2,4Ghz Yagi + Receive Wifi from an Aircraft? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 26, 2020, 11:28:20 pm
content: Hi1) On Aliexpress a lot of seller offer insane looking 2,4Ghz Yagi Antenna:https://de.aliexpress.com/item/4000049543741.htmlDoes that Antenna even work for sending and transmitting on the Wifi Band?2) Does anyone here try to receive with such Antenna the Onboard Wifi in an Aircraft?Well I would say its possible since there are other Signals who can be received over many KM with a line of sight.Thanks

author: Yansi
author_rank: Super Contributor
timestamp: May 26, 2020, 11:55:02 pm
content: And from where did you get the idea this is a 2.4Gz band antenna for wifi? I see that nowhere mentioned in the above linked sale. It clearly is for a very different technology (4G cellular) and I even don't see any means to tell for which band it is suitable, as clearly the antenna design photographed there is a rather narrow band type, certainly not workable in all specified ranges.//EDIT: The supplied description seems to even supply with numerous other invalid specs, such as about the directivity. Strahlung of an yagi antenna is definitely not "omni".But okay, I see wifi mentioned in the title. Very confusing.Stay away from it. You can't even tell what you are buying, as per the supplied product photos and description.If you want a yagi for wifi, you can definitely buy locally from a reputable sales center.

author: M0HZH
author_rank: Regular Contributor
timestamp: May 27, 2020, 12:02:15 am
content: QuoteThe specifications are ridiculous.There are however legit high-gain 2.4GHz antennas (like this one) used for long-distance directional links. You wouldn't be able to link to an airplane WiFi for multiple reasons, starting with ACK timeout (WiFi packets timeout over 1000m range unless configured specifically for long range). However, people use these antennas to link to amateur radio satellites, for example QO-100 has an uplink on 2.4GHz and you only need 1-2W to reach it, downlink is on 10GHz so any satelllite TV antenna can receive it.

author: cdev
author_rank: Super Contributor
timestamp: May 27, 2020, 03:28:46 am
content: In my experience, 2.4 GHz is eaten up pretty fast by smaller diameter coax.The antenna may be a perfectly fine 2.4 GHz yagi, but unless you need all that coax I would chop it off and put whatever connector on the shortened piece keeping in mind that every 3 db eats up half your power.On second thought, only do that if you know how to solder a new one on.You are not going to be able to pick up wifi from passing planes.OTOH If you have permission, you might be able to use wifi from some friend's house some distance away. It depends on how much density there is between you and their access point. brick house-bad. glass window-good

author: OwO
author_rank: Super Contributor
timestamp: May 27, 2020, 05:42:50 am
content: Search aliexpress for "wifi yagi antenna", and you will find many 18-element yagi antennas. The gain is highly exaggerated and the actual gain is around 18dBi.

author: OwO
author_rank: Super Contributor
timestamp: May 27, 2020, 05:44:46 am
content: An actual 24dBi 2.4GHz antenna looks like this and is almost 1 meter across:

author: james_s
author_rank: Super Contributor
timestamp: May 27, 2020, 06:14:52 am
content: Even if you had an incredibly high gain antenna, it would take some crazy precision to track a moving aircraft. The next issue is that the WiFi is inside the plane which is made of aluminum so I suspect there is not much signal to work with even up close, except for what leaks through the windows.

author: Ian.M
author_rank: Super Contributor
timestamp: May 27, 2020, 07:03:09 am
content: Also, one of the main problems with permitting in-flight use of personal devices is interference with ground based cellular networks. A phone held next to an aeroplane window may well have line of sight to hundreds of cellular towers, + is moving rapidly so the network has severe difficulty handling the rate of cell to cell handoffs required. Multiply that by 100 for the number of passengers sitting next to a window, and a single flight on takeoff or landing approach could easily wipe out cellular coverage in any urban area its passengers could see.Therefore any airline that encourages in-flight use of personal devices with active RF networking, has almost certainly equipped their aircraft with fully EM screened windows, to contain any WiFi or micro-cellular service they provide to within the aircraft.Due to the screened windows, I'd also bet you can no longer get a GPS fix on a commercial flight by holding a personal GPS (with unrestricted firmware) against a window, the way you used to be able to before in-flight WiFi became common. Please be careful if you want to test that, as its no longer advisable to be seen fiddling with a GPS in flight due to TSA/security-theatre paranoia, so I'd recommend a laptop and a USB GPS puck, with the puck hidden in your jacket used as a pillow against the window, and refraining from displaying any sort of live map where nearby passengers might see it!

