Motorola trunking beep situations

[Josh]

I cannot figure this out. I was watching 'FOX 2' news this evening where they had a report regarding speeding on Michigan freeways. So, they hung out with the MSP all day long video taping.

Being 100% APCO-25 trunking, how come their radios (Astro Sabers and Astro Spectras) made that 'bee bee beep' trunking key-up noise? I know this is something that analog does, but the MSP, too?

This screws me up because my local PD and the other communities on the system (Astro on the 3.6k control channel) does not have the beep noises but rather delays the audio through the time it would take to get a repeater channel and yack, making about 1/4 second delay between when the person speaks and a nearby radio receives.

Is it just a case of turning the talk beeps off? It seems that when I did that on an analog TRS some time ago with a Maxtrac800 that I had to wait until the radio was ready otherwise the first 1/2 second was cut off.

At any rate, another question in the same category that perhaps someone monitoring the MSP system can answer. The MSP patrol car was up on a bridge on the newscast announcing the cars they were trying to get stopped and their speeds over the radio. I know some of the MSP's talkgroups are encrypted (which sucks) but can anyone say whether or not this is the case in their traffic stings?

-Josh

[Josh]

I cannot figure this out. I was watching 'FOX 2' news this evening where they had a report regarding speeding on Michigan freeways. So, they hung out with the MSP all day long video taping.

Being 100% APCO-25 trunking, how come their radios (Astro Sabers and Astro Spectras) made that 'bee bee beep' trunking key-up noise? I know this is something that analog does, but the MSP, too?

This screws me up because my local PD and the other communities on the system (Astro on the 3.6k control channel) does not have the beep noises but rather delays the audio through the time it would take to get a repeater channel and yack, making about 1/4 second delay between when the person speaks and a nearby radio receives. It would seem to me that the APCO standard could eliminate any delay in talk and beeping noise because the 9.6k control channel could handle the radio keying up 3 times as fast so there'd just be no need to have it.

Is it just a case of turning the talk beeps off? It seems that when I did that on an analog TRS some time ago with a Maxtrac800 that I had to wait until the radio was ready otherwise the first 1/2 second was cut off.

At any rate, another question in the same category that perhaps someone monitoring the MSP system can answer. The MSP patrol car was up on a bridge on the newscast announcing the cars they were trying to get stopped and their speeds over the radio. I know some of the MSP's talkgroups are encrypted (which sucks) but can anyone say whether or not this is the case in their traffic stings?

-Josh

[Twisted_Pear]

I'm not quite sure what your exact question is but I'll give'r a go.

The purpose for a talk permit tone is to signify the call request has been granted. That delay is due to the system taking the request and then saying it's okay to talk, go to channel so and so. You would presume 9600 baud would provide a quicker channel access time but hey, it's Motorola....everything needs a delay. I think it's better than the radio prompting, "Are you sure you wish to talk?"

-Wayne

[Josh]

I'm not quite sure what your exact question is but I'll give'r a go.

The purpose for a talk permit tone is to signify the call request has been granted. That delay is due to the system taking the request and then saying it's okay to talk, go to channel so and so. You would presume 9600 baud would provide a quicker channel access time but hey, it's Motorola....everything needs a delay. I think it's better than the radio prompting, "Are you sure you wish to talk?"

-Wayne

No, maybe I should simplify it.

Some trunked radio systems feature the access beeps and 'real-time' talking while other trunked radio systems don't and you can start talking immediately after pressing the PTT button however in any other radio receiving your transmission the audio is delayed for about 1/4 second or more. (This creates a really neat echo if one radio is near another. I have yet to hear any feedback)

I thought that the lack of permit to talk beeps was in the APCO standard seeing as how the astro system using the "delay in talk, no permit tones" system is basically apco-25 (except for the 3.6k control channel), that the MSP system would be the same way except little/no delay in audio through another radio because the control channel acts 3 times as fast being 9.6k rather than 3.6. It would/should require less time to access and therefore require either No access tone PTT beeps needed whatsoever.

I guess it probably doesn't make sense to anyone if my city is the only one taking advantage of their trunked system wth no permit to talk beeps as I've described.

