For closer range, ELRS is robust enough it seems any kind of antenna placement is fine as long as it is not pressed against the carbon frame. However going out further, maybe medium range around 1km, then it seems the dipole null points do have an effect.
On most of my builds I have the dipole oriented horizontally, so the antenna null points are pointing left and right of the drone. When far out and turning around, I often see the LQ drop as the null point faces the home point, but usually not enough to result in a RX LOSS. Checking my DVR, I see that the screen actually momentarily flashed RX LOSS in such a situation, and dynamic power on the transmitter went from 25mw to 1watt, but there was no control loss. I flew a second build where the antenna was oriented vertically (and turned the radio antenna to match), not quite as far out but pretty close, and noticed LQ barely dropped when turning and the transmitter remained at 25mw throughout the 12 minute flight.

So if you plan to fly out further (mid range) and don't want to install a diversity receiver, is a vertical orientation better? With the null points pointing up and down, unless  you are right above you, or doing a flip/loop at distance, there will be very little chance of pointing the null point back home.

I think a vertical antenna orientation is probably a better option with ELRS.

I was flying two 5" quads at the weekend in the same location (open fields with a few trees and hedgerows around). One was a Crossfire equipped quad, and the other was an ELRS equipped quad (set at 250Hz packet rate). I've never had a failsafe with any of my Crossfire equipped quads (knock on wood), but with my ELRS equipped quad I suffered two failsafes at the weekend at a distance of around 470m away. Luckily that quad is equipped with GPS so the RXLOSS triggered GPS Rescue. Flying my Crossfire equipped quad had no such problems when flying it in exactly the same GPS coordinate position as I was flying the ELRS equipped quad. Both quads have a dipole T antenna mounted in a horizontal orientation.

I definitely feel that the 900MHz Crossfire RC link is more reliable, dependable and secure than the 2.4GHz ELRS RC link. I guess changing the orientation of the ELRS antenna to a vertical position might help to mitigate the RXLOSS issue I experienced.

If you are getting RXLOSS at that range, it sounds like something is very wrong with your setup. Have you done the benchtest? Do you have any DVR or telemetry logs?
https://www.expresslrs.org/quick-start/p...bench-test


And yes, vertical antenna mounting is preferable for long range as you avoid the antenna nulls. You can also use a diversity receiver with two antennas, and mount them properly so they cover the other's nulls.

Vertical is better, its just not handy in most cases.
I has vertical antenna mounting on my 7inch range-cruiser.

Hey guys, I'm currently having a problem with my receiver.
I have the iflight Evouge F5D Digital with a TBS Nano RX. (Crossfire)
My radio is the TBS Tango 2 pro.
The connection was no problem and all the AUX channels also work, but I have no sticks inputs.
I feel like I've tried everything and can't get any further.
I hope that you can help me further.
Many thanks in advance.

Greetings
Tobias

PS.: It’s looks like this:
(Only the AUX channel are moving, but my Failsafe is deactivated.)

(13-Jun-2024, 07:31 PM)V-22 Wrote: If you are getting RXLOSS at that range, it sounds like something is very wrong with your setup. Have you done the benchtest? Do you have any DVR or telemetry logs?
https://www.expresslrs.org/quick-start/p...bench-test

I do believe it was the antenna null points, at that spot the drone was in front and off to the left. When it rotated and the dipole was pointing back home, basically both antennas had their null points pointing at each other (or close to it). The radio also ramped up to 1W in another spot (also during the same kind or turn) but no RX LOSS was displayed.

Here is the DVR, I also flew a drone with the vertical antenna (blue props in view) although not exactly the same locations I think they were close enough. That radio stayed at 25mw throughout that 12 minute flight. I believe the RSSI dbm values were quite similar.

(13-Jun-2024, 09:33 PM)mstc Wrote: I do believe it was the antenna null points, at that spot the drone was in front and off to the left. When it rotated and the dipole was pointing back home, basically both antennas had their null points pointing at each other (or close to it). The radio also ramped up to 1W in another spot (also during the same kind or turn) but no RX LOSS was displayed.

Here is the DVR, I also flew a drone with the vertical antenna (blue props in view) although not exactly the same locations I think they were close enough. That radio stayed at 25mw throughout that 12 minute flight. I believe the RSSI dbm values were quite similar.

That was in response to Snow's post, but I see you also had a brief RX LOSS in your video. You can see the LQ drops rapidly at one point during the turn, while the RSSI dBm is still -90 or better. This suggests there is some strong RF interference at that point causing the RSNR to drop below 0. If you put the RSNR element in your OSD or enable telemetry logging on your radio you should be able to see exactly what's happening. 

Have you done the bench test? What RSSI dBm do you see with TX and RX 1m apart and TX set to the lowest power?

I was flying with @mstc at this location. Now I know why I kept losing you as I tried to follow behind your quad, you were way out there for a little while!

(13-Jun-2024, 10:25 PM)V-22 Wrote: That was in response to Snow's post, but I see you also had a brief RX LOSS in your video. You can see the LQ drops rapidly at one point during the turn, while the RSSI dBm is still -90 or better. This suggests there is some strong RF interference at that point causing the RSNR to drop below 0. If you put the RSNR element in your OSD or enable telemetry logging on your radio you should be able to see exactly what's happening. 

