TC Furlong

by Scott Helmke

This blog post is the fourth entry in an ongoing series all about wireless systems – background info, best practices, and useful tips & tricks. Click here to get caught up on the previous articles.

This is the fourth blog article in our wireless series. In the previous article I wrote about actually finding (or more often, predicting) good frequencies for wireless microphones and other wireless audio devices using simple built-in features. This article will be about using standalone frequency coordination software.

There’s a saying that goes something like “Marconi invented interference when he built his second transmitter”. We can’t really confirm that, but there’s a lot of truth to the saying. And I would imagine that like every other successful inventor he had to come up with a solution, possibly one that Tesla had already found, but that’s a different topic altogether.

What Do Frequency Coordination Softwares Do?

Wireless systems manufacturers have been providing some type of system for dealing with multiple channels for many years now. While it’s straightforward to calculate intermod frequencies and generate lists of safe frequencies, it’s only been in recent years that the average audio tech has had access to enough computing power to actually do it themselves for large systems. And today we have several choices in standalone software to help coordinate large groups of wireless systems.

These software applications do roughly the same thing. You enter your location (usually just a postal code), and you enter information about the wireless systems you want to use. For instance, you might have six channels of Shure ULXD in the G50 band, along with four channels of Sennheiser Evolution IEM in the A band. The software uses your location to figure out which TV channels to avoid, based on FCC databases of TV broadcasters. The software then calculates frequencies for all the gear that you have entered. There may also be remote control of attached wireless gear, including the ability to use attached receivers to scan the local RF spectrum instead of relying on downloaded information.

Which Frequency Coordination Software Should I Use?

The first really modern software application dedicated to coordinating large event wireless is Intermod Analysis System (IAS) from Professional Wireless. This software downloads FCC data on TV stations and includes a large database of wireless products from different manufacturers. It’s not cheap, being about $550 for the professional version. But for years it was the only solution available for coordinating large wireless systems, and it has been a mainstay in the professional event world.

The main competition to IAS is Shure’s Wireless Workbench (WWB). This software started as a tool for coordinating and controlling only Shure wireless products, originally the UHF product line which had an early system for networking receivers together. As Shure has developed more and more products with modern networking they’ve continued to update the software, and within the past few years Shure added other manufacturers’ products to the coordination database. With the most recent versions of WWB it is possible to coordinate large events spread over multiple stages, even if you are not using Shure gear. Below is a recording of a webinar we hosted with Shure in 2020, where we discussed the features of the latest WWB update, and analyzed a coordination done in WWB for a large multi-stage music festival:

Other manufacturers do have software for coordination, but limited to compatibility with their own products and with limited coordination tools. Sennheiser’s Wireless Systems Manager (WSM) does allow users to create profiles for non-Sennheiser gear, whereas Shure already has many profiles included in WWB.

Which software should you use? Shure’s WWB is an easy choice, since it is completely free to download and use. Professional Wireless’s IAS is more of a professional tool, allowing you to trade certain risks in return for more frequencies. If you have a large amount of Shure systems which can be controlled by WWB, then being able to deploy your coordination to the equipment with just a few mouse clicks is a huge time saver compared to manually tuning everything. If you have a large Sennheiser system then you might find it worthwhile to use WSM even with its limited coordination features.

Conclusion

The uncomfortable truth about coordinating large wireless systems is that a lot of people are doing it, and a lot of those people are not professional wireless technicians. Quite often it’s the school theatre teacher who has been “gifted” with a motley assemblage of different wireless systems from different manufacturers, and who has to figure out how to make them all work together. For almost anybody who works in live audio and might be using wireless microphones, I strongly recommend downloading Shure’s WWB and watching a few videos to learn to use it. It’s not especially difficult to learn, and can make a huge difference in the success of your events.

Stay tuned for the next article in the series. Next up, we’ll give you some guidance to help you choose the right wireless gear for your next rental or purchase.

Need help with a frequency coordination for your next show? Frequency coordination is just one of the many services we offer.

Interested in purchasing a wireless system? Reach out to our Sales Team at 847-367-9588 or sales@tcfurlong.com for comprehensive help selecting the right system – in the right frequency band – for your needs.

We also carry hundreds of channels of production wireless equipment in our rental inventory, and our experienced Project Managers can help design and implement a wireless system for your next show. Reach out to them today at 847-367-9588 or rentals@tcfurlong.com to get started.

by Scott Helmke

This blog post is the third entry in an ongoing series all about wireless systems – background info, best practices, and useful tips & tricks. Click here to get caught up on the previous articles.

