Betaflight doesn't show you SNR and that's a problem 

Configured my first quad in BF4.4 now and wondered, why crsf_use_rx_snr didn't work anymore... Turns out they just added the feature and you can now just activate it in OSD! Yep, they listened!

One of the ways I used to teach SNR, MER and Error Vector Magnitude was giving one person in my class a piece of paper with a bunch of random 1's and 0's written on it, and another a blank paper with a pen. I would ask the entire room to be quiet and have the one student read to the other the 1's and 0's. The student who wrote it down would read it back and verify there were no "errors". I would give them each new sheets and this time the entire class would make a lot of noise while they did the exact same activity. This demonstrated that there were more "errors" as well as a requirement for the person reading the numbers to raise their voice. In certain digital radios, the transmitter will actually increase its output power to compensate for a noisier environment to try to talk over the noise floor. This is something severely lacking in fpv and model RC is more dynamic radio transmitters. Utilizing a pilot sub carrier like we do in 802.11 protocols to essentially link Tx and Rx using a very narrow, low density channel, could seriously improve link quality at a much further distances imo.

You can throw SNR on a channel once you have the telemetry info back on your radio. That channel you can visualize on your OSD. A useless round trip but doable.

Thank you Joshua.👍 I always follow your lessons. May you always be healthy.. 😊

This has to be the best info I’ve learned this week, no lie! Thanks Josh!!!!

Mind = Blown. This helps so much in understanding why those receiving quality metrics never really corellated with reality. Gonna try CRSF SNR now. Thx!!!

Great video Joshua. I just enabled this and added it next to LQ in my OSD. Thanks!

You've really perfected your rock concert analogy . Great video content much appreciated.

Configured, I'll try it tomorrow, excellent video

Bravo sir. Keep rolling out the hits!

Fantastic, Joshua! Thanks a lot!!! 😃 Stay safe there with your family! 🖖😊

Great video. SNR is THE measurement to start with. I can have all the signal, but if my separation from the noise floor is 15dB, won't really matter

Jb you are as usual, top one

Thanks Joshua, from Santa Cruz Ca.

Building a long range drone definitely gonna use this feature!!

Other examples of SNR: Guitar amplifiers...turn up the gain control and noise is added to the signal between the guitar and the speaker, though this is often a desirable effect known simply as overdrive or distortion. The more you turn up the gain, the more distortion (noise) is added to the signal. Cameras...when you need to let more light in to obtain good exposure but the aperture is already at its widest and the shutter speed cannot be taken any lower without inducing motion blur, you increase the ISO, but doing so adds image noise. The ISO control applies gain to the signal (the signal is the image data as it travels from the sensor to the memory card) and the more you increase the ISO value, the more image noise will seen in the final outputted photograph. Beyond a certain ISO value (this varies from camera to camera) the image will be so corrupted by image noise that the photograph will have little discernible detail and will look like a speckled mess.

Thanks Joshua. 👍 Now we only need real life tests to prove which indication is the most reliable. You know, like years ago when you were running up and down across your property and testing various receivers. 😉😁

That was excellent and going forward I will use SNR. However on most of my builds I don't have any other osd than battery voltage. I do however have my Tx call out the Elrs power output as it changes when on dynamic. When I first did this it amazed me how much of a difference it made to match up the antennas on tx and rx. When I had horizontal to vertical the output power was up and down like a yo yo from max 250 to 10mw and I wasn't to far from myself. (Null point and kwad orientation) vertical to vertical works much better. In fact on my T-lite with max 250mw I hardly ever climb above 10mw! I'm therefore not distracted by my osd and my ears keep track of the audio alerts

Excellent explanation, as always (and I'm saying this coming from a HAM background). But I do wonder how you managed to avoid the term "link budget" so far.

I have just tried that and SNR is so much more stable easier to read. Thank you so much for the explanation. In my enviroment 4dB SNR = 27% RSSI. Do I have to change the rssi_dbm_alarm threshold or it will stay at the same point despite of unity change? Anyway it would be nice to be able to set the RSSI alarm to a given SNR value.

I notice the level of interference to my GPS camera drones goes way up here in the winter when 100,000 people show up to this town all in RVs with thier own internet hot spots . This makes the range on my controls go way down and has even caused me to not have any control so I think it would be useful to see what the value is so know if I can fly in a particular area . I had a 4drc F9 go nuts and fly away and I suspect that was due to interference. Never found it . Never seen it fly that fast either 😅😁 When the seasonal people leave I have no problems with any of my drones.

