comtek IFBs, VHF is a veritable oasis of solitude for low power wireless audio devices like wireless microphones and in-ear monitors. This is the main draw to VHF, and make no mistake: it’s a big one.

• Better Range
  Because of the propagation characteristics of VHF frequencies, signals are able to carry farther with the same amount of transmission energy than they are at UHF. Well-designed VHF equipment, operating with the same transmitter power, under the same conditions, and the same gain antenna, will travel farther than a UHF signal.

• Less In-Line Attenuation
  The generosity of VHF propagation extends into coaxial cables, too. You get much less in-line attenuation (signal loss inside cable) with VHF equipment than you do with UHF, which means you can do longer coaxial cable runs with fewer or no amplifiers, and use less expensive types of cable and expect the same performance.

Cons of VHF

• Larger Antennas & Components
  This is probably the biggest hangup. Because VHF frequencies have longer wavelengths, the devices themselves tend to be larger, heavier, and more expensive if they are engineered to the same quality standards as current-day UHF gear. For example, the wavelength of 180 MHz is about 5.5’. Whereas a 550 MHz signal has a wavelength of only 1.8’.

  Because of the long wavelengths of low band VHF (54-88 MHz), it’s unlikely that we’ll see much, if any, performance equipment manufactured there at all. Designing the antennas and electronics for a flawlessly reliable wireless microphone or in-ear for low band VHF are practically impossible without resorting to some wacky, expensive, and aesthetically unappealing tricks.

Non-performance equipment, like IFBs and intercoms however can use low-band VHF, since the audio quality of the audio feed is less critical. Comtek already offers a few products in that range.

• Incentive Auction Uncertainty
  There are still TV stations that use VHF frequencies. Most of them are public access or low power TV stations. But others may return.

  One of the “incentives” built into the incentive auctions is the option for a broadcaster to swap their UHF license for a VHF license and still get a payout. How many broadcasters will bite on that worm is yet to be seen. It’s possible that an uncertain number of current UHF stations will take the bait and move down to VHF, further crowding what is (remember) only 76 MHz.

• Low Power Pig Pile
  If all wireless audio manufacturers suddenly started making lots of gear in VHF, we’d have a problem.

  As James Stoffo once told me, “VHF is like that bar that used to be crowded, but now no one goes to anymore. There’s nothing wrong with the bar—it’s just that people have the perception that it was crowded, so they don’t go there anymore.” 

  If people (manufacturers) started going to the VHF bar again in droves, it would get crowded. And it would get crowded a lot faster than it took to crowd up UHF, because of its relatively small size.

  It might be argued the pig pile problem has happened in the last 1-2 years at 2.4 GHz. Since 2013, just about every major manufacturer has rolled out a 2.4 GHz band microphone.

  The result?

  It is very difficult to use multiple channels of 2.4 GHz microphones in any realistic venue. If you only need one 2.4 Gig mic—you’re fine. But need four, eight, or 12 channels of 2.4 wireless? Don’t look to tech support to solve that problem, look to religion; the 2.4 GHz ISM band is simply too utilized, even without adding a spectrum hogging microphone to the mix. WiFi and bluetooth devices use 2.4 GHz spectrum, too, and their use has exploded at 2.4 GHz even more than wireless audio.

• Higher Noise Floor
  In most locations, the noise floor at VHF is slightly higher than it is at UHF. The difference, though, is small. And the noise floor in a large-scale production is always going to be elevated.

IS VHF the Answer?

VHF is not “the” answer to wireless audio’s impending spectrum shortage. But it is one of several answers that, combined, will lead us out of the darkness ahead.

Future regulatory and technological seismic shifts will not allow us to keep all of our equipment exclusively in UHF for much longer.

Instead, the numerous low power wireless devices used in large-scale productions will have to fan out across the spectrum in combination with the correct deployment of tools like external antennas, filtration, and new modulation schemes if we are to continue to use them in the same quantities.

There is almost no other alternative.

Luckily, we’ve got RF options. We have VHF, we have the unlicensed bands at 900 MHz, 1.9 GHz, and 2.4 GHz, as well as (debatably) 5.8 GHz. There are plenty of additional bands open to holders of Part 74 and Part 90 licensees, as well as new bands that are slated to open to license holders post-auction, including the 169–172 MHz band, the 944–952 MHz band, the 941– 944 MHz and 952–960 MHz bands, the 1435–1525 MHz band, and the 6875–7125 MHz band. More on those here.

We won’t be kissing UHF goodbye, at least not yet. We’ll just be saying hello to unfamiliar spectrum elsewhere, making wireless production band-planning far more fragmented, but still doable.

Want better wireless? Download our eBook on three essential concepts for correctly deploying and maintaining interference-free wireless audio systems.

Shure Europe Now the Exclusive Distributor of RF Venue Products In Europe, Middle East, and Africa

Today, we’re excited to announce that Shure Europe and RF Venue, Inc. have entered into an exclusive distribution agreement across the EMEA regions.

Shure Europe’s regional distribution offices in Germany, the United Kingdom, and BeNeLux – alongside Shure Europe’s third party distribution partners across EMEA – will now distribute and sell RF Venue antenna and signal distribution products..

“We’re pleased to partner with the world’s leading wireless audio brand to bring RF Venue products to EMEA regions,” our CEO Chris Regan commented. “Shure Europe’s marketing, distribution, and fulfillment capabilities will provide RF Venue customers in those regions the highest level of sales and support. RF Venue products are highly complementary to Shure wireless systems, so this agreement is a great fit for both organizations.”

Over the last two years, we’ve seen our international base of customers increase substantially. Reduced UHF spectrum and the overall increase in number of wireless microphones has been a worldwide trend, and audio professionals everywhere realize that operating demanding wireless systems requires superb tools, like those that RF Venue and Shure offer, while still remaining cost-effective.

Our distribution agreement with Shure Europe will give those customers—both existing and new—faster and more complete access to RF Venue products and support, in their home countries and native languages.

“RF Venue antennas and distribution systems complement our extensive Shure wireless offering very well,” said Ron Marchant, General Manager Shure EMEA. “This distribution partnership strengthens our wireless market position across the EMEA region by offering a more comprehensive set of RF solutions for the most demanding applications. We look forward to working with RF Venue going forward.”

Region specific information on RF Venue products can now be found on the Shure EMEA and UK websites.

Shure UK

Shure BeNelux

Shure Germany

*Leading image courtesy Shure EMEA.

WRC-15 Upholds UHF Broadcasting and Wireless Microphones As Services of Value – In Europe, Asia, and Africa – For Now

The World Radio Congress (WRC) is held every few years by The International Telecommunications Union (ITU), who invite an esteemed congress of delegates from 193 member states (FYI, only three countries are missing) to discuss and vote on wide-ranging and critical topics relating to radio and telecommunications.

