Cellphones From Flight 93

At least 2 people in my church, including my Sunday School teacher, saw the plane that hit the Pentagon, and they saw it live -- as it hit.

 

I think there was some of both, but not sure--didn't really read all the detail, though I have seen a history channel report. That was a story I haven't followed as close on the details.

Anyway, back to the question: Any data available that shows c phones don't work at 30KF? </font>[/QUOTE]Is there any DATA that shows cell phones DO work at 30K feet?

 

So, you're saying they work at altitude but you don't have any evidence to prove it? I presented evidence that proves that they do NOT work.

 

Ed Certainly is right about don't go to Ontario for cellphone coverage, if this data is any indication.


Do you notice that at 2100 feet the thing is already messing up. Even at 1000 feet it has a 50 percent failure rate.

We have hills that you can drive up on that are 1000 feet. I have been up with a pilot here in Oklahoma in a small plane and he always calls home and other places with his cellphone. I have never seen it NOT work. It works better than on the ground. Mind you he doesn't usually go over 8 or 9 thousand feet, but this data where the phone starts falling off at 1000 feet just shows you that even on a 2000 foot tower the cellphones wouldn't work.

I cannot believe an engineer would even post this data and call it GOOD. My goodness, my house is 600 to 1000 feet above the major part of my county. This data says I shouldn't be able to use the phone between about 30 and 50% of the time.

The base units must really be lousy in Canada. Mercy.

Are you REALLY providing this as data to rebutt my conversation?

Besides, this isn't data anyway, this is four to eight phone calls at each level. Do you call that a sampling?

You're an engineer, aren't you straightandnarrow? If so, give me some calculations that you do yourself. Let's look at some path analysis before you tell me how bad the cellphones in Canada are.

If you can't provide me with any calculations, then I guess I will--if that's what it take to set this issue to rest.

AND, I ask one more time, are you calling me a liar when I say I made several calls from a Lear Jet at 37,000 feet while traveling across a variety of terrain in Southeastern US including over heavily populated Florida and thinly populated Arkansas with its big mountains?

Are you doubting that I did this? and do you have legitimate explaination as to why it worked? </font>[/QUOTE]Once again, we're talking about altitude not elevation above sea level. Why can't you get that straight? I've never called you a liar. I'm just asking you for data as you asked me for data. You rejected my own personal observations over the same general area where flight 93 crashed so why should I accept your one data point over an entirely diffent place?

This data is consistent with my own. I couldn't get a ready for service signal until about 1,500 feet.

 

Ed Certainly is right about don't go to Ontario for cellphone coverage, if this data is any indication.


Do you notice that at 2100 feet the thing is already messing up. Even at 1000 feet it has a 50 percent failure rate.

We have hills that you can drive up on that are 1000 feet. I have been up with a pilot here in Oklahoma in a small plane and he always calls home and other places with his cellphone. I have never seen it NOT work. It works better than on the ground. Mind you he doesn't usually go over 8 or 9 thousand feet, but this data where the phone starts falling off at 1000 feet just shows you that even on a 2000 foot tower the cellphones wouldn't work.

I cannot believe an engineer would even post this data and call it GOOD. My goodness, my house is 600 to 1000 feet above the major part of my county. This data says I shouldn't be able to use the phone between about 30 and 50% of the time.

The base units must really be lousy in Canada. Mercy.

Are you REALLY providing this as data to rebutt my conversation?

Besides, this isn't data anyway, this is four to eight phone calls at each level. Do you call that a sampling?

You're an engineer, aren't you straightandnarrow? If so, give me some calculations that you do yourself. Let's look at some path analysis before you tell me how bad the cellphones in Canada are.

If you can't provide me with any calculations, then I guess I will--if that's what it take to set this issue to rest.

AND, I ask one more time, are you calling me a liar when I say I made several calls from a Lear Jet at 37,000 feet while traveling across a variety of terrain in Southeastern US including over heavily populated Florida and thinly populated Arkansas with its big mountains?

Are you doubting that I did this? and do you have legitimate explaination as to why it worked? </font>[/QUOTE]You're really an engineer and you don't accept live test data? Equations are more important than real data? Come on. Get real. Show me your own equations that say cellphones work at altitude.

