I cannot (nor do I wish to) take on yet another subscription as I already pay a hefty amount of monthly for stuff that my wife wants and/or things that are more financially beneficial than this hobby. That said, you more than anyone has made my understanding and enjoyment of this hobby the experience I want to have. I wish there was a better system for ongoing support that doesn't require me to work two jobs to maintain. Thanks JB.
Thought I had finally found the video to prove to my wife that drones are not "Expensive toys for grownup kids" instead of the sophisticated and highly technical test beds of technology that they are. I explained that the inverse square law is also useful for calculating radiation exposure from nuclear sources bla, bla, bla... any way now she says that my drones are just "expensive toys for grownup NERDS". meh... I give up. Thanks anyway JB.
just point out to her almost every aerial shot you see on the TV these days is shot with a drone. People take that for granted. A shot that used to cost $30,000 with a heli now cost $300 with a drone. And if China ever shows up at the beach, they can meet my kamikaze drones.
I'm really enjoying these slides about math! For part 2, please discuss signal to noise ratio and basic antenna patterns, and their affect on range. Thanks!
From The Crossfire manual. RSSI Relative signal strength indicator How “loud” the signal is, that the receiver “hears”. But this also includes noise. The RSSI is exponential which results in a massive drop at the beginning and slows down the lower it gets. In general: double the range will result in a drop of -6dBm. An example: ● RSSI at 0m = -10dBm ● RSSI at 1m = -16dBm ● RSSI at 2m = -22dBm The CROSSFIRE can go down to -130dBm before the link breaks up. If you use RSSI as a sensor by the channel/ output map menu or as an OpenTX telemetry sensor, it will be shown like this: ● -0.1dBm = 100% ● -130dBm = 0%
Thanks for this info. I use crossfire and had being looking for this information. Will you happen to know how to do the calibration of a radiomaster t16 pro, so it properly read the RSSI. If I stand 2 feet from my quad it reads Close to -30dbm most of the time.
Great video! I encourage everyone to get their amateur radio license. It's cheap, there are great free study guides available, you'll learn something, and likely make amateur radio less boring. There are a lot of great resources for antenna theory when you decide to start rolling your own as well.
As an RF engineer and a ham operator, your explanation is spot on. I don't have a drone (yet), so there's not much in this hobby that I can speak about with any authority. However, this is my day job. Another way to increase range is a better antenna. You mentioned polarization, and that is certainly a part of it, but even with the correct polarization, a better antenna has the benefit of improved tx range AND rx range. My first step for improving range is always, "get the best antenna possible".
I think it worth to mention that TX & RX separation is more logical & historical than practical, because most of modern protocols are digital and actually bidirectional (same as WiFi). So, both TX and RX are not really receiver and transmitter, they are both transceivers! That's the reason why we can get telemetry signals back from RX to TX, because RX transmits it. I assume transceiver on a quad RX is weaker than on a TX and we supposed to loose telemetry earlier than main controlling signal. But in order to adjust the power and the number of update per second (like ELRS doing), TX should constantly track a feedback from RX, so I wonder what happens with ELRS and similar when they no longer hear feedback from RX - are they treating this as being disconnected or they have a fallback values for max power and lowest update rate in order to work on unidirectional mode "blindly"?
Gotta hand it t you, you put things into perspective. When my customers, chip manufacturers, complain about the RF power supplies being "out of tolerance" by 0.5% I want to point them to your videos. Different ball game with 3-5KW supplies, but the same principles.
Ooooh I love and hate the inverse square law. As soon as you said that, I knew exactly where this video was going. Great explanation, Joshua, thank you!
Very interesting video. I would love to see one discussing the different antennas used on radio transmitters and video receivers and their propagation patterns.
If we compare it to light (and BTW, radio IS light, just in a frequency we can't see), I guess people think about a laser pointer, instead of a lamp (which would be closer to our antennas). Like, with a laser pointer of less than 1w you can put a light point in the next building... Perhaps even in pretty distant buildings... But a 60w lamp (I mean the old ones, from Edson) barely can illuminate a room. A 5w laser can cut 6mm MDF or plywood! That's exactly because a lamp doesn't focus all the light in one direction (neither deals with the frequency and so on, which a laser also does). A lamp emits light in 360° x 360°! (Perhaps x 360° again?) So, anyway... We need to think about lamps, not lasers in this hobby. 😬 Thanks for the video, Joshua! Stay safe there with your family! 🖖😊
Nice of you to include the dB concept, but if I were you I would have put that as an extra info toward the end (perhaps even shortly covering antenna gain while you are at it 🤣). As I personally suspect that the "simple" formula √(currentPower/referencePower) is much easier to learn. It only needs the inverse square law and allows to compare range already..
