Air to Ground Telephone in San Antonio?

[mr_hankey]

anyone ever hear anything on these?

generally, cell phones are banned from in-flight use on commercial flights, but what about private jets?

should there be a phone call on one of these frequencies in this service now and again...probably at $8/minute?

or is this part of the band dead?

Air to Ground Telephone                                     [22.521]

        Ch      Ground    Airborne

    Signaling   454.675  (459.675)
         6      454.700   459.700
         7      454.725   459.725
         5      454.750   459.750
         8      454.775   459.775
         4      454.800   459.800
         9      454.825   459.825
         3      454.850   459.850
        10      454.875   459.875
         2      454.900   459.900
        11      454.925   459.925
         1      454.950   459.950
        12      454.975   459.975



        Transmissions are FM. Ground stations repeat the airborne
    half of the conversation, and transmit a continuous tone when
    idle. From one to four channels are assigned in a particular
    area.
        Service is used on private aircraft.

 

[crayon]

I am not familer with these frequencies for avation telephone comms. Where did you get them? Do you know if any companies make comm equipment to use them?

I am familer with what AirCell is doing. They marketed two types of airborne cellular phone transceivers. The AT.01 and the AGT.01. The AT.01 is strictly airborne. The AGT.01 actually has two cellular transceivers, one for airborne operations and the other when the aircraft has 'weight on wheels' for ground ops.

AirCell has its own nationwide cellular network. (no comments about using a cellphone on an aircraft, *sigh* please.) They also have a another model that uses LEO Iridium for sat comms.

These are usually installed in general avation aircraft, dunno that the airlines use for onboard telephone comms.

 

[mr_hankey]

Iridium???

didn't they all fall to earth with Skylab(tm)?

the air-to-phone freqs are off Rich Well's http://strongsignals.net website.

but i didn't know that AirCell existed...interesting.

 

[crayon]

AirCell

Iridium's communications satellite network consits of 66 LEO's operating from 1616MHz to 1625.5MHz. Max power level for airborne transceivers is 7 watts.

Iridium

 

[blantonl]

I believe those 450 MHZ Airphone frequencies are way depreciated. They used to transmit a tone on the base frequencies, however I don't think they are used anymore.

Iridum's assets were purchased by someone, now I believe that the US Army and the rest of the military are the only real users of the network... go figure, it's a better communications network than the Army has...

 

[ericcarlson]

I believe the phones currently in use on commercial passenger flights use the 800 MHz air-to-ground telephone frequencies. The planes are on 894/895 MHz and ground stations are 45 MHz lower. These were originally AM but they're probably all digital now.

Here's one link; Google for more if you want...
http://www.qsl.net/kf6aaq/scanner/airphone.htm

-Eric

 

[mr_hankey]

there's still one up near Randolph - you can hear the constant tone...

i can't remember which without consulting my records, but i've never heard any voice traffic on it in 5 years...

 

[mm]

Those were and still are our FliteFones as the line was called. They are still being serviced and repaired but we don't manufacture many anymore.

They are mainly for buisness jets. The original line began back in the 1970s, in fact they were the starting product for Wulfsberg Electronics of Overland Park KS. back before they broadened out into the public safety FM avionics field. I still have one in front of me with the original push button dial handset and it still works so there are some ground stations still active.

You are correct in that a lot is being transfered over to 800 Mhz but the old FliteFone 454 Mhz radio/telephones are still cheaper than Iridium and the present 800 airborne cell phones but most likely not for long.


Mike M
Senior RF Eng.
Wulfsberg Elec.
Prescott, AZ.

 

[mr_hankey]

crayon,

Modulation DEQPSK (Iridium)
Modulation FM (AirCell)

what is the "DE" in DECQPSK?

there is also more information on the varying frequencies used by different AirCell products:

AirCell AST 3500 (Satellite and Cellular)

Operating Frequency 824 MHz to 894 MHz
Operating Frequency 1565 MHz to 1626.5 MHz
Operating Frequency 1530 MHz to 1660.5 MHz
Operating Frequency 824-894 MHz and 108-118 MHz and 329-335 MHz

all information taken from:

http://www.iridium.com/product/iri_product-detail.asp?productid=472&method=specification

 

[DaveH]

Try scanning the uplink side (I believe that is the correct sense even thought the direction is
"downwards"), anyway, the 459.675 to 459.975 part. If you are not near any ground station
(whichever still exist), you may hear the air side.

