The weird relationship between range and output power

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  • Опубликовано: 29 окт 2024

Комментарии • 96

  • @monolith2001
    @monolith2001 2 года назад +36

    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.

  • @cbrrunner3656
    @cbrrunner3656 2 года назад +52

    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.

    • @ianwalton284
      @ianwalton284 2 года назад +4

      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.

    • @Ubiquities
      @Ubiquities 2 года назад +1

      Feeling both attacked personally and proud at the same time.

    • @bentprops_
      @bentprops_ 2 года назад +1

      Sounds like you may need a new wife. Wives are just low technology, less obedient versions of drones

    • @Editer38738
      @Editer38738 2 года назад

      When payday hits
      Iflight gets my $$
      Cheers from Knoxville Tn

    • @cbrrunner3656
      @cbrrunner3656 2 года назад +1

      @@bentprops_ she just likes to give me a hard time. 😉

  • @gadgetrc94
    @gadgetrc94 2 года назад +9

    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!

  • @chriswhitehead6095
    @chriswhitehead6095 2 года назад +2

    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%

    • @ls4life544
      @ls4life544 2 года назад

      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.

  • @wearemany73
    @wearemany73 2 года назад +4

    Superb explanation of how transmission range diminishes over distance. 👍

  • @Seltro_
    @Seltro_ 2 года назад +7

    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.

    • @andrewgilbertson4226
      @andrewgilbertson4226 2 года назад +4

      FPV got me into ham radio. Now I have two hobbies none of my friends understand.

  • @gearhead366
    @gearhead366 Год назад

    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".

  • @youtubxkip
    @youtubxkip 2 года назад +2

    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"?

  • @bigbellyflyer
    @bigbellyflyer 2 года назад +1

    When ever I think I’m smart, I watch Bardwell…
    Thanks Joshua, you are amazing.

  • @grindz145
    @grindz145 2 года назад

    Best explanation of this topic I've ever seen. 👏

  • @aowi7280
    @aowi7280 5 месяцев назад

    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.

  • @decommonifyable
    @decommonifyable 2 года назад

    Lol, I watched the video about the antennas, funny to see an old style Bardwell video.

  • @Joeyzoom
    @Joeyzoom 2 года назад +2

    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!

  • @Wild_FPV
    @Wild_FPV 2 года назад

    I learned something today for sure 😆Thank you JB for educating us on the things we should probably know about our hobby.

  • @MysteryD
    @MysteryD 2 года назад

    Fantastic video, glad I'm seeing it. Nearly missed it.

  • @annonomus6675
    @annonomus6675 2 года назад

    Great video. So many people get it wrong about distance. Haven't had that much math instruction since high school. Memories of math anxiety

  • @KiloFoxtrotJosh
    @KiloFoxtrotJosh 2 года назад +2

    Very interesting video. I would love to see one discussing the different antennas used on radio transmitters and video receivers and their propagation patterns.

    • @zo_fpv
      @zo_fpv 2 года назад

      It would be awesome if he could try building a helical antenna just for comparison.

  • @j-rodfpv1137
    @j-rodfpv1137 2 года назад

    Another great Friday night math video , I was starting to think you were slipping , lol great video. Very informative ..

  • @corvinusm2081
    @corvinusm2081 2 года назад

    Ok, that makes a lot of sense! Thank you JB!

  • @jamesmichaelcabrera9613
    @jamesmichaelcabrera9613 2 года назад

    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

  • @MCsCreations
    @MCsCreations 2 года назад

    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! 🖖😊

  • @Cre8ionz.
    @Cre8ionz. Год назад

    Wow ! very informative for pro's ☝🏼

  • @propabilityfpv
    @propabilityfpv 2 года назад

    JB has the best informative content out there

  • @offtheground9152
    @offtheground9152 2 года назад

    Great Info Joshua!

  • @Wikiwix
    @Wikiwix 2 года назад +2

    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..

  • @brentsheldon8667
    @brentsheldon8667 2 года назад

    Very good video you made it easy to follow along.

  • @manski209
    @manski209 2 года назад +2

    I've just earned my masters degree in FPV, thank you JB. 😎

  • @AD-lr2ww
    @AD-lr2ww 2 года назад

    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"

  • @jwc4520
    @jwc4520 2 года назад

    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.

  • @2_stixs-fpv680
    @2_stixs-fpv680 2 года назад

    ok,got me on this one, better said than i could.

  • @jojo42069
    @jojo42069 2 года назад

    Forget the formula? YES!!!

  • @ChainsawFPV
    @ChainsawFPV 2 года назад

    This was not the first video to watch on a Saturday morning. My brain hurts.