WRC-15 concluded on the 27th of November, lasted an entire month, spanned 40 topics, and was attended by 162 of the 193 Member States.

Among those topics was a debate on the continued relevance of terrestrial over-the-air television broadcasting.

Although the topic was low on the priority list, it was still on the agenda, and it had its day in the sun.

As reported by the EBU:

“…representatives reached a consensus that this spectrum, currently used by broadcast services such as digital terrestrial TV [DTT] and radio microphones, is too important to be allocated to mobile services. They agreed that there would be no change to the allocation in the 470-694 MHz band either now, or at WRC-19 in four years’ time. Instead there will be a review of the spectrum use in the entire UHF band (470-960 MHz) at the WRC in 2023. Only then will it be decided whether to make further changes to the Radio Regulations.”

The EBU is an interest group similar to the NAB, so their interpretation of the representative’s consensus is upbeat.

This could be taken as good news for traditional broadcasting everywhere and, by extension, wireless microphones that operate in UHF spectrum, but many organizations seemed to have overstated the positive ramifications of the decision for the United States.

The NAB was even more blunt and politically charged than the EBU in a statement released yesterday.

“NAB was pleased by the global unity demonstrated at WRC-15 for the importance of a vibrant system of over-the-air broadcasting. Of the 162 nations attending the conference, more than 140 countries rejected the wireless broadband industry’s anti-broadcasting UHF spectrum grab and recognized that frequency band is harmonized to provide television services on a worldwide scale. This broad consensus should send a strong message that while wireless broadband services are important for those who can afford the fees, that service should not come at the expense of a ubiquitous over-the air TV service that is available to all for free.”

Yet this statement seems odd coming from an American organization, because America was not part of that “global unity.”

The ITU’s decision to safeguard the UHF broadcast band until 2023 was agreed upon only in Region 1—Europe, Africa, and Asia. North America and the United States are in Region 2.

Any positive windfall for broadcasters from WRC-15 will not be felt here in America.

It seems that the ITU has identified UHF OTA broadcasting as a radio service and spectrum allocation worth saving in the absence of other alternatives, and that preserving the UHF band for broadcasting is part of a longer term transition to other mobile internet/broadband services.

As long as the digital divide exists, OTA broadcasting plays a critical role in delivering information and entertainment to impoverished, disenfranchised, minority populations, as well as the general public in times of peace and disaster, free of charge.

But the digital divide is unlikely to last forever.

As described in the Lamy Report given to the European Commission in 2014, terrestrial broadcasting is recommended to exist in tandem with mobile broadband, and a reassessment of the UHF allocations from broadcasting is suggested to commence in 2025, right around that second to next WRC conference in 2023.

The United States, meanwhile, has the workings of some sort of mechanism to close the digital divide within its own population through the Connect America Fund. In their own words: “Broadband has gone from being a luxury to a necessity for full participation in our economy and society – for all Americans.”

Oh, and did I mention?- Google, Facebook, and Elon Musk have already launched balloons, satellites, and high altitude drones to blanket the earth with broadband internet coverage—free of charge to those who can’t afford it.

This morning, there seemed to be widespread jubilation among the broadcasting community at the WRC-15 outcome on terrestrial broadcasting in Region 1. But I think that jubilation jumps the gun.

Sure, the ITU is a big deal. What they say and do matters. And as an intergovernmental body they in some cases define the technical and legal standards by which radio and telecommunications activities are conducted globally, and in others, make powerful recommendations that participating states usually heed.

The coverage casts the illusion that the WRC-15 decision will somehow percolate from the roundtable at Geneva, cross the Atlantic, and infiltrate the minds of congressmen and women—wrenching them awake from their wireless broadband industry induced stupor to the daylight reality of the power of over-the-air TV in 2015.

The disparate connection between opinions on the importance of broadcasting in Region 1 and Regions 2 and 3 could also allude to a concerning trend: global disharmony and the US as lone wolf.

The United States picks and chooses what to align with on the international consensus on spectrum policy, sometimes following, sometimes affirming, but leading less often than it historically has—and receiving more pushback on what it proposes when it does decide to lead.

America and the FCC wants to lead forcefully as an agent of global peace through power, and, critically, power through superior technology. Spectrum technologies, and spectrum regulation concepts originating in the United States are a small, but still real, component of our assertion of influence on the global stage.

But what was missing from the US broadcaster reaction of the consensus at WRC-15 was not that a consensus on preserving the UHF for broadcasting was reached. It was that the United States was not part of that consensus; the resulting agreement (which as I understand it does not have the binding authority of international law) was a fragmentation of member states on the allocation of the remaining UHF band, with the U.S. dragging Region 2 into the minority due to its hellbent quest to recover UHF spectrum via the incentive auctions—an ingenious but unproven mechanism planned by no other nation.

In preparation for WRC-15, US delegates issued this proposal in March, which I found through the NTIA:

Recognizing the growing need for mobile spectrum below 1 GHz, the current deployment and future development of broadcasting systems, and the differing national priorities of the member states as regards UHF broadcasting, it is necessary for WRC-15 to adopt a regulatory solution that would:

• Enable administrations to preserve and protect broadcasting and other services in the UHF range,
• Consider ways to facilitate the development of future broadcasting systems, and
• Allow administrations flexibility to address the mobile spectrum shortage consistent with their domestic requirements.

To achieve these objectives, the United States proposes modifications to the Radio Regulations that would add an allocation to the mobile services and identification for IMT in the range 470-694/698 MHz except for the 608-614 MHz band in Region 2. The United States also proposes retention of the primary allocation to the Broadcasting Service in the 470-890 MHz frequency range, including the mandatory application of No. 9.21, which would ensure that the existing services, such as broadcasting, maintain coordination priority (i.e., remain super-primary) vis-à-vis IMT systems.

Further…

Globally harmonized allocations to the mobile service in the 470-698 MHz frequency range would enable introduction of innovative broadband services while preserving access to spectrum for the existing services, such as broadcasting. A new allocation to the mobile service would provide administrations with the flexibility to maximize spectrum utilization.

As the EBU release makes clear, the rest of the world did not agree with the United States’ proposal that the UHF band should become new home to mobile broadband services. They rejected the proposal because terrestrial broadcasting in Europe, Asia, and Africa is important in ways that we, isolated by two oceans, and richer than any other country in the world, cannot fathom.

I think it’s important to recognize that that rejection by consensus does not by default mean the United States will follow suit in preserving the remaining licenses of OTA broadcasters between the commencement of the auctions next year and 2023.

To conclude, and in other words, we are not on the same page with the rest of the world when it comes to OTA broadcasting, and that means broadcasting (and wireless microphones) are still in immediate danger of disruption, even though we have traditionally led the world in efforts to “harmonize” allocations, as well as other issues that I am not as qualified to discuss.

Is that because United States policy is so far advanced beyond the ITU’s comprehension that it can it afford to dissent or contradict proposals from delegates from the other 192 ITU member states?

