To delay or not?

[toad99]

After finally getting frustrated by so many extremely short transmissions interrupting my Uniden scanners, I set all channel delays to 0 seconds via Proscan. What's interesting is that for the Oklahoma City metro trunk system, the scanning resumes immediately after the end of transmission, as I would expect, but the OKWIN statewide system does not drop the carrier (and the scanning resumes) until about 2 seconds after the transmission ends, which results in the default 2 second delay becoming about 4 seconds. Is the carrier drop delay in the OKWIN system something that is programmed by the system radio technicians? It would be useful if Uniden scanners could be set to ignore the channel delay setting for transmissions of less than a certain length, like the Proscan recorder function does.

 

[brian86]

Harris P25 Trunked Radio Systems Drop the Carrier and release the talk frequency immediately after the subscriber radio stops transmitting. Motorola P25 and Smartnet Radio Systems tend to hold the frequency for a couple seconds after the subscriber radio stops transmitting waiting for another subscriber radio to transmit before releasing the channel.

 

[toad99]

I believe the OKC P25 system is a Harris system, and I have read that Harris systems have poor audio quality. The OKC system suffers from random distorted audio (massive clipping of voice when the user gets too close to the mike). Looking at the audio waveforms on an oscillosope from the OKC system, it appears that the OKC system radios simply clip high audio levels to avoid overmodulation instead of automatically attenuating the audio level. Somehow their radios manage to handle the distortion, since the dispatchers can understand the units when I can't make out a single word. Back when OKC used ProVoice EDACS, it was bad then. The OKWIN P25 system, which I think is Motorola, has generally excellent audio.

 

[prcguy]

I believe the OKC P25 system is a Harris system, and I have read that Harris systems have poor audio quality. The OKC system suffers from random distorted audio (massive clipping of voice when the user gets too close to the mike). Looking at the audio waveforms on an oscillosope from the OKC system, it appears that the OKC system radios simply clip high audio levels to avoid overmodulation instead of automatically attenuating the audio level. Somehow their radios manage to handle the distortion, since the dispatchers can understand the units when I can't make out a single word. Back when OKC used ProVoice EDACS, it was bad then. The OKWIN P25 system, which I think is Motorola, has generally excellent audio.

I suspect the Harris system is working fine and its Uniden that is having a problem. I can't imagine a $500 consumer radio being the perfect reference radio and all the multi thousand $$ police radios in a multi million $$ radio system being junk. Harris radios have a very good voice leveling scheme to optimize intelligibility, they don't just clip audio and create distortion. BTW, I have both Motorola and Harris P25 radios here and prefer the sound of the Harris radios on P25, although I can't say I've listened to them through one of my police scanners.

Nearly all repeaters have a hang time and transmit for several seconds after the base or mobile stops transmitting and that is programmed in by whoever determined the needed system parameters, that's normal. The question would be on a trunked system does the transmitters send data during the hang time that your scanner decodes as a live channel keeping it on that channel for the duration of the hang time.

 

[toad99]

In OKC we have a talkgroup for the fire department that is for alerting. It uses a digitally generated synthetic voice that announces fire station, nature of call, etc. The audio level of this talkgroup is actually a bit higher than the other voice radios on the system, the level is always consistent, and the audio quality is very good. The audio waveform is not clipped at all. Other talkgroups, with human speakers, can be visibly (via oscilloscope, audio extracted from the ethernet feed on my SDS200) and audibly clipped below the level of the aforementioned alert talkgroup. So something is clipping the audio when someone just overloads their microphone. When a user is speaking at a normal level at an assumed nominal distance from the microphone, the audio is perfectly fine, just as good as the fire alert talkgroup.

The OKC police department talkgroups are also linked to the Oklahoma statewide P25 system, and they exhibit the same clipping distortion there. Other talkgroups on the state system sound fine, so I would guess that the clipped audio is being sent to the state system.

 

[Jon1984]

I also noticed that the okc pd there radio Id's never change example 506173 is the same all the time the old radio id's use to start with 106 noted it changed when the encrypted law dispatch secondary I'm thinking there links to the phase 2