Old me is telling young me "If you paid attention to math in school like you were told, you'd have an easier time understanding and playing with your cool flying camera toys when you get older"
Explain range verses frequency , explain encoded multiplexing, the math gets really fun. It is a place where computers shine,. Personally my nemesis was a Calc problem where the answer, was the exponent buried deep within the formula. Missed that problem twice , hurt my feelings . This has been a fun refresher of things long forgotten , in real life these problems seldom came up ... never found that nemesis math problem used for anything , which is good . Take care.
hi friends I have an unrelated question I recently bought th diatonic mamba f405 mk2 fc because I accidentally lifted a couple pads on my old fc but anyways I cannot get the rx3/tx3 cart to work for my dji osd I use ELRS 1 watt as my link this board has three parts but the tx3/rx3 will not give any telemetry should I give up because the company has given minimal assistance I'm stumped
because power/performance is not a lineal relation. Tipically a 10 base log, so to double your range you have to roughly x10 your power. That's why compared to 100mW switching to 300mW will be more noticed than switching from 300 to 500. The more it rises, the less effect it has on the range (by comparison!). That's basicaly why the dB scale is a log scale (+6dB = x2).
FYI all measures are relative, there are no absolute measures. For example, the boiling point of water is 100C but only at STP. Radio waves suffer rapid degradation under water and very little in space. Relativity is a very important concept.
That's a useful video, and right as far as it goes, but what it doesn't taken into account is real life environment and obstacles. Unless you are in an open empty space, the inverse square law isn't that likely to apply accurately in practice. Take a simple example: you fly behind a big tree or grove of trees (leaves are damn good at absorbing signal at those frequencies), so your video breaks up badly. It's done that because the received level has probably dropped suddenly by a lot. So, switch from - say - 25 to 200mW (assuming it is legal), and do it again. In theory that will give root 8 times the range - over twice. Actually it might well be virtually no different because the signal drop behind the trees was so big that boosting it by 8x made little difference. Maybe you get a few feet further behind the trees before it drops out, but not much else. So, it is probably worth pointing out that whilst the inverse square law works fine when there are no obstacles that adversely affect signal conditions, in real world situations, the further you go, the more signal absorbing and reflecting obstacles there are likely to be in the way, and these will cause the range not to increase like one might expect. If one is flying high up in open sky it will work better (no obstacles) - but we probably won't be doing that, will we, because it might be illegal ....
Hi sir very valuable information you have provided,my quad motors are rotating variable speed one was rotating very slowly and some motors are rotating at full speed , I'm using omnibus F4 pro SD card version flight controller please help me to resolve this problem sir
It's really hard (nearly impossible) to really intuitively understand how oppressive 1/r^2 is. Worse is how dB anything works... and this is my day job
In terms of the "new" AKK 10W vtx: So basically, the VTX at 10W should have 3x the range over it at 1W. But that is not the case, as we can tell from the reviews. How comes?
Only watched till 0:27 so far: no, does not seem the same, 300 vs. 100mW = 300% and 500 vs. 300mW = 166%. Signal strength is not linear with distance, because the area where the rays spread over goes up squared. So you would need 900 mW to get the same effect over 300 mW. Now let's see if this is totally wrong ;)
So if decibels never express an exact amount of anything how does it describe sounds? Doesn't it have to be exact at some point? Like how do you know what 100 dB Is if you don't know what 1 dB is? Or I'd there some consistent sound they use as a base?
Wait! What!? You're saying most FPV-ers are confused by a logarithmic scale and have trouble understanding RF, you don't say, I couldn't have guessed ... :D
Please answer me if I am correct or not. So does it means that if we choose 1000mW (1W) of transmit power and choose 50 Hz of packet rate, We will have the most range. Please someone answer me, thanks in advance
Had bad education.found out later in life math laws. Add first subtract second multiply third divide fourth on all math equations. Correct me if I'm wrong.
