PL Tones & Bing Co-pilot

[Samyham]

I had a question for AI. I liked the answer and I hope it helps others that, like me, lack experience. I'm only copying the last of a few questions I asked trying to clarify my question. Bing co-pilot, like a couple of other AI's I've used, does tend to 'misunderstand' things.

Question: I think I'm close to understanding but I will define my last question more. The two busy conversations are going on at the same time on the same simplex frequency while each of the two conversations are using different PL tones. If both conversations are busy with replies often taking 30 or more seconds, can a reply preclude or interrupt the other conversation from transmitting since each of their PL tones precludes them from hearing the other conversation or, for that matter, anyone else on that simplex frequency? If so, how would the interrupted party know or understand what is happening? Would listening for a courtesy tone which might taking longer than expected, be an answer?

Answer:
Yes, your understanding is correct! Listening for a squelch tail (the residual noise after a transmission ends) and paying attention to any courtesy tone (if present) can indeed help avoid confusion in the scenario of two busy conversations using different PL tones on the same simplex frequency.

Here’s a brief recap:

1. Squelch Tail:
   • After a radio transmission concludes, there’s often a brief squelch tail—a residual noise—before the radio returns to receive mode.
   • The squelch tail serves as a cue that someone has transmitted and allows the interrupted party to be aware of ongoing activity.
2. Courtesy Tone:
   • Some radios emit a courtesy tone after a transmission.
   • However, the courtesy tone might not be immediate; there could be a slight delay.
   • If the interrupted party hears the courtesy tone, they know that someone else is speaking.
3. Good Etiquette Matters:
   • Ham radio operators practice patience and adaptability.
   • If a collision occurs, they yield to the ongoing conversation.
   • Acknowledging interruptions and allowing others to break in ensures smooth communication.

So, paying attention to these cues helps maintain order and clarity during busy simplex conversations. 📻🌐

73

 

[JustinWHT]

As for any FM simplex (same channel) use, *regardless of PL tones*, the strongest signal swamps out the weaker signal (FM capture effect), or if nearly the same you'll hear a grumbling sound...or the interference distorts both PL tones and no one hears anything . The threshold is the if the stronger signal is 2x the weaker signal, then weaker signal isn't heard.

For AM the weaker signal can be only 1% of stronger signal and it will be heard, though distorted, it will be heard. For this reason aviation radio uses AM.

As for squelch tail - commercial radios usually use squelch tail elimination. In olden days when vibrating reeds were used, the transmitter reed was bumped in reverse phase after mic key released and receiving reeds stopped vibrating and audio was muted. That is accomplished by the transmisitting radio.

 

[Samyham]

Very interesting. Thanks for the reply. Regarding squelch tail, I'll have to consciously pay attention for short open squelch after the sender stops transmitting (?). Good to know commercial radios eliminate even that.

 

[JustinWHT]

Personally I dislike the trailing "roger beep". For a project we used Motorola trunk system radios. After you keyed you'd have a wait a second for radio to sync up, and you heard a 2 or 3 tone beeping letting you know to start talking

 

[Samyham]

Oh Man! That sucks. I guess you get use to it if it's part of the job.

 

[nokones]

As for any FM simplex (same channel) use, *regardless of PL tones*, the strongest signal swamps out the weaker signal (FM capture effect), or if nearly the same you'll hear a grumbling sound...or the interference distorts both PL tones and no one hears anything . The threshold is the if the stronger signal is 2x the weaker signal, then weaker signal isn't heard.

For AM the weaker signal can be only 1% of stronger signal and it will be heard, though distorted, it will be heard. For this reason aviation radio uses AM.

As for squelch tail - commercial radios usually use squelch tail elimination. In olden days when vibrating reeds were used, the transmitter reed was bumped in reverse phase after mic key released and receiving reeds stopped vibrating and audio was muted. That is accomplished by the transmisitting radio.

That would be if the "Reverse Burst" function was selected and I believe it takes a signal level of 6 dB or greater to provide capture of a co-channel signal.

 

[JustinWHT]

Good point, software driven radios may have reverse burst as an option. You might get be right with 6 dB, I'm going from memory what I read 40 years ago.

 

[nokones]

Good point, software driven radios may have reverse burst as an option. You might get be right with 6 dB, I'm going from memory what I read 40 years ago.

Ditto on the memory for me three for my experience 40 years ago!

 

[chief21]

For those using a unique CTCSS (tone squelch) on a shared frequency, good operating practice requires that one first monitor the frequency (by momentarily disabling any CTCSS) before transmitting. Many radios will allow a button to be assigned for this MONITOR function.

 

[nokones]

For those using a unique CTCSS (tone squelch) on a shared frequency, good operating practice requires that one first monitor the frequency (by momentarily disabling any CTCSS) before transmitting. Many radios will allow a button to be assigned for this MONITOR function.

With a real radio like a Motorola the monitor feature disables the receiver decoder to CSQ which is known as PL Defeat whereas a cheap Chinese POS just blows squelch noise..

 

[JustinWHT]

Does anyone remember when the metal microphone hang up clip disabled the tone squelch (and reverted to carrier squelch) when you pulled off the mic?

 

[nokones]

That's the "HUB Defeat" function. If my memory serves me right either the Micor or the earlier models had a switch on the side of the clip to enable or disable that feature where as the newer models are by CPS

 

[AK9R]

The Kenwood TK-x90 mobile radios had that feature, too.

 

[nokones]

The Kenwood TK-x90 mobile radios had that feature, too.

So does my Kenwood TK880

 

[jeepsandradios]

When programmed properly every MSI radio still does that. My 8500 goes into monitor as soon as I pick up the mic.

 

[JustinWHT]

Other than using FRS for your family in an amusement park; in an active MURS area; or some other unique use, I can't think of any situation where using carrier squelch to monitor first would be necessary.

 

[N5XPM]

Does anyone remember when the metal microphone hang up clip disabled the tone squelch (and reverted to carrier squelch) when you pulled off the mic?

The mic clip was grounded in this setup. Loss of ground connection with the mic enabled carrier squelch. The other option was a spring loaded button on the back of the microphone that sensed when the mic was removed from the clip. The microphone hanger did not require a ground wire to activate carrier squelch in these models.

 

[Project25_MASTR]

The mic clip was grounded in this setup. Loss of ground connection with the mic enabled carrier squelch. The other option was a spring loaded button on the back of the microphone that sensed when the mic was removed from the clip. The microphone hanger did not require a ground wire to activate carrier squelch in these models.

There is also the system Motorola used later on in their non-public safety radios where the hanger button was isolated from the backing plate on the microphone. Short the connection (like you are hanging the microphone up in a metal hanger) and you enable HUB function.

 

[kayn1n32008]

Personally I dislike the trailing "roger beep". For a project we used Motorola trunk system radios. After you keyed you'd have a wait a second for radio to sync up, and you heard a 2 or 3 tone beeping letting you know to start talking

It would be on the order of less than 300ms. That is the time needed for the radio to transmit its ID and request a channel grant on the talkgroup(channel) your radio was sitting on the control channel input. The triple beep(talk permit tone) is played after the controller grants a voice channel and your radio changes to it and starts transmitting.

 

[kayn1n32008]

Oh Man! That sucks. I guess you get use to it if it's part of the job.

The TPT, talk permit tone, aka triple beep(4 with TX clear alert enabled on unencrypted talk groups) is to tell you that the tru k system has assigned a voice channel, and you can now start speaking.