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Author Topic: US Centers non-combined freq  (Read 5368 times)
boxchucker
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« on: November 02, 2011, 11:10:35 PM »

Any controllers on this board that can explain why you guys never combine your freqs?

I'm looking for US controllers specifically.

For example, after checking in with Boston Center, I can hear the controller respond to planes on other frequencies but the other plane is never retransmitted onto all freq for everyone to listen to get a picture and know when to hop in on the freq.
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sykocus
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« Reply #1 on: November 03, 2011, 05:33:57 AM »

Any controllers on this board that can explain why you guys never combine your freqs?

I'm looking for US controllers specifically.

For example, after checking in with Boston Center, I can hear the controller respond to planes on other frequencies but the other plane is never retransmitted onto all freq for everyone to listen to get a picture and know when to hop in on the freq.

Often when traffic is not at it's peak different sectors which might have been worked by separate controllers are combined into one. If that's the case then the controller "picks up" the frequencies. However he will want to keep the aircraft on the frequency assigned to the airspace they are in. That way if the sectors become busy again and get split back off all the aircraft are already on the frequency they need to be.

Another reason a single controller has more then one frequency is required because environmental conditions (interference, topography, etc.) preclude a single frequency from covering the whole sector. If that's the case the transmitters are located in separate locations so putting all the aircraft on the same frequency is counterproductive.

It maybe technically possible to link the receiver of one radio into the transmitter of another. I don't have much experience with the VSCS that the large centers use, but I haven't heard of such a capability. I'd imagine there are some complications to overcome like what if an aircraft on freq A and freq B key up at the same time. Who get's priority and or do they both cancel each other one. As it would stand normally both could be heard and the controller deal with them one at a time. Also in the 2nd example there would probably be a significant delay in the as the information travels from freq A's receiver site to the center's switch then to freq B's transmitter site.
« Last Edit: November 03, 2011, 05:57:05 AM by sykocus » Logged

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davolijj
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« Reply #2 on: November 05, 2011, 01:01:02 AM »

I believe what you are referring to is known as cross-coupling frequencies, whereby an aircraft transmits on one frequency and it can be heard on all of the controller's other frequencies configured to the radar sector.  They use this function in Europe as well as Canada.

The reason controllers in the U.S. do not use it is because the voice switching and communications system (VSCS) in use at the ATRCCs do not have the functionality to support the feature. 

The Harris-developed VSCS – based on independent, distributed processors and switches – allows air traffic controllers to establish all air-to-ground and ground-to-ground communications with pilots and other air traffic controllers. The system offers unprecedented voice quality, touch-screen technology, dynamic reconfiguration capabilities to meet changing needs, and an operational availability of 0.9999999.

The system was designed by Harris Corp. back in the 1990s and although the Cross-couple feature was included in the original design it was not carried through to field facilities.
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« Reply #3 on: November 05, 2011, 10:34:14 AM »

New York Center is using frequency cross-coupling on their Oceanic Sectors. ZNY Sector 82 on 126.025 is cross-coupled with Sector 83 on 133.525, Sector 86 on 133.500 cross couples with Sector 65 on 125.925, when it's slow I've heard all 4 sectors cross-coupled together. (hint: this would make an interesting feed if anyone is in range of any of these ground stations). I've also heard cross-coupling done on some Cleveland Center low sectors, someone mentioned here on this forum in another thread that it was being tested there. So far these are the only 2 areas in the US I've heard it used.

Cross-coupling is used extensively in Canada, for those interested, a good example of this can be heard on Montreal Center on the YUL ACC (Noranda Sector) 133.975 feed here on LiveATC. During normal hours this controller is cross-coupled to around 5 frequencies and during the overnight hours up to around 18 frequencies are linked together. It's easy to tell when an aircraft is transmitting on a cross-coupled frequency as there is a distinct sort of tinny sound to their transmissions and always the same strength as the controller.  



