| Electronics > Projects, Designs, and Technical Stuff |
| Digital FPV video for drone racing |
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| Kilrah:
--- Quote from: StillTrying on January 20, 2019, 12:26:30 pm ---After looking at some of the small fast quad FVP videos I don't think this is solvable by making the video digital. Even when using 2 receiver diversity BOTH receivers very often drop out at the same time, often for many frames. --- End quote --- Sensitivity of an analog receiver is really low. Digital with proper modulation/error correction should be capable of doing quite a bit better, but whether that's possible with existing analog hardware is questionable. --- Quote from: TheDane on January 20, 2019, 12:34:27 pm ---I am wondering why you are trying to re-invent something that already exists. --- End quote --- There's a dozen or so attempts at it around, but none of them is quite to the point of really being usable, mostly because they all try to stay within the bounds of existing stuff with minor modifications instead of starting something from scratch that is really developed for the specific purpose. Hence gotta keep trying to approach the problem differently, and yes it will likely involve an FPGA on each side... even the display solution needs to be somewhat custom. |
| ogden:
--- Quote from: Kilrah on January 20, 2019, 01:28:51 pm ---Sensitivity of an analog receiver is really low. Digital with proper modulation/error correction should be capable of doing quite a bit better, but whether that's possible with existing analog hardware is questionable. --- End quote --- Even if miracle happens and one can find analog video transceiver with phase performance good enough to run better than BPSK or 2FSK/4FSK modulation, it anyway would be insanity to design modem for analog video 5.8GHz transceiver, because excellent MIMO 5.8GHz digital transceivers exist and they are widely used: https://wikidevi.com/wiki/Atheros#AR9200.2FAR9500_series |
| Marco:
--- Quote from: Kilrah on January 20, 2019, 01:28:51 pm ---whether that's possible with existing analog hardware is questionable. --- End quote --- Direct FM modulation isn't that bad. The only real problem apart from the potential lack quality of the mixers/LNAs is the way the cheap receiver syncs to the carrier (the VCO gets phase aligned with the carrier). With an IQ demodulator you can handle phase misalignment digitally and fast, now if it loses sync with the carrier you're simply screwed for a bit. Could be solved with a better receiver, but as I said ... kind of a big project. |
| Marco:
--- Quote from: ogden on January 20, 2019, 01:58:54 pm ---because excellent MIMO 5.8GHz digital transceivers exist --- End quote --- They are very polite compared to the analogue video transmitters. Being impolite has advantages for robustness, ignoring tragedy of the commons that is. |
| ogden:
--- Quote from: Marco on January 20, 2019, 02:03:07 pm --- --- Quote from: ogden on January 20, 2019, 01:58:54 pm ---because excellent MIMO 5.8GHz digital transceivers exist --- End quote --- They are very polite compared to the analogue video transmitters. Being impolite has advantages for robustness, ignoring tragedy of the commons that is. --- End quote --- :-// Could you explain what you mean? |
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