How many wireless channels fit in one TV channel?

As a planning rule of thumb, a clean 6 MHz TV channel comfortably carries about four channels of modern digital wireless and can be pushed to around eight in good conditions. Older wideband analogue systems need more room per carrier, and the real limit is whatever your coordination software says once intermodulation is accounted for.

What is the minimum spacing between wireless microphone frequencies?

There is no universal number — each system publishes its own minimum carrier spacing based on its modulation and receiver filtering, and those figures differ substantially between manufacturers and generations. Use the number from your own gear's documentation, and never simply space carriers evenly, because equal spacing places third-order intermodulation products directly on top of other carriers.

Do I need coordination software for a four-channel bag?

It is strongly advisable even at four channels, because four carriers already produce roughly two dozen third-order intermodulation products and the bad combinations are not obvious by inspection. Every major wireless manufacturer provides a free coordination tool, and running it costs a couple of minutes.

When should I re-scan during a shooting day?

Re-scan after the rest of the crew arrives with their radios, video links and LED fixtures, after any move to a new location, and any time a channel that was solid starts taking hits. A scan is a snapshot of one moment at one spot, and a film set changes its RF environment substantially between call time and the first shot.

Planning a shoot

How to coordinate frequencies for a multi-channel bag

RF ScoutUpdated July 26, 20265 min read

Coordinating a multi-channel bag is a fixed sequence, not a knack: pick a block that is clear at your location, scan with every transmitter switched off, assign carriers with your manufacturer's coordination software rather than by eye, verify the set is free of third-order intermodulation products, walk-test every position in the scene, and write the whole thing down. As a rough capacity guide, a single clean 6 MHz TV channel comfortably holds a 4-channel bag and is tight for eight; sixteen channels wants three to four clean TV channels and serious attention to antenna placement. Re-scan after the rest of the crew and their radios arrive, because your morning scan describes a location that no longer exists.

Four channels is a scan and a bit of luck. Eight is a plan. Sixteen is a job of work that starts the night before. The workflow below scales across all three; what changes is how much of it you can get away with skipping, and the honest answer is that the people who skip steps are the people standing in a field at lunch re-coordinating while the first AD watches.

The night before: choose where to live

Get the actual location. Not the production office, not the nearest town — the address, or the coordinates if it is a field. RF congestion changes over a few miles.
Find out which TV channels are occupied there. Run the address through RF Scout or another spectrum lookup and note which channels come back Recommended and which are Avoid, and why. Broadcast is the one part of the picture that will be exactly the same at 6 a.m. as it was last night.
Translate channels into blocks. Your gear does not tune in TV channels, it tunes in manufacturer blocks. The block pages map one onto the other; the Lectrosonics, Shure and Sennheiser guides do the same in prose.
Pick a primary and a fallback block. Something goes wrong roughly as often as it goes right. A second block you have already vetted turns a crisis into an inconvenience.
Move what you can out of UHF. Camera hops, IFB and comms in 1.9 GHz or 2.4 GHz give the UHF spectrum back to the channels that actually need range and reliability. On a 16-channel day this is the single biggest win available.

On location: the order of operations

Set up the receive antennas where they will actually live. Scanning from a different position than you will work from produces a scan of somewhere else. Details in scanning and walk-testing.
Turn off every transmitter you own. All of them. Bag, cart, spares in the case, IFB, comms, the one taped inside a prop. A scan with your own gear radiating is a scan of your own gear.
Scan the candidate block. Let it run long enough to catch intermittent traffic rather than a single sweep, and repeat it on the fallback block while you are there.
Assign carriers with coordination software. Every major manufacturer ships one, and there are third-party tools that handle mixed fleets. They pick sets that are free of intermodulation products; picking by eye does not, no matter how experienced the eye.
Respect the manufacturer's minimum spacing. Each system publishes a minimum carrier-to-carrier spacing for its own modulation — use that number, not a number from an article. Narrowband digital systems pack tighter than older wideband analogue designs.
Deploy and check every receiver actually locked to its transmitter, with the right name on the right channel, before anyone gets dressed.
Walk-test the set. Every mark, every doorway, every hallway the scene might wander into.
Write it down. Frequency, block, TV channel, transmitter serial, cast name. On a card in the bag, not only in the receiver's memory.

