Caption a walkie-talkie channel for about $94

The one thing on set nobody has solved

Earpieces assume you can hear. Speaker mics assume you can hear. On a film set, in a warehouse, at a race pit or on a construction site, the radio is how the day is coordinated, and there is no accessible version of it.

Relaying is not a solution. It makes another person into your infrastructure, it lags behind the conversation, and it puts you in the position of constantly asking for help to do a job you are perfectly capable of doing.

Playing the radio out loud is not a solution either. On a set it is disruptive during a take, and on most channels the traffic is not for the room to hear.

So: wire the radio directly into your iPhone. It is silent to everyone around you, the transcript stays on your device, and your wrist taps when your name goes out over the air.

Buy an interface, not an adapter

One decision determines whether your rig works at all, so make it before you buy anything.

Something between the radio and the phone has to turn analog audio into digital. An audio interface does that job itself. It arrives on your phone as a proper audio device with its own microphone input, iOS offers it to apps, and it works the first time on any radio.

The alternative you will see recommended is a plain headphone dongle, which is cheaper because it does none of that work. It asks your phone to record from the microphone pin of a 3.5 mm connection, which means the audio has to land on exactly that pin, at roughly microphone level, wired to the standard a phone expects. Whether the adapter in front of it does that is undocumented internal wiring that varies by manufacturer.

When it is wrong it fails completely and invisibly. We tested a Motorola push-to-talk cable into an Apple USB-C dongle: the iPhone saw the dongle perfectly well and reported it as a playback device with no microphone on it. There was nothing for any app to record from, at any volume. You cannot fix that with a setting, and you cannot tell which way it will go until the parts are in your hands.

Skip it. The interface costs more and it takes the gamble out.

Getting the volume right is most of the job

Once the parts are connected, one setting decides how good your captions are, and it is not in the app. It is the volume knob on the radio you are receiving on.

The instinct is to turn it all the way up, and that makes captions worse. Past roughly the middle of the range you stop adding detail and start adding distortion, and distorted speech is harder to transcribe than quiet speech. Around halfway is the sweet spot on every radio we have tried.

You do not have to guess at it, though, which is the useful part. Open Settings, then Audio, and Buddy shows a live Input Level meter for whatever it is recording from. Have someone key up and talk while you watch it.

Aim for speech peaking between −20 dB and −6 dB. Too quiet and words get dropped. Pegged at the top and they get mangled, which is the worse failure of the two because a mangled word still arrives looking like a real one.

When you find the spot, put a wrap of tape on the knob. On this setup the radio's volume is your gain control, and every day after this becomes a five-second job.

The meter is also the fastest answer to "why is this not working". If it stays flat while someone is clearly talking, the problem is somewhere in the cable chain or the volume knob, not in the app. If it names your interface at all, the hardware side is already fine.

What you need

The setup we recommend is three parts, about $94 total, plus an iPhone with a USB-C port.

Check your radio's connector before buying anything. This is the easiest way to waste money here. Baofeng and most consumer radios use a Kenwood-style two-pin plug. Motorola production radios like the CP200d use a Motorola "M1" two-pin plug, which looks similar and does not fit. Newer digital Motorolas use a multi-pin connector instead. The Motorola section below has the details.

The cheaper option, and what it costs you

The BTech APRS-K1 Pro is one cable from radio to phone with a converter built into it, around $35. It is the tidiest rig here by a distance and there is nothing else to buy.

It also produced noticeably worse captions than the interface, and it needed the radio turned up much further to give a usable signal at all. Those two facts are related. It starts with less, so it asks you to make up the difference with volume, and volume amplifies hiss right along with the speech.

If cable clutter genuinely matters more to you than accuracy, it is a real option and it will work. For following a channel your job depends on, the interface is worth the extra money.

Using it with Hearing Buddy

Once the audio is in, the app works the way it always does. The radio is just another thing Buddy listens to. A few features earn their keep more than usual here.

Nothing is ever played out loud. The radio's speaker is disconnected the moment you plug in, and Buddy only listens to incoming audio. It never plays it back. Everything stays on your device. Channel traffic on a production or a work floor is often confidential, and it stays that way.