Or is it for some other more alarming, sinister, or dysfunctional reason that we blaze our own trail?—ahead, or behind.

RF Venue Releases VANTAGE: OS X Spectrum Scanning and Monitoring Software for RF Explorer

We usually refrain from talking about our own products on this blog, but occasionally we need to make an exception.

Last week, we released a long anticipated native Macintosh OS X spectrum analysis and frequency monitoring application for use with RF Explorer® portable spectrum analyzers as well as RF Venue’s rack-based RF Explorer® RackPRO, called VANTAGE.

Vantage is the first professional third-party RF Explorer interface and coordination program that was built exclusively for the Macintosh OS X environment.

“For years, RF Explorer spectrum analyzers have been cost-effective, accurate analysis tools used by countless audio professionals and radio enthusiasts,” our CEO Chris Regan said after launch last week. “They allow visualization of the radio spectrum at a superb price, and connecting them to a computer through USB lets you do some very powerful things.”

“As Mac users ourselves, we’ve shared our customers’ interest in a robust, but very easy-to-use native Mac application for our RackPRO as well as the larger RF Explorer family of spectrum analyzers. Vantage will enable even the most novice wireless operators to visualize, monitor, and manage their facility’s RF systems without any steep learning curve.”

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The new software was designed with reliability and speed in mind.

Vantage is composed of three core features – spectrum scanning, frequency monitoring, and CSV file exports of scan data.

Users can manipulate scan range and monitor frequencies on the fly, and easily run Vantage uninterrupted in the background while using other programs simultaneously.

The export feature generates CSV files compatible with Shure Wireless Workbench® (WWB) and Professional Wireless Systems’ Intermodulation Analysis System® (IAS), so audio professionals can improve their existing coordination workflows in WWB and IAS by augmenting them with wideband scan data from an RF Explorer in any frequency range.

Vantage is compatible with the entire range of RF Explorer models. Depending on which RF Explorer is connected, Vantage can scan frequencies as low as 15 MHz, to as high as 6.1 GHz – filling a critical need for wideband scanning of the entire UHF broadcast band (470-698 MHz), as well as wireless systems operating in VHF, 900 MHz, and 2.4 GHz.

“RF Venue is committed to developing for the Mac and is continuing work on the Vantage codebase,” Chris continued, “with new advanced features planned to launch in the near future. We’ll be making new features available to all Vantage users via application upgrades.”

Vantage is available to try for free for 14 days at http://www.rfvenue.com/vantage, and priced at $99 per license.

13 Simple Tools Under $100 That Seriously Improve Wireless Audio Performance

Improving your wireless microphone or in-ear monitor system doesn’t have to be expensive. There are a lot reasonably priced accessories that might actually be more effective at improving range and reception than upgrading to the most expensive model from your favorite manufacturer.

1. Yamaha Sound Reinforcement Handbook

PRICE: Free-$24.16

The first two items on the list are knowledge resource tools, not things. (“Give a man a fish,” and so on…)

In January I polled about a dozen leading live sound engineers and professors at the country’s leading audio education programs for their most recommended books on professional audio.

Yamaha’s Sound Reinforcement Handbook made or topped the list with almost everyone. It’s been released in a few editions over the years, and is sometimes referred to as “the bible” of live sound.

New copies are available from Amazon, and free copies of outdated editions can be found as PDFs on the web.

2. Pete Erskine’s RF Coordination for Roadies

PRICE: Free

Pete Erskine, along with other wireless consultants like James Stoffo and Steve Caldwell, was among the first to pioneer wireless audio frequency coordination that was reliable and scalable for large broadcast and special events.

Pete’s brief manual RF Coordination for Roadies (click here for the mobile friendly link) has taught an entire generation of RF techs how RF coordination for IMD and other best practices are done. I consider it required reading for anyone who uses more than one channel.

Pete uses Professional Wireless System’s IAS and a small list of other quality tools to explain his process, though there are other tools available for those on a budget (like the RF Explorer in combination with IAS, listed later in this post).

3. Multi-Meter

PRICE: $30-$100

A multi-meter is an indispensable tool for tracking down problems with cables, among other things.

We demonstrated how to use a multi-meter set up as an ohm-meter to check for electrical shorts in coaxial cabling in this video:

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If you master Ohms Law, you can also do other things with a multi-meter, like tracking down and fixing broken components.

Multi-meters are priced from budget to ridiculous, but even simple analog ones should be more than enough.

Consider the Rolls MU118 to cover the basics, or the Paladin 1543 for more advanced continuity testing.

4. Ferrite Beads/Cores

PRICE: $2-$4

Ferrite cores and/or beads filter radio frequency interference collected by a cable unintentionally acting as an antenna while allowing audio signal to pass through. They are extremely useful for keeping out unwanted “cellphone buzz” as well as other kinds of mysterious interference. Some techs use them on every single input for complete protection from cable ingress. And at the price, why not?

I wrote an entire post on using ferrite cores to fight interference, and where to buy them, here.

5. WiFi Explorer

PRICE: $14.99

WiFi is more important to the audio pro than ever, and there are lots of new models of 2.4 GHz microphones that use the same spectrum bands as most WiFi. You can stumble around trying to get a signal for your board control or mic, or, you can use WiFi Explorer to know exactly what is going on, and what signal belongs to what router/WAP.

I learned about WiFi Explorer from Justin McClellan of Communication Handled. He posted on social about the importance of WiFi diagnostic tools, so I’ll let him explain it:

“Being an audio tech has now forced us to also learn some networking. Along with the hardwired networks we also have to deal with crowded venues when using wireless network systems to monitor and control gear.”

6. Brand-Name Batteries

PRICE: $0.65-$3 for AAs, each

There is probably some debate on this subject, and I think each individual has his or her own ritual when it comes to batteries. Namely, how to make absolutely sure that they don’t go dead while a mic is on stage.

But what can’t be debated is that brand-name batteries, on average, maintain their minimum voltage for longer periods of time than budget or generic batteries, and are also less likely to leak electrolytes or, when lithium is involved, explode.

Rhett Allain at Wired did an experiment on the differences between name-brand and off-brand batteries and their ability to hold a charge over time, and I defer to his results.

If your average on-stage time is less than one or two hours, and you (as many techs do) replace the batteries every single time that mic goes up on stage, and you have the money, and done the economics, maybe brand-name batteries don’t make sense for you.

Then again, why take the risk?

A good source for disposable and rechargable brand-name batteries that have been field tested for maximum life is Gotham Sound.

7. Bandpass Filters

PRICE: $30-$300

The (superb) performance of Anatech #AE548B9620 548 MHz bandpass filter.

Bandpass filters are external filters attached after the antenna but before the antenna input on a distributor or mic receiver’s front end, and strongly attenuate interference above and below a low and high frequency, which is called the “pass band.”

