ARTCC transmitting and receiving stations

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DanielH

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Daniel
Are there different receiveing and transmitting stations for the same center frequency? Going into airports in a certain area of Indy center control I seem to not be able to hear the controller and then attempt to contact them and can hear the controller loud and clear. Are center controller able to choose where they transmit based on the aircraft location?
 
Yes.

Bob Gardner
 
DanielH said:
Are there different receiveing and transmitting stations for the same center frequency?
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Yes, in some large Center sectors.

Going into airports in a certain area of Indy center control I seem to not be able to hear the controller and then attempt to contact them and can hear the controller loud and clear. Are center controller able to choose where they transmit based on the aircraft location?
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Yes, but probably not those in Indy Center.
 
roncachamp said:
Yes, but probably not those in Indy Center.
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Beg to differ. Not only are there different frequencies used in parts of Indy Center (including parts of KY and WV), sometimes the sectors are combined.
 
wsuffa said:
Beg to differ. Not only are there different frequencies used in parts of Indy Center (including parts of KY and WV), sometimes the sectors are combined.
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Of course. But the question was, "Are there different receiveing and transmitting stations for the same center frequency?"
 
roncachamp said:
Of course. But the question was, "Are there different receiveing and transmitting stations for the same center frequency?"
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Yes, and the controller can select which location he wants to use.
 
Canada is doing something really neat. Flying around up there late last year and I noticed that when the controller told an aircraft to switch frequencies, I would hear the response from the airplane, and then hear the airplane checking in on the 'new' frequency and centers response. I obviously wasn't the only one scratching my head as someone else asked the question of why can we hear the airplane when it is supposed to be on a different frequency? The controller said it was something new they were doing, a repeater maybe? Anyway, if he's working three different frequencies for example, as a pilot you are able to hear aircraft on all frequencies and the controller as well. Haven't a clue myself of HOW it works, but it would be nice to have down here in the states too!
 
Speed said:
Canada is doing something really neat. Flying around up there late last year and I noticed that when the controller told an aircraft to switch frequencies, I would hear the response from the airplane, and then hear the airplane checking in on the 'new' frequency and centers response. I obviously wasn't the only one scratching my head as someone else asked the question of why can we hear the airplane when it is supposed to be on a different frequency? The controller said it was something new they were doing, a repeater maybe? Anyway, if he's working three different frequencies for example, as a pilot you are able to hear aircraft on all frequencies and the controller as well. Haven't a clue myself of HOW it works, but it would be nice to have down here in the states too!
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Why would that be nice to have here?
 
roncachamp said:
Why would that be nice to have here?
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At the very least, it would help avoid pilots stepping on each other's transmissions to the same controller.

It's also somewhat disconcerting to hear only half a conversation. I pick up info that helps with my own SA when I can hear conversations between ATC and other traffic.

So I agree it'd be nice.
 
Jim_R said:
At the very least, it would help avoid pilots stepping on each other's transmissions to the same controller.

It's also somewhat disconcerting to hear only half a conversation. I pick up info that helps with my own SA when I can hear conversations between ATC and other traffic.

So I agree it'd be nice.
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On one hand it appears that would tie up multiple frequencies with the same transmission. On the other hand if there is only one controller handling those frequencies then the repeaters shouldn't generally affect actual ATC utilitization of those bands.
 
Jim_R said:
At the very least, it would help avoid pilots stepping on each other's transmissions to the same controller.
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I don't see how.

It's also somewhat disconcerting to hear only half a conversation. I pick up info that helps with my own SA when I can hear conversations between ATC and other traffic.
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The aircraft on the other frequency are some distance away or there'd be no need for another frequency. How does hearing them help your SA?
 
Jim_R said:
At the very least, it would help avoid pilots stepping on each other's transmissions to the same controller.

It's also somewhat disconcerting to hear only half a conversation. I pick up info that helps with my own SA when I can hear conversations between ATC and other traffic.

So I agree it'd be nice.
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Not hearing the other aircraft but hearing the controller doesn't bother me at all. It bothers me when I can hear another aircraft but not the controller.
 
