LIstening to aircraft frequencies...
 

Do aircraft and folks on the ground talk to each other on 2 different
frequencies? I seem to hear the ground controllers and the actual pilot on
2 separate frequencies talking to each other.

Also, there seem to be a large number of frequencies to listen to regarding
aircraft around here, but which should I concentrate on? I'm just
interested in listening to the planes and the ground controllers and such.

Dave
--
You can talk about us, but you can't talk without us!
US Army Signal Corps!!
www.geocities.com/davidcasey98
Just added Albuquerque Police beat map and
the EDACS frequencies to the site!

Aviation communications are generally Simplex, i.e., you listen and talk
on the same frequency. You should hear both sides of the conversation
on the same frequency.

You can hear inflight aircraft for quite a distance. An aircraft at an
altitude of 3000' above ground level has a line-of-sight distance of ~80
miles. An aircraft at an altitude of 30,000' has a line-of-sight
distance of ~250 miles.

The on-the-ground range of the ground based stations is quite small,
typically a few miles. And, other than tower, stations talking to
inflight aircraft may not be located on the airport.

Walt

David Casey wrote:

Do aircraft and folks on the ground talk to each other on 2 different
frequencies? I seem to hear the ground controllers and the actual pilot on
2 separate frequencies talking to each other.

Also, there seem to be a large number of frequencies to listen to regarding
aircraft around here, but which should I concentrate on? I'm just
interested in listening to the planes and the ground controllers and such.

Dave
--
You can talk about us, but you can't talk without us!
US Army Signal Corps!!
www.geocities.com/davidcasey98
Just added Albuquerque Police beat map and
the EDACS frequencies to the site!

David Casey wrote:
Do aircraft and folks on the ground talk to each other on 2 different
frequencies? I seem to hear the ground controllers and the actual pilot on
2 separate frequencies talking to each other.

Also, there seem to be a large number of frequencies to listen to regarding
aircraft around here, but which should I concentrate on? I'm just
interested in listening to the planes and the ground controllers and such.

Dave

Here is what you're hearing which probably gave the impression
of ATC and the aircraft using two different freq.

This is common at night time where there is less
traffic and less controllers on duty. Since you didn't mention any
frequencies I'll use this as an example, this was an actually example of
someone with the same question who lives in Boston, MA. Lets say
you're hearing the ground controller (ATC) on 124.4 but you're hearing
the aircraft answering on 118.25. One controller is probably
controlling three different sectors. The controller in our example is
keying up
the mike and his voice is being broadcast on 120.6, 118.25, 133.0, and
124.4 at the same time. The antenna site for 124.4 is probably near you
as that is the only one you are hearing. The other three antenna sites
are located near the center of the North sector, West sector, and South
sector, too far away from you to hear. So, you might hear Boston say
"Delta 411 decend to one four thousand" on 124.4000. However it was
also broadcast on the three other freqs but you were just too far away
from those antennas to hear it. But now you can hear Delta 411 on
118.25 say "out of 210 for one four thousand Delta 411". You heard the
Deltas reply because he was much higher and in line of site with your
radio. This would give the impression of Duplex but in reality Delta
hear ATC on 118.25.

If you tell us where you're located someone here might be able to help
you with local ATC freqs for your area.

George
http://www.MilAirComms.com

GeorgeF wrote:


David Casey wrote:
Do aircraft and folks on the ground talk to each other on 2 different
frequencies?

Here is what you're hearing which probably gave the impression
of ATC and the aircraft using two different freq.

This is common at night time where there is less
traffic and less controllers on duty. Since you didn't mention any
frequencies I'll use this as an example, this was an actually example of
someone with the same question who lives in Boston, MA. Lets say
you're hearing the ground controller (ATC) on 124.4 but you're hearing
the aircraft answering on 118.25. One controller is probably
controlling three different sectors. The controller in our example is
keying up
the mike and his voice is being broadcast on 120.6, 118.25, 133.0, and
124.4 at the same time. The antenna site for 124.4 is probably near you
as that is the only one you are hearing. The other three antenna sites
are located near the center of the North sector, West sector, and South
sector, too far away from you to hear.