This is the third blog article in our wireless series.  In the first article I talked about how wireless microphones fit into unused space in the TV broadcast spectrum, and in the second article I talked about other frequency bands outside of the UHF spectrum.  This article is about actually finding (or more often, predicting) good frequencies for wireless microphones and other wireless audio devices.

What is Intermodulation?

Now that we know roughly what space we have available for our wireless channels, we can talk about actually deciding what frequencies to use.  If it’s just one channel, we can usually just pick a random frequency in between TV stations.  But if we’re using two or more channels then we have to work around a rather inconvenient problem with wireless audio devices – frequency intermodulation or, more commonly, “intermod”.

Intermod is the result of what happens when two (or more) transmitters or other devices are placed close together.  Because the circuitry inside isn’t especially linear, and because a full RF shield around the circuitry would be cost and size prohibitive, the signals that are being transmitted by one device will leak into the circuitry of the other device. This results in extra frequencies being generated, based on the design of the transmitter circuitry and other things. If you hold two transmitters together in your hand, a frequency scan will show those two frequencies along with others that have been generated by intermod. In the image below, the small “spikes” are frequencies generated by intermod. And those extra intermod frequencies will cause interference just as much as any “real” frequency transmission.  This adds a huge amount of complexity to finding frequencies to assign to our wireless channels.

The good news is that intermod is predictable.  Based on the characteristics of the circuits inside wireless systems, we can calculate the likely intermod frequencies and avoid using them. This becomes a huge amount of math to do, so specialized software is used to do the calculations.

Finding Good Frequencies & Avoiding Intermod

The simplest way to find good frequencies is to use the groups and channels that are loaded into wireless systems.  These are calculated by the manufacturer and take intermod into account – each group will have a number of channels which can be used together safely, assuming you don’t try to use more than one group.  This is often supplemented by a webpage provided by the manufacturer that will recommend specific groups and channels based on your location.  For example, Shure has their Wireless Frequency Finder page which allows you to enter your location (just the Zip code is enough) and which product series you are using.

Another approach to finding frequencies is to use the built-in scanning function found in most wireless receivers. The usual process is to turn off all your transmitters, run the scan on the first receiver, and use the first frequency it finds.  The associated transmitter would be turned on and programmed to that frequency, and then the process is repeated on the second receiver.  This approach has the advantage of avoiding any local interference, but the downside is that it is tedious to perform on a large system.

Conclusion

The frequency finding methods I’ve talked about so far are good if your wireless microphones are all the same – same manufacturer, same model, and the same frequency band.  Typically you can get away with using the above methods if you have more than one frequency band, as long as the bands do not overlap.  But if you have gear from more than one manufacturer, and/or different product lines, you can’t use the built-in groups and channels safely.  And the scanning functions may not make good predictions for avoiding intermod.

The answer is to use software which can coordinate frequencies for large systems, such as Shure’s Wireless Workbench or Sennheiser’s Wireless System Manager.  In our next article, we’ll take a look at frequency coordination software, and discuss how it can aid in larger scale wireless system deployments.

Interested in purchasing a wireless system? Reach out to our Sales Team at 847-367-9588 or sales@tcfurlong.com for comprehensive help selecting the right system – in the right frequency band – for your needs.

We also carry hundreds of channels of production wireless equipment in our rental inventory, and our experienced Project Managers can help design and implement a wireless system for your next show. Reach out to them today at 847-367-9588 or rentals@tcfurlong.com to get started.

by Scott Helmke

This blog post is the second entry in an ongoing series all about wireless systems – background info, best practices, and useful tips & tricks. Click here to check out the previous article and get caught up.

In the previous blog post I wrote about using production wireless systems in the unused gaps between TV stations in the UHF band, and how we’ve lost a lot of the spectrum that we used to take for granted.  The obvious next question is “is there any other spectrum available for production wireless?”

The answer is generally yes, although there isn’t a lot of spectrum lying around empty and available for us to use. 