I will tell you one reason they don't. Cell sites are built to send their signal along the ground to cellphones in the cell. They are not designed to send a signal up into the air. The signal reaching airplanes is merely leakage of the intended signal and far weaker than the intended signal.

 

Are you really an engineer Phil? Coulda fooled me.

 

BTW, the Flight 93 tape at the Moussaoui was hear Wednesday.
THe OKLAHOMAN says "... 13 of the terrified passenges and
crew members made 35 air phone calls and two cell phone
calls ... "
(however, I know later that had they been flying near
Montreal, Canada, they wouldn't have been able to make
the two cell phone calls.)

 

Ed Certainly is right about don't go to Ontario for cellphone coverage, if this data is any indication.


Do you notice that at 2100 feet the thing is already messing up. Even at 1000 feet it has a 50 percent failure rate.

We have hills that you can drive up on that are 1000 feet. I have been up with a pilot here in Oklahoma in a small plane and he always calls home and other places with his cellphone. I have never seen it NOT work. It works better than on the ground. Mind you he doesn't usually go over 8 or 9 thousand feet, but this data where the phone starts falling off at 1000 feet just shows you that even on a 2000 foot tower the cellphones wouldn't work.

I cannot believe an engineer would even post this data and call it GOOD. My goodness, my house is 600 to 1000 feet above the major part of my county. This data says I shouldn't be able to use the phone between about 30 and 50% of the time.

The base units must really be lousy in Canada. Mercy.

Are you REALLY providing this as data to rebutt my conversation?

Besides, this isn't data anyway, this is four to eight phone calls at each level. Do you call that a sampling?

You're an engineer, aren't you straightandnarrow? If so, give me some calculations that you do yourself. Let's look at some path analysis before you tell me how bad the cellphones in Canada are.

If you can't provide me with any calculations, then I guess I will--if that's what it take to set this issue to rest.

AND, I ask one more time, are you calling me a liar when I say I made several calls from a Lear Jet at 37,000 feet while traveling across a variety of terrain in Southeastern US including over heavily populated Florida and thinly populated Arkansas with its big mountains?

Are you doubting that I did this? and do you have legitimate explaination as to why it worked? </font>[/QUOTE]You're really an engineer and you don't accept live test data? Equations are more important than real data? Come on. Get real. Show me your own equations that say cellphones work at altitude.

I will tell you one reason they don't. Cell sites are built to send their signal along the ground to cellphones in the cell. They are not designed to send a signal up into the air. The signal reaching airplanes is merely leakage of the intended signal and far weaker than the intended signal. </font>[/QUOTE]You are correct in that the signal does have a high antenna gain; however, that certainly does not preclude signals from reaching air-craft.

If you will recall, at one time we used to send all of our telephone calls fromm point to point by microwave. So did Russia.

These antennas have a MUCH greater gain in both the horizontal and vertical directions.

Therefore, the beam is more of a pencil beam than spreading out like a cell-base.

Now, how do we receive that if we want to spy on it? We pick up the signal with a satelllite that is low on the horizon and picks up the main lobe of the signal beaming into space.

This same effect can occur with cellphones and this is the reason a cell-phone in a plane will (often not always) lock onto a cell-tower that is far on the horizon. The curve of the earth allows for this effect.

If you need equations to prove that a line-of-site microwave signal cannot provide a good SN+N/N then I can certainly provide those to you, but it suprises me you cannot figure this out yourself. If you want me to do all of the work proving that a microwave can be used from aircraft to ground even with cell-antenna gain, then I can certainly do that. I don't have time this weekend, but next week.

In the meantime I will bump this thread up so it doesn't get lost.

Your remarks asking me whether or not I'm really an engineer---well, I'll just ignore those because you have not posted anything proving your case.

Part of the responsibility is on you. Believe it or not engineers don't ALWAYS have to do a forumala to prove that a signal will reach from point A to Point B. This is what they teach in engineering school, but I found out the hard way that often highly trained engineers just out of school can do forumlas all day long, but they cannot do anything real world until they obtain the experience.

Once you have experience, then often you can just say: That works, and you know it will instinctively. Often forumlas are not required. But, if you need them we can do that.

