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Wavelengths and Antennas : why the sizes of those antenna booster thingies ?

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I have been wondering what is best, a sanhans type amplifier OR a better antenna w/ no amp.

Saw this vid and was impressed, a nice experiment and controlled decently well.


it is using ItElite MaxxRange Antenna (Full Kit) for a dji type controller.

I believe this is just a 2.4ghz antenna (or 2 inside) which is all dji uses, and the size of the antenna seems comparable to those for yuneec controllers.

If you view the Utub above this static mounted, although a bit higher than normal standing humans is quite impressive in its distance BUT it is in flat country.

One of the points i wanted to make was that of the 'beam' shape of antennas, many of you know this some not, but normal use antennas have both a vertical and a horizontal beam shape (actually it is 360 degrees in all directions but lets keep it simple), the above vid shows this, on this day and conditions, it well may be diff if you move any metal including the coax conns around or even if temp is diff, everything can slightly or massively alter, and of course this is with NO trees and other obstacles in the way.

but normally the beam shape is symmetrical, the same on both sides from the 0 axis (the center where the antenna is pointed), the same for vertical and horizontal so his flight result is a bit one sided, could be due to one side having better propagation of signal or just a better connection on that side of antenna, who knows.

now wavelength, a 2.4ghz wavelength is approx 4" (wavelength is the sinusoidal shape of an ocean wave, it then begins again on next wave), the 5.8ghz is half that, ~2" long.

these are longer than are visible light, or gamma rays, or x-rays, etc, but pretty short, and a rule of thumb is if a obstacle thing (leaf, rain) is approximately a single wavelength long or larger, it can block or absorb that frequency, so if you think 4" and 2" then you can see that tree leaves and bushes can easily decrease the signal of our controller/drones, so fly higher, reposition.

How about the shape of an antenna, a straight one for 2.4ghz wifi or a spiral one, same for 5.8ghz video wifi, why straight or spiral.

Straight antenna are likely the length similar to the wavelength of the signal of interest, the 2.4ghz is really something like 2.2ghz --> 2.4+ghz range, same for the 5.8ghz it is a small range of frequencies mandatde by the fedgov/fcc in murca, same for other countries, actually agreed to for the earth to prevent interference.

A spiral has to be the same, approx the wavelength in diameter, and it might make it slightly more directional but not much (go see write up about yagi antennas and driven elements, reflectors, etc antennas actually are NOT simple & many types too - i know someone who uses an old small satellite dish for 2.4ghz wifi - works very well but then so do many others!!).

Spirals vs straight simply may only just be smaller rather than better, it is ALWAYS in the testing, theory many times fails in the performance of an antenna (a designer once told me that testing is the only way to be sure, theory may fail in real world).

The itelite dbs & Hawk are just printed circuit board antennas, which they may be spiral shaped or some other shape but must be associated to the wavelength of the antenna in dimension, IOW, generally either 1/4, 1/2, 1/1 of the wavelength is what is used for antennas of all types, 1/1 is best.

Thus, the question of 'is an amplifier better $100 spent OR is $100 for a 'better' antenna' ?? You can purchase 2000mw or even 10,000mw amplifiers for 2.4ghz same likely for 5.8ghz, these are really illegal for our use but then those loud exhaust on motorcycles, trucks, cars are likely illegal too, so are we legal is up to us !

It is all about signal strength and if more than a straight wire the length of the wavelength then it likely has 'gain'.

The more directional an antenna, the MORE gain it has, it is simply focusing the transmit power in a smaller area and that antenna should also be good enuf to receive a signal well too.

So an amplifier (booster) can 'drive' a signal thru tree leaves,etc OR a very directional antenna can also.

** both transmitters and receiver in our drones and controllers are amplifying in both directions, so even a straight wire antenna has 'gain' but it is purely electrical amplifier gain NOT antenna gain **

So what is the ultimate answer, I don't know, but to preserve your warranty an external antenna or a external amplifier is best rather than breaking open the controller/drone and adding antennas, once the warranty is past, do whatever.

BUT BUT BUT, do your research, ie get real world data about your chosen solution, amplifier, antenna or both, and remember it IS a TWO way communication, from BOTH drone and ground controller !!

ps: i saw a total BS vid about the FPVLR antenna, but it was NOT the factory guy doing it, but a dealer guy (greed!), thus i mostly forgive him, but the problem is did you know it was totally bogus what he did and 'surmised' ? OF COURSE NOT, so the ONLY proof is in the flying distance, no matter your choice - that is FACT no fake news/nonsense !!!!

I have no clue if this helps anyone but maybe it helps the thinking, but bottom line, do NOT believe the PR but ONLY trust the proven flight distances !!!

