Mode FPV video analog

Analog drone and FPV goggle video links: channel plans, scan, live picture with sound.

Group	TV
Default frequency	5806 MHz
Default sample rate	20 Msps
In the mode list	Drone video links, 5.8 GHz and 1.2 GHz

New in 0.2.7. Tested on generated signals only so far; recordings of real signals are welcome.

What it does and how it works

The mode FPV video (analog) (TV group) receives the analog video links of drones and FPV goggles: composite video (PAL 625 lines or NTSC 525 lines) frequency modulated onto a carrier about 17 MHz wide, with a sound subcarrier. It is receive only. The picture decoder is the one of the Analog TV mode in its FM video setting; this mode adds the channel plans, the level of every channel, a scan, the sound and the recording.

Channels

Band	Channels 1 - 8 (MHz)
A	5865 5845 5825 5805 5785 5765 5745 5725
B	5733 5752 5771 5790 5809 5828 5847 5866
E	5705 5685 5665 5645 5885 5905 5925 5945
F (Fat Shark)	5740 5760 5780 5800 5820 5840 5860 5880
R (Raceband)	5658 5695 5732 5769 5806 5843 5880 5917
L (Low race)	5362 5399 5436 5473 5510 5547 5584 5621
1.2 GHz	1080 1120 1160 1200 1240 1280 1320 1360

Pick the band and channel in the tuner, click a cell of the Channels screen, or type the frequency. The receiver takes the channel of the plans nearest to the radio's centre (within 4 MHz) down to baseband itself, so a few MHz of tuning error do not matter. Bands share frequencies (R5 5806 MHz and A4 5805 MHz are the same channel).

What it shows

• Video: the live picture with the system, the colour system and the channel; Snapshot saves a PNG, Record saves up to 5 pictures a second as numbered PNG files in a new folder under <data folder>/fpv/. The on-screen display of the flight controller (battery, timer, RSSI) is part of the picture; it is shown, not decoded.
• Channels: the 7 x 8 grid with the level of each channel over the noise floor (bars), and Scan 5.8 GHz / Scan 1.2 GHz. A scan tunes the radio over the channels (about 9 MHz apart, 0.7 s each) and measures every channel that lies inside the capture; at the end it tunes to the strongest transmitter (or goes back, when "Tune to the strongest" is off).
• Spectrum: the capture with the channels inside it marked.
• Sound: the sound subcarrier (6.0 or 6.5 MHz, found by itself or set) is FM demodulated and played; mute and volume are the program's.

What the numbers mean

The level of a channel is the power within +-5 MHz of its centre. The noise floor is learnt from the lower part of the spectrum and falls to the quietest capture seen (it rises only by 0.2 dB a second), so scan once with nothing transmitting nearby, or start on an empty channel, for the levels over the noise to be right. A channel counts as occupied at 8 dB over the noise.

Needs

A radio that gives 16 Msps or more (a HackRF at 20 Msps). A 20 Msps capture holds one channel with a few MHz to spare; two 5.8 GHz channels are never in it together except neighbouring bands' duplicates. Tuning to 5.8 GHz needs a radio that goes there (HackRF, or a PlutoSDR with the extended range).

Test signal and tests

The built-in test signal is an FM video transmitter on the tuned channel: PAL or NTSC test card or colour bars, a 1 kHz tone on a 6.5 or 6.0 MHz subcarrier, noise, an offset and an AC-coupled transmitter (core/include/dect2/fpv/fpv_gen.h). tests/fpv runs it through the receiver: PAL and NTSC lock, the sound tone, an off-centre channel, an empty channel and a scan. Checked against synthetic signals only, not yet against a real transmitter.

Credits

Written clean-room: the channel plans are the transmitter makers' nominal frequencies; the picture decoder is the project's own analog TV decoder. See THIRD_PARTY.md.

Tips and caveats

• Receive only; nothing is sent. Encrypted traffic is never decoded.
• Try it without a radio: the mode has a built-in synthetic test signal.
• Receiving and the law: see Legal.

Related pages

• All modes, TV
• Supported radios, Troubleshooting, FAQ