How much spectrum does a bag actually need?

These are rules of thumb for planning, not specifications. Real capacity depends on the modulation, the receivers' front ends, how close the transmitters are to each other, and how hostile the location is. Treat the numbers as the amount of clean spectrum to go looking for, then let the coordination software tell you the truth.

Rough spectrum budget by channel count
Bag size	Clean 6 MHz TV channels to aim for	What to expect
4 channels	1	Almost always fits inside a single clear TV channel. Still worth running through coordination software — four carriers already generate two dozen third-order products.
8 channels	1–2	One clean channel is achievable but tight; two channels, ideally not adjacent to each other, is comfortable. Coordination software is no longer optional.
16 channels	3–4	Expect to split across blocks or bands. Antenna placement, transmitter separation and getting comms out of UHF matter as much as the frequency plan does.

Physical coordination matters as much as the numbers

Keep transmitters apart from each other. Two transmitters touching in a bag or on the same actor mix in each other's output stages and generate intermod that no frequency plan can avoid. A few inches of separation is worth more than it sounds.
Keep transmitters away from receive antennas. A bodypack resting against the bag's antenna is a strong-signal problem of your own making.
Separate the receive antennas from each other by a meaningful fraction of a wavelength, and keep them clear of the operator's body, the cart's metalwork and the battery pile.
Give the antennas height and sightlines before you give them gain. See why wireless drops out near a TV tower for what happens when you reach for the amplifier first.

Documentation is a coordination tool

Write down the frequency list, the block, the TV channels it sits in, and the scan you based it on. Three reasons. When a channel starts misbehaving at hour nine you need to know instantly whether it was ever clean. When another department turns up with wireless of their own, you can hand them the list and stay out of each other's way. And when you come back to the same stage in three weeks, last time's plan is a far better starting point than a blank scan.

One honest caveat about this tool: RF Scout scores locations, it does not yet compute intermod-free sets for your gear. That is on the roadmap. Until then, use it to choose where to work and your manufacturer's coordination software to decide exactly where the carriers land.

Score your location first, then coordinate inside the channels that came back Recommended.

Start with a clear block

Common questions

How many wireless channels fit in one TV channel?: As a planning rule of thumb, a clean 6 MHz TV channel comfortably carries about four channels of modern digital wireless and can be pushed to around eight in good conditions. Older wideband analogue systems need more room per carrier, and the real limit is whatever your coordination software says once intermodulation is accounted for.
What is the minimum spacing between wireless microphone frequencies?: There is no universal number — each system publishes its own minimum carrier spacing based on its modulation and receiver filtering, and those figures differ substantially between manufacturers and generations. Use the number from your own gear's documentation, and never simply space carriers evenly, because equal spacing places third-order intermodulation products directly on top of other carriers.
Do I need coordination software for a four-channel bag?: It is strongly advisable even at four channels, because four carriers already produce roughly two dozen third-order intermodulation products and the bad combinations are not obvious by inspection. Every major wireless manufacturer provides a free coordination tool, and running it costs a couple of minutes.
When should I re-scan during a shooting day?: Re-scan after the rest of the crew arrives with their radios, video links and LED fixtures, after any move to a new location, and any time a channel that was solid starts taking hits. A scan is a snapshot of one moment at one spot, and a film set changes its RF environment substantially between call time and the first shot.

Sources

Related notes

Field Notes are general reference, not legal advice or a substitute for the rule text. Spectrum rules change; verify anything you are relying on against the current source before you transmit. See the methodology and disclaimer.