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 27, 2020, 07:47:48 am
content: The listed specs don't actually cover the 2.4 GHz WiFi (well, ISM) band fully. But I doubt those specs are correct anyways.What exactly is your goal in receiving aircraft WiFi? It won't work because of the delay (you need to be able to tweak some stuff in the protocol to enable thisprovided you could receive the signaland you don't have access to that).

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 27, 2020, 09:22:20 am
content: build your own yagi. can be an interesting learning experience, and so you can suit your need such as lightest weight possible for onboard of an aircraft. i wont believe china made antenna so much after my experience with a GHz mushroom antenna bought and measured on a VNA. i built one yagi for broadband internet receiver dongle that worked on long china cheap coaxial cable (maybe by luck, from not receiving, to be able to receive and surf. how many dB gain? i was not sure i didnt have a T&M tool) you can google such as..https://www.instructables.com/id/Easy-to-Build-WIFI-24GHz-Yagi-Antenna/https://itstillworks.com/build-yagi-antenna-7557621.htmlhttps://jtecheng.com/?p=957etc. my reference was from skyscan.ca but it seems now its suspended. attached is the saved information from the site (old internet explorer mht file), and yagi building VB app and source code that i made using that reference... (anybody can give comment if i did something wrong) fwiw...

author: Syntax Error
author_rank: Frequent Contributor
timestamp: May 27, 2020, 09:50:11 am
content: Line of sight? Most aircraft visible from the ground are five to ten miles away, and moving at 400+ knots. Well out of range of the 100mW on-board wifi modules inside a metal fuselage. It is also very-very illegal to try and hack into an aircraft's systems.If you are interested in long range wifi communication, check out the home build 'cantenna'.https://en.m.wikipedia.org/wiki/Cantenna

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 27, 2020, 01:42:27 pm
content: QuoteWell it was late and I picket one who look like the other one.https://de.aliexpress.com/item/32850170557.htmlQuoteits not available (any more)QuoteWell that is not good.Well I would like start with receive Data at first if its possible.QuoteThe life way to far away for that.QuoteWell that stuff would be used only Outdoor since every mW counts.QuoteDo you have one?Quotesince the transmit there possision later its possible to move the antenna by some mini computer and a motor.QuoteThats who i would Aim for.QuoteWHAT?!QuoteNo?QuoteI can talk only for my Eurowings Flight and there was no problem with that. About which Airline do we talk about?QuoteNever heard of.QuoteThat sound a very suspicious behaviour.Normally when I want to track it I push the PCB Antenna between the window shade and use my SDR Dongle for. When the flight attended ask what I do I just say listen to Radio.QuoteGet an SSID, MAC first.Quotewell I thought it where to easy.QuoteI want to build a UHF one.QuoteNobody sayed that I would like to do...QuoteI guess the Aircraft System are not connect to the Public Aircraft Wifi.QuoteWell I dont have a C band Sat Dish and the KU Band is in use.

author: Syntax Error
author_rank: Frequent Contributor
timestamp: May 27, 2020, 02:34:58 pm
content: So you fully understand, the wifi inside an aircraft is NOT public wifi*. Any attempt to make an unauthorized connection will certainly get you arrested and likely land you in prison. Possibly charged under the US Patriot Act 2001if you ping an American aircraft. Other governments may not be so lenient.* For plane passengers, the FAA state, "[portable electronic] devices must be used in airplane mode or with the cellular connection disabled. You may use the WiFi connection on your device if the plane has an installed WiFi system and the airline allows its use." cite:https://www.faa.gov/news/press_releases/news_story.cfm?cid=TW189&newsId=15254

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 27, 2020, 02:49:05 pm
content: QuoteIts on a Public Freq.QuoteWho should arrest me and for what?Quote...I give a shit about the US law!Quotesince I am not a I dotn care about that.

author: M0HZH
author_rank: Regular Contributor
timestamp: May 27, 2020, 04:20:16 pm
content: Quote from: Syntax Error on May 27, 2020, 02:34:58 pmEasy there Hollywood, there are still 194 more countries where the PATRIOT act and FAA press releases from 7 years ago don't apply. It's confusing as hell, each coming up with different laws for their territory, air space and citizens.

