CFI with a stuck mic on CTAF -- dual received?

AndRotate

AndRotate

Filing Flight Plan
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AndRotate
In all seriousness, though, how do you get someone to unstick their mic? Does anything actually work?
 
AndRotate said:
In all seriousness, though, how do you get someone to unstick their mic? Does anything actually work?
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I think that all you can hope to do is find them on the ground afterward.
 
Treat as nordo and continue on with life. I was just doing pattern work one time and was receiving but not transmitting. Took me two laps to figure it out.
 
Middle finger usually makes me feel better but that's about it.

As we were taxiing up there were 2 announcing in the pattern and a third that was keying to announce but couldn't hear anything. Could tell one of the 2 was a student and they had to figure out what the other guy was doing as it was unclear he was doing pattern work. After the guy with the mic issue landed and was clear of runway i let him know could hear him keying but not hearing anything. He keyed to acknowledge but couldn't hear anything still. Half surprised the other 2 didn't say anything before I did as they were up working around him.
 
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If they are listening on 121.5 on a second radio, you can transmit there to tell them.
 
Larry in TN said:
If they are listening on 121.5 on a second radio, you can transmit there to tell them.
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I’ve heard that call on 121.5 but in my plane (Warrior) if one radio is transmitting the other is blocked out by a relay, so I’m not sure the person can always receive even on a second radio/frequency.

The “test”, I think, is to have the second radio go to the overhead speaker and then set that radio to the same frequency as the first (if your audio panel allows this). If you can’t hear your voice in the speaker when you broadcast you have the relay. Don’t be fooled by side tone in your ear from the first radio.

Haven’t tried it but I suspect having ALL radios go to the speaker would offer the same test, since I’m not sure a side tone is produced when using the speaker. Could be wrong about that part.

Maybe this is true for GA but airliners/big planes have completely independent radios. Then again, if they did, they’d probably know of the stick mic issue on the frequency.
 
Llewtrah381 said:
I’ve heard that call on 121.5 but in my plane (Warrior) if one radio is transmitting the other is blocked out by a relay, so I’m not sure the person can always receive even on a second radio/frequency.

The “test”, I think, is to have the second radio go to the overhead speaker and then set that radio to the same frequency as the first (if your audio panel allows this). If you can’t hear your voice in the speaker when you broadcast you have the relay. Don’t be fooled by side tone in your ear from the first radio.

Haven’t tried it but I suspect having ALL radios go to the speaker would offer the same test, since I’m not sure a side tone is produced when using the speaker. Could be wrong about that part.

Maybe this is true for GA but airliners/big planes have completely independent radios. Then again, if they did, they’d probably know of the stick mic issue on the frequency.
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In general, don't do that, it will/could set up a horrendous feedback squeal.
 
Just another down side of asynchronous communications.
Anyone else remember an attempt (50 years ago or more) to get aircraft communications split to two separate frequencies? One for transmit, one for receive.
It obviously had problems with the technology that was available at the time, but it certainly would be doable now.
 
Shepherd said:
Just another down side of asynchronous communications.
Anyone else remember an attempt (50 years ago or more) to get aircraft communications split to two separate frequencies? One for transmit, one for receive.
It obviously had problems with the technology that was available at the time, but it certainly would be doable now.
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Xmit 122.1, listen over the VOR. ;)
 
Shepherd said:
Just another down side of asynchronous communications.
Anyone else remember an attempt (50 years ago or more) to get aircraft communications split to two separate frequencies? One for transmit, one for receive.
It obviously had problems with the technology that was available at the time, but it certainly would be doable now.
Click to expand...


Could easily do it with just one frequency using suppressed carrier upper and lower sidebands. And that technology has been around forever.
 
Shepherd said:
Just another down side of asynchronous communications.
Anyone else remember an attempt (50 years ago or more) to get aircraft communications split to two separate frequencies? One for transmit, one for receive.
It obviously had problems with the technology that was available at the time, but it certainly would be doable now.
Click to expand...
With all of the hoops required to be authorized for PRM approaches at an air carrier I can’t imagine just how ****ed up the implementation of that would be if it was anything other than setting one channel/frequency and using the radio same as we do now.
 
Tarheelpilot said:
With all of the hoops required to be authorized for PRM approaches at an air carrier I can’t imagine just how ****ed up the implementation of that would be if it was anything other than setting one channel/frequency and using the radio same as we do now.
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This was what they were proposing.
You wouldn't set frequencies, you would pick an airport assigned "channel" and it would automatically set the frequencies. Honestly, I don't remember why they killed it.
 
Shepherd said:
Just another down side of asynchronous communications.
Anyone else remember an attempt (50 years ago or more) to get aircraft communications split to two separate frequencies? One for transmit, one for receive.
It obviously had problems with the technology that was available at the time, but it certainly would be doable now.
Click to expand...
So if everyone is listening on a different frequency than they are transmitting on, how is anyone going to hear anything? I think I missed something.
 
Salty said:
So if everyone is listening on a different frequency than they are transmitting on, how is anyone going to hear anything? I think I missed something.
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It's a long time ago. But an airport would get a pair of frequencies as a channel. You would select that channel and some magic happened in the little box and you would talk and it would transmit on one frequency and they would receive it on another.
The problem was the wizard couldn't get the magic in the box to work. It's so long ago I don't remember the details.
 
pmanton said:
That happened right over our airpark, except the "CFI" giving "instruction" was a student pilot instructing a non pilot.
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Oops

I wonder if their entire cockpit conversation was recorded by LiveATC?
 