-Josh

[ExKa|iBuR]

The setting for the Talk Permit tone can be disabled in the RSS, if you want.


Mike

[Josh]

The setting for the Talk Permit tone can be disabled in the RSS, if you want.


Mike

I know this, however if disabled, would I be able to press the button and talk or would I still have to wait the second or less required to access the system?

The local PD has it disabled, however they can simply key up and talk. No waiting, no beeping. The thing is the audio is delayed in the radio and doesn't get transmitted until the channel is secured and thus puts a delay between the time the guy talks and another radio receives. It isn't in real-time.

-Josh

[apco25]

There is a slight inherent delay on a any type of trunking systems for the channel grant to be recognized by the radio and the system itself. The talk permit tone dih dih dih sound simple signifies that the grant occured and does not actually add pre-time to the key up and channel grant of the radio itself. The delay is still there without the tone, you don't talk any faster. Supposedly the 9600 bps controll channel will give a faster channel grant but there will still be a slight delay for everything to sync up. I doubt the grant time is going to be faster in a way that the user would notice. Convetional radios have pre-time issues to through repeaters. Nothing is as fast as simplex. CSQ opens fastest followed by PL and them DPL.

The thing I notice is many officers do not like the talk permit tone because its usually set too loud in volume compared to the rest of the audible warnings generated by the radio, Police often don;t like it because it gives them away tactically. Although with the proliferation of nextel using the same tone most bad guys probably ignore it and don't recognize it as a sign of a public safety radio.

I like the tone because I know I have the channel granted and can talk. Radios without it tend to be short keyed by the operator.

[apco25]

Actually I think I just realized what you are talking about. MSP using a totally digital system. The delay you are experiencing has nothing to do with pre-time or talk permit tones. You're encountering the analog to digital conversion time delay which induces a slight non real-time decoding of the audio.

The simple example of this is key up on a digital radio next to someone else with a digital radio and you'll get the echo chamber effect.

Of course the channel grant times still apply, but the digital audio delay from the anolog to digital encode decode process can't be changed and will cause the issues you are talking about.

just the nature of the beast.

[Josh]

If the case is that there is no way to be able to talk while the PTT grant is occuring without clipping off the first few seconds of TX time, then my PD has something very different going on.

The delay that their radios exhibit is time about the same time that it takes for the radio to access the system but the officer is able to speak into the radio to have it come out of another radio a word later. It is really hard to get feedback on it in this fashion. I've never heard any feedback at all, just an echo that can grow louder and louder. I should have to make a recording for you to understand what I mean I guess.

-Josh

[Josh]

Actually I think I just realized what you are talking about. MSP using a totally digital system. The delay you are experiencing has nothing to do with pre-time or talk permit tones. You're encountering the analog to digital conversion time delay which induces a slight non real-time decoding of the audio.

The simple example of this is key up on a digital radio next to someone else with a digital radio and you'll get the echo chamber effect.

Of course the channel grant times still apply, but the digital audio delay from the anolog to digital encode decode process can't be changed and will cause the issues you are talking about.

just the nature of the beast.

Well there we go. Can it be stated that the radio can also be trying to get access to a channel while the analog to digital conversion is occuring and by the time it does, the analog/digital conversion is complete and can pass through immediately?

-Josh

[apco25]

like I said if its 9600 baud at MSP or another system it should grant the channel faster. however the digital delay caused by the conversion is a fixed rate and doesn't change. You won't notice the delay unless another radio is around and within in earshot of the first radio. You'll get the same problem with a digital radio even if you are using it in the anolog mode with other anolog radios.

[apco25]

don't forget the anolog to digital conversion is continual through the transmission. As long as you speak analog voice to the radio it will have to be converted.

[xts3000]

If you turn the volume up on the radio that is close to you and key up and talk, you will get a feedback noise. It is hard to describe what it sounds like. In an conventional astro system you get that echo effect also. It is the radio converting the voice over to the digital. Going through a repeater you get a longer delay compared to simplex, but you still get that delay in the audio.