Excellent answer! I have also heard the same controller's voice being
transmitted on civilian and military frequencies simultaneously.


If you tell us where you're located someone here might be able to help
you with local ATC freqs for your area.


Another good source of aviation frequencies is www.airnav.com

On Wed, 20 Aug 2003 22:11:08 -0400, GeorgeF wrote:

[snip to save space]

Deltas reply because he was much higher and in line of site with your
radio. This would give the impression of Duplex but in reality Delta
hear ATC on 118.25.

Makes sense. Thanks!

If you tell us where you're located someone here might be able to help
you with local ATC freqs for your area.

I'm in Albuquerque, New Mexico.

Dave
--
You can talk about us, but you can't talk without us!
US Army Signal Corps!!
www.geocities.com/davidcasey98
Just added Albuquerque Police beat map and
the EDACS frequencies to the site!

On Thu, 21 Aug 2003 03:06:46 GMT, Craig Davidson wrote:

Another good source of aviation frequencies is www.airnav.com

Thanks, I'll check it out.

Dave
--
You can talk about us, but you can't talk without us!
US Army Signal Corps!!
www.geocities.com/davidcasey98
Just added Albuquerque Police beat map and
the EDACS frequencies to the site!

Craig Davidson wrote:
GeorgeF wrote:


David Casey wrote:

Do aircraft and folks on the ground talk to each other on 2 different
frequencies?


Here is what you're hearing which probably gave the impression
of ATC and the aircraft using two different freq.

This is common at night time where there is less
traffic and less controllers on duty. Since you didn't mention any
frequencies I'll use this as an example, this was an actually example of
someone with the same question who lives in Boston, MA. Lets say
you're hearing the ground controller (ATC) on 124.4 but you're hearing
the aircraft answering on 118.25. One controller is probably
controlling three different sectors. The controller in our example is
keying up
the mike and his voice is being broadcast on 120.6, 118.25, 133.0, and
124.4 at the same time. The antenna site for 124.4 is probably near you
as that is the only one you are hearing. The other three antenna sites
are located near the center of the North sector, West sector, and South
sector, too far away from you to hear.


Excellent answer! I have also heard the same controller's voice being
transmitted on civilian and military frequencies simultaneously.

Yes that is normal as well. One reason for that is lets say a Military
aircraft is coming up on an ATC freq, the military aircraft can hear the
controller talking to a civilian plane so the military aircraft will
wait for him to stop talking. Then he knows the freqs are clear. If
ATC didn't do that a military plane could call up on freq however the
same controler would be on the civialian freq talking at the same time
causing ATC to miss the military's call.

George
http://www.MilAirComms.com

In article om,=20
says...
=20
Here is what you're hearing which probably gave the impression
of ATC and the aircraft using two different freq.
=20
This is common at night time where there is less
traffic and less controllers on duty. Since you didn't mention any=20
frequencies I'll use this as an example, this was an actually example of=
=20
someone with the same question who lives in Boston, MA. Lets say=20
you're hearing the ground controller (ATC) on 124.4 but you're hearing=20
the aircraft answering on 118.25. One controller is probably=20
controlling three different sectors. The controller in our example is=20
keying up
the mike and his voice is being broadcast on 120.6, 118.25, 133.0, and
124.4 at the same time. The antenna site for 124.4 is probably near you
as that is the only one you are hearing. The other three antenna sites
are located near the center of the North sector, West sector, and South
sector, too far away from you to hear. So, you might hear Boston say
"Delta 411 decend to one four thousand" on 124.4000. However it was
also broadcast on the three other freqs but you were just too far away
from those antennas to hear it. But now you can hear Delta 411 on
118.25 say "out of 210 for one four thousand Delta 411". You heard the
Deltas reply because he was much higher and in line of site with your
radio. This would give the impression of Duplex but in reality Delta
hear ATC on 118.25.
=20
If you tell us where you're located someone here might be able to help=20
you with local ATC freqs for your area.

