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Home✈️AircraftMulti-Rotore-Multi-Rotor Main DiscussionOther › HD FPV in 2019 - Let’s talk about HD & FPV tech
11-17-2019 02:08 PM  6 months ago
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TerenceChan

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Singapore

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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.

Watch at YouTube

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11-17-2019 02:11 PM  6 months ago
TerenceChan

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Singapore

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Here’s my findings with the Fatshark HD FPV system! As you can see, the Byte Frost is no slouch!

Watch at YouTube

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11-26-2019 01:47 PM  6 months ago
Darren Lee

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Woodstock, GA

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I've been flying the DJI FPV system for a couple months now. Love it!

Team Synergy / Rail Blades / Morgan Fuel
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11-26-2019 11:05 PM  6 months ago
skew

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KY

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TerenceChan Here’s my findings with the Fatshark HD FPV system! As you can see, the Byte Frost is no slouch!
Obviously you have not flown with the DJI's! I am no means a DJI fan boy but after flying them for a few weeks Fat Shark better go back to the drawing board because your still watching a worn out VHS tape compared to the experience with the DJI HD
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11-27-2019 01:22 AM  6 months ago
TerenceChan

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Singapore

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Darren Lee I've been flying the DJI FPV system for a couple months now. Love it!

Thanks for dropping by Darren.
I am very impressed with the DJI system too. I like exploring different HD tech so I bought the fatshark’s system since my buddy already has the DJI.
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11-27-2019 02:14 AM  6 months ago
TerenceChan

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Singapore

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skew Obviously you have not flown with the DJI's! I am no means a DJI fan boy but after flying them for a few weeks Fat Shark better go back to the drawing board because your still watching a worn out VHS tape compared to the experience with the DJI HD
I had flown my Buddy’s DJI Digital HD before I bought the ByteFrost. My first thought when he handed me the goggles was, “hey this is extremely light-weight for a vr-looking pair of goggles!” After I put it on, I said “Wow, the screen is almost as big as my Oculus2 VR but I can’t see any screen lines or pixels like on my Oculus!” In terms of the HD experience, it was not a jaw-dropping experience for me because I was already enjoying HD on the Connex and a pair of cinemizers. Being able to see every blade of grass and that FPV experience as if you are watching “Discovery” channel on HDTV are not new to me. However, the transition from a small HD screen of my Cinemizers to the DJI one that is almost double in size while preserving every bit of clarity, is certainly very pleasing. In fact, the only issue I had, was getting motion sickness after 5mins. The big display actually made the “fish eye” effect more pronounced even though I knew that FOV of the DJI HD camera was definitely not wider than the 1grams camera (170deg) on my mini whoop.

I agree that the ByteFrost quality is not as clear as the DJI, but it is certainly not VHS tape. I will be honest, the DVR of the ByteFrost does a bad job in recording the live footage, and that degraded-quality recording got worse after uploaded to YouTube. A more realistic analogy for ByteFrost would be DVD quality as compared to VHS/VCD for the analog FPV.

To see the true quality of ByteFrost, I would suggest everyone to watch this clip below which the owner took the trouble to record with external DVR and also rendered the video’s encoding/properties to match the YT’s compression to show a more accurate representation of the real-life HD experience of the ByteFrost.

Watch at YouTube

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11-27-2019 11:22 AM  6 months ago
TerenceChan

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Singapore

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One more video that looks pretty impressive

Watch at YouTube

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11-30-2019 09:08 AM  5 months ago
TerenceChan

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Singapore

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Faster recovery for ByteFrost’s HD transmission
Demo of faster video recovery from full “static” after firmware update

Watch at YouTube

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12-04-2019 10:30 AM  5 months ago
TerenceChan

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Singapore

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Finally, for the DJI FPV digital, it is possible to set Betaflight OSD

Watch at YouTube

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12-09-2019 05:42 AM  5 months ago
TerenceChan

