Prohibited bands
TV Channel 37: 608 to 614 MHz Is Prohibited
Quick answer
Television channel 37, 608 to 614 MHz, is prohibited for wireless microphones in the United States and always has been. It is reserved for radio astronomy and for the Wireless Medical Telemetry Service, which monitors hospital patients. No church system may transmit here at any power.
This is the six megahertz gap in the middle of every wireless frequency chart, and the one band on this site that has never been available to anyone. It sits directly above the UHF working band and directly below the 614 to 616 MHz guard band, which makes it easy to step into by accident when a receiver is set by hand rather than by scan. The two services that live here are radio astronomy and hospital patient telemetry, and both are exactly the kind of neighbour you do not want to transmit on top of.
What is in 608 to 614 MHz and why it is closed
Channel 37 was never assigned to a broadcaster. It was set aside decades ago because radio astronomy needs a quiet window in this part of the spectrum, and it was later shared with the Wireless Medical Telemetry Service, the radio link that carries heart rhythm and vital sign data from a patient to a nursing station. Neither of those services can move and neither can tolerate a transmitter in the room next door.
Both occupants of 608 to 614 MHz are protected services, which is why no microphone may transmit there regardless of licence or power.
| Occupant | What it does | Why a microphone must stay out |
|---|---|---|
| Radio astronomy | Observatories listening for extremely faint natural signals | A microphone transmitter nearby is many orders of magnitude louder than the signals being observed. |
| Wireless Medical Telemetry Service | Hospital links carrying patient vital signs to nursing stations | Interference can interrupt patient monitoring. This is a safety of life service. |
| Wireless microphones | Not permitted, at any power, licensed or unlicensed | There is no exception, no low power allowance and no waiver route for a church. |
Channel 37 predates the 600 MHz incentive auction by decades. It was not taken away from wireless microphones in the repack, because it was never theirs.
How churches end up here by accident
Nobody sets out to transmit in channel 37. It happens three ways. The first is a manufacturer tuning range that straddles the gap: a system quoted as tuning from 596 to 620 MHz physically covers legal spectrum, prohibited spectrum and the duplex gap in one sweep, and the only thing keeping it legal is which number is on the display. The second is manual entry by a volunteer copying a frequency from an old card. The third is a group scan that produces a tidy set of evenly spaced frequencies without regard to what is in between them.
The defence against all three is the same: set frequencies by the receiver scan, then read the number on the display and check it against the band table before anybody speaks into anything. Anything between 608.000 and 614.000 MHz is wrong. If your system will not let you exclude a range, that is a good reason to replace it, and digital wireless systems generally handle it better.
Where the legal spectrum sits either side
It helps to see the neighbourhood in one view, because channel 37 is surrounded by three very different legal positions within twelve megahertz.
Legal full power operation stops at 608 MHz and does not resume above channel 37 except for a 2 MHz sliver at 20 mW.
| Range | What it is | Status for a church |
|---|---|---|
| 602 to 608 MHz | TV channel 36, top of the UHF working band | Legal if the channel is unoccupied at your address |
| 608 to 614 MHz | TV channel 37 | Prohibited. Radio astronomy and medical telemetry. |
| 614 to 616 MHz | Duplex gap segment | Legal at 20 mW. Two or three very low power channels. |
| 617 to 652 MHz | 600 MHz service band downlink | Illegal to operate. Sold to mobile carriers. |
The narrowness of these boundaries is the point. Six megahertz separates a perfectly legal frequency from a prohibited one, which is why the number on the receiver display is worth reading twice.
What to do if you already own equipment that reaches into channel 37
Owning it is not the offence. Transmitting in it is. A system whose tuning range crosses 608 to 614 MHz can be used perfectly legally provided every assigned frequency sits below 608 MHz, so you do not need to throw anything away. What you do need is a written plan, a habit of setting frequencies by scan, and a check of the display before each system goes into service.
This is different from the 600 MHz service band, where gear tuned only to 617 to 652 or 663 to 698 MHz has nowhere legal to go and is genuinely worthless. If you are looking at a secondhand system, read buying used church sound equipment before money changes hands, and read the megahertz range printed on the receiver rather than trusting a band letter.
Sources
Frequently asked questions
Why is TV channel 37 off limits to wireless microphones?
Because two protected services share it. Radio astronomy observatories listen for extremely faint natural signals in this window, and the Wireless Medical Telemetry Service carries hospital patient vital signs on the same frequencies. A microphone transmitter is overwhelmingly louder than either can tolerate, so the band is closed to microphones with no low power allowance and no waiver route.
Was channel 37 taken away in the 600 MHz repack?
No. It was never available. Channel 37 has been reserved for decades, long before the incentive auction, which is why it appears as a gap in charts drawn well before 2017. What the repack removed was television channels 38 to 51, the spectrum from 614 to 698 MHz. Channel 37 was simply never part of the microphone allocation.
My receiver can tune to 610 MHz. Does that make it illegal to own?
Owning it is fine. Transmitting in 608 to 614 MHz is not. Several manufacturer tuning ranges physically sweep across channel 37 because the hardware covers a continuous span. Keep every assigned frequency below 608 MHz, set frequencies by receiver scan rather than by hand, and check the displayed number before the system goes into service.
Is there any low power exception for channel 37?
There is not. The 20 mW allowance people remember applies to the 614 to 616 MHz guard band segment, which sits above channel 37, not inside it. Within 608 to 614 MHz there is no permitted power level for a wireless microphone, licensed or unlicensed, and no church application that changes that.
How would we even know if we were interfering with a hospital?
You would not, which is precisely the problem. Medical telemetry receivers are inside a building you cannot see into, and the failure shows up as a dropped patient monitoring trace rather than as noise in your own system. That asymmetry is why the rule is absolute rather than a matter of being careful about distance.
What is the safe upper limit for a church wireless frequency?
Treat 608 MHz as a hard ceiling for normal operation. Everything from 470 to 608 MHz is available subject to local television occupancy, the 614 to 616 MHz segment is legal only at 20 mW and holds two or three channels at best, and everything above 616 MHz is either prohibited or illegal to operate. Plan below 608 MHz and you will not have to think about it.
Researched, not professional advice. This page is compiled from published manufacturer specifications, operator manuals, FCC rules, published standards and owner-review consensus, not hands-on testing. Sound system design, rigging loudspeakers overhead, and any electrical work are jobs for a qualified professional: have flown loudspeakers and their attachment points signed off by a structural engineer or a certified rigger, and have all wiring done by a licensed electrician to your local code. Wireless microphone rules change, so confirm the current FCC position before buying. As an Amazon Associate we earn from qualifying purchases.