Shepherd said:
It's a long time ago. But an airport would get a pair of frequencies as a channel. You would select that channel and some magic happened in the little box and you would talk and it would transmit on one frequency and they would receive it on another.
The problem was the wizard couldn't get the magic in the box to work. It's so long ago I don't remember the details.
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I see. Thanks
 
We had someone flying with a stuck mic up my way a few months ago. The amazing/annoying part was they must have had a plane with a ridiculous amount of fuel, because I heard them for over an hour on the way to breakfast, then they were still on the air two hours later all the way on my way home...over 4 hours total. You’d think it would eventually burn up the final amplifier in their radio. I even knew where they where at, because I could hear the pilot pointing out landmarks to his passenger. At one point in my flight the offender and I were only about 10 miles apart and I seriously considered looking for them, but then I realized I wouldn’t know what to do if I found them.
 
Salty said:
I see. Thanks
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FYI - there's a pretty good article on duplex radio comms in the March issue of IEEE Spectrum. Frequency-division duplexing has been done for a while, but there's work in progress to do it over a single frequency, which would greatly improve spectrum efficiency.

The "magic" that @Shepherd references, though, is present in your cell phone and its network. Essentially, duplex (or multiplex) tower comms would work similarly to a cell phone conference call. Rather than selecting a frequency, you'd select a "channel" that would be on at least two (possibly more) frequencies assigned by a network controller, just like you now dial into a conference call.
 
Half Fast said:
The "magic" that @Shepherd references, though, is present in your cell phone and its network. Essentially, duplex (or multiplex) tower comms would work similarly to a cell phone conference call. Rather than selecting a frequency, you'd select a "channel" that would be on at least two (possibly more) frequencies assigned by a network controller, just like you now dial into a conference call.
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I thought cell phones were FHSS and CDMA these days?
 
Larry in TN said:
If they are listening on 121.5 on a second radio, you can transmit there to tell them.
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Nope...when you key your transmitter, it mutes your receive audio on both coms wired to your audio panel.

You could send him a text message :).

I thought the advantage of AM is that even though someone has a stuck mic, you can still receive a transmission from another station..with the annoying heterodyne squeal included.
 
asicer said:
I thought cell phones were FHSS and CDMA these days?
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They are. That's why I said "possibly more" frequencies; there's no reason frequency hopping couldn't be done.

Of course, the system would have to be much more reliable than a typical cell phone network. I was just using that as an example to illustrate how duplex comm might be done.
 
Doug Reid said:
I thought the advantage of AM is that even though someone has a stuck mic, you can still receive a transmission from another station..with the annoying heterodyne squeal included.
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Works with SCSSB, too, but I seem to recall that you don't get the squeal for some reason. Been a while since I was on the air, though, so I could be misremembering.
 
Had what seemed like a 20 minute conversation a few weeks ago. Non pilot passenger must have thought he needed to use the PTT in the airplane to talk to pilot.
 
Half Fast said:
Works with SCSSB, too, but I seem to recall that you don't get the squeal for some reason. Been a while since I was on the air, though, so I could be misremembering.
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SSB is still a form of amplitude modulation however, the reason that you don't get the squeal when two stations transmit is because SSB does not transmit the carrier (SC). The carrier is "inserted" at the receiver by a BFO (beat frequency oscillator).
 
Joe_B1 said:
SSB is still a form of amplitude modulation however, the reason that you don't get the squeal when two stations transmit is because SSB does not transmit the carrier (SC). The carrier is "inserted" at the receiver by a BFO (beat frequency oscillator).
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Right. Plus SSB is more power efficient and spectrum efficient. So if we want AM, why aren’t we using SSBSC?
 
If you think that switching to the other sideband is going to be a cure to someone close by stuck on the channel, you're in for a bit of a surprise.
 
flyingron said:
If you think that switching to the other sideband is going to be a cure to someone close by stuck on the channel, you're in for a bit of a surprise.
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No, I just think SSB would be a better use of spectrum, provide better range on the same power, and not squeal like a banshee when two people transmit on top of each other.
 
Half Fast said:
No, I just think SSB would be a better use of spectrum, provide better range on the same power, and not squeal like a banshee when two people transmit on top of each other.
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This is true but as are many things in aviation, it's inertia. They are not going to switch to SSB for general comms because it would mandate that everyone buy new radios. Also, tuning with SSB is less forgiving than AM. Since the receiver is inserting the carrier for demodulation of an SSB signal, the tuning requirements are more critical.
 
There are documented procedures to "autotune" SSB. Since most modern radios are probably going to be DSP-based to begin with, it's probably not all that hard. Of course, with some thought you probably could mandate a stuck-mic unjammer circuit (a lot of radios just have continuous transmit timeouts as it is).
 
Fair enough, with today's electronics tuning radios is not a big deal. However, retrofitting the entire fleet with new comm radios is. Moving to a sideband scheme would make every am radio obsolete. As far as the efficiency of SSB goes, given the 10 or 15 watts the current radios transmit at, shifting to SSB would not be a worthwhile benefit.

Sure, SSB does have benefits but do those benefits outweigh the costs?
 
flyingron said:
If you're going to obsolete everything, why replace a 90 year old technology with a 70 year old one. Just go digital.
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Why half-do it? With good enough TCAS, we can all just go NORDO.
 
Shepherd said:
Just another down side of asynchronous communications.
Anyone else remember an attempt (50 years ago or more) to get aircraft communications split to two separate frequencies? One for transmit, one for receive.
It obviously had problems with the technology that was available at the time, but it certainly would be doable now.
Click to expand...

more recently there was a proposal for VHF comm radios that would divide each of the (then existing) channels into 4, and included the ability of the channels assigned to ATC to override the others. I'm drawing a blank on the name of the system. Unfortunately, the world went with the 8.33kHz spacing because Europe needed the extra channels before the other system would be ready

edit: NEXCOM VDL-4 (I think)
 
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