The use of 243 (guard)

[autovon]

Yes, in our NAS, this is for sure. Multicasting is about the best way to describe it.

Thanks for the reply. I should have explained better, hopefully this makes sense. Frequencies used here are just examples.

Let's say I'm on 120.050 talking to a controller at FL320 over South Dakota. Somewhere out there is aircraft B on 135.25. The controller tells aircraft B to contact them on 120.050. I hear aircraft B readback they are switching to 120.050, even though I'm not tuned to that frequency. Then, I hear aircraft B check in on 120.050.

The audio sound for the controller sounds the same throughout this example. For aircraft B, when they are on the other frequency (135.25), the audio sounds tinny and there is about a half second hang time (like a repeater) on their transmission. When they check in on 120.050, it sounds normal. The sound signature and being able to hear other airplanes not on my frequency sounds exactly like the cross coupling, bandboxing (whatever its called) that is used in NAV CANADA, Europe, and elsewhere.

I've heard this a handful of times in the US, for sure on at least one of Minneapolis Center's frequency. The audio signature heard in the above example is not just that one airplane. As other planes check in on the 'other' frequency, they all sound tinny and have a very brief hang time when they unkey.

 

[AirScan]

I should have explained better, hopefully this makes sense.

What you are describing, as you noted, is frequency cross-coupling. Contrary to what spanky15805 says, it is available and used in the USA, although not all ARTCCs seem to use it yet (Boston for one). The US system, unless it has been updated recently, only has the ability to cross-couple 2 frequencies. This differs from Canada were the NAV Canada system has the ability to cross-couple multiple frequencies.

 

[autovon]

What you are describing, as you noted, is frequency cross-coupling. Contrary to what spanky15805 says, it is available and used in the USA, although not all ARTCCs seem to use it yet (Boston for one). The US system, unless it has been updated recently, only has the ability to cross-couple 2 frequencies. This differs from Canada were the NAV Canada system has the ability to cross-couple multiple frequencies.

Thanks! I figured as much, but never read anywhere that it was a capability in the NAS.

 

[AirScan]

Thanks! I figured as much, but never read anywhere that it was a capability in the NAS.

Here is an example, from the ZDC SOP Manual (2014).

"SECTION 10. VSCS CROSS COUPLING

2-74 The VSCS cross coupling feature allows the transmissions of an aircraft on one frequency to be instantly rebroadcast on a second frequency. This reduces the number of blocked transmissions when using two different frequencies. In order to utilize the cross coupling feature, sectors must be designated in the VSCS database and paired with one (and only one) other frequency.

Each frequency must be visually located on top of one another on the VDM. Cross coupling is activated by selecting the “XCPL” function button on the bottom bar on the VDM screen and then touching a cross couple eligible frequency (highlighted by a purple color bar). This process is repeated with the second frequency in order to establish bi-directional cross coupling. Once cross coupling is established, arrows will appear pointing to the frequency which it is paired to. All UHF and VHF pairs must be activated separately. Cross coupling will remain in place until it is deactivated (turning off a frequency WILL NOT deactivate cross coupling). Cross coupling is deactivated by repeating the same steps used to activate it."

 

[dlwtrunked]

I have been hearing civil aviation come up on 243 and a friend of mine who used to be an air traffic controller told me civil shouldn't have 243, but rather 121.5 which was what I suspected as well. But never the less I hear planes like United et al come up on 243. Do civil aircraft have this capability, or is there some kind of rebroadcast going on with 121.5?

All U.S. FAA ARTCC centers have and always have had 243.0 MHz (you can see that in any of the FAA Chart supplement books). When you say "civilian aviation", who do you mean-what call signs or aircraft?

 

[alcahuete]

Cross-coupling is definitely used in the US, but unlike other countries, ours is set up in a really stupid manner. You can only use 2 frequencies, and cross-coupling does not work even with 2 frequencies if there are more than 2 RCAG sites involved on one of the frequencies. It is incredibly stupid, because the sectors that usually benefit from cross-coupling the most are larger sectors with multiple radio sites. And of course, on the mid-shift when every sector is normally combined to one or two sectors, you can't use it. Too many frequencies and too many radio sites. SMH...

So the reason you don't see cross coupling used a lot is because it's so difficult to find sector configurations in which it can actually be used.