I appreciate your efforts in trying to bring the technical aspects to the masses and beginners but I'm sorry to say that in the process of trying to simplify the math and add tools for easier calculations you kind of just made in 10 times harder than it had to be. Using a table and db to ratio conversion for a simple "how much extra range" calculation? Just say square_root_of(newpower/previouspower)= range ratio. Thats it. Nothing extra is required. I don't see the entire point with using the table and dB conversions. Everyone has a calculator on their phone if they really must know the exact ratio, otherwise all you would have to learn is the basic formula, as well as perhaps memorize the square root of 2. Most cases anyone would only really be calculating 2x or 4x increase in output power.
I cannot (nor do I wish to) take on yet another subscription as I already pay a hefty amount of monthly for stuff that my wife wants and/or things that are more financially beneficial than this hobby. That said, you more than anyone has made my understanding and enjoyment of this hobby the experience I want to have. I wish there was a better system for ongoing support that doesn't require me to work two jobs to maintain. Thanks JB.
Thanks for your generosity.
Thought I had finally found the video to prove to my wife that drones are not "Expensive toys for grownup kids" instead of the sophisticated and highly technical test beds of technology that they are. I explained that the inverse square law is also useful for calculating radiation exposure from nuclear sources bla, bla, bla... any way now she says that my drones are just "expensive toys for grownup NERDS". meh... I give up. Thanks anyway JB.
just point out to her almost every aerial shot you see on the TV these days is shot with a drone. People take that for granted. A shot that used to cost $30,000 with a heli now cost $300 with a drone. And if China ever shows up at the beach, they can meet my kamikaze drones.
Feeling both attacked personally and proud at the same time.
Sounds like you may need a new wife. Wives are just low technology, less obedient versions of drones
When payday hits
Iflight gets my $$
Cheers from Knoxville Tn
@@bentprops_ she just likes to give me a hard time. 😉
I'm really enjoying these slides about math!
For part 2, please discuss signal to noise ratio and basic antenna patterns, and their affect on range. Thanks!
From The Crossfire manual.
RSSI
Relative signal strength indicator
How “loud” the signal is, that the receiver “hears”. But this also includes noise.
The RSSI is exponential which results in a massive drop at the beginning and slows down the lower it gets.
In general: double the range will result in a drop of -6dBm. An example:
● RSSI at 0m = -10dBm
● RSSI at 1m = -16dBm
● RSSI at 2m = -22dBm
The CROSSFIRE can go down to -130dBm before the link breaks up. If you use RSSI as a sensor by the
channel/ output map menu or as an OpenTX telemetry sensor, it will be shown like this:
● -0.1dBm = 100%
● -130dBm = 0%
Thanks for this info. I use crossfire and had being looking for this information. Will you happen to know how to do the calibration of a radiomaster t16 pro, so it properly read the RSSI. If I stand 2 feet from my quad it reads Close to -30dbm most of the time.
Superb explanation of how transmission range diminishes over distance. 👍
Great video! I encourage everyone to get their amateur radio license. It's cheap, there are great free study guides available, you'll learn something, and likely make amateur radio less boring. There are a lot of great resources for antenna theory when you decide to start rolling your own as well.
FPV got me into ham radio. Now I have two hobbies none of my friends understand.
As an RF engineer and a ham operator, your explanation is spot on. I don't have a drone (yet), so there's not much in this hobby that I can speak about with any authority. However, this is my day job.
Another way to increase range is a better antenna. You mentioned polarization, and that is certainly a part of it, but even with the correct polarization, a better antenna has the benefit of improved tx range AND rx range. My first step for improving range is always, "get the best antenna possible".
I think it worth to mention that TX & RX separation is more logical & historical than practical, because most of modern protocols are digital and actually bidirectional (same as WiFi). So, both TX and RX are not really receiver and transmitter, they are both transceivers! That's the reason why we can get telemetry signals back from RX to TX, because RX transmits it. I assume transceiver on a quad RX is weaker than on a TX and we supposed to loose telemetry earlier than main controlling signal. But in order to adjust the power and the number of update per second (like ELRS doing), TX should constantly track a feedback from RX, so I wonder what happens with ELRS and similar when they no longer hear feedback from RX - are they treating this as being disconnected or they have a fallback values for max power and lowest update rate in order to work on unidirectional mode "blindly"?
When ever I think I’m smart, I watch Bardwell…
Thanks Joshua, you are amazing.
Best explanation of this topic I've ever seen. 👏
Gotta hand it t you, you put things into perspective. When my customers, chip manufacturers, complain about the RF power supplies being "out of tolerance" by 0.5% I want to point them to your videos. Different ball game with 3-5KW supplies, but the same principles.