=09A great, succinct answer that makes it clear to many of us who may=20
have suspected something like this, but weren't quite smart enough to=20
ask the question in just the right way in order to have it make sense.=20
Hats off to George.

--=20
--
From the sunrise side of Mo-Pac's famous Kirkwood Hill - N 38=B034'53", W=
=20
90=B022'32", 680'
"=A1Y tu madre tambien!"

Frank wrote:
David Casey ...

^ Do aircraft and folks on the ground talk to each other on
^ 2 different frequencies?

It is common with flight service stations. The FSS transmits on 122.0 and the
pilot may be required to transmit on 122.1.

Frank


Actually in cases where "duplexed" is used for FSS FSS at those times
transmits via a VOR (108-118 MHz) that is close to the plane. The pilot
will tune his COM radio to 122.0, 122.1 or what ever other frequency is
is listed on the sectional above the VOR's information block. The pilot
whould then transmit on that frequency.

FSS would receive the pilot on 122.0, 122.1 etc. The pilot however
would turn up the volumn on his NAV radio and have it tuned to closest
VOR to his location, FSS would be transmitting through the VOR on the
VOR's frequency via a dedicated phone line link.

Great example where I have actual experience with this was when I was
living and flying out of the Lancaster, PA area. The Lancaster VOR
freq (LRP) is 117.3 MHz however FSS was to far away (located in
Williamsport, PA) to be heard by an aircraft at low altitudes. However
since the plane was flying at 1,000' or higher FSS could receive my
signal on 122.0 however I would be two far away to hear FSS's reply on
122.0 so I would be listening for the reply on 117.3 as the Lancaster
VOR was only a few miles away where has FSS in Williamsport was about
100 miles away.

Now so FSS actually knows that you're expecting them to reply on a VOR
freq instead of direct on 122.0 here is how you would make your radio
call "Williamsport Radio, Cherokee 9335W receiving Lancaster VOR".

George
http://www.MilAirComms.com

GeorgeF wrote:

In my last post I used the term NAV and COM. Let me clearify what they
really are. An aircraft (anything from a 4 seat Cessna to a Boeing 747,
it doesn't matter the radios are just about the same) generally has 2
NAV/COM radios. Each NAV/COM is in reality 2 radios in one box, the
NAV side and the COM side. The NAV side, which stands for Navigation is
a receiver only and will receive VOR (naviational radio beacons) signals
from 107-118 MHz. The COM side, which stands for Communication is a
transceiver used for talking to ATC (Air Traffic Control), FSS (Flight
Service Station), or other aircraft. This radio will tune 118-136 MHz.

If you look at this pictu http://www.wingsonline.com/sterubp.jpg
you'll see part of a Cessna instrument panal. On the right side
starting at the top you'll see a box with lots of little buttons. This
is the audio/mike panel. It controls the where the audio from all the
radios goes, you can have one or all radios going to the overhead
speaker or to headphones. It also controls which transceiver your mike
would be connected to. In reality most small 4 seat planes can have up
to 9 radios:
COM-1 for communications
COM-2 for communications
NAV-1 for VOR, ILS (instrument landing system) navigation
NAV-2 for VOR navigation
ADF Automatic Direction Finder (usually tunes 200 KHz to 1600 KHz)
DME Distance Measuring Equipment, using radio wave to measure distant to
a VORTAC
MBR - Marker Beacon Receiver, used as part of the ILS system
TRANSPORDER - Send's code and altitute to ATC's radar screen
ELT - Emergency Locator Transmitter (transmits on 121.5 & 243.0 MHz)

And today many small planes have GPS so that would be the 10th radio on
board....

In the picture I refered to above if you look under the audio panal
you'll see two NAV/COMs, since they're turned off they just look like 4
independent radios and in reality that is what they are.

Hope you enjoy the "Aircraft Radios-101" course...There will be a quiz
later...

George
http://www.MilAirComms.com