Adding a bandpass filter performs miracles when operating in crowded spectrum, or when a spectrum analyzer reveals strong interference very close to, but not on, the tuned frequency of a receiver.

Receiver’s have built in “tracking filters,” which are integrated circuits (microchips), that create a bandpass filter around whatever frequency you tune to. These tracking filters aren’t particularly good though, and they often aren’t narrow enough, or don’t have large enough attenuation to keep out-of-band interference from leaking into front-ends when that interference is really strong.

If you want to pack a large number of channels into a small amount of spectrum that is extremely crowded, supplementary filtration is about the only way to do it—though you really need to know what you’re doing.

Bandpass filters can also be used by less experienced users operating smaller systems as an extra layer of protection from nearby sources of interference of any type.

(the links to products are in this list, I just haven’t set up the formatting so you can see them yet! (apologies) Hover over the all caps words for the links.)

• Mini-Circuits Surface-Mount Bandpass Filters: $30-$50
  They’ve got the cheapest UHF band filters out there, starting at $30. Unfortunately their selection isn’t all that large, and none of the UHF stuff I could find was fitted with connectors, so using them is only possible for fixed applications, and you’ll need to know some electronics. Order HERE.
• Microwave Filter Co., 3278 Series Factory Tuned DTV-UHF Bandpass Cavity Filters: $215-$300.
  I know! More than $100, sorry. But these are really great. An EXCELLENT SERIES OF FILTERS that filter out everything outside of one DTV station—that is, everything around any 6 MHz UHF DTV channel is filtered out. You specify which station you want to filter when you order, and if you have a screwdriver and a spectrum analyzer with tracking generator, you can retune these babies to whatever 6 MHz pass-band you want.
• Anatech LC Bandpass Filters, 60 MHz Passband: $289-$355
  Anatech has AN AWESOME SELECTION OF CONNECTORIZED FILTERS with all sorts of passbands. They are a bit pricey because each one is made to order. JAMES STOFFO recommends the ones with 60 MHz passbands, which by mixing and matching let you get pretty close to aligning with the frequency bands of popular wireless manufacturer factory ranges.
• Professional Wireless Systems Custom Range Filter: $375
  I don’t care how far above $100 this is. PWS will custom tune AN AMAZING FILTER for you to whatever range you need. Unlike the other three companies mentioned above, PWS only makes products for wireless audio and, thus, has superb customer support and will always know what you’re talking about.

8. Blackwrap

PRICE: $25

Blackwrap (used by the lighting department, usually), or thick black aluminum foil, can be used to control troublesome radio frequency electromagnetic waves that cause interference by creating a radio wave “cage” around the offending device.

I wrote at length about how to use blackwrap to control RFI from video walls here, but it can be used to contain interference from any electronic device (circuit breaker, power supplies, etc) if you know where that naughty device is located.

9. BNC Coaxial Cable Termination Kit

PRICE: $85

Ever wanted to make you own custom length coax cables? Or salvage the good parts of a long length of coax that has one crushed portion or hole without throwing the whole thing away?

With this cable termination kit, now you can. Loosely follow these instructions, (your workflow will vary slightly if you use all the tools we suggest) and here’s what you’ll need:

(the links to products are in this list, I just haven’t set up the formatting so you can see them yet! (apologies) Hover over the all caps words for the links.)

• Stripper: To remove both insulation and dialectic to expose the center conductor (THIS is the same stripper we use to build RF Venue cables, it strips instantly, instead of taking 10-30 seconds. Highly recommended)
• Clippers or scissors: You may need to cut back the braided shield after you strip if the shield is too long for the ferrule. There are SPECIAL, INEXPENSIVE CLIPPERS available, but the wire on the braid is so thin an old pair of scissors work if you only plan on terminating a few, and don’t mind damage to your scissors.
• Crimper: THIS is a good budget crimper. The crimper we use to build RF Venue cables is THIS ONE.
• BNC Connectors: The actual connectors required for use with industry standard RG8X are 50 OHM MALE CRIMP-ON BNC.

10. ZAPD-1+

PRICE: $60

The Mini-Circuits ZAPD-1+ is an extremely versatile and low-cost RF distribution accessory that can be used to do all sorts of things. In fact, I wrote an entire post on all the cool things you can do with the ZAPD-1+.

11. RF Explorer

PRICE: $99-$300

Although the most popular (and recommended) model is $139, a tad over $100, the RF Explorer is just about the least expensive wide-band spectrum analyzer you can get. Depending on which model you purchase, it can scan as low as 15 MHz to as high as 6.1 GHz. You can use it to visualize spectrum all by itself, or plug it into a computer to do more powerful analysis and monitoring.

For PC users, you can use the RF Explorer Client or Clear Waves. For Mac OS X users, there is Vantage.

12. Connector Weatherproofing Kit

PRICE: $40

A grassroots attempt at weatherproofing a WiFi router using silicone, courtesy “Binary Koala”.

Most external wireless audio antennas are not designed to live outside, so it’s very important that if you do use antennas outside you weatherize them and, more importantly, the connectors and coaxial cable connecting the antenna so that moisture doesn’t seep into the cable or device.

Just a few drops of water inside a cable or connector can significantly alter the electrical characteristics and signal loss of an antenna and cable run.

If the antenna has an enclosure that covers the metal elements, you’ll want to seal every last open seam, hole, and juncture with silicone. Make sure to rub down these places with alcohol before applying the silicone for perfect adhesion.

Then, you’ll want to use heat shrink tubing combined with silicone to wrap up the connectors to make absolutely sure it’s completely impossible for water to get in.

(the links to products are in this list, I just haven’t set up the formatting so you can see them yet! (apologies) Hover over the all caps words for the links.)

• SILICONE
• HEAT SHRINK TUBING
• HEAT GUN FOR HEAT SHRINK

You can also protect antennas underneath an acrylic dome, although the domes are more expensive than aforementioned weatherization kit.

13. Fixed Attenuators

PRICE: $15-$50

Fixed attenuators weaken (attenuate) RF signal traveling through coaxial cable.

Why would you want to to weaken instead of strengthen signal?

First, to avoid overload on the front-end of wireless microphone receivers. Mic receivers are sensitive, and it’s easy for front-ends to encounter too much signal—like when a transmitter gets too close or when in-line amps are misused.

Second, a trick we learned from James Stoffo to alter signal-to-noise ratio on gigs where interference from video walls is problematic. Read about it here.

Want better wireless? Download our eBook on three essential concepts for correctly deploying and maintaining interference-free wireless audio systems.

How Adding an External Antenna Can Actually Make Wireless Problems Worse

External antennas are an incredibly effective tool for solving interference and dropout problems of all kinds.

But, it is possible to use an external antenna incorrectly in a way that increases problems instead of making them better, or use them in situations where their benefits are either unwarranted or inappropriate.

Amplification of Interfering Signals

When a stock whip/dipole antenna is replaced with an external antenna, and that antenna stays in the booth or FOH, performance improvements come mostly (but not entirely) from an increase in directional gain.