Lol, I watched the video about the antennas, funny to see an old style Bardwell video.
Ooooh I love and hate the inverse square law. As soon as you said that, I knew exactly where this video was going. Great explanation, Joshua, thank you!
I learned something today for sure 😆Thank you JB for educating us on the things we should probably know about our hobby.
Fantastic video, glad I'm seeing it. Nearly missed it.
Great video. So many people get it wrong about distance. Haven't had that much math instruction since high school. Memories of math anxiety
Very interesting video. I would love to see one discussing the different antennas used on radio transmitters and video receivers and their propagation patterns.
It would be awesome if he could try building a helical antenna just for comparison.
Another great Friday night math video , I was starting to think you were slipping , lol great video. Very informative ..
Ok, that makes a lot of sense! Thank you JB!
Exactly what I need. I'm trying to build a sub 250 long range but I want to be able to have a little fun with it
If we compare it to light (and BTW, radio IS light, just in a frequency we can't see), I guess people think about a laser pointer, instead of a lamp (which would be closer to our antennas).
Like, with a laser pointer of less than 1w you can put a light point in the next building... Perhaps even in pretty distant buildings... But a 60w lamp (I mean the old ones, from Edson) barely can illuminate a room. A 5w laser can cut 6mm MDF or plywood!
That's exactly because a lamp doesn't focus all the light in one direction (neither deals with the frequency and so on, which a laser also does). A lamp emits light in 360° x 360°! (Perhaps x 360° again?)
So, anyway... We need to think about lamps, not lasers in this hobby. 😬
Thanks for the video, Joshua!
Stay safe there with your family! 🖖😊
Wow ! very informative for pro's ☝🏼
JB has the best informative content out there
Great Info Joshua!
Nice of you to include the dB concept, but if I were you I would have put that as an extra info toward the end (perhaps even shortly covering antenna gain while you are at it 🤣).
As I personally suspect that the "simple" formula √(currentPower/referencePower) is much easier to learn. It only needs the inverse square law and allows to compare range already..
Very good video you made it easy to follow along.
I've just earned my masters degree in FPV, thank you JB. 😎
dam I failed it
Old me is telling young me "If you paid attention to math in school like you were told, you'd have an easier time understanding and playing with your cool flying camera toys when you get older"
Explain range verses frequency , explain encoded multiplexing, the math gets really fun. It is a place where computers shine,. Personally my nemesis was a Calc problem where the answer, was the exponent buried deep within the formula. Missed that problem twice , hurt my feelings . This has been a fun refresher of things long forgotten , in real life these problems seldom came up ... never found that nemesis math problem used for anything , which is good . Take care.
ok,got me on this one, better said than i could.
Forget the formula? YES!!!
This was not the first video to watch on a Saturday morning. My brain hurts.
youre 6 months late... i needed this earlier
thank you so much for that Video !
Comments: JB can’t even math or RF good omg
JB:
Love your vids. No I haven't watched this one all the way through. What Db rating is better for vtx antennas? Lower db or higher db?
hi friends I have an unrelated question I recently bought th diatonic mamba f405 mk2 fc because I accidentally lifted a couple pads on my old fc but anyways I cannot get the rx3/tx3 cart to work for my dji osd I use ELRS 1 watt as my link this board has three parts but the tx3/rx3 will not give any telemetry should I give up because the company has given minimal assistance I'm stumped
This kinda stuff goes in one ear and out the other with me tho I'm sure alot of others will gain from this vid tho 😉🤙
because power/performance is not a lineal relation. Tipically a 10 base log, so to double your range you have to roughly x10 your power. That's why compared to 100mW switching to 300mW will be more noticed than switching from 300 to 500. The more it rises, the less effect it has on the range (by comparison!). That's basicaly why the dB scale is a log scale (+6dB = x2).
FYI all measures are relative, there are no absolute measures. For example, the boiling point of water is 100C but only at STP. Radio waves suffer rapid degradation under water and very little in space. Relativity is a very important concept.
But 100 degrees Celsius is an absolute amount of heat energy. And 1 gram of mass is 1 gram absolutely.
I’m prolly going to be watching this video a lot!
What would be the best frequency that tx or vtx should transmit in to best go through concrete in buildings ? Like best for bando
That's a useful video, and right as far as it goes, but what it doesn't taken into account is real life environment and obstacles.
Unless you are in an open empty space, the inverse square law isn't that likely to apply accurately in practice.
