Getting irritated recently listening to sq tails recently.
In the commercial world there are a myriad of ways to remove that ear splitting noise when someone unkeys. I've googled around but can't find any ham-friendly solution to remove the noise on my side. Anyone seen a viable method before?
A possible experiment I thought of would be a computer program that monitors carrier levels:
1. Feeding the radio output into a program that delays the audio before muting circuit in the controller
2. Program starts muting before the squelch tail gets through the audio delay
3. Program feeds out audio (to speaker/headphones)
I'm wondering if this can be miniaturised and implemented into a small board that taps directly into the radio (have to find space inside!) or plugs into the CAT port.
Eliminating Squelch Tail
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VK5PJ
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Re: Eliminating Squelch Tail
Hello,
you could see if the local repeater supports sub audible tone on transmit, then set your rx to only open on those sub audible tones, this will in all probability make the squelch tail go as the tone decoder will kill the rx audio before the squelch cct has time to let the tail through.
On the audio delay side of things, no need for a PC, you can use a small audio chip called a "bucket brigade", this is how echo effects were created back in the days before digital processing, the cct works just like the name implies, the audio is passed from one bucket to another bucket by a high speed timer, this causes a small delay compared to the live audio, you then get the squelch cct to drive a switch to stop the delayed tail audio coming out of the last part of the bucket brigade and your speaker. This was used on some of the early repeaters to kill of the squelch tail on the repeaters receiver so you did not get a double tail on your Rx.
thoughts from the past brought to you by ME
you could see if the local repeater supports sub audible tone on transmit, then set your rx to only open on those sub audible tones, this will in all probability make the squelch tail go as the tone decoder will kill the rx audio before the squelch cct has time to let the tail through.
On the audio delay side of things, no need for a PC, you can use a small audio chip called a "bucket brigade", this is how echo effects were created back in the days before digital processing, the cct works just like the name implies, the audio is passed from one bucket to another bucket by a high speed timer, this causes a small delay compared to the live audio, you then get the squelch cct to drive a switch to stop the delayed tail audio coming out of the last part of the bucket brigade and your speaker. This was used on some of the early repeaters to kill of the squelch tail on the repeaters receiver so you did not get a double tail on your Rx.
thoughts from the past brought to you by ME
Peter Sumner, vk5pj
You have enemies? Good. That means you've stood up for something, sometime in your life.
- Winston Churchill
You have enemies? Good. That means you've stood up for something, sometime in your life.
- Winston Churchill
Re: Eliminating Squelch Tail
Good afternoon,
The solution to your problem is really dependant on the gear you're using, and the signals you're receiving.
I've solved that problem in two ways on commercial systems that use CTCSS, one of which inverts the CTCSS for a few cycles when the PTT is released, fooling the CTCSS decoder into thinking there CTCSS has gone and mutes the RX.
The other way I did it for one particular commercial client was to implement a tail on their (many) voice repeaters, of say 2 seconds, but turn off the CTCSS on the repeater tail after 500ms. The mobiles hear a short tail, which softly mutes after the CTCSS goes off.
For that to work, you have to be transmitting CTCSS on the repeater output, and decoding the CTCSS for mobile receiver mute.
Depending on your receiver and the situation, yours could be interesting to solve, especially if there's no tone or other "valid signal" signalling present.
The solution to your problem is really dependant on the gear you're using, and the signals you're receiving.
I've solved that problem in two ways on commercial systems that use CTCSS, one of which inverts the CTCSS for a few cycles when the PTT is released, fooling the CTCSS decoder into thinking there CTCSS has gone and mutes the RX.
The other way I did it for one particular commercial client was to implement a tail on their (many) voice repeaters, of say 2 seconds, but turn off the CTCSS on the repeater tail after 500ms. The mobiles hear a short tail, which softly mutes after the CTCSS goes off.
For that to work, you have to be transmitting CTCSS on the repeater output, and decoding the CTCSS for mobile receiver mute.
Depending on your receiver and the situation, yours could be interesting to solve, especially if there's no tone or other "valid signal" signalling present.
Tim, VK4TIM.
QG62MM, Brisbane.
QG62MM, Brisbane.
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VK/9V1CJ
Re: Eliminating Squelch Tail
Tim, you're referring to the 2 primary commercial methods of phase shifting or reverse burst which is pretty much standard on any commercial radio, and the snag is both the TX and RX side need to implement the same method.
For amateur radio I know of no radio that has these in-built, And even if they had it CTCSS is rarely used. Hence the thought of using a delay circuit - Peter VK5PJ suggests a "bucket brigade" (need to research on that). It would be a "universal cure".
Actually a simple VOX circuit already has some inherent ability to remove squelch, if you can implement a delay. Eg w/o a delay the circuit mutes after 50ms. If you implement a delay of 60ms you literally "cut the squelch". The question is how to implement the delay hardware wise - capacitors in series (aka "bucket brigade"). Will be interesting to see if it can be fit into the case of an existing commercial radio.
Computer wise I believe it will be much easier as the computer is doing all the work.
For amateur radio I know of no radio that has these in-built, And even if they had it CTCSS is rarely used. Hence the thought of using a delay circuit - Peter VK5PJ suggests a "bucket brigade" (need to research on that). It would be a "universal cure".
Actually a simple VOX circuit already has some inherent ability to remove squelch, if you can implement a delay. Eg w/o a delay the circuit mutes after 50ms. If you implement a delay of 60ms you literally "cut the squelch". The question is how to implement the delay hardware wise - capacitors in series (aka "bucket brigade"). Will be interesting to see if it can be fit into the case of an existing commercial radio.
Computer wise I believe it will be much easier as the computer is doing all the work.
Re: Eliminating Squelch Tail
This is designed for repeaters and repeater controllers, but could be adapted to what you're looking for.
http://www.nhrc.net/nhrc-dad/
73's
Rob...
http://www.nhrc.net/nhrc-dad/
73's
Rob...
Re: Eliminating Squelch Tail
Hi,
If you want repeaters that are more like a phone than conventional analog FM repeaters, perhaps you should preview DSTAR or the like.
Owen
If you want repeaters that are more like a phone than conventional analog FM repeaters, perhaps you should preview DSTAR or the like.
Owen
Re: Eliminating Squelch Tail
ctcss squelch works for me on those repeaters that transmit tone.
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VK7DB
Re: Eliminating Squelch Tail
I think you'll find they both use the same IC. In fact, these ones sound nicer than the NHRC delays, IME.
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VK1VMA
Re: Eliminating Squelch Tail
A low pass audio filter with a 2700-3000Hz cutoff could help quite a bit in reducing the harshness of the squelch tail.
Easy to do in software, if that's the way you want to go.
Easy to do in software, if that's the way you want to go.