I am running Crossfire and while I have not had any failsafes like I I had in my Frsky (XM+/RSXR) days, I do still get periodic "Link Quality" messages in the OSD at random times when I am not that far away. I enabled SN in Cli as you reco'd and what an eye opener as my SNR rarely gets above 25 and is often in single digits. I am running 500mW (dynamic) and wondered if maybe the power switching is causing these brief "Link Quality" messages. This happens with my Evoque, Roma V2 and Flywoo Baby 1.6 (all CRSF of course). I have a Cinerace20 coming this weekend and expect it will do the same.

Great explanation Joshua. One question, when turning on SNR in betaflight what happens to the dBm alarm? Does it stop working completely? Still works the same way (by using rssi dBm)? Or is it looking at the SNR value, thus the threshold should be changed? Thanks!

for me its a tough call, i fly in odd places where its possible i fly up a mountain and suddenly i see 10 people, each, no doubt, with a phone, then theres also the possibility of people approaching me where i'm sitting. i havent even sorted out lq on my nirvana crossfire/dji v2 set up yet, i think i could make the nirvana beep on the snr and then a glance at lq could tell me to expect trouble, but it would be nice to just see snr before i even take off.

Joshua, how are you? I would like to know if you recommend the use of dynamic power in crossfire. thank you from Brazil

it would be super nice to have the link to the artist who made your tshirt/where to buy it in the description of every video since you basically always wear super cool FPV art tshirt, don't you think?

Any advice on where to place the antenna for the best range possible? I am using T-antenna style elrs rx on my quad and fixed wing. Thanks.

I did this on a happymodel x12 v2.1, using the v4 Mobula 7 frame some robo 19500 motors and a Foxeer antenna with the Runcam 4 and a custom canopy I 3D printed in tpu,long story short with this turned on my link quality warning goes intermittently crazy dropping from 7:100 to 75 in very close range just flying a small circle, turned this off and everything is great again. Perhaps because the receiver is spi I need to use a different command to utilize this feature.

From Texas

So does this work with the custom Betaflight branch you shared in the last vid to get LQ and RSSI dBm? I tried it, but I’ve yet to even get that first part completely working. But for when I do, and others surely wondering, do the LQ/RSSI dBm hack and SNR reporting play nice?

I flew 6 miles yesterday; 9.5km. My tx was only putting out 25mw @100LQ. I don't think it's a major problem. At least for my area.

good vid...

Hi!! My Tango 2 just failsafe at 1w, 15 mts from the drone and with an SNR of 30db and a LQ of 2:100...

Test done with rx ep1, betafpv and matek (all 2.4ghz) with 3 differents TX and RSNR (And TSNR) are between 12db and 14db. It seems that is not the same scale 🤔

Wish BetaFlight had a DJI MSP OSD button.... then the OSD tab would only show the DJI options that work...

From Indonesia

What about the OSD RSSI DB warning once you've set `crsf_use_rx_snr = on`? The warning level set in the CLI is based on the RSSI DB but that wouldn't capture the case of a noisy environment.

Should the SNR on the radio have the same value as the SNR on the quad/OSD?

I've only ever looked at it after on sdlog. To see times I was close to failsafe when not too far Tons wifi towers where I am. Town city wide wifi being blasted to from optimum & others

I just go by putting the LQ on RSSI in the DJI googles and working on the principle that if it drops below 90, it’s time to turn back, because if I’m far enough away that crossfire can failsafe, I’m in a whole lot more shit for flying that far away than I am my craft failsafing and switching to GPS rescue or RTH in iNav, cos we’re not allowed to fly further than we can see in the UK. Honestly if you’re flying further than you can walk/see, you should have some sort of rescue setup and shouldn’t rely on the craft telling you you’re about to failsafe in the OSD.

Best would be to aggregate the three metrics into one using an algorithm to approximate as best as possible when we approach the failsafe point...

when using the command 'crsf_use_rx_snr = on' on the CLI, will the SNR show on the osd for ELRS recievers too or is it only for crossfire recievers quads?

just did this command in the cli set "crsf_use_rx_snr = on" and the snr worked but the rssi also went back to 99! before it was at 80-90 when a meter between each other and then dropped of to 50-60 when between 5 rooms or so. Now it seems to be working again! using crossfire. now only drops to around 95-99 through 5 rooms when on 1w

Thanks alot.. Do you think frsky R9m with elrs is getting old. You dont use it anymore?