Have you done the bench test? What RSSI dBm do you see with TX and RX 1m apart and TX set to the lowest power?

I do need to add logging on my radio, I suspect the OSD update is too slow. I notice there are quite a few frames where the LQ is blank and looks like it lags a little as well. As for RF interference, I see that in the second spot as video was also affected (behind a pond and next to a building complex), but in the first spot where I actually got RX LOSS I wonder if the null points were enough to cause that.

I did not do the bench test, as ELRS has worked so well I never felt the need to do so, and the one time I did for debugging it was fine. But I will do a bench test just to double-check and post back.

@fpvme Now you have your 1W VTX you can probably start pushing out your envelope. That video glitching at 0:53, that was when you plugged in your HDZ

(13-Jun-2024, 10:25 PM)V-22 Wrote: Have you done the bench test? What RSSI dBm do you see with TX and RX 1m apart and TX set to the lowest power?

At 25mw 1m away

With drone between the antennas (facing the radio)
-15      -30 (transmitter antenna rotated 90)

With antenna facing radio (clear line)
-10      -28 (rotated 90)

(13-Jun-2024, 11:44 PM)mstc Wrote: @fpvme Now you have your 1W VTX you can probably start pushing out your envelope. That video glitching at 0:53, that was when you plugged in your HDZ

It's true! I have the gps rescue set up now. But I live a valley under the trees? The time has come to find a lookout with a great view and give it a whirl.

I'm surprised the hdzero had that effect! Maybe because my drone was so much closer to us at that point. Sorry about that!
Will have to be more mindful in the future, I'm just used to being the one that gets swamped by dji.

(14-Jun-2024, 02:13 PM)mstc Wrote: At 25mw 1m away

With drone between the antennas (facing the radio)
-15      -30 (transmitter antenna rotated 90)

With antenna facing radio (clear line)
-10      -28 (rotated 90)

This is fine, and also demonstrates the importance of matching antenna orientation. 

Quote:but in the first spot where I actually got RX LOSS I wonder if the null points were enough to cause that.

No, you can see your RSSI dBm drops down to -90 at worst, which is still well above the sensitivity limit of the receiver. What it does suggest is there is some strong background noise in the 2.4GHz band there (about -90 dBm) which is drowning out the RC signal. If you log RSNR or put it in your OSD it should be clear. 

Here is a quick video on setting up telemetry logging on your radio (OpenTX, but same process for EdgeTX):

Quote:I suspect the OSD update is too slow. I notice there are quite a few frames where the LQ is blank and looks like it lags a little as well.

Could be caused by excess MCU load. You can also increase the OSD refresh rate and enable fast serial in msp-osd to smooth out the OSD: https://github.com/fpv-wtf/msp-osd?tab=r...-unitvista

What PID loop rate are you running? Can you post the output of `status` in the BF CLI? You are not running the OSD on soft-serial, are you?

(14-Jun-2024, 07:24 PM)V-22 Wrote: Could be caused by excess MCU load. You can also increase the OSD refresh rate and enable fast serial in msp-osd to smooth out the OSD: https://github.com/fpv-wtf/msp-osd?tab=r...-unitvista

What PID loop rate are you running? Can you post the output of `status` in the BF CLI? You are not running the OSD on soft-serial, are you?

Its a F405 running at 1.6k loop. I will give fast serial a try (no not on soft serial), but the other elements seem to be updating, I only notice the LQ seems to disappear as it gets near the RX LOSS. 

Quote:# status
MCU F40X Clock=168MHz (PLLP-HSE), Vref=3.30V, Core temp=41degC
Stack size: 2048, Stack address: 0x1000fff0
Configuration: CONFIGURED, size: 4100, max available: 16384
Devices detected: SPI:2, I2C:0
Gyros detected: gyro 1 locked
GYRO=BMI270, ACC=BMI270, BARO=BMP280
OSD: MSP
System Uptime: 62 seconds, Current Time: 2024-06-14T18:37:38.364+00:00
CPU:21%, cycle time: 308, GYRO rate: 3246, RX rate: 15, System rate: 9
Voltage: 1 * 0.01V (0S battery - NOT PRESENT)
I2C Errors: 0
SD card: Not configured
Arming disable flags: RXLOSS CLI MSP RPMFILTER

Edit : I guess it is because the OSD starts flashing it as a warning when it gets too low, failed to realize that when checking frame by frame.

(14-Jun-2024, 07:42 PM)mstc Wrote: Its a F405 running at 1.6k loop. I will give fast serial a try (no not on soft serial), but the other elements seem to be updating, I only notice the LQ seems to disappear as it gets near the RX LOSS. 



Edit : I guess it is because the OSD starts flashing it as a warning when it gets too low, failed to realize that when checking frame by frame.

You should be running a 3.2kHz PID loop and DSHOT300. There is no reason to run slower. 

Do you have `displayport_msp_fonts = 0,0,0,0` set in the CLI? Or have the multicolor fonts uploaded?

I would suggest to mount the antennas indipendently, they should be as faraway from eachother as possible. It might not be your main issue but it might be benefical.