The radio keys up and transmits nothing
PTT works, the meter swings, the fan comes on — and the far end hears an unmodulated carrier. This is the most common fault in digital modes and it is almost never the software. Here is the order worth checking, quickest and most likely first.
1. The mode — check this first
Most radios take transmit audio from the microphone unless they are explicitly in a data mode. In plain USB or plain FM the rig will key up, show power and transmit nothing at all, because it is faithfully modulating a microphone nobody is talking into.
- HF: use the data variant —
USB-D,DATA-USBor whatever your rig calls it. Not plain USB. - VHF FM: use
DATA-FM. Plain FM is microphone-only on a great many radios. - If it works on HF and not on 2 m, this is why — the two bands use different audio paths and are configured separately.
Rig-specific: the FT-991A menu 071 trap and the IC-7300 USB-D setting are both this fault wearing a model number.
2. Where the computer is sending audio
- The software’s playback device must be the radio’s codec, not the laptop speakers. It is an easy thing to set once and lose after a reinstall or a USB port change.
- A radio that appears and disappears as USB devices are moved can end up numbered differently, so the device selected last week may not be the radio this week.
3. Muted or ducked by the operating system
Windows will quietly duck or mute an application’s output on its own — especially after an update, or when another program has taken exclusive use of the device. The radio is fine, the cable is fine, the mode is fine, and nothing comes out.
- Check the per-application volume in the system mixer, not just the master.
- Open Signal reports the stream and the device volume in its log at startup, and restores its own mixer volume if Windows has interfered with it — so the log is worth reading before you start unplugging things.
4. Drive set to zero
Worth ruling out, because it looks identical from the far end. If a previous session ended with the level wound right down — or the rig’s own USB audio input level is at zero — you get a clean, silent carrier.
Once audio is arriving, setting it properly is a separate job: audio levels and ALC covers what the level should actually be, and why more is not better.
What this is not
- Not a slanted or torn picture. That is a clock problem, and a different page — slanted pictures.
- Not a weak signal. If the far end reports a carrier with no tones, nothing is being modulated at all — no amount of power fixes that.
Common questions
My radio keys up but transmits no audio. What is it?
Nine times in ten it is the mode. Most radios take transmit audio from the microphone unless they are in a data mode, so a rig in plain USB or plain FM will key perfectly and modulate nothing. Check the mode first — USB-D or DATA-USB on HF, DATA-FM on VHF FM — before changing anything else.
How do I know the computer is actually sending audio anywhere?
Watch the transmit meter in the software rather than the radio. If the software shows audio leaving and the radio shows no modulation, the fault is between them — wrong output device, a muted mixer, or the radio taking audio from somewhere else. If the software shows nothing either, the fault is in the software's output selection.
Why does it work on HF but not on 2 metres?
Because many radios route transmit audio differently per mode, and a setting that works on SSB does nothing on FM. On a Yaesu FT-991A this is the menu 071 trap specifically. On other rigs it is usually a separate data-mode setting for the FM side. It is not a fault — it is two different audio paths.
Could Windows be muting it?
Yes, and it does. Windows can duck or mute an application's output on its own, particularly after an update or when another program grabs exclusive use of the device. Open Signal reports the stream and the device volume in its log at startup and restores its own mixer volume if Windows has interfered with it.
Is a dead carrier harmful?
It wastes your transmitter and occupies a frequency for the length of a picture — minutes, not seconds — while sending nothing anyone can decode. It will not damage a healthy radio at digital-mode power levels, but it is worth catching quickly out of courtesy to everyone else on frequency.
I have checked everything and still get nothing.
Try receiving through the same interface first. If the software cannot hear the radio either, the problem is the cable or the device selection rather than the transmit path, and you have halved the search. A second computer or a phone recording the radio's audio also settles quickly whether anything is being transmitted at all.
More about Open Signal
Software that tells you what it sent
Open Signal reports the transmit audio peak after every transmission, and the audio devices it is using at startup — so a dead carrier shows up in the log rather than in a reception report. Receiving is free forever.