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Singapore

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Converting the ByteFrost Groundstation into a pair of grab-n-fly Goggles (just like the DJI Digital FPV Goggles)

Watch at YouTube

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12-13-2019 02:44 PM  5 months ago
TerenceChan

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Singapore

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A good narration of what’s going on with ByteFrost HD and DJI HD

Watch at YouTube

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12-19-2019 03:43 AM  5 months ago
TerenceChan

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Singapore

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Working with old Naze32 Flight Controllers
Because the HD FPV “byte frost” vtx, micro luminier CP antenna and runcam-HD camera weigh about 26g, that is twice the weight of analog 600mw vtx stuff, my quad was having annoying wobbles in flight. I hooked up the old generic naze32 of the quad to Cleanflight and it said “setup is only available after upgrading firmware version”, Chrome must have upgraded my Cleanflight as it was more than a year since I used it. As I did not want to use CLI commands to change PIDs, I clicked on the “Flash Firmware” button. Bad mistake! The programming failed and bricked my flight controller! The 2016 board appeared to be too old for even the oldest CF firmware in the drop down selection.

I had to desolder the dsm2 rx to access the boot loader pads and short them with a jumper wire. Cleanflight was able to read the board after that but still giving the same flash failure. In the end, I used betaflight and flashed it with a BetaFlight’s naze fw. Thank goodness, it worked!

After soldering the dsm2 rx board back to the FC and reconnected it to Betaflight, I realized Betaflight could not recognize the “Default Serial (Spektrum)” for the dsm2 rx in the Configuration page. It simply would not save that selection and only “PPM Input” could be saved. I have a micro Lemon dsm2 rx that uses PPM but the PPM input pin is located at the bottom side of the FC (a pad labeled as “PPM”). I decided not to go that route as it would be a waste of the original dsm2 rx board and besides, I dreaded the hassle of removing the FC which is now stuck to the quad frame with special 3M foam tape ( rc heli’s gyro type).

After evaluating my options, I downloaded an old version of Cleanflight (v1.22) configurator to my PC, thinking that a configurator as old as the FC board, would definitely be able to flash Cleanflight firmware to the board. Sharks, the v1.22 Cleanflight configurator bricked the FC again, even though I was already flashing it with the old v1.9 CF firmware that was originally in the FC. Strange, how did the factory flash it then?

GRRRrr.. again I had to desolder the rx and resolder that jumper wire to short the 2 boot loader pins.
This time I used Betaflight configurator to flash the same v1.9 CF firmware and to my surprise, it completed without error!

I then closed the Betaflight configurator and opened the Cleanflight configurator v1.22, which connected easily to the FC .. so far so good! After soldering the dsm2 rx board back onto the FC, it was the moment of truth to see if the receiver could be detected. I connected it to Cleanflight configurator again and went to the receiver page. Voila, the channel bars were responding to stick movements on the radio and all the mapping were correct!

Oh, i forgot to mention that the jumper wire had to be removed after flashing firmware , else the FC would not work after a reboot (which occurs after saving new settings).

Phew! That was a tiring way to spend the evening! Nevertheless, I finally got to increase the P, I and D (more increment for “I”) to compensate for the increased weight. Most of the wobbles are gone now.

If anyone needs the BF naze fw / CF naze fw/ old CF configurator to flash or unbrick your old naze FC:
http://www.tiny url.com/naze32old

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12-24-2019 04:02 AM  5 months ago
TerenceChan

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Singapore

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Here’s my test of the improved DVR (.24fw) against an external HDMI recorder (EasyCap 280). Now, the improved ByteFrost DVR’s recording looks exactly like what we see in its live video (unfortunately my uploaded video below doesn’t because YouTube degraded the actual quality).

Watch at YouTube

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01-18-2020 05:16 PM  4 months ago
TerenceChan

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Singapore

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DJI has done it again!
Well DJI Digital HD transmitter had just gotten smaller with the latest release of their Caddx Vista.