Directional coverage pattern of the 9 dBd CP Beam.

Directional gain is usually good, because of the effective amplification of signals in front of a directional antenna, but directional gain increases the signal strength of all signals within the antenna’s coverage pattern, not just yours.

Most external antennas are “directional” antennas—in that they have increased sensitivity to radio waves in one direction, and decreased sensitivity (rejection) in others.

A reference dipole antenna has a gain of 2.15 dB. A directional LPDA (aka paddle or shark fin) might have a gain of 4-7 dBd, and helical antennas are available with gains as much as 12 dBd.

High gain antennas increase the effective signal strength by increasing the density of radio energy in certain directions, similar to the way a lens or telescope focuses light into a small space (thereby increasing the apparent brightness to an observer) without increasing the amplitude of the source of the light itself.

Adding a directional antenna at the booth and pointing it at the stage usually makes things better because a directional antenna is “focusing” in on the transmitters on the stage and delivering a stronger signal of those transmitter signals to the receivers.

CP Beam helical antennas backstage, courtesy RMB Audio.

However, antennas aren’t intelligent. Antennas can’t differentiate your signal from someone else’s or a source of interference. If a source of interference (like a DTV station or noisy LED panel) falls in the same direction as the transmitter you want to pick up, the noise will be amplified just as much as the signal.

LED panels and TV stations are the most common culprits in this scenario, but unintentional interference can come from nearly any electronic device, and if another intentionally radiating device, like an intercom or microphone from a roaming news crew wanders into the coverage pattern of your directional antenna which were previously being attenuated, buckle up.

Transmit Antenna Contaminating Receive Antenna

In a rack, IEM transmitters often live right next to wireless microphone receivers. Letting IEMs and mics share a rack while using stock whips/dipoles can result in disastrous wireless because the IEMs are spitting out lots of RF while the mic receivers are trying to listen for very low amplitude RF coming from the stage. Cramped together in a metal cabinet is not the best place for the two species of device to live.

A solution is to separate IEMs and mics into different racks spaced a good distance apart, paired with both antenna combiners and distributors (great refresher at this link if these terms are confusing to you), each with their own separate antenna.

A transmit and receive antenna (CP Beam and Diversity Fin) deployed in Times Square, pointed in opposite directions, and offset horizontally, to avoid contamination.

Sometimes, techs might not separate mics and IEMs into separate racks, but know enough about RF to get rid of stock whips and feed the rack’s combiner outputs into an active signal/antenna combiner and the receiver outputs into an amplified antenna distributor. Unfortunately, if you place the external mic receive antenna and IEM transmit external antennas too close to one another, the comparatively high amplitude RF emitted from the IEM transmit antenna can easily bleed into the mics’ receive antenna, which is looking for very weak signals and may end up picking up or being overwhelmed by the IEMs instead.

We always advise our customers to place transmit and receive antennas at least 10 feet apart, minimum, to avoid unintentional interference between IEMs and mics, and never point the two directly at one another, no matter how far apart they are.

Improperly Deployed or Broken Cabling or Connectors

If you’re using an external antenna, you’re also using coaxial cable to connect that antenna to the receiver or antenna distributor.

There are more links in the signal chain, and therefore more links where mistakes can be made or equipment can malfunction.

When trouble occurs, cables and connectors are usually the last things to get inspected, when they should be the first!

Coaxial cable is fragile and easily damaged. The damage can occur inside the cable, or just as commonly at the BNC or SMA connectors terminating the cable on either side. If you have the resources, always check your cable to make sure they are transmitting RF signal properly.

I don’t have enough fingers on my hands to count the number of times we’ve tracked what a customer thought was a “bad antenna” to a severely damaged cable or missing center pin.

Long cable runs can also cause dropouts by reducing signal strength through in-line attenuation. The longer the cable run, the more in-line attenuation you get. Industry standard RG8X steals about 1 dB per 10 feet. 200 feet of RG8X reduces signal strength by about 20 dB (a lot). Even if you have a directional antenna attached to the front of that 200 foot run with 7 dB of gain, you’re still down 13 dB at the receiver, which can increase the likelihood of dropouts.

Active Antennas on Short Cable Runs

So called “active” antennas do not increase received signal strength at the antenna. Active antennas are just passive antennas with in-line amplifiers on the back.

They are not, should not, be used to “pick up more signal” because that’s not what they do. Rather, active antennas boost the amplitude of the signal gathered by the antenna in front of it to compensate for long, lossy feedlines. Much more on this common misconception here.

Active antennas can be very useful when cable runs longer than about 100 feet are in use, but when active antennas are used with short cable runs the signal delivered to the rack can easily be too strong, overwhelming the sensitive front-end of receivers and causing audible distortion or noise.

We frequently get calls from small venues, churches, and events where FOH or the rack position is near to the stage, and an active paddle is mounted on a small stand on top of the rack and connected to receivers with a 5 foot shorty—the perfect recipe for RF overload and ensuing screeching and hissing over the PA.

Want better wireless? Download our eBook on three essential concepts for correctly deploying and maintaining interference-free wireless audio systems.

At INBOUND15, Our Two Worlds Collide

A strange thing happened two weeks ago.

Hubspot, the web product we use to manage our marketing analytics and CRM (customer relationship management), held a convention called INBOUND in Boston, as they do every year.

INBOUND was a large, world class corporate conference. 14,000 people attended. There were dozens of intriguing panels and talks. Headline speakers included Aziz Ansari, Amy Schumer, and Todd Rowe of Google, among many, many others. The scenic design of the show and conference hall was superb, as was the A/V design and services.

What’s strange about that?

Well, once we got to the conference we realized we knew a lot of the people working backstage—literally behind the big “INBOUND” letters perched up on stage in Hall B—the people that make the show go off without a hitch.

For us, INBOUND15 was far more than a conference. It was living proof that our customer outreach and marketing using the Hubspot platform is working, and a great chance to see our products in action. All of the wireless microphones used by the keynote speakers were sent through a pair of our CP Beams, a special type of antenna we manufacture called a circularly polarized helical.

Here is one of those CP Beams backstage, to the right of the display.

And up close…

We thought it would be cool to write an overview for two audiences of the INBOUND15 conference from the perspective of the production of the live event.

The first audience, our audience, contains live sound professionals, A/V integrators, and other audio nerds who use RF Venue wireless antennas and distribution accessories everyday, but might like a glimpse behind the scenes at a corporate event of this caliber and scale.

The second, fellow users of the Hubspot marketing platform who attended the events and keynotes in Hall B (the main, big hall), who were dazzled by the lights and colors and flying cameras, and have marginal curiosity in how all that stuff works.

As we have discussed at great (great) length before, the days of stuffy, boring corporate events are a thing of the past. Gone are the shaky spotlights, the screeching microphones. The popup tables with scorched coffee and stale bagels? Nowhere to be found.