  • @nightrider8496
    @nightrider8496 2 года назад

    youre 6 months late... i needed this earlier

  • @Woodyyes--
    @Woodyyes-- Год назад

    thank you so much for that Video !

  • @abertheham
    @abertheham 2 года назад +1

    Comments: JB can’t even math or RF good omg
    JB:

  • @davisauto8423
    @davisauto8423 2 года назад

    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?

  • @brownsquirrel2828
    @brownsquirrel2828 2 года назад

    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

  • @P8FPV
    @P8FPV 2 года назад +1

    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 😉🤙

  • @miquelmarti6537
    @miquelmarti6537 2 года назад

    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).

  • @rctrix9063
    @rctrix9063 2 года назад

    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.

    • @JoshuaBardwell
      @JoshuaBardwell  2 года назад

      But 100 degrees Celsius is an absolute amount of heat energy. And 1 gram of mass is 1 gram absolutely.

  • @earry509fpv
    @earry509fpv 2 года назад

    I’m prolly going to be watching this video a lot!

  • @qpmkro
    @qpmkro 2 года назад

    What would be the best frequency that tx or vtx should transmit in to best go through concrete in buildings ? Like best for bando

  • @Nkkdxn45j
    @Nkkdxn45j 2 года назад +1

    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 ....

  • @jimbo_bp8309
    @jimbo_bp8309 2 года назад

    Hey, does anyone know whether if I bought a Rtf kit that came with 50c batteries I can buy new ones that are 110c?

  • @kpurushothaman6421
    @kpurushothaman6421 2 года назад

    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

  • @Atlas_FPV
    @Atlas_FPV 2 года назад

    Great video, so 700mW to 1200mW on DJI gives a ~20% range increase?

  • @vicenteriquelmezavala2110
    @vicenteriquelmezavala2110 Год назад +1

    hello joshua
    great video
    does this math also work for both analog and digital video link??

  • @tehllama42
    @tehllama42 2 года назад

    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

  • @malnasimon7041
    @malnasimon7041 5 месяцев назад

    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?

  • @1Hippo
    @1Hippo 2 года назад

    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 ;)

  • @TheJacobbridges25
    @TheJacobbridges25 Год назад

    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?

    • @JoshuaBardwell
      @JoshuaBardwell  Год назад

      That's right. The decibel scale used for sound is pegged to some absolute amount.

  • @sandersassen
    @sandersassen 2 года назад

    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

  • @limer2202
    @limer2202 2 года назад

    Gracias, casi nadie habla de esto, buen video👍

  • @NoorullahYaqoubi
    @NoorullahYaqoubi 3 месяца назад

    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

  • @musicfreak115
    @musicfreak115 2 года назад

    Great video! Thanks for simplifying everything

  • @gqp4800
    @gqp4800 2 года назад

    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.

  • @kinzokushirogane1594
    @kinzokushirogane1594 2 года назад

    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.

  • @minkorrh
    @minkorrh Год назад

    If it's anything like light, it probably just follow the inverse-square law.

  • @kaptkrunchfpv
    @kaptkrunchfpv 2 года назад

    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!

  • @Krunked
    @Krunked 2 года назад

    inverse square law... easy as that isnt it? nm, ill watch the video :P

  • @DAKARTECH
    @DAKARTECH 2 года назад +1

    sorry i give up 😅

  • @jeramboo8511
    @jeramboo8511 2 года назад

    *waiting for Sander Sassen to correct you.*

  • @pox122229
    @pox122229 2 года назад

    Darn 2

  • @ChrisQuadFPV
    @ChrisQuadFPV Год назад +1

    My attention span just got shorter. 😭

  • @boo7948
    @boo7948 2 года назад

    pog❤

  • @mzhuravlev61
    @mzhuravlev61 2 года назад

    Хау ту пей тву доллерс фром Руссия, зей нот акцепт пеймент. Тсенк уою.

  • @ErickFpV7
    @ErickFpV7 2 года назад

    Para mi esta en chino

  • @anthonystownsend
    @anthonystownsend 2 года назад

    Poor dude just had his ignorant comment ripped to shreds lol.

  • @Flumphinator
    @Flumphinator 2 года назад +1

    FPV is dying for adaptive phased arrays.

    • @ianwalton284
      @ianwalton284 2 года назад +1

      we have to wait for the military to let us have it.

  • @RiloFPV
    @RiloFPV 2 года назад

    first
    ;D

  • @michael1968-m9b
    @michael1968-m9b 2 года назад

    People like the fpv but your videos do scare some off from this hobby so stop coming up with these so called complicated situations

    • @JoshuaBardwell
      @JoshuaBardwell  2 года назад +2

      No.

    • @kottonfpv2666
      @kottonfpv2666 2 года назад

      All he is doing is trying to educate people and let people know that FPV isn't all flying and smiles.