PS: LOS can mean Loss of Signal, OR Line of Sight, confusing to me, i have always thought Loss of Signal but both pertinent to this hobby/biz !!
 
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I've always found the further you push for distance problems are more likely to happen, the 4hawks can get me further and out of sight, which is a little unnerving, there will be a distance when your drone will return to home when signal is lost, and also what happens if your battery gets to second warning and your still hundreds of meters from a landing place.
 
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@CrashALot my remarks are aimed at a USA perspective.

I got my first FCC amateur radio license in 1964 (yes, I may be ancient compared to you). I did a lot of work with antennas and antenna designs but slacked off about 20 years ago.

The amount of output power on the 2.4GHz and 5GHz frequencies is limited by the FCC in the US. Therefore a power output amplifier is of little use.

A well designed amplifier for reception "might" be beneficial but that's iffy unless it has excellent noise reduction.

LOS for drones and most radio work refers to Line of Sight.

The patch antennas are directional as you describe.

Orban-Patch-Antennas-2009-rev.pdf

When considering antennas the best measurement of capability with regards to gain (measured in db) is provided by a radiation pattern and bandwidth. Directional antennas should be pointed in the correct direction.

Please keep in mind that 2.4GHz and 5GHz are quite high frequencies and you should know from your experience with home wi-fi that they don't penetrate obstacles very well if at all. Few drone pilots can get signals through wet leaves on trees as an example.

The antennas provided with most sUAS are generally suitable for most LOS flight.

As you say, the signal from the sUAS to the controller is a weak link. Not really a great way to improve the antennas on the aircraft or amplify their output.
 
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as you all know solid distance of the video and telemetry signal equates to reliability for overall communications and is not necessarily being used for distance of flight, if you fly within the measured/tested 'reliable' area of your setup, all things are good and safe, and no LOS (What does LOS stand for?) - Loss of Signal in this usage.

as to amplification, i am sure that it is how you measure it, and it is never at the amplifier but at a distance and likely across a prescribed set of angles in front of the broadcasting antenna, which is all that matters, 'what is the signal strength you are broadcasting'.

but it is hard to convey that envelope of radiated energy, it is a complex integral equation, thus some power amount is used to keep it simple, but measurements are all that matters really.

so if you have crappy low gain 360 degree or bipolar 2x 180 degree (null lobes on sides) antennas, then amplification may not exceed what is lawful or may be well under legal limits, but if you have a directional antenna then it may exceed limits but then what is more 'polluting' a 360 or a 30 degree directional pointed only at device that wants that signal ?

i am not willing to go look it up, but i am sure the Murcan fcc has specs on how to measure and likely amounts of possible interference tolerated &/or produced, etc.

but then should a garage door opener interfere with a flying drone or a high powered 802.11 adapter neither likely very directional ?

and what is the purpose of a coax but to decrease or eliminate interference, so always use good coax cable from transmitter to antenna.

btw, sanhans makes a 2.4/5.8ghz wifi amp (for TX and RX) with single input/output that determines the freq inputted and sets its 'mode' accordingly, meaning if you have a dual freq setup like yuneec, then that single amp could be used for either frequency, but unfortunately NOT both at same time !! ;)
 
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In the world of Radio Controlled aircraft, LOS has always been considered LINE OF SIGHT. How far out can you still see the aircraft with unaided eyes and maintain control.
In the Radio world LOS usually means Loss of Signal.
For the 5.8 Ghz band that the Yuneec products use to transmit video on, they used clover leaf or circular polarized antenna to help minimize interference. Since most home wifi and point to point Wifi on 5.8 Ghz uses vertical or horizontal polarization, there is much less chance of interference from these devices.
Also keep in mind, that in the USA, to have type acceptance from the FCC, each transmitter is "type accepted" with a manufacture supplied antenna. Just changing the antenna can void the FCC type acceptance.
 
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Eagle's Eye Video

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This is not directed at any single individual, but for the purposes of this board can we all agree to be more concerned with written clarity and less concerned with pixel conservation... if referring to loss of signal, how about we all simply spell it out ??? :rolleyes:
 
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The bottom line: A dime of antenna equals a dollar of radio power.
And FWIW: The Typhoon H 5.8gHz antenna is LHCP..
 
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PatR

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And FWIW: The Typhoon H 5.8gHz antenna is LHCP..

That little fact may have been overlooked by more than a few. As I have no need or desire to fly beyond line of sight I have found the stock antennas more than adequate out to further than I can safely see the aircraft so I haven’t changed any Tx antennas. I did install dipoles on the aircraft 2.4 though. But if I were to change Tx antennas I’d make darn sure the polarization was correct before buying any.
 
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