Because of flush stakeholders (in this case, the awesome and successful company Hubspot), and the power of live events as marketing and community building machines, the resources and technical expertise poured into today’s corporate events equal or exceed those of even the glitziest music concert or special event.

INBOUND15 was no exception.

Most corporate events outsource the pre-show design work—scenic design, booths, kiosks, animation and other audiovisual content—many months before the event begins. This design work is accomplished by many different design companies and freelancers. Most of the design work in Hall B was done by CG Creative.

Then, the design work is handed off to production companies, subcontractors, and freelancers, who actually bring in cameras, speakers, microphones, projectors, and lots of other cool things to put the designs to work.

At INBOUND15 there were two main areas where production companies worked: the Expo Floor and “Club Inbound,” and the General Session room (Hall B) where all Keynotes and Spotlight Breakouts were done. Freeman Audio Visual was responsible for the A/V support and equipment on the Expo Floor, and they brought in Alford Media, a Texas based veteran event technology support company, for the General Session room.

Alford’s team arrived at the Boston Convention Center many days before the start of the event to begin the grueling process of “load-in,” which is when all of the equipment, carefully packaged in large, black, rugged flight cases, is unloaded from semi-trucks and “loaded in” to the venue.

Time is often short, so there is what appears to be (but is not) complete chaos, as supervisors and stage managers shout at people to put this case here, that case there. Technicians unfurl miles and miles of fiber optic, power, and coaxial cable where it needs to go.

Then, technicians begin assembling and testing the equipment. Cameras get powered up, cranes start flying, audio fader programmed, wireless microphone frequencies are coordinated and, these days, much of it is intelligently networked together via fiber optic or CAT-5 (ethernet) cable.

The stage manager will then typically begin blocking talent or stand-in talent to focus the lights and do tech rehearsals to make sure everything works.

We, RF Venue, work most closely with the second group, the people who actually put on the production, because our products are used to improve the reliability of wireless audio equipment.

Within that second group there are roughly three divisions: audio, video, and lighting. Each of the divisions sets up a “village” out of flights cases somewhere backstage. At INBOUND15, Audio Village, Video Village, and Lighting Village were behind the cyc (short for cyclorama, the big piece of fabric that was stretched across the stage). Here’s Audio Village:

and Video Village:

There is also a mixing console and control station located in the middle of the audience, called Front of House (FOH for short). The picture leading this article was taken from FOH by Allison McMahan, Communications Administrator at Alford Media.

I spent a number of hours backstage with the Alford crew during and in-between keynote speakers, and with our customer and friend, Justin McClellan of Communication Handled, who was responsible for all of the wired and wireless intercoms, monitoring wireless audio frequencies, as well as some video tasks that I don’t fully understand.

Here is Justin at work:

Pretty cool, right?

Here you can see the wired communications rack where Justin controls audio communications between crew members and security. In this case a Riedel ARTIST Digital Matrix Intercom was in use.

The entire audio team consisted of Audio Engineer Steve Ellis, Communications/RF Technician Justin McClellan, Audio Monitor Engineer Ryan Sartel, and Audio-Video Recording Tech Andrew McIntire. The FOH engineer was Steven Pollema, from CG Creative.

Here’s Steve, Justin, and Ryan.

I often compare live event productions to baseball. There are long stretches of extreme boredom punctuated by intense moments of fear and scrambling when something goes wrong or the crew needs to move fast to stop something bad from happening. The stretches of non-activity are especially grueling on corporate shows which go on, literally, for days.

But don’t mistake the nonchalant demeanor of the techs during these stretches for lack of skill or attention. What they do is really, really hard, and they are always paying attention, even if it doesn’t look like it.

Above is an image of the “video flow” chart put together on a dime by the video department. It was dark back there, so I didn’t get the best photograph, but this gives you a taste of the skill it takes to pull off an event like INBOUND.

Modern show technology skills are a mashup of old school hand-me-down knowledge, electrical engineering, IT networking, fine craftsmanship, and the herding of cats.

There are a lot of people who can do it, but very few who can do it well. Alford, Freeman, and CG are among the small number of elite companies that do it well, and that’s why they get booked again and again for corporate events of this caliber.

Now, let’s get into the nitty gritty tech details of the audio equipment used at the show.

Alford was using a new technology at the proof-of-concept stage from Riedel called MEDIORNET, that allows any type of signal—audio, video, lighting controls, communications—to be converted into and passed through fiber-optic cable, simplifying signal distribution and lowering the quantity and types of cables required for a show.

There were five Martin line arrays (big, tall speakers) each consisting of nine MLAs and one MLD. Additional Martin speakers included 80 MLA compacts, 12 DD6s, 32 DSX Sub-bass boxes, and 16 MLA Minis.

That’s a lot of speaker.

The FOH console was a Digico SD5. The monitor console was a Digico SD11.

There were 24 channels of Shure UHF-R (which were using our CP Beam antennas), a few in-ear monitors from Sennheiser for the opening musical act, Riedel ARTIST wired comms, and two racks of Radio Active Designs UV-1G for wireless comms.

This was a big show with a lot of very cool, expensive toys to drool over. We had a blast both at INBOUND15 and hanging out backstage with Alford Media, Communication Handled, and the other contractors and freelancers involved.

Until next year!

Special thanks to Allison McMahan and Alford Media Services for some of the photographs used in this article, including the leading FOH image.

HeadsetGate Is Not a Conspiracy, and We Can Prove It

We know a thing or two about how wireless headsets used by the NFL work. We also actually know the technicians who are responsible for operating wireless intercoms (as they are more formally known) and other equipment during NFL games.

And we gave these people a call—though none would speak on the record, we got to the bottom of what actually happened last night.

Based on the evidence we’ve gathered, we are almost positive that the radio broadcast signal from the Patriot’s Official radio station, “The Sports Hub” on 98.5 MHz, heard in Steelers’ headsets, was caused by an unintentional electrical malfunction, rather than deliberate sabotage.

[Thoughts? Scroll down all the way to the bottom for Disqus comments.]

Let’s first debunk why it is almost impossible for the Patriots to have intentionally interfered with the Steelers’ on-field intercom system by signal jamming using airborne radio waves.