Incidentally, if this is considered to be banned listening in the U.S. i.e. radiotelephones,
don't do the above (plus you may have to "burn" this message and swallow the ashes...!).

I have from time to time heard a bit of such activity, but not much, and I can't usually localize
the position (could be 100's of miles away at those heights).

Dave

 

[crayon]

Those were and still are our FliteFones as the line was called. They are still being serviced and repaired but we don't manufacture many anymore.

It never ceases to amaze me just who the heck hangs out around here!! Thanks for posting Mike, and welcome to the group! I think that we might have met at an AEA convetion in Alanta, GA .. were you there?

what is the "DE" in DECQPSK?

Differentially Encoded Quaternary Phase Shift Keying

I think you may also find this referred to as: pi(as in 3.14xxx)/4

Spoken as 'pi over 4'.

 

[mm]

Differentially Encoded Quadrature Phase Shift Keying if my memory is still working. Too much RF and that's what happens after 20 years or so.

 

[crayon]

Here is an outstanding paper on DEQPSK:

http://www.uwm.edu/~lqing/digitalcomreport.pdf

Enjoy!

 

[mr_hankey]

ironic i brought this thread up...

a *ahem* "friend" just heard TWO calls in 15 minutes from 2 private aircraft commenting on a 1) diversion due to mechanical failure and 2) a storm forcing the pilot to circle for awhile before landing.

the real kicker was my "friend" hearing the pilot of one of the private aircraft radio in that he would be landing after circling on one of the Civ Air Freqs!

 

[crayon]

Those were and still are our FliteFones as the line was called. They are still being serviced and repaired but we don't manufacture many anymore.

It never ceases to amaze me just who the heck hangs out around here!! Thanks for posting Mike, and welcome to the group! I think that we might have met at an AEA convetion in Alanta, GA .. were you there?

Welp, I was digging through all of my business cards and came across a the Wulfsberg's card that I was sure that I had from the AEA convention.

Turns out it wasnt you. (you already knew that didnt ya ) It was a chap by the name of Nick Cain. Does he still work for Wulfsberg?

 

[kkn50]

We still use that system on a private jet that I fly on.

I never turn the cell-phone off when we are up but it becomes unusable rather quickly after takeoff anyway.

 

[mr_hankey]

I never turn the cell-phone off when we are up but it becomes unusable rather quickly after takeoff anyway.

i've noticed this too...why is this?

i remember an allegation that 9/11 hijackees were able to make a cell phone call from the planed destined for the Pentagon (or was it the White House) and relay information about their hijackers, etc...but i've noticed once you are airborne, most cell phones cannot affiliate with any towers...does it have to do with altitude or distance?

 

[nd5y]

I never turn the cell-phone off when we are up but it becomes unusable rather quickly after takeoff anyway.

i've noticed this too...why is this?

i remember an allegation that 9/11 hijackees were able to make a cell phone call from the planed destined for the Pentagon (or was it the White House) and relay information about their hijackers, etc...but i've noticed once you are airborne, most cell phones cannot affiliate with any towers...does it have to do with altitude or distance?

There are several reasons.
An airliner is a big aluminum tube that is shielded a lot better than a car,
unless you have the antenna right in the middle of a window.

Cellular systems are designed for very low power short distance use and
most cell sites have down-tilt antennas to reduce the range and
pick up nearby signals better.

AMPS, TDMA-136 and GSM systems reuse the same channels every 3 or 4
cell cites apart, which in high density metro areas can be only a few miles,
so if you are up very high at all you will be within line of sight distance of
many many cell sites at the same time.

Your phone will be hearing many control channels at the same time,
all interfereing with eachother and unreadable, and will constantly search
for a control channel to camp on.

It also works the other way, your phone can cause interference to
many other cell sites farther away, and can confuse the system
if many sites are hearing it at the same time.

I have limited knowledge and no experience with CDMA so I don't know
if it has the same issues, since the cell cites are designed to have
neighboring cells on the same channel.

Tom ND5Y