Cellular Antenna

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Samuel Seidel

Pre-takeoff checklist
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Sam
I’m curious to know if there’s been any research done on cellular connectivity between 5-10k feet. I’m curious to know if it would be feasible to install an antenna on the belly of the plane and access consumer LTE towers.
 
This may not be true in all cases, but I was told cell phones are not usable much higher than 2500 AGL.
 
^^depends on terrain, but I've gotten great service at 6k+. I just wouldn't rely on it for a steady connection as you hop from tower to tower or away from populated areas.
 
Depends heavily on the antennas installed on the tower. Some have a vertical pattern width of only 15 degrees. Couple that with the depression angle set for the particular site, and you could be within a mile of a tower and a thousand feet high and not reliably hit it. At 6 thousand feet, you might be hitting a tower almost a hundred miles away.
 
Craig said:
Depends heavily on the antennas installed on the tower. Some have a vertical pattern width of only 15 degrees. Couple that with the depression angle set for the particular site, and you could be within a mile of a tower and a thousand feet high and not reliably hit it. At 6 thousand feet, you might be hitting a tower almost a hundred miles away.
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True, I've been flying in northern Maine, 50-70miles from the border, and had my phone pinging Canadian towers. I know because Verizon sent me a Welcome to Canada text along with various international plan options lol.
 
DeltaPopAviation.com has one just for 3g, so I suspect LTE is too tough a nut if he hasn’t made that version.

Without an antenna, I get spotty data and occasional phone calls below 6k and below 145 kts. Texts slightly better reliability.
 
For what it’s worth, I’ve got a 5G capable iPhone (which reverts to LTE when the former is unavailable) and I can rarely get a signal above about 3,000ft here in the southeast.

Can’t say how well your proposed installation would work, as I don’t know anything about it, but it’s worth a shot.
 
RyanB said:
For what it’s worth, I’ve got a 5G capable iPhone (which reverts to LTE when the former is unavailable) and I can rarely get a signal above about 3,000ft here in the southeast.

Can’t say how well your proposed installation would work, as I don’t know anything about it, but it’s worth a shot.
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I’m betting on the thought that the reason for that is you are in a tin can and putting the antenna with clear line of sight will improve things.
 
Samuel Seidel said:
I’m betting on the thought that the reason for that is you are in a tin can and putting the antenna with clear line of sight will improve things.
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It certainly may cause some interference, but I’ve had my phone up by the window a lot and it never seemed to change anything. I’m sure there’s a lot of folks with experience on these types of things, but I’m definitely not one.
 
I fly commercial airliners a fair bit and it’s common to see time and messages updated occasionally as the phone gets some service for a moment or two at 35,000’.
 
Here's another data point, I have a T-Mobile phone and an AT&T phone. The T-Mobile phone is useless almost right after leaving the ground. AT&T is often good up to 7,000' could be engineering, frequencies, towers, orb the phones themselves, I don't know.
 
Just to verify, you are researching this for text/sms/data and not voice right?

Up here in our flatlands I've had text messages make it out up to around 6000agl...but depends on location. So curious what you find.

I have a portable external antenaae for my Verizon hotspot to help get 4g inside the hangar. Maybe a test fkight with it in the plane is in order. But I have a hunch the angled pattern of the cell tower transmission will still be the limiting factor.
 
I've been told that the reason service is so hit or miss in an airplane is 1) the ground antennas are designed to provide good signal horizontally and not vertically and 2) at altitude your phone "sees" too many antennas and the phone keeps switching between antennas causing connection problems.

I have no idea if any of this is correct. My experience is that sometimes I can get a good signal and sometimes I can't.
 
The "too many towers" thing hasn't been true for a long time. The problem was never "too many towers" actually, it was that the signal was received WELL by too many towers. The way the old analog cellular (which by the way is illegal to use in planes) worked was when you lit up too many cells to reduce the power to stop that, but at altitude, that was ineffective. However, it didn't stop you from making the call, just tied up capacity.

The problem in today's digital phones is indeed the fact that the antennas are directional to put the signal where they EXPECT the mobiles to be and that isn't overhead. My phone wakes up and starts delivering pent up texts around 2000 feet and I've found that texts tend to start working before voice calls will.
 
I have seen texts and emails at 6000ft or so. And that is with the phone on the glare-shield.
In the days of 900mHz cell systems, I lived at the edge of Nextel territory and used a Wilson external antenna on my car. It added a good 20 miles to the range. Given the geometry of cell signal propagation, a belly mounted antenna should increase the altitude at which a phone can at least receive texts. The problem these days is to find a phone with a separate SMA jack for the antenna. Has been years that I have seen an antenna jack on a phone.
 
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There's always the passive repeater of putting an antenna inside the plane with a connection to one outside the plane. Amusingly, this is how you can reach PCT from the ground at VKX, Dave hung one up on the appropriate frequency up the hill.
 
flyingron said:
My phone wakes up and starts delivering pent up texts around 2000 feet and I've found that texts tend to start working before voice calls will.
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Cutting off imessage and cellular data in the settings option of an iphone will force it to use traditional text messaging and that seems to go through more often at altitude
 
Each generation of cell seems to work less at altitude. From the very limited reading on it, due to capacity and design the range is getting shorter with more towers all running lower power with more directional antennas. Allowing multiple cell phones to use the same frequency, channel and time split when in different zones of the tower.

And the towers are not aimed up...

Tim

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