  
« Last Edit: March 18, 2012, 12:59:12 PM by JetScan1 » Logged
boxchucker
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« Reply #4 on: November 06, 2011, 09:43:19 PM »

thanks dave and jet. Exactly what I was looking for.
On a interesting side note like the montreal nouranda pointed out by jetscan, if you listen to saskatoon or thunderbay terminal during quiet hours they are cross-coupled sometimes.
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JetScan1
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« Reply #5 on: November 07, 2011, 09:41:03 AM »

Quote
if you listen to saskatoon or thunderbay terminal during quiet hours they are cross-coupled sometimes.

Another interesting example is Ottawa (YOW) and Quebec City (YQB) Terminal (Approach/Departure) that are cross-coupled together during the overnight hours, these two airports are 200 miles apart, with one controller (located at the Montreal Center) working both of them.

Technical information on frequency cross-coupling can be found in this document.

https://faaco.faa.gov/attachments/ED-136_Operational_and_Technical_Requirements.pdf

The FAA has also published a National Airspace System (NAS) Voice System (NVS) Draft that outlines cross-coupling specifications.

https://faaco.faa.gov/attachments/NVS_Specification_v0_09-BL-2011-09-13.pdf

Whether or not this means it might become more common in the US remains to be scene ? Anyone in the know, or have heard it being used at other FAA facilities ?


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klkm
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« Reply #6 on: November 07, 2011, 04:32:17 PM »

New York Center is using frequency cross-coupling on their Oceanic Sectors. ZNY Sector 82 on 126.025 is cross-coupled with Sector 83 on 133.525, Sector 86 on 133.500 cross couples with Sector 65 on 125.925, when it's slow I've heard all 4 sectors cross-coupled together. (hint: this would make an interesting feed if anyone is in range of any of these ground stations). I've also heard cross-coupling done on some Cleveland Center low sectors, someone mentioned here on this forum in another thread that it was being tested there. So far these are the only 2 areas in the US I've heard it used.



 

Sector 83/82 is in a different area then 86/65 so they are never all cross-coupled together.  The feature is available but it tends to cause the freq to break up a bit, so most still prefer to just put one freq on speaker and the other on headset and work it that way.  The reason for the split of freq is the size of the sector for 86/65 there is about a 40-50 mile overlay where the a/c can still pick up the controller but after that they will be lost if the freq is not changed over, which is the reason for not combining every a/c to one freq.  In the US most sectors that can be combined to one freq will put all the a/c on that one freq when it is slow.  This would typically be a sector that can be split high and low, on the midnights they will combine the two to one frequency, but like someone said if geographically or environmentally it is not possible you will have to work it on multiple frequencies.  But, if you are trying to get a picture of the traffic, the traffic you can't hear is likely 100's of miles away so don't worry about it. 
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JetScan1
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« Reply #7 on: November 07, 2011, 06:26:36 PM »

Quote
Sector 83/82 is in a different area then 86/65 so they are never all cross-coupled together.

My mistake, I must have been hearing things then.

Quote
The feature is available but it tends to cause the freq to break up a bit ...

Interesting, thanks for the info.

« Last Edit: March 18, 2012, 01:00:25 PM by JetScan1 » Logged
dave
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« Reply #8 on: November 17, 2011, 07:29:56 AM »

Not exactly related to this thread, but it does relate to Sector 86.  Does anyone know if the Douglaston RCAG is still in service?  I was very close to it yesterday and could not detect any RF activity there.  It's listed as having 121.125 and 134.375 (ZNY Sector 86) but I wonder if it is just a backup site.
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JetScan1
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« Reply #9 on: March 18, 2012, 12:58:28 PM »

An update on frequency cross-coupling. I notice that Indianapolis has started using it on some of their low sectors. You can hear this on the ZID Indy RCAG radio here on LiveATC, where 124.525 appears to be cross-coupled with 128.075. I've also noticed them doing it with 120.475 and 123.925 as well.
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