Let’s suppose there were no regulations on fitting antennas to your Aircraft.
The metal hull on most Aircraft shield mobiles/ SIM enabled iPads from picking up weather etc. A sensible option would be to set up a Wifi hotspot with external antennas, preferably two antennas to allow for diversity reception where 1 + 1 = more than 2. There are units like the Teltonika RUT950 which I have used in a building or “MiFi” devices which have batteries and external antenna connectors
I would imagine the best idea would be to have a couple of very thin, flat panel antennas with say 3 db gain that would look “down” at the cellphone towers. A whole hotspot installation could be fitted either in the hull or even in a plastic wing tip assuming the strobes don’t cause issues with interference.
I would guess such a set up would have a link quality of at least 10-20db better than using a phone in the cabin (lots of smartphones have awful antennas with very negative gain). So that is 10 to 100 times better than using your phone as a hotspot. You can’t just move the Teltonika type “rubber duck” LTE antennas to the bottom of a hull as they radiate sidewards. Most car/auto antennas also radiate sideways.
If regulations were not an issue what antennas would you use? Is there actually a legal LTE aviation antenna?
I have a WiFi hotspot inside the aircraft that allows me to pick up weather in-flight. It requires no external antenna.
It is called the ADL130.
Archer-181 wrote:
The metal hull on most Aircraft shield mobiles/ SIM enabled iPads from picking up weather etc.
Is this really the major problem? I thought that it was that antennas on cellphone towers are (on purpose) directed along the ground.
It is called the ADL130.
That is a good solution for weather, and SMS-style messages, but doesn’t give you internet. The ADL just goes to a private server and is usable only with their app. More here. I have the ADL150.
The only satphone (at any remotely reasonable price) which gives you internet is Thuraya, which gives you 50kbits/sec at some $5/MB. Not reliable however.
@Archer-181 I think the issue is elsewhere, not signal strength. On a typical flight in Europe, I have a strong GSM signal some 90% of the time, especially if I place the phone against the window. But there is no connectivity, except very sporadically, for say a minute at a time. I suspect the networks have implemented strategies which blacklist a device (a SIM card) if it has connected to too many towers concurrently, as must be the case with the many thousands of airline passengers who leave their phones on and would otherwise bring down the system, by generating massive inter-cell management traffic. I have seen indications of this; if e.g. I first enter France I get a connection but after a few minutes it disappears, while the signal level remains at all five bars. That is for a specific network e.g. Vodafone; another network might implement something different. One German pilot claimed to get constant connectivity across Germany which I never got when flying there. I also get a strong signal (at say FL100) across Belgium but absolutely zero connectivity on both basic GSM (SMS) and data (GPRS/3G/4G).
What one could do is implement a “box” which connects to the 4G network and runs an aggressive (and illegal, per the GSM specs) strategy of disconnecting and reconnecting, and providing an internet connection behind which a lot of this activity is taking place, with retries, grabbing every brief connection by detecting a signal and immediately dialing the *99# to get a data connection, etc. It would probably help if there was more than one SIM card (different networks) in there. What would the market be? Probably small, since some 99% of traffic is low level VFR traffic and they get 3G/4G anyway. At the top end, stuff like Inmarsat provides decent speed internet, at a big cost.
Interesting. Thanks for the replies. So it probably isn’t signal levels that is the issue then!
I have been looking at the ADL weather solution so probably need to go down that route.
I would be interested to know which of two theories:
Is correct.
There is no question that if you fly offshore at 1000’ you get good strong 4G, but that could be explained either way.
If there is a lock-out it has to involve more than two towers, because a ground based phone will normally be getting a signal from several towers. That is incidentally how they get your location for crime investigation purposes. The location, derived from the relative signal strengths, is stored along with the phone activity (IMEI, numbers, SMS content, etc). Various previous threads on this in the distant past.
Also it’s clear that not all networks operate it. I can fly across the UK and never get locked out in the way it happens in Belgium and to a lesser extent France. I am on Vodafone but outside the UK one is roaming to all sorts of networks.
The bizzare intricacies of GSM network config seem to be known to only a few… There was one guy posting in a UK usenet group uk.telecom.mobile, and we have had a few here who used to work in that field. I recall @byteworks was one of them.
In propagation “lift” conditions caused by thermal inversions, one might be able to communicate with many towers as the signal can go tens/hundreds of km along a sea path.
I remember there is a definite range of something like 12 km (from memory) as they time you out digitally. Your signal takes too long to return. Cell towers near ferry ports are often configured to allow double the distance so the get revenue from punters on Britanny Ferries and the like.
That is why your phone works half way across the English channel in a boat – but who knows what the issues are in the air. I suspect Peter is along the right lines.
Peter wrote:
If there is a lock-out it has to involve more than two towers, because a ground based phone will normally be getting a signal from several towers.
But I wrote “two towers on the same frequency” which is not the same.
Isn’t the whole point of cellular that adjacent towers work on different frequencies (or are differentiated in some other way) and there is some kind of four (or five) colour map problem in place ensuring that someone on the ground can never be in contact with two towers on the same frequency, but that safeguard is lost in the air?
Archer-181 wrote:
In propagation “lift” conditions caused by thermal inversions, one might be able to communicate with many towers as the signal can go tens/hundreds of km along a sea path.
Does it really work that way with the frequencies used by cellphones (900 MHz and up)? That is contrary to what I’ve ever read about radio wave propagation.
