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Oct 19, 2019, 08:44 PM
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Quote:
Originally Posted by Marrrv
Can be digital and not MIMO you know
It's not about MIMO. It's about using digital filtering and build-in signal redundancy techniques to suppress ISI effects.
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Oct 19, 2019, 09:03 PM
Registered User
It looks like some on this forum don't realize the full potential of digital transmission in error rejection, including multipathing effects. I don't want to go into gory details, but there are practical solutions for this issue. Here is an excerpt from fpv.blue blog on circular vs linear antennas for digital video making some points on the topic of ISI due to multipathing:

"Circular polarisation is popular with analog FPV because of its ability to attenuate reflected signal propagation paths by a few decibels. You don’t want reflected paths in analog FPV as they will be interpreted by the analog receiver at the same time as the actual, non reflected RF signal, reducing the performances of the latter.

However, fpv.blue, being a digital system, can completely reject reflected paths. We have a nice guard interval option in our modulation menu, where you can select the length of this guard interval. If you are flying to another galaxy you might want to use 1/4 as a guard interval (one quarter of the symbol length will not be interpreted and the receiver will sleep waiting for echoes to go away).

1/4 can reject reflected paths up to 64 kilometres away (see the menu for more details). We really should be removing this option as the free space path loss for 64 kilometres is huge anyway and people might be selecting it, decreasing video bandwidth for no reason. A more reasonable value is 1/16, that is selected by default."
Oct 19, 2019, 10:39 PM
Registered User
Quote:
Originally Posted by yurpet
Yes, with a 3’ coaxial cable. It is a 24 dBi L-com WiFi antenna.
Do you gain better reception and longer distance using the 24dB connected to you DJI goggles? I’ve been thinking of a ground station setup for my long range thermal glider, using my antenna trackers. It would mean that I’d still need to have parts of my 2.4 ghz analog system onboard for the ground antenna trackers to work.
Last edited by jamesn1960; Oct 19, 2019 at 10:47 PM.
Oct 20, 2019, 12:15 AM
Registered User
Quote:
Originally Posted by DDCKL
Stay with Taranis and crossfire! Open TX and 900mhz. I bought the Flymore Kit. I regret it. Not using the transmitter ater 1 flight. Switched back to Taranis and Crossfire micro.

Goggles + 2 air units is the way to go. Less money but more flyables!
Thanks I have purchased 2 air unit package
I'm now waiting on the frame to arrived
Oct 20, 2019, 12:24 AM
Registered User
Quote:
Originally Posted by Snaydher
How much cost this setup with all recommended parts by DJI?
That's a really nice setup

Doing the same build

LASER HD Frame USD $69
DJI FPV Fly More Combo $929
4 x T-Motor HOM KV1750 $92
T-Motor F55A PRO II + F4 HD Stack $109

Around $1200 + taxes
Oct 20, 2019, 12:28 AM
Registered User
Quote:
Originally Posted by jamesn1960
Do you gain better reception and longer distance using the 24dB connected to you DJI goggles? Iíve been thinking of a ground station setup for my long range thermal glider, using my antenna trackers. It would mean that Iíd still need to have parts of my 2.4 ghz analog system onboard for the ground antenna trackers to work.
Yes, of course, the reception is greatly improved. Distance doubles every 6 dB, so, theoretically speaking, it should increase about 8-fold compared to the omnidirectional dipole. I didn't test the full range of this antenna with DJI FPV yet, but with Connex Prosight it grew from about 800 m to 6000 m, which is close to the theoretical value minus some dB loss in the coaxial cable. I wear the antenna on my chest instead of a tripod, which makes possible aiming without a tracker using slow torso rotations and monitoring the video bitrate. It was easier with Connex Prosight, because it showed a much more obvious signal degradation, when the antenna was misaligned.
Oct 20, 2019, 02:53 AM
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xsergo's Avatar
Quote:
Originally Posted by Snaydher
How much cost this setup with all recommended parts by DJI?
It depends on your region. In Europe it is like 1330 EUR.
Oct 20, 2019, 02:56 AM
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xsergo's Avatar
Quote:
Originally Posted by cafu02
That's a really nice setup
Thanks!
Oct 20, 2019, 05:11 AM
Registered User
Quote:
Originally Posted by yurpet
Yes, of course, the reception is greatly improved. Distance doubles every 6 dB, so, theoretically speaking, it should increase about 8-fold compared to the omnidirectional dipole. I didn't test the full range of this antenna with DJI FPV yet, but with Connex Prosight it grew from about 800 m to 6000 m, which is close to the theoretical value minus some dB loss in the coaxial cable. I wear the antenna on my chest instead of a tripod, which makes possible aiming without a tracker using slow torso rotations and monitoring the video bitrate. It was easier with Connex Prosight, because it showed a much more obvious signal degradation, when the antenna was misaligned.
Thank you, Iíll soon be converting my 2.4ghz FPV long range 5mtr thermal glider to DJI so keen to try some high gain antennaís
Oct 20, 2019, 06:05 AM
Registered User
I had the video recording issues on my air unit today...stuttering FPV feed, then finally a SD card error. My SD cards are SanDisk Ultra 64GB A1...not the v30 ones that are recommended (or actually required). One drone even switched the card to say "Read Only"...and never made another attempt to record to it.