author: LaserSteve
author_rank: Super Contributor
timestamp: May 28, 2020, 12:51:50 am
content: Get a ham license and a private pilot's permit. Make friends with an aircraft mechanic, and get a STA to put an antenna on the bottom of your private aircraft. Then you can sign "This is" "Insert call sign here" Slash "Aeronautical Mobile". Which is legal in most of the world and has been done up to 10.3 Ghz or higher.Even with a quad array of these antennas pictured in the link below, I'd be shocked if you can detect the WIFI carrier off a descending, banking, airliner even with a low noise figure preamp and a spectrum analyzer.Considering how hard it is to get a connection in flight, on board, I'd be stunned if you can detect it after the window attenuation.https://directivesystems.com/2304-mhz-above/13-cm-antennas/dse1321lyrmk/Antenna linked for educational purposes, much better then your average linear element YAGI, but not so great bandwidth.Check out the Friis Equation, it is a starting point for figuring out what you can and can't do.Hint, the inflight WIFI is kept dialed down to prevent interference from it's second harmonic + mixing products causing a problem with something else important on the aircraft. Not that I would actually know, but from looking at a band chart it is near certainty.Steve

author: KaneTW
author_rank: Frequent Contributor
timestamp: May 28, 2020, 01:35:20 am
content: An interesting exercise, but ultimately futile. The free space path loss over, let's say, 10km at 2.4GHz is 120dB. At the low signal levels you'd get from an airplane you'll get barely anything. Certainly not enough to support even the lowest wifi bitrate.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 28, 2020, 02:56:06 am
content: Quote from: Lord of nothing on May 27, 2020, 02:49:05 pmSo is your neighbours wifi--- would you pirate that?Possibly you need a password for the aircraft one just like if you wanted to use the one next door.QuoteSyntax Errorprobably quoted the US act because it is the most publicised.The sting in the tail was "Other governments may not be so lenient".QuoteAt the end of the day, it is not the law of the land that will prevent you doing this, but rather, the laws of physics.Just about "everybody & their cat" has WIFI at home, but in my house, I can with luck, see two others beside my own---------the iPad quite often even drops the latter!The aircraft is going to look like quite a good "screened room" for RF , so the signal level leaking out of the windows is all that you get to play with.WIFI is a low power system to start with, so you will need a lot of antenna gain.The downside is that the more gain, the more directional, making tracking a major problem.Commercial systems that track aircraft by interrogating & listening for response from their transponder usually have the backup of classic "passive" RADAR systems to point them in the right direction to begin with.You won't have that, so how do you acquire the plane to start with?By eye?If a plane is passing over at 30,000 ft, you are unlikey to see it, unless you are lucky enough to see a contrailTracking is indeed used to pick up weak signals from satellites, but that is an easier problem.Low orbit satellites often take from 20-30 minutes to go from horizon to horizon------an aircraft may take, say 3 minutes.A further complication is that not all airliners have WIFi, but even if they did, there are many transport &Military planes which don't.

author: james_s
author_rank: Super Contributor
timestamp: May 28, 2020, 05:59:53 am
content: Quote from: Ian.M on May 27, 2020, 07:03:09 amI've never heard of this.Yes mobile phones do not work well in the air for the reasons you mention, I've tried it myself. There is no need for shielded windows though, phones all have airplane mode that turns off the cellular radio, but you can turn WiFi and Bluetooth on in that mode. I've never bothered to pay for onboard WiFi since it was around $40 per flight on the planes I've been on that had it but I did have a look at the signal. You connect and it gives you a captive portal that requires a credit card to access. Even if you did connect to one from outside the plane, it's still a crappy and expensive hotspot that doesn't give you anything but a login page unless you pay.

author: james_s
author_rank: Super Contributor
timestamp: May 28, 2020, 06:04:29 am
content: Quote from: vk6zgo on May 28, 2020, 02:56:06 amYou must be a bit more isolated than I am. I just checked from here on my sofa and I can see 15 other WiFi networks besides my own with my laptop and this is a single family home with greenbelt on two sides. I am up on a hill though which likely increases the amount that I can see.I've wondered how it even works in the big highrise apartment buildings in the cities, it's remarkable that WiFi works at all in that environment.

author: KaneTW
author_rank: Frequent Contributor
timestamp: May 28, 2020, 12:04:58 pm
content: A lot of flights explicitly allow you to keep the radio on. Lufthansa for example provides inflight cellular.I haven't heard of that tower overload argument either, though.

author: WPXS472
author_rank: Regular Contributor
timestamp: May 28, 2020, 11:04:33 pm
content: I am not going to comment on the legality or difficulty aspects of this. But, I did buy an antenna once that looked very similar to the one you referenced. It even had 20 ft. of tiny coax as well. It worked about as well as a wet noodle. Actually, I think a wet noodle would have been better.

author: james_s
author_rank: Super Contributor
timestamp: May 29, 2020, 05:15:26 am
content: Quote from: KaneTW on May 28, 2020, 12:04:58 pmI don't know if it negatively impacts the towers, but I have tried mobile phones from the air before and the phone certainly gets confused. Over about 3,000 ft the signal comes and goes and the phone can't figure out what tower to talk to.