On the other hand, why don't YOU provide some forumlas showing me that it DOESN'T work.

 

The transcript of the cockpit tape is available on the internet at:

http://wid.ap.org/documents/flight93cockpitvoice.pdf

It says nothing about air phone calls and cell phone calls although it can contain sounds from the passenger cabin using the cockpit ceiling microphone. Here's the ABC News version.

http://abcnews.go.com/US/print?id=1837422

I can't access the Oklahoman story without subscribing.

 

The best way for us around this thorny problem is too accept what King George and the administration says. Please quit digging for the truth, because the truth is an awesome weapon, which we might not be able to handle. Maybe they were calling King George on those cell phones. He was on the way to Omaha, Nebraska where I guess the White House was moved to.

 

The main reason that cellphones weren't a major issue is that this was the first time that the aircrafts blackbox recorder was actually given to the public, by playing it to the court. The results of this tape were passed out to the news media by the press who was in the courtroom. The tape was played to the jurors at the same time a flight simulation of the aircraft gave the altitude and attitude of the aircraft.

The news stories simply focused on the cockpit tape.

Now, straightandnarrow, I need some help from you if we are going to do this. I need a signal strength that you can live with in order to show this works. What SN+N/N can you live with? Please provide this in dbm, because that is where I am going to wind up when I calculate all of this.

Remember that we are now dealing with digital transmission, so I also need a bandwidth you will live with, under the assumption that Shannon's law fell about twenty years ago.

Provide me with signal level in dbm at the receiver input (I'll handle the antenna gain/pattern and line-loss) I'll even base them on real cellbase antennas, well assume level 4.

Remember that over twenty year ago, we were easily detecting digital signals 20 db below the noise floor in the military. This technology is now being used by cell systems. I would guess this has been surpassed, but we'll be conservative here and use technology I actually worked with.

Give me those numbers and we'll see if we can't meet them.

You are going to have to make some real world assumptions too that your calculations don't show you. Calculations can only go so far, then there is the REAL world.

By the way, what fade margin can I live with? Well assume 50/50 fade margin calculations, okay?

 

bump

 

bump

Wanna give me some numbers you will accept StraightandNarrow? I'm waiting. I will give you formulas if you get me acceptable numbers.

 

I'm sorry. I've been pretty busy. I haven't had a chance to look at this. I'll see what I can do.

 

No biggie, its been busy here too. I'll go ahead and see if I can't start working on some path charts; we'll see what we come up with.

 

I still need some numbers if we are going to wrap this up. I also need to understand exactly what you would like the formula to cover. Do we need to prove that a hand-held radio working in the microwave band can reach the ground and hit a directional antenna? If so these are simple equations and essentially do little more than show that the signal is line-of-sight. Rule-of-thumb based on experience can show you this, but it can also be calculated if you wish.

If you want to look at interference based on ground units then we need a LOT more information concerning the base station itelf. Just how many transmit channels are there; how many receive channels and exactly what is the ratio of control to comm?

From 2000 feet you are going to find the horizon at approximately 80 miles (I believe, unless I have forgotten my numbers.) Line-of-sight using microwave has been accomplished for years using less than 2 watts of transmission power.

If we are going to deal with interference, then what is the receiver capture ratio that you can live with?

All of these numbers can be right off the top of your head, so please provide them so that I can show you and the rest of the board that I'm not blowing smoke when I say cell-phones can be used from airplanes.

Thank you and bump!

 

I don't get it. You want me to prove to you that cell-phones work from 2000 plus feet HAAT, but when it comes down to giving me a few simple numbers that you can live with.

Are you over your head? If so, why not just admit that I may be right.

Why didn't you just come up with some numbers, say -117 dbm sn+N/N would be adequate--or something else that is reasonable. Can you not give me these numbers. I need some real world specifications. I have even pulled the data-sheets on standard base-unit antennas.

By the way, I have a friend who's company built major cell-bases for Sprint. I'll use his antenna and line-losses.

Or should we just call this a win by default?

 

I guess that this is a dead issue and we can assume that there is no doubt that the passengers talked to the ground using cell-phones on at least two occasions.

Debate won by default. . . sad, I really wanted to prove this issue. Any other takers?