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Dongle Report
There are hundreds of RTL-SDR dongles, and how one of them does in the plugin can only be seen on that dongle. The dongle report runs the plugin's own measurements on the dongle that is plugged in and puts what they find into one file. Make one
- when a dongle misbehaves and you ask for help: the report says most of what would otherwise be asked for;
- when your dongle is not in the table of measured dongles: the report tells the project how it does.
Open the Station Manager, go to Maintenance, and find Dongle Report at the bottom.
- Leave Include short recordings selected unless the file has to be small. With recordings it is about 40 MB before it is packed, without them a few kilobytes.
- Press Make Report and confirm. A station that is playing is stopped.
- The page names each step as it goes. On a Raspberry Pi 5 it takes a little over a minute; slower boards need longer.
- When it is done, the page says what it found. Download Report gives the ZIP file; Show Summary shows the summary on the page.
Cancel stops a report that is being made. Starting a station while a report is being made also ends it: the station takes the dongle. A scan or an antenna tool that is running is not interrupted; the report is refused until it has finished.
The last report is kept on the player, in /data/rtlsdr_radio_report, and stays on offer on this page until the next one is made or the plugin is uninstalled.
| Step | What happens | Tool |
|---|---|---|
| 1 | The dongle is asked what it is (its name, tuner and gain steps) and read from for eight seconds at 2.4 million samples a second, to see whether samples are lost | fn-rtl_test |
| 2 | The gain measurement checks itself on a signal it makes up. This needs no dongle and tells whether the tool works on this player | fn-rtl-gain -t |
| 3 | The FM band is surveyed as an FM scan does it, with the region, the raster and the kind of scan (fast or detailed) of your settings, but without the tuning correction: the dongle is measured as it is. Your station list is not changed | fn-rtl-gain -b |
| 4 | The gain is measured for the six strongest stations found, one by one, as it is when a station is played | fn-rtl-gain -f |
| 5 | Recordings, about a second each, of what the dongle delivers (see below) | fn-rtl_sdr |
| 6 | The summary is written and everything is packed into one ZIP file |
| Recording | Why |
|---|---|
| The 2 MHz of the FM band around the strongest station, at the highest gain, at the gain the survey chose, and at a low gain | How the tuner behaves when it is driven hard, and what the automatic gain made of it |
| The same stations once more with the tuner set 500 kHz higher | Whatever moves with the tuning is made in the dongle and is not on the air |
| The 2 MHz of the FM band with the most stations | Ordinary reception |
| Two DAB channels of your own station list, each at the highest and at a middle gain | DAB reception and the error of the dongle's crystal. Without DAB stations in the list nothing is recorded for DAB |
A recording is the raw signal from the dongle (8-bit I/Q samples), not sound.
| File | Holds |
|---|---|
report.txt |
The summary, to be read |
report.json |
The same as data |
rtl_test.txt, selftest.txt, fm-survey.txt, fm-survey.err, fm-gain.txt
|
What the tools printed |
fm-<frequency>-<gain>.iq, dab-<frequency>-<gain>.iq
|
The recordings: the frequency the tuner was set to in Hz, the gain in dB |
The report names the player's model, the Volumio and plugin versions, the dongle as it describes itself, the plugin's reception settings, and the frequencies received at your place, which show roughly what region you are in. It does not name the player, your network, your account, your station list or anything else that is plugged into the player.
The ZIP file with recordings is too large for most forums, and the community thread takes attachments from established members only. Either
- paste the text of Show Summary into your post, and
- put the ZIP file on a file transfer service of your choice and post the link.
| Line | What to look at |
|---|---|
| Tuner, Gain steps | The plugin is measured with R820T, R820T2, R828D and E4000 tuners. Another tuner is of interest in itself |
| Samples lost | Should be "none". Lost samples point at the USB port, a hub, the cable or the power supply |
| Gain tool check | Should begin "selftest: ok" |
| Gain chosen, taken down for overload | In how many 2 MHz slices of the band the tuner had to be turned down because a strong station made it invent signals |
| Stations | How many stations a scan lists at the Balanced (+8 dB), Sensitive (+5) and Very sensitive (+3) settings |
| Made in the tuner | Channels that looked like stations and were refused because they went away with the overload |
| Tuner's mirrors | Channels that looked like stations and were refused as the tuner's mirrored copy of a stronger station (see Dongles) |
| Dongle's tuning | How far the dongle tunes off frequency, in parts per million, told from the carriers of the stations received well. Low-cost dongles show 10 to 60; the plugin corrects for it by itself (see FM tuning correction) |
| Stations table | For each station: how far its stereo pilot stands above the noise (and in its weakest moment), how far its carrier is from the channel's centre, and its power. A station marked "no pilot (mono)" is read by its carrier instead |
| Settings | The plugin's reception settings, among them the kind of FM scan the survey was made with and the tuning correction in use |
| Problems | Anything that did not go as it should while the report was made |