I also had a period where the latency was 55ms+ (at 3m away)...and frame rate was extremely low...for about 2 minutes. A few power cycles alter, and it went back to normal. But it was unflyable during that time. I don't know if it had overheated, or what...but the OSD (what little that is there) could certainly have told me.... It wasn't doing low latency or fast video, so it had plenty of bandwidth to relay errors....

I've been flying these SD cards for probably 20 flights now and never a single issue. Now both drones in the same day failed recording... Going to go locate the SanDisk Extreme now...its double the SanDisk Ultra for speeds.
Oct 20, 2019, 09:23 AM
Registered User
Looking at doing a build with DJI with 6s. I have the DJI stuff but does anyone have any recommendations for changes?

Frame - ImpulseRC APEX 5"
FC/ESC - iFlight Succex-D F7 TwinG & 60A
Motors - T-Motor F60 Pro III 1750Kv
Power Cable - XT60 Pigtail 14AWG
Cap - 50V 1000uf
Google Upgrade - TrueRC X-Air 5.8GHz
Air Unit Upgrade - Lumenier AXII 5.8GHz
Buzzer - Vifly Finder 2 Buzzer

Was looking at the Holybro Kakute F7 but only has 40A rating on the ESC. Was also looking at the T-Motor F4 Stack but barely has storage for blackbox and isn't a F7.
For motors, I was thinking of staying around 1750kv to keep the amps/heat down.

If I am missing anything, let me know, would appreciate it. Money isn't a big factor, wanting to make a mix of freestyle and speed. Just an all around fun quad.
Oct 20, 2019, 12:39 PM
Registered User
Why 6S? Just do 4S. 6s isn't really worth it in my opinion... I had 6S, I changed out my motors and went back to 4S. If you are a pro racer, and I mean really pro...maybe... But I have seen pro racer's on 4s still doing great....

I believed the hype for a bit, tried it, was disappointed it didn't really do much more other than having a fatter battery... Accidentally fried a 4s drone by plugging in wrong battery, and then I said I was done and changed out motors and retired my 6S batteries.
Oct 20, 2019, 02:20 PM
Registered User
So I recently got these - they're amazing! However, on both of my air units the recording on the air unit stops after around one minute, while the goggles record the entire flight. Has anyone else had issues with the air unit flight recording stopping?
Oct 20, 2019, 02:22 PM
Aalesund, Norway
Testing out my new X-air antennas. The signal drops very very fast !!
Range test DJI FPV with TrueRC X-Air's (7 min 36 sec)
Oct 20, 2019, 04:15 PM
Registered User
Anyone who has used the Av in much, have you found the connection is a little flaky? If I bump the AV plug during transmission the screen goes black and says DJI for a couple seconds and sometimes I get the image back or it goes to a blue screen. Not very comforting for use with analog input. I wonder if my AV in is faulty.


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