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| | |-+  What's a Cell Call on HF?
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Author Topic: What's a Cell Call on HF?  (Read 2653 times)
blucenturion1
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« on: January 09, 2013, 03:36:54 PM »

New York, Gander, Santa Maria use the term "standby for cell call" and two tones are then heard. What's that all about? I worked HF Airways in the AF, but cells didn't exist then, so I'm clueless here. TIA
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RonR
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« Reply #1 on: January 09, 2013, 03:52:36 PM »

It's actually "Sel Call" and it's a method that HF radio operators use to call a specific aircraft when they are in oceanic airspace.  The tones you hear are specific to an aircraft and will be different for each aircraft.  When the receiver on the aircraft receives these tones it will set off a chime or some other sound in the cockpit telling the pilots that the HF radio operator is trying to reach them.  In this way the pilots don't have to "maintain a listening watch" on the HF frequency and thus don't have to endure the static noise that would be heard when there is no transmission.  If for some reason the Sel Call check doesn't work, and it does happen, then the pilots have to maintain a listening watch on the frequency.  I hope that explains it.

Ron

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InterpreDemon
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« Reply #2 on: January 09, 2013, 04:10:58 PM »

SelCal is the acronym for "selective calling". Because it is virtually impossible to "squelch" the HF receiver of noise, static and undesired communications, a "listening watch" for calls from ATC would add significantly to cockpit workload and distraction. SelCal is a tone activated squelch system that keeps the receiver muted until the proper tone code is received. It is actually two pairs of tones, similar to telephone "touch tones". When a controller wants to contact a particular aircraft he transmits the tones, the receiver decodes them, unlocks the audio and the controller as well as any other transmissions can then be heard. In addition there is usually a chime indication so that even if the pilots were listening in the background they are alerted when a call comes for them. If their SelCal system is not working properly they are required to continuously listen, which is why you will hear them getting a SelCal check prior to entering Oceanic airspace.
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RonR
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« Reply #3 on: January 09, 2013, 04:13:05 PM »

Some more detailed info here:

http://www.hfunderground.com/wiki/FAA_Flight_Control/SELCALL
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Rob K
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« Reply #4 on: January 17, 2013, 12:11:48 PM »

New York, Gander, Santa Maria use the term "standby for cell call" and two tones are then heard. What's that all about? I worked HF Airways in the AF, but cells didn't exist then, so I'm clueless here. TIA

It's selcal.  Should be all the info you need on my site - http://www.selcalweb.co.uk

 grin
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