📱 Multi-Rotor › HD FPV in 2019 - Let’s talk about HD & FPV tech

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Home › ✈️Aircraft › Multi-Rotor › e-Multi-Rotor Main Discussion › Other › HD FPV in 2019 - Let’s talk about HD & FPV tech

11-17-2019 02:08 PM 17 months ago

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TerenceChan

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HD FPV in 2019 - Let’s talk about HD & FPV tech

Since this is also a thread for people looking to start FPV flying as a hobby, I should probably share my findings on the DJI FPV digital system first because it is a very popular choice for High Definition First Person View(HD-FPV) flying . For starters, DJI HD FPV system is available since Sept 2019, it is such a great product, other than (IMO,) the 5.8g radiation of up to 1W fired by the goggles to the user’s head at point blank when the goggles are set to FCC mode. In CE mode, the goggles transmit at a low power 0.25W which makes it less of a concern for most Europeans whom under the law, could only use 25mw for 5.8g anyway. At this point, you would probably be asking, “Are you mistaken? Only the transmitter emits radiation, the receiver in FPV goggles only receives video signal so the goggles have no radiation!”
Well, first of all, indeed all other fpv goggles only receive video signal. However, the receiver in our goggles still produces radiation because most receiver modules have some sort of an LNA (low noise amplifier) in-built. I know there are LNA units by Mini-Circuits for amplifying the received 5.8ghz signal and you put that between your goggles antenna and the goggles’ SMA. They work just like the usb-powered booster which comes with most HD TV antenna. The inbuilt amplifier is different as it is an essential component in the receiver module itself to ensure rated specs such as > 92% sensitivity or >97% sensitivity for expensive receiver such as the ClearView unit. This radiation is very little as compared to 700mw to 1w of power transmitted by DJI goggles (again in FCC mode).

Yes, the goggles use 2 of its 4 antennas to transmit the receiver signal strength info to the DJI digital video transmitter (HD VTx), also known as the DJI air-module so that the air-module knows exactly how much data bitrate it needs to drop for its transmission to minimize latency issues at times of poor video reception. This translates to “more-blocky” video in terms of the video degradation instead of displaying freeze frames (as in the Connex HD FPV system). This tech is amazing.

Having said this, I personally think that the HD system by Fatshark called “Byte Frost” is pretty neat too. It almost eliminates the latency issue entirely with a different technique, more pixels in the received video are simply turned into snow artifacts as the video reception gets poorer. Hence, you see breakups which are similar to analog FPV video except that the snow bits look kinda squarish rather than grainy. All right, that’s enough of my rambling, here’s the video comparing the dji HD system against the old connex HD system.