Jim_R said:
At the very least, it would help avoid pilots stepping on each other's transmissions to the same controller.


So I agree it'd be nice.
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This. Then I wouldn't have to hear "I had two aircraft calling at the same time...." type of response from ATC, which I hear a lot in the states.
 
Speed said:
This. Then I wouldn't have to hear "I had two aircraft calling at the same time...." type of response from ATC, which I hear a lot in the states.
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Please explain. Aircraft on the same frequency step on each other. How does a system that allows aircraft on different frequencies to hear each other prevent them from stepping on each other?
 
roncachamp said:
Please explain. Aircraft on the same frequency step on each other. How does a system that allows aircraft on different frequencies to hear each other prevent them from stepping on each other?
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I mean when two aircraft are talking to the same controller on two different frequencies when the same controller is working both.
 
roncachamp said:
Please explain. Aircraft on the same frequency step on each other. How does a system that allows aircraft on different frequencies to hear each other prevent them from stepping on each other?
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Not prevent, but make less likely.
 
Speed said:
I mean when two aircraft are talking to the same controller on two different frequencies when the same controller is working both.
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So how does a system that allows those two aircraft to hear each other prevent them from stepping on each other?
 
roncachamp said:
So how does a system that allows those two aircraft to hear each other prevent them from stepping on each other?
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Because you can then HEAR the other airplane and you don't talk while the other is talking.

Usually the set-up will allow pilots on any of the frequencies to hear each other by re-transmitting all transmissions across all the frequencies (i.e. if the same controller uses frequency 1, 2 and 3, and an aircraft on frequency 1 calls, pilots on frequency 2 and 3 can also hear ATC and the pilot on frequency 1).

It's used over in Europe too - from the European Action Plan for Air Ground Communication Safety - Cross-coupling of RTF frequencies is often employed to improve pilot and controller situational awareness: transmissions on one frequency are simultaneously retransmitted on the second. However cross-coupling can give rise to enhanced probability of simultaneous transmission due to the increased number of audible transmissions.

And further down, one of the recommendations - If a controller is providing ATS for two or more areas, the relevant channels must be located on the controller working position being used. Preferably, channels should be cross-coupled to prevent simultaneous transmissions by aircraft.
 
Speed said:
Because you can then HEAR the other airplane and you don't talk while the other is talking.
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Don't be silly. Aircraft on the same frequency can HEAR each other and do talk while the other is talking.
 
roncachamp said:
Don't be silly. Aircraft on the same frequency can HEAR each other and do talk while the other is talking.
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If I can hear someone else talking, I will be less likely to transmit until they are done. I admit that, even when we are on the same frequency, there is an appreciable chance that altitude and / or distance will prevent me from hearing other aircraft anyway; however, if transmissions handled by the same controller are rebroadcast via the controller's transmitters, I am much more likely to hear aircraft that are so separated from mine.

It won't stop two aircraft from keying up at the same time (and it won't stop aircraft from transmitting g even when the other aircraft can be copied direct), but it would reduce situations where one aircraft, not realizing the controller was busy, transmits anyway.

-- Chris Kovacs, talking to airplanes on radios badly with marginal success since 1989 ;)
 
roncachamp said:
Smaller sectors.



We're not talking about backup transmitters or BUEC.
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Roger on the smaller sectors.

I could change towers for different parts of the sector, or change transmitters on the same tower. All were on the same freq. we are taking 1970-80s technology.
 
BillTIZ said:
I could change towers for different parts of the sector, or change transmitters on the same tower. All were on the same freq. we are taking 1970-80s technology.
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We're not talking about backup transmitters or BUEC.
 
roncachamp said:
Please explain. Aircraft on the same frequency step on each other. How does a system that allows aircraft on different frequencies to hear each other prevent them from stepping on each other?
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The issue was "avoid pilots stepping on each other's transmissions to the same controller." Not on the same frequency, two different frequencies (different sectors?) handled by the same controller. When the controller transmits they have the option of broadcasting on all of their frequencies or just the one that has been assigned to the aircraft they're calling but they can also activate every transmitter assigned to their sector. In that case you can hear the controller talking and wait for a break but if an airplane on a different frequency transmits at the same time the controller has to sort out the multiple responses. IIRC a controller can temporarily disable reception on all but one of their frequencies but they don't always do that.
 
gismo said:
The issue was "avoid pilots stepping on each other's transmissions to the same controller."
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Is there another way to step on each other's transmissions?