VHF

The two VHF frequency bands (88-108MHz and 174-216MHz) are available aside from avoiding TV stations.  However, using those lower frequencies usually means larger antennas are needed.  Also, there are some other sources of interference which could cause problems.  RF noise radiating from unshielded network cabling (and almost all Cat5/Cat6 cabling is unshielded) is much more of an issue in the VHF band than in UHF.  I have also seen LED stage lighting to cause a lot of noise in the VHF band, even in cases where UHF microphones were not affected. Interestingly, it also appears that modern digital TV works better in UHF than VHF, and so nobody is in a hurry to start a new DTV station in the VHF spectrum.  

As far as VHF products go, Shure manufactures a VHF version of their ULXD microphone systems, including VHF antennas.  Radio Active Designs makes the UV-1G wireless stage intercom system which uses a proprietary AM technology to fit a large number of frequencies into the VHF band.  And if you’ve still got some old VHF relic that still works, it’ll probably still function just as well as it ever did.  TC Furlong Inc. has ULXD in both UHF and VHF bands available for rentals, as well as a RAD UV-1G wireless intercom system.

2.4GHz

A popular frequency band for inexpensive microphone systems is the 2.4GHz WiFi band. A large number of products are available for this band, usually marketed for amateur uses.  This frequency band is often usable for one or two channels of wireless audio, but rarely more than that simply because of the limited amount of space available and because it is shared with many other devices.  This can be a risky place to put wireless microphones, because you usually don’t see much interference until the audience shows up and starts using the WiFi on their phones.  On the plus side, wireless microphone systems in this band tend to be very easy to set up and use, since frequencies are chosen automatically and will adjust or ‘frequency-hop’ to avoid interference if possible.

900MHz

There are some specific frequency bands in the 900MHz range available for production wireless.  902-928MHz is available, though it can suffer from the same problems as the WiFi band.  Microphone systems in this band tend to be inexpensive, and carry the same concerns as 2.4GHz systems.

Another band is 944-952MHz, which is actually *not* available unless you have a specific license and are able to coordinate with other licensed users in that band.  944-952MHz is the “Studio Transmitter Link” (STL) band, which as the name suggests is allocated for broadcasters to connect studio locations to broadcasting towers. While many such studio links are now being done over the Internet, this band is still tightly regulated.  Manufacturers of wireless microphones in this band tend to be picky about who they will sell to because of the licensing concerns. Shure sells their PSM1000 systems in the X1 band, for instance, but recommends that potential users use Shure’s Wireless Workbench software and suitable hardware to scan for unused frequencies.  My own advice on using the 944-952MHz band is that you should work with a regional RF coordinator to make sure that you aren’t causing any problems for the primary users of this (or any) frequency band. For a deeper dive and more resources, head to the National Spectrum Management Association website.

The DECT Band

The DECT band (short for ‘digital enhanced cordless telecommunications’), 1920GHz-1930GHZ in the USA, is used for things like cordless phones.  It’s also used by some wireless intercom systems such as Clear-Com’s FreeSpeak II. This band has the same limitations as the 2.4GHz WiFi band, though the ‘frequency-hopping’ technologies in higher end products like FreeSpeak II allow for reliable performance in all but the most adverse conditions. FreeSpeak II in the 1.9GHz DECT band is available in our rental inventory.

Conclusion

To sum up, UHF is still the best spectrum for high quality wireless microphone and IEM use.  It’s the spectrum with the best RF characteristics for wireless audio, but also where you’ll find the highest quality products.  Other bands are available but limited in various ways.  If you need to have more channels of audio than you can fit into UHF in your locale, then consider prioritizing critical channels for UHF and moving other channels (such as backstage intercom) to other bands.

Stay tuned for the next article in the series. Next week’s topic: finding good frequencies. What is intermodulation and how can you avoid it? What is the basic process for setting up a simple system with a few channels of wireless? Check back in for the answers.

Interested in purchasing a wireless system? Reach out to our Sales Team at 847-367-9588 or sales@tcfurlong.com for comprehensive help selecting the right system – in the right frequency band – for your needs.

We also carry hundreds of channels of production wireless equipment in our rental inventory, and our experienced Project Managers can help design and implement a wireless system for your next show. Reach out to them today at 847-367-9588 or rentals@tcfurlong.com to get started.

by Scott Helmke

Welcome to the first in a series of posts about the practical theory for successfully using wireless microphones. Because this is such a big topic we’ve decided to break it into a series of smaller chunks, so stay tuned for future articles in this series.

How Does a Wireless Mic Work?

