Wireless Microphone Systems: Look to Digital; Don’t Wait Until 2020

Understanding the wireless spectrum will help you navigate where your new digital units will sit in the new wireless spectrum.

Here we go again! When the FCC announced the sale of the 600 MHz band, it caused a lot of churches to rethink how they were going to approach wireless going forward. Losing an entire band would be devastating, right?

Well, from a technical stand point, it’s not as bad as you think. 

In terms of budget, digital units are going to run 10 to 20 percent higher than analog units. That's just a fact.

Here are a few reasons why:

1. There is still a lot of wireless spectrum available. If you include VHF, you have TV channels 2-36 available to you. But for strictly UHF users, you really only have TV channels 14 (475 MHz) to 36 (607 MHz).

Keep in mind some of these channels are reserved for emergency services. Please see the diagram slide to understand what is reserved in your area.

Now if you start thinking digital wireless, you not only have 475 MHz to 607 MHz available to you, but you also have the 900 MHz band.

Most countries do not allow wireless microphones to transmit in the 900 MHz band, but the U.S. does allow it. The downside, though, is this band is shared with other consumer devices. An upside is it does have greater penetration through obstacles and can diffract around and over obstacles like buildings or trees, compared to higher unlicensed ranges like 2.4 GHz. However, there is limited amount of bandwidth in the spectrum, making it impractical for professional users who need to get many channels of wireless on the air.

Speaking of 2.4 GHz, this band is available on an unlicensed basis throughout much of the world. It offers a wider frequency range than the 900 MHz band, but systems may experience more interference from other wireless technologies like Wi-Fi and Bluetooth.

In order for wireless microphones to be successful at 2.4 GHz, they need to be "smart," or able to change frequencies on the fly to avoid interference. Devices using 2.4 GHz work in a larger frequency band and can potentially offer more channels and greater potential density than lower frequency devices. Shorter wavelengths make line-of-sight setup between transmitters and receivers important for the most reliable operation. 

2. You get better spectrum efficiency - Not all digital wireless systems offer this, but the major manufactures like Shure and Sennheiser do. Essentially they can modulate your system in a manner that allows for much higher channel counts in the reduced wireless spectrum. This is because digital wireless signals are more predictable than analog signals, allowing for tighter channel to channel frequency spacing. As a result, digital systems can deliver nearly twice the channel count in the same part of the wireless spectrum as analog systems.

It helps to know that you can get more channels of UHF out of digital units. Hopefully, this will give you the ability to keep your wireless channel count the same. Also, understanding the wireless spectrum will help you navigate where your new digital units will sit in the new wireless spectrum.

The issue then arises how some will have to get rid of your old units.

Some churches have invested a ton of money in wireless, and it's creating a little bit of a panic to hear that they have to now purchase all new units. 

Well you will be happy to hear that Shure, Sennheiser and other wireless system manufacturers are offering rebate programs, allowing you to turn in your old units and receive a credit on your new units. Many are even taking gear that is not theirs, allowing you to put all manufacturers on the table and shop for what is best for your church. 

The date to be fully switched over is July 13, 2020, but you can't wait for that date. The 600 MHz band is already being used and if you wait until 2020, odds are that you will start to experience issues before then and be stuck without wireless.

You want to start looking for new units right away. Knowing that, what should you look for?

Well, in my opinion, you should start looking at digital units. I'm not exclusively saying you need to go digital. You can still use analog wireless units, but from what I am seeing, and how the spectrum is getting smaller and smaller while more and more people are transmitting, it seems like digital is the way to go. This is especially true since the church market uses so much wireless.

Of course, if you don't use that many wireless units or frequencies, you have a few more options. But if you are going to head in the digital route, here are some things I would consider when looking for new digital wireless units:

1. In terms of budget, digital units are going to run 10 to 20 percent higher than analog units. That's just a fact. Start preparing your senior pastor or whoever makes the money decisions that, from a budget perspective, you will either have to reduce your wireless need, or be prepared to spend a little more than you have in the past.

2. Make sure you know the battery life of the unit when you compare a digital device to an analog device. You should get 30 to 40 percent more battery life out of a digital device.

3. You want to understand the latency of the digital device. All digital devices will have some latency. Latency is the delay that is added when it is converting the analog audio signal to digital in order to transmit it. In most cases, that same signal is then processed back to analog on the other side. This causes a delay in the signal.

I highly advise that the tech spec for the latency delay be 5 milliseconds or less. That is very acceptable, but with digital units, it needs to be taken into account. The reasoning behind knowing your latency is because every unit in your digital audio/video chain will add some latency. That all adds up and at some point will result in lip-sync issues. So make sure you track each device's latency and keep yourself informed as to how much of it you will have in the system.

4. I have seen some out there selling units as digital, but they are not. If it's truly digital, the unit will make the conversion from analog and everything is essentially sent as digital code, yup, it's all just 1's and 0's at that point and it will be unaffected by the radio link. It either makes it to the receiver or it doesn't. The receiver only respects the digital code being transmitted.

To figure out if the unit truly is digital, look closely at the specifications. A digital device should never have a “compander.” Analog units would use a compander to compress the signal for transmission and then expand the signal on the other side. You can also look at the audio frequency response. Digital units will be 20 Hz to 20,000 Hz with no compander. Analog units will vary, but most good receivers sit in the 40 Hz to 18,000 Hz range.

Using wireless does bring some headaches. Clearly it requires us to keep up with the latest, understand what is happening in the wireless spectrum and keep track of how the FCC is handling the frequencies we currently transmit in. It can all be overwhelming. You can always avoid the frustration by going wired.

In my opinion, it's always a good idea to evaluate each need and ask ourselves if we really need to be wireless. But let's not give up on wireless.

I believe if we do the proper research, understand our exact need, keep quality, correct use case and reliability as our main targets, we can always use this powerful instrument of worship to allow our church leaders to better engage the audience.

Ultimately helping everyone attending to better understand, hear and receive the Gospel of Jesus Christ.

(A special thanks to Michael Moore and Davida Rochman of Shure and Andrew Kornstein of Sennheiser for the information they helped provide for this piece.)

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