• The wireless intercoms in use by the NFL use UHF band frequencies, not broadcast band FM. A common misconception that seems to live mostly on twitter is that the Patriots were jamming the Steelers’ coach intercoms by broadcasting The Sports Hub feed over the airwaves through the stadium in some unusual way. The Sports Hub is broadcast on 98.5 MHz. Coach and player intercoms use frequencies between 470-900 MHz. To jam in the traditional and crudest capacity you need to broadcast on the exact same frequency at a higher power than the jammed frequency, not on a frequency many hundreds of megahertz apart. It is technically possible to patch an audio feed into a UHF transmitter and rebroadcast on UHF frequencies for the purposes of jamming, but…
• The intercoms in use by coaches are encrypted. In order for the Steelers to hear an audio feed of the sports broadcast, somebody would have had to have cracked the encryption as well as use the correct frequency in order to spoof the coaches’ beltpack receivers into demodulating the rogue signal as legitimate audio, as well as being transmitted at a higher power than the opponent’s base-station. Furthermore, that audio would replace the coach communications, not appear as another, second, mixed in signal. The Steelers reported hearing The Sports Hub on top of their internal communications, which strongly points to the Sports Hub Signal entering the signal chain far, far “upstream” as we call it, from the beltpack radio receiver, prior to both radio modulation stage (the transformation of audio signal into airborne radio waves carrying audio intelligence) and encryption stage.
• Intentional RF jamming in the absence of the encryption key would manifest as incoherent noise or dropouts. Can we be any clearer on this? The Steelers did not report noise or dropouts, only a broadcast audio stream.
• Any intentional jamming using radio waves would immediately be detected, located, and stopped by the stadium Game Day Coordinator. At every single NFL game, there is a highly trained member of the Society of Broadcast Engineers called a Game Day Coordinator present who controls and closely monitors every single radio frequency signal in the stadium using software and spectrum analyzers. Monitoring team radio signals for sabotage and surveillance is the reason the Game Day Coordination program was created in the first place. We’ve talked to the head of the GDC Program, Karl Voss, at length about the GDC program before (http://blog.rfvenue.com/karl-voss/). A malicious radio jammer could fire up a jamming device, sure, or broadcast on a specific frequency at high power, or even broadcast on a specific frequency with the right encryption key, but all of this activity would never, ever escape the all seeing eye of the Game Day Coordinator, because the jamming would either be broadband (occur across a wide range of frequencies), be frequency agile (occurring intermittently across a wide range of frequencies), or reveal itself through high power, since successful jamming requires the jammer to overpower the received signal strength of the jammed party.

So, what really happened?

The NFL official statement is this:

”In the first quarter of tonight’s game, the Pittsburgh coaches experienced interference in their headsets caused by a stadium power infrastructure issue, which was exacerbated by the inclement weather… The coaches’ communications equipment, including the headsets, is provided by the NFL for both clubs use on game day. Once the power issue was addressed, the equipment functioned properly with no additional issues.”

The NFL’s statement is correct.

Some possible explanations

A poorly grounded audio or power cable in the wired portion of the intercom system that lives in the coaches’ booth, and connects to the wireless cart on the field, acted as an antenna (anything made from metal can be an antenna), and picked up The Sports Hub radio network. The Sports Hub has its own transmitter inside Gillette stadium, so the received power levels are unusually high. The shielding on a poorly grounded cable received the Sports Hub radio wave signal, and introduced it into the audio circuit in one of many different places—we don’t know exactly where (the coaches’ booth is a best guess). It is much more likely that this is the explanation if the Sports Hub broadcast inside Gillette Stadium is AM instead of FM.

The Steelers reported “intermittent” interference most likely because at the time of the game it was raining, and rain easily compounds grounding problems and makes them less predictable.

As to their report that the interference “strangely” disappeared once they walked over to the Patriots’ sideline to confront, that could very well be a coincidence, or the emotions of the person working for the Steeler’s who wrote the report getting in the way of an objective view of the situation.

The wired intercom system is connected to a number of different systems. There are hundreds, possibly thousands of possible roads of ingress for the interfering signal—mixing consoles, jacks, comm controllers—and a plugged or wired cable carrying the Sports Hub signal could have accidentally been introduced at any of these, though tracking down which one is almost impossible.

Back to the NFL’s statement. When we hear the word “infrastructure,” we think of large buildings, high voltage power lines, and lightning rods.

That is not the type of infrastructure the NFL is referring to. What they mean by “infrastructure” is the complex, low-voltage communications system, and its many power supplies, that is set up at each and every NFL stadium to provide coaches and players with secure, reliable communications, both wireless and wired.

Let’s talk about the building blocks of every NFL stadium’s intercom system, which few seem to understand.

Kevin Seifert at NFL Nation said:

The NFL and its corporate sponsors, primarily Bose and Microsoft, provide the hardware and other equipment necessary to maintain communications for both systems.

Wrong.

Bose and Microsoft have almost nothing to do with on and off-field communications. Bose simply supplies the noise-canceling headsets (the microphone and headphone) that plug into the radio transceivers, and Microsoft, as far as we can tell, pays to supply the branded carts that the intercom systems ride inside, and nothing else.

The real wireless intercom system is provided by a small company called Telex, now owned by RTS.

The NFL uses heavily modified, custom built Telex BTR-1 systems for the cart to coach and player wireless links.

These carts sit on the sidelines of both home and away teams and are filled with “intercom base-stations”: the devices that receive and retransmit wireless signals received from radio intercom transceivers worn by coaches and built into player helmets.

These Telex systems are so special they have a special name known only to those who use them: “Lombardi Systems,” and if you have ever watched professional football, you’ve seen them with your own eyes.

We’re not stupid enough to put up a screen grab of NFL network footage showing one of these carts, but luckily, we have in our archives a photograph of a cart taken by Jeff Watson that contained a newer type of intercom system, the RAD UV-1G, that was used for portions of the Super Bowl and Pro Bowl.

These carts are prime real estate and appear in multiple camera shots, so they are covered in the corporate marks of whatever company paid the most to place them there, but the guts (surprise!) aren’t filled with Microsoft Surface tablets. This is not a Lombardi System, but under ordinary circumstances, and at last night’s game at Gillette, it was.

Most of the mainstream media has focused on the wireless link between Lombardi cart and coaches + players. But Lombardi carts are connected (trunked) to wired intercoms running into the stadium and up to the coaches’ booth. This allows coaches to communicate with coaches and players down on the field, and vice versa. They can push a button and talk to one person, or everyone.

The wireless infrastructure is essentially bulletproof to the type of interference the Steelers heard yesterday.

The wired infrastructure? Not so much.

Both coaches’ booths are required to have at least six intercom jacks (where a headset can be plugged into). The booths are also outfitted with wired intercom main-stations (that route signal here and there and let a controller speak to one or many people on command). The jacks and main-stations are connected to dedicated power supplies, and the main-station is also connected to the NFL control booth.

More formally, these types of wired intercoms are known as “two-wire party lines.” [Edit, I’m unclear as to whether the NFL uses party-line only, or party-line/matrix hybrids, probably the latter.]

We have been told by anonymous sources that the electrical grounding procedures on all two-wire comms is dangerously out of date due to something called the Pin 1 Problem.

An audio or high quality power cable is usually shielded—an inner conductor carrying signal is covered in aluminum or copper that protects the conductor and signal from RFI (radio frequency interference).

The shield is always conducting ambient radio waves and turning them into electrical waveforms, but once the cable reaches the device, the RF energy that is in the shield is directed away from the audio circuit: that it is “electrically grounded.”