A wireless microphone works by transmitting a radio signal from the microphone (also called a transmitter) through the air to a nearby receiver. Each transmitter must have its associated receiver, which takes the radio signal and turns it back into audio so that it can be connected to an audio system. This works great and doesn’t require much thought, as long as you only have one microphone and receiver to work with. Each channel (one transmitter, one receiver) of wireless must have its own frequency to avoid interfering with other channels. The very cheapest of wireless systems don’t allow any tuning of different frequencies at all, while inexpensive systems have the ability to tune, but over a limited range. Professional shows that have a lot of wireless channels use the most expensive wireless systems, which are designed to have a wider tuning range and to work better in large systems. While we’ve used wireless microphones as an example, the same concepts apply broadly to all production wireless systems (IEM, wireless intercom, etc.).

What Else is the RF Spectrum Used for?

Beyond the need to simply have each wireless channel on its own frequency, the space that most wireless microphones work in is already filled with other transmitters, in particular television stations. The reason for this is mostly historical – before digital television (DTV) became available, analog TV stations had to be spaced apart from each other. In the USA every TV channel (both analog and digital) is assigned 6MHz of space in the frequency spectrum. VHF stations are assigned 54-88MHz and 174-216MHz, while UHF stations are assigned 470-608MHz. Early wireless microphones in the TV bands tended to use VHF frequencies, but eventually as technology improved the UHF band became the most popular space for microphones. The frequencies in the UHF band tend to work well for wireless microphones, allowing small antennas but still good distance – if you watch old concert films you might see some rather large antennas in the background for the VHF microphones. Joni Mitchell’s “Shadows and Light” film shows an antenna about 6’ tall right behind her onstage, to pick up the signal from her wireless guitar transmitter.

The open spaces between TV stations has generally been the most open space available over the whole frequency spectrum, and almost all of the rest of the spectrum has been claimed, assigned, and jealously guarded for other uses. There are a few safe spaces that have been designated as available for wireless microphone use, but almost all of the products currently available use the UHF band. But as analog TV has been replaced by digital TV, the need to provide empty space between stations has gone away. DTV stations can be packed tight together, leaving only enough room in between to fit possibly one wireless microphone channel. In the analog TV days a wireless microphone that had a tuning range of 30MHz could always find space between TV stations, since the TV stations had to be spaced out. The original UHF TV band went all the way up to 806MHz, most of it empty space.

What Does the RF Spectrum Look Like Today?

Here’s a scan taken in Chicagoland from 2017. All the blocks which look like city buildings are DTV stations. Any space in between those stations, aside from a small bit at the left of this scan, was legal for wireless microphones. You can see the TV channels at the bottom of the image:

Over the years the spectrum from 616-806MHz has been auctioned off by the government to companies for use in mobile phone and internet services. The TV stations that occupied that spectrum have been “repacked” into the remaining space, further crowding out wireless microphone use.

Here’s a scan from the same location from fall of 2020, after the most recent repack. The mostly empty space on the right side is now reserved for other services and not legal for wireless microphones. And some of the space at the left edge, channels 14 and 15, is not allowed for wireless microphones:

Back in 2017, before the latest auction and repack, there were roughly 17 open TV channels available in most of Chicago. Now, post-repack, there are only 9 open channels. Click here for more details on the 2017 FCC auction of the 600MHz band, and the 2020 repack.

What Does This Mean for You?

On to the practical. For finding good frequencies the first task is to figure out what TV stations are actually broadcasting in your area. Usually this can be done with manufacturer tools such as Shure’s Wireless Frequency Finder webpage, or their Wireless Workbench software. The ideal way to find all the local TV stations is with an onsite scan, which requires either a wireless mic receiver which can be networked to Wireless Workbench, or some radio scanning equipment. For just one or two wireless channels it’s enough to simply tune to a frequency not occupied by a TV station. And most modern wireless systems include some simple form of automatic frequency selection which can avoid active TV stations.

Finding good frequencies for a larger number of channels will be coming up in a future post. Stay tuned!

Stay tuned for the next article in the series. Next week’s topic: alternatives to UHF wireless. What other frequency bands are available for wireless users, and when should you consider them? Check back in for the answers.

Interested in purchasing a wireless system? Reach out to our Sales Team at 847-367-9588 or sales@tcfurlong.com for help selecting the right system for you.

We also carry hundreds of channels of wireless in our rental stock, and our experienced Project Managers can help design and implement a wireless system for your next show. Reach out to them today at 847-367-9588 or rentals@tcfurlong.com to get started.