Five minutes of radio settings that buy real accuracy

Most of the remaining caption errors come from the radio rather than the phone. These help:

• Set the receiving radio's volume to roughly halfway. This matters more than any other setting on this page, and the instinct to turn it all the way up is wrong. Past about the middle of the range you are adding distortion rather than detail, and captions get worse.
• Use wide bandwidth (25 kHz) rather than narrow (12.5 kHz) if your radios support it. More high-frequency detail survives the trip, and high-frequency detail is exactly what tells "fringe" apart from "French".
• Set squelch so an idle channel is completely silent. Open-channel hiss is a constant stream of noise into the captions and can invent words out of nothing.
• Turn the roger beep off. That end-of-transmission tone is a loud non-speech burst landing exactly where a sentence ends.
• Turn VOX off. On any setup with a transmit path, voice-activated keying can put your room on the air without you touching anything.
• Stay on the same band as your crew. Most workplaces run UHF because it handles walls and interiors better.

You can talk back, too

The push-to-talk adapter carries a small microphone and a transmit button alongside the audio it feeds your interface. Press the button, speak, and your voice goes out over the channel exactly as it would from any standard earpiece kit.

Your own transmissions will not appear in your captions, though, and it is worth knowing why rather than assuming something is broken. Radios are half duplex. While you are transmitting, the radio is not receiving, so the line feeding your phone carries nothing at all during the moment you are speaking. Your voice goes out over the air without ever passing the phone.

There is a way to get it, and it is the reason we recommend the AI-Micro specifically. It has two inputs. The radio goes in the first. A microphone on you goes in the second. Buddy captions both, so your side and the channel's side land in the same transcript, in order.

The microphone does not need to be anything special. An old pair of wired iPhone earbuds with the inline microphone works, which is the kind of thing most people already have in a drawer. Wear it, key up the push-to-talk button as normal, and your voice goes out over the air while the earbud microphone picks up the same words for your captions.

That closes a loop that has never really been closed before. If you voice on the channel but cannot hear the response, you have historically had no way to confirm what actually went out. You say something into a device and hope. Now you read your own words and the reply to them, in order, on one screen.

We tested this properly rather than in theory: two people, one outside and one inside a building, one radio each. Both of us could follow the whole conversation on our phones, both sides of it, without either of us hearing the channel. That is a conversation over two-way radio between two people who cannot use one, which is not something that was possible before.

If you do not voice on the channel, none of this gets in your way. The setup receives perfectly well with the second input empty.

If your radio is a Motorola

The Motorola CP200d is the film and TV standard. It is what rental houses stock by the case. It uses a Motorola two-pin plug, known as M1, which is physically different from the Kenwood-style plug on consumer radios. M1 also covers the CP100d, CP125, CP150, CP185 and DTR series.

Everything else in this tutorial is identical and only the first part changes. Use an M1 push-to-talk cable with a 3.5 mm female jack, around $13, in place of the Kenwood-style adapter, then into the interface exactly as above.

Do not try to save the cost of the interface here. Motorola is the specific case we tested for the dongle problem described earlier, and it fails: an M1 push-to-talk cable straight into an Apple USB-C dongle gives you a phone that sees the dongle but finds no microphone on it. Neither part is faulty and neither datasheet mentions any of this. They simply were not built to meet in the middle.

If the production runs newer digital radios instead, such as the XPR 3300e, XPR 3500e, XPR 6000 or 7000, or APX, those use a multi-pin side connector rather than M1 and need a multi-pin-to-two-pin adapter before anything else. That is an extra part and an extra thing to go wrong. Borrowing a CP200d is usually easier.

One tip worth more than any of the hardware: ask whoever runs comms for a spare radio rather than modifying your own. Every production has a bin of them. A dedicated radio wired to your phone means your working earpiece stays untouched, and if the caption setup ever misbehaves you unplug one thing instead of re-rigging in the middle of a shot.

What is tested and what is not: the M1 push-to-talk cable was confirmed on a Motorola to fail with a plain Apple dongle, which is why that build is not recommended anywhere on this page. The M1 cable into an interface has not been through the same side-by-side testing we did on a consumer radio, but it removes that failure mode entirely rather than gambling on it.

When something is wrong

Work through these in order. The first one answers most of it in about two seconds.