It comes in at 31g with the camera and antenna, a few grams heavier than the byte frost (28g). It has no onboard SD card recorder and a single antenna unlike its first standard-size unit which has 2 antennas

What’s interesting is, with only one antenna, the transmission module has to drop the CDD or Cyclic Delay Diversity. CDD requires the 2nd antenna for the delayed data channel. And looking at the plots below which showed the SNR (Signal to Noise Ratio) over cyclic delay for indoor and outdoor, we could expect to see it perform noticeably poorer in indoor and perhaps slightly poorer in outdoor, as compared to the standard size unit.

Watch at YouTube

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02-04-2020 04:42 PM  3 months ago
TerenceChan

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Singapore

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A well balanced high performance omni
If you are willing to cough 30usd for the VAS 5.8ghz skyhammer antenna, you are getting a 5.25db-gain array of 2 circularly-polarized omni antennas (each one is a VAS “ion” antenna), which is the highest-gain circularly-polarized omni antenna in the world (an array is used as a single antenna so we could ignore the fact that it is made up of 2 antennas). The radiation gain pattern of the skyhammer looks like a burger with an over-stretched patty in the middle. The gain is measured from that “patty”. And that patty is the actual radiation pattern that is used for the video signal coverage. At 5.25db, the “patty” is already pretty thin which means that the skyhammer is suited for low-altitude fpv flying only. If one were to increase the separation distance between the two VAS ion antennas of the skyhammer, it is possible to get a maximum gain of 5.4db but the “patty” would be so thin that it is really easy to get out of the skyhammer antenna’s coverage if the drone flies higher (say above the trees’ line). After trying out various separation distances in the antenna array simulation, I get 5.1db of gain with 43mm separation, and I get a thicker “patty” than the skyhammer, with losing only a bit of radius of the “patty”. I then cut off the SMA connectors of two pagoda antennas that I have, and soldered them to a home-built microstrip PCB (matching network or Wilkinson splitter) so that they merge to produce a perfect 50ohm. Alright, I will leave you to watch my build video and the test results of it on the Fatshark HD FPV system.

Watch at YouTube

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03-29-2020 08:53 AM  58 days ago
TerenceChan

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Singapore

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2.3” prop iFlight DC2 running DJI HD
After the release of the smaller Caddx Vista (smaller form-factor equilvalence of the DJI Digital FPV Air-unit), not only are companies producing smaller frame-drones such as Beta95x DJI HD Whoop, they are also more selections in the 2” to 2.5” props class. Here is a stylish 2.3” prop drone designed for the DJI HD air-unit, the iFlight Titan DC2

Watch at YouTube

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04-07-2020 07:27 AM  49 days ago
TerenceChan

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Singapore

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Super-amped ByteFrost FPV with 2.5W booster
Amplifying the Fatshark HD FPV video transmission from 450mw to 2500mw.

Watch at YouTube

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04-12-2020 09:12 AM  44 days ago
TerenceChan

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Singapore

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Does LNA work for digital FPV?
Short answer is “Yes”. Find out more from the test video below.

Watch at YouTube

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05-02-2020 08:37 AM  24 days ago
TerenceChan

rrNovice

Singapore

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PCB Biquads & Dipoles for digital FPV
PCB Biquads and micro Dipoles made a good linear polarized setup for digital FPV. Here’s why:

Watch at YouTube

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05-11-2020 01:25 PM  15 days ago
TerenceChan

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Singapore

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Video range on papers for the DJI Digital FPV System is up to 4km (for 700mw output setting). In the real world, it is about 3km (line-of-sight distance) under the right RF conditions. The system would therefore benefit from directional antennas (such as the Biquad) on the receiving side, particularly in an urban setting, with a high humidity and a high RF noise floor. In the below video, I did FPV range test of the Biquad + Dipole setup in a few urban places which we would like to fly FPV in, and the results speak for themselves.

Watch at YouTube

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