So what does that do to your warnings set up for rssi -dbm? Are those still active as rssi -dbm? Or has the snr value taken it's place there too? For example, my rssi -dbm warning is set at -95 dbm since I'm running 500hz ELRS. What should I do about that warning value if snr has taken it's place? Set it to something like -6 dbm?

Fun fact: emuflight offers all the link related informations in the OSD at once Sad to say, that ELRS SNR does not work for me (it says CRSF for all the link Infos).

Hey JB. Are you sure about SNR treshold? We really can't go below 0db SNR? Official lora documentation stand for: A value closer to +10dB means the received signal is less corrupted. LoRa can demodulate signals which are -7.5 dB to -20 dB below the noise floor. This is the beauty of lora modulation!!!

Is there an option to place a feature request on the betaflight github? Perhaps we can get some momentum by creating a feature request for 4.4 and adding comments to show support. For now it seems like the most comprehensive option is to set an alert on the radio for low RSSI dBM OR low LQ OR low SNR (with a delay so it doesn't go off when there is a slight blip). This way you get a warning even if you can't see all three on screen and can make a decision on whether or not to turn around.

It would be ideal if betaflight or flight controller could combine/calculate these measurements depending on what you select in betaflight and output a value from 0-100. Maybe also be able to preconfigure the values that it bases its 0-100 displayed connection quality. Ah pipe dreams 😂

thx josh! New video: how is tememetry transmitted ? big mystery .... Is RX have... a TX ??????

A Betaflight GitHub PR (11062) was raised back in November 2021 to add a dedicated RSNR element to the Betaflight OSD. That PR has been earmarked for inclusion in the Betaflight 4.4 release. My comment keeps getting deleted if I include a GitHub link, so you will have to search the Betaflight GitHub repo pull requests log manually for PR 11062 if you want to see the details.

@Joshua Bardwell how can i get SNR on my DJI goggles?

The receiver RX must always send back with at least the same transmission power as the transmitter TX, right? how does the receiver know with how much power he has to transmit? I would find that interesting to know and understand. because here in Germany you are only allowed to transmit at 2.4 GHz with 100mw. how does the telemetry receiver know that? Thanks

I use CRSF and never have a negativ number o.O using DJI at the moment an have only one indicator for my Connection... would love to have LQ in DJI OSD

Man it’s all so confusing. So out of all the predictable warnings that you’re about to failsafe, this is the one to do?

One interesting complication is that LORA can actually receive signals BELOW the noise floor.

In the meantime, is there any way to see both SNR and RSSI dBm on the OSD?

Is signal to noise ratio, at least as it’s shown in betaflight really signal to noise delta? Ratio implies division, or some sort of percentage.

Someone who knows Ghost protocol says that Ghost FW does not send SNR to BF.... maybe yet :)

Do we still need to do the dbm output test at 10mw on Controller and minus 10 or does this cancel that out as I'm setting up a new quad.. Thanks for the video.

Dang... I really need to fork over the doe and get onto crossfire or even tracer. I'm still using old school regular RSSI on flysky and frsky : (

I have what I think is failsafe in the past and I've never sure if it's the video or the radio that failsafe how can you tell?

I don’t even display RF signal anymore in the osd. No LQ, no RSSI, nothing. With Crossfire or ExpressLRS range is more than good enough for anything. Dynamic power active, that’s it.

Reason SNR isn't shown is because the values are 1) inaccurate due to clipping of the input data and 2) misleading as LoRa based signalling can work below the noise floor. SNR is in theory useful, but unfortunately pilots are going to see inaccurate and misleading SNR.

And they got rid of LQ in 4.3. Its been broke or gone for F405 boards.

Great video. Does not not work on BF 4.1.0 It does however work on BF 4.2.0

So is Snr in DB or percentage

0:01 nah.. there are 4 metrics, and the 4th is the easiest and most important for most of us with Crossfire and similar, especially with dji hd.. video quality is my #1 metric for turning around. There’s only so much we can digest per second, all these various (usually) cryptic numbers become relatively useless unless its a calm high flying distance rig. But its nice to know, so I learned something today.

so will this show in DJI goggles?

👍👀🇭🇷

Talking about your affirmation from 1:57: "The further away you are the weaker the signal is, the more corrupted packages there are." I don't think you're right. You could have 100 LQ but 25 RSSI and be miles out. You can see that on falconRad's video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-e5ewAHjnQtQ.html.

As a person that watches a lot of RU-vid, thanks for getting rid of the 10-second intro. I don’t need that. I just want the info. Thanks!

@betaflight fix this!!!

-8dB TSNR 🦾