Pin 1 (the audio cable shielding) should be directly connected to the chassis so any RF signal running through the shielding is diffused through the chassis rather than injected into the audio circuit.

Unfortunately, on most of the wired intercom jacks and main-stations used by the NFL, modern grounding procedures (“infrastructure”) are not used, and occasionally cable shielding can conduct RF and make it into the audio stream.

The RF signal (in this case, The Sports Hub Signal) may have infiltrated the signal chain before the encryption or RF modulation stages in the transceivers on the Lombardi (which is quite secure from jamming).

It should be said the wired intercom system is connected to a number of different systems. There are hundreds, possibly thousands of possible roads of ingress for the interfering signal—mixing consoles, jacks, comm controllers—and a plugged or wired cable carrying the Sports Hub signal could have accidentally been introduced at any of these by a mistake of installation or human operator error—we’re not just talking about accidental ingress and demodulation of an RF signal here anymore, an actual patch into a board or crossed wires are also somewhat possible.

Grounding on two-wire intercoms usually works OK, most of the time, but shabby installation, and rain, can make things worse.

To complicate matters, because the wired intercoms are party-lines, and they are connected to the Lombardis, there is no telling where, exactly, the interference is bleeding through, unless you tear down the system, cable by cable at every jack, main-station, base-station, and power supply.

What about that “almost”?

Earlier we said we were “almost” sure that the interference was accidental.

There are still a lot of people on twitter who think this is a conspiracy, so we’ll concede that it is possible that the Patriots were able to intentionally tamper with the Steelers’ comm system and produce the type of interference observed. The home team is responsible for installing and maintaining the wired comms infrastructure, after all.

We aren’t going to explain how this would be done, because we don’t want to give out instructions on how to sabotage a comm system to all the naughty coaches out there reading this post. NFL style intercoms are used at high school and college stadiums across the country, too.

But we will say that, although theoretically possible, such tampering would require a lot of people, leave behind a lot obvious physical clues, and probably include an inside man or “mole” planted on the comm controllers or consoles of the Steelers.

In other words, even if you were able to get away with it for a game or two, it would never hold up to the scrutiny of a formal NFL review, which the Steelers, Patriots, and NFL all agree is not being pursued.

Less than 24 hours after the beginning of “HeadsetGate,” HeadsetGate is over.

For the time being, football fans will have to look elsewhere for evidence of the foul play that (maybe) explains the Patriots’ success.

Please address editorial and other enquiries to info@rfvenue.com

Leading image courtesy “Art01582”

The Tradeoff: Higher Gain Antenna, Narrower Beam-Width

One of the tradeoffs with high gain antennas is that the higher the gain, the narrower the beam of coverage. This is usually a good thing—but not always.

For example, the CP Beam has a gain of 9 dBd, creating a beam-width of 43°. This narrow beam width is exactly what you want if the antenna is positioned a reasonable distance away from the microphones or belt packs on stage (say, at FOH, or in the wings in monitor world). It provides increased range and reception by focusing more of the RF energy into that area. It also attenuates signals that fall outside of the beam, allowing you to strategically place helical and other high gain antennas and point them away from interference sources, like LED walls, and towards the signal of interest.

However, if a high gain antenna is placed in close proximity to talent using or wearing a wireless microphone or beltpack, the talent could move outside of the coverage area of the antenna, causing a dropout.

The CP Beam, actually, is not that directional, if you include the entire field of antenna design, and the polar plot above shows that it will still receive energy 360° around the element, but in differing amounts. In front of the element the CP Beam will increase the apparent signal strength of a signal, to the sides, it will moderately attenuate the signal.

There are antenna designs that have much sharper—nearly complete—rejection of off-axis signals, but we very rarely see these types of antennas in pro audio. The following polar plots show the extreme rejection of various types of “end-fire array” antennas.

End-fire array antenna patterns, the image of which mysteriously appears on WikiMedia with no author to attribute. The left most point of each of these patterns (where you see the small bouquet of smaller lobes, would be located at the center of the polar plots above. Now THAT’s rejection.*

The point is that antenna coverage patterns and (if specified) beam widths should be considered when setting up a system to ensure the antenna allows sufficient coverage for the movement of talent in a given space, especially if there is poor signal-to-noise ratio—which would, were the talent to wander off of the main axis of an antenna like the CP Beam, increase the chances of dropout.

An Omnidirectional Antenna with High Antenna Gain is Impossible to Construct

Lot’s of people want to have their cake, and eat it too. Which is why we’re writing this post, to clear up the misunderstanding; Many want an antenna that will focus RF energy equally in all directions—i.e. a high gain omnidirectional antenna that will provide higher gain and longer range in all directions.

This simply isn’t possible.

That higher gain antennas have narrower beam-widths is a function of physical laws. Engineers have been able to figure out some impressive and acrobatic designs for antennas that shape radio waves in incredible ways, but so far they have been unable to dupe the simple reality that if an antenna focuses RF more strongly in one direction, it will be less strong in another.

There are a number of omni-directional antennas on the market that claim to improve reception while providing an omni-directional coverage pattern. That is, they promise a single antenna will increase signal strength, and therefore increase range equally in all directions. These antennas are usually dipole antennas mounted in a housing that allows remote placement, but are otherwise no different than stock dipoles that ship with receivers.

Sometimes, these antennas are combined with integrated amplifiers and marketed as “high gain omni-directional antennas.” Such language is misleading because as we’ve learned, omni-directional antennas must, if you are using the correct mathematical definition of antenna gain, have low directional gain.

You can have an exceptionally well constructed and electrically efficient antenna with an omnidirectional pattern that may very well increase range, but it is not increasing range through directional gain, but rather in its ability to collect a greater percentage of available RF energy from the environment. For example, a half-wave dipole will probably collect more energy than a quarter wave whip (monopole) antenna that might be used as a lower cost stock antenna on some receivers.

You can also have a high gain antenna that radiates more strongly across one horizontal or vertical plane in degrees of one axis (elevation angles), but not others.

An example of a radiation pattern of a horizontally omnidirectional antenna
but still not truly (spherically) omnidirectional.

These are sometimes called “high gain omni-directional antennas,” and here the use of that term is more appropriate, but not truly omni-directional; the coverage area is like a horizontal pancake, or wheel, rather than an omni-directional sphere. (which, by the way, does not exist. Even the most evenly radiating dipole antenna still has two nulls located at the top and bottom of the element.)

Still, a lot of people want the best of both worlds. They want an antenna that will increase range while allowing their talent to roam wherever they please. That is in part why the Diversity Fin antenna, although not a single antenna, was designed and is now popular. It is effectively able to provide both directional and omni-directional coverage by combining two antenna elements on the same board, and the diversity receiver votes between which antenna has the best signal.

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Leading image courtesy Seth Sawyers.