Not on the same frequency, two different frequencies (different sectors?) handled by the same controller.
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Right. Given that aircraft on the same frequency step on each other, how does a system that allows aircraft on different frequencies to hear each other prevent them from stepping on each other?

When the controller transmits they have the option of broadcasting on all of their frequencies or just the one that has been assigned to the aircraft they're calling but they can also activate every transmitter assigned to their sector. In that case you can hear the controller talking and wait for a break but if an airplane on a different frequency transmits at the same time the controller has to sort out the multiple responses. IIRC a controller can temporarily disable reception on all but one of their frequencies but they don't always do that.
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Where do controllers choose that option? What is your source of information?
 
Speed said:
Canada is doing something really neat. Flying around up there late last year and I noticed that when the controller told an aircraft to switch frequencies, I would hear the response from the airplane, and then hear the airplane checking in on the 'new' frequency and centers response. I obviously wasn't the only one scratching my head as someone else asked the question of why can we hear the airplane when it is supposed to be on a different frequency? The controller said it was something new they were doing, a repeater maybe? Anyway, if he's working three different frequencies for example, as a pilot you are able to hear aircraft on all frequencies and the controller as well. Haven't a clue myself of HOW it works, but it would be nice to have down here in the states too!
Click to expand...

What you are describing isn't quite a "repeater" in the technical sense but rather a "patch". The benefit, which one poster appears obtuse about, is that other aircraft are aware of when the CONTROLLER is being talked to by another aircraft (previously unheard on another frequency) and in an optimal situation choose not to transmit at the same time...

My experience in dispatching public safety is that the patch can be quickly enabled and disabled with the touch of a button or two, and its easy for the controller or dispatcher to see which channel is the source of a patched transmission... (which allows for easy de-selection in the event of a stuck mic on one of the patch channels). I used patch to simulcast from trunked 800 to our legacy VHF system for pager dispatch of EMS and fire assets.

I could see it being useful for a controllor working several positions on a slow shift. I could not see it being effective being used at La Guardia or DFW during the push..
 
It's called frequency cross coupling. Canada, Europe and some oceanic sectors use it. I've read at least two centers have it as well. It works just as described above. You can hear another aircraft on a separate freq, that way you aren't both transmitting at the same time. Increases SA for all involved.
 
Doggtyred said:
What you are describing isn't quite a "repeater" in the technical sense but rather a "patch". The benefit, which one poster appears obtuse about, is that other aircraft are aware of when the CONTROLLER is being talked to by another aircraft (previously unheard on another frequency) and in an optimal situation choose not to transmit at the same time...
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Optimal situation? Why do aircraft on the same frequency step on each other?
 
I would think that controllers would appreciate not having two planes talking to them at the same time...which the possibility of is reduced when aircraft can hear each other. Apparently not though.
 
DanielH said:
I would think that controllers would appreciate not having two planes talking to them at the same time...which the possibility of is reduced when aircraft can hear each other. Apparently not though.
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We do appreciate it. I've been in ATC for nearly thirty years, I've had aircraft step on each other when one frequency was in use and when multiple frequencies were in use. I never noticed a significant difference in the stepping rate.
 
roncachamp said:
Optimal situation? Why do aircraft on the same frequency step on each other?
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Because they can't hear each other.

Aircraft transmit at low power with poor ERP characteristics. When they are at low altitude and separated by a great distance, they can't hear each other.

And you're right, a patching solution will not fix that. Rebroadcasting on the same frequency at remote sites might, but there might be issues doing that as well, depending.
 
ChrisK said:
Because they can't hear each other.

Aircraft transmit at low power with poor ERP characteristics. When they are at low altitude and separated by a great distance, they can't hear each other.
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Wrong. Aircraft that can hear each other step on each other.
 
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