Take a simple example: you fly behind a big tree or grove of trees (leaves are damn good at absorbing signal at those frequencies), so your video breaks up badly. It's done that because the received level has probably dropped suddenly by a lot.
So, switch from - say - 25 to 200mW (assuming it is legal), and do it again. In theory that will give root 8 times the range - over twice. Actually it might well be virtually no different because the signal drop behind the trees was so big that boosting it by 8x made little difference. Maybe you get a few feet further behind the trees before it drops out, but not much else.
So, it is probably worth pointing out that whilst the inverse square law works fine when there are no obstacles that adversely affect signal conditions, in real world situations, the further you go, the more signal absorbing and reflecting obstacles there are likely to be in the way, and these will cause the range not to increase like one might expect.
If one is flying high up in open sky it will work better (no obstacles) - but we probably won't be doing that, will we, because it might be illegal ....
Hey, does anyone know whether if I bought a Rtf kit that came with 50c batteries I can buy new ones that are 110c?
Hi sir very valuable information you have provided,my quad motors are rotating variable speed one was rotating very slowly and some motors are rotating at full speed , I'm using omnibus F4 pro SD card version flight controller please help me to resolve this problem sir
Great video, so 700mW to 1200mW on DJI gives a ~20% range increase?
hello joshua
great video
does this math also work for both analog and digital video link??
The math is the same. It's true for any RF link.
@@JoshuaBardwell great
thank you
It's really hard (nearly impossible) to really intuitively understand how oppressive 1/r^2 is.
Worse is how dB anything works... and this is my day job
In terms of the "new" AKK 10W vtx: So basically, the VTX at 10W should have 3x the range over it at 1W. But that is not the case, as we can tell from the reviews. How comes?
Only watched till 0:27 so far: no, does not seem the same, 300 vs. 100mW = 300% and 500 vs. 300mW = 166%. Signal strength is not linear with distance, because the area where the rays spread over goes up squared. So you would need 900 mW to get the same effect over 300 mW. Now let's see if this is totally wrong ;)
So if decibels never express an exact amount of anything how does it describe sounds? Doesn't it have to be exact at some point? Like how do you know what 100 dB Is if you don't know what 1 dB is? Or I'd there some consistent sound they use as a base?
That's right. The decibel scale used for sound is pegged to some absolute amount.
Wait! What!? You're saying most FPV-ers are confused by a logarithmic scale and have trouble understanding RF, you don't say, I couldn't have guessed ... :D
Gracias, casi nadie habla de esto, buen video👍
Please answer me if I am correct or not.
So does it means that if we choose 1000mW (1W) of transmit power and choose 50 Hz of packet rate, We will have the most range.
Please someone answer me, thanks in advance
Yes correct.
Great video! Thanks for simplifying everything
Had bad education.found out later in life math laws. Add first subtract second multiply third divide fourth on all math equations. Correct me if I'm wrong.
Lol is this a troll post?
I appreciate your efforts in trying to bring the technical aspects to the masses and beginners but I'm sorry to say that in the process of trying to simplify the math and add tools for easier calculations you kind of just made in 10 times harder than it had to be. Using a table and db to ratio conversion for a simple "how much extra range" calculation? Just say square_root_of(newpower/previouspower)= range ratio. Thats it. Nothing extra is required. I don't see the entire point with using the table and dB conversions. Everyone has a calculator on their phone if they really must know the exact ratio, otherwise all you would have to learn is the basic formula, as well as perhaps memorize the square root of 2. Most cases anyone would only really be calculating 2x or 4x increase in output power.
If it's anything like light, it probably just follow the inverse-square law.
What I dont understand about Math, is why its Maths everywhere else in the world. Doesnt even sound right, but then again we love our inches and feet!
inverse square law... easy as that isnt it? nm, ill watch the video :P
sorry i give up 😅
*waiting for Sander Sassen to correct you.*
Darn 2
My attention span just got shorter. 😭
pog❤
Хау ту пей тву доллерс фром Руссия, зей нот акцепт пеймент. Тсенк уою.
Para mi esta en chino
Poor dude just had his ignorant comment ripped to shreds lol.
FPV is dying for adaptive phased arrays.
we have to wait for the military to let us have it.
first
;D
People like the fpv but your videos do scare some off from this hobby so stop coming up with these so called complicated situations
No.
All he is doing is trying to educate people and let people know that FPV isn't all flying and smiles.