SDS100/SDS200: SDS100 Audio Weird Issue

[K9JRF]

I'm having a weird issue with the SDS-100 and I can't seem to figure it out. I have tried filters, and IFX , changed squelch from 0 to 15 and can't seem to resolve it.

The SDS-100 when a transmission comes in 2 out of 5 times, it has this audio sound at the start of the transmission. Its only occurs on the SDS-100, my 536HP doesn't do it and actual radio doesn't do it. Its just the SDS-100. I have the two audio wave file (links listed below) of the same transmission, same scanner profile in both radios, (1) one on the SDS-100 which you can hear the sound at the beginning and (2) of the 536HP. It's an 800mhz trunked radio system.

Its driving me crazy hearing it constantly.

SDS-100 Audio Transmission
536HP Audio Transmission

 

[dave3825]

Not sure what the beginning sound is but is that a smartzone system? If so its real distinct on the 100

 

[Whiskey3JMC]

Sounds like you have an EDACS channel or more programmed conventionally? System needs to be programmed as EDACS trunked and the preamble should go away

https://www.sigidwiki.com/images/1/19/Edacs_analog_fm_2.mp3

 

[Ubbe]

It's an analog system and the SDS100 has a digital delay. If you look at the wave diagram and the 536 audio you'll see that when the guy stops speaking you hear all his syllables and the following mic crunch when he release the PTT and after that there's a delay of silence until the squelch cut the audio. If you look at the end of the SDS100 audio you'll see that the squelch cut the audio so quick that the last syllable are almost gone and of course all the rest with the mic crunch and silence are also gone.

At the start of the 536 audio you hear a silence and the squelch opens and you hear the background hum before he starts to speak. The SDS100 audio opens the squelch when there's still data modulation and then you hear the hum followed by the voice.

The problem are the same with most digital scanners, both Whistlers TRX to some extent but more so with Unidens SDS, and that are that the audio mute and unmute operates on the direct signal but the audio are then always going thru a converting process from analog to digital as the recording needs digital data and that process creates some 200mS delay to the sound but the firmware in these scanners are not designed to also delay the mute and unmute 200mS so it would be in sync with the streaming digital audio.

Perhaps @JoeBearcat can ask Uniden if they can do a better sync between mute/unmute and audio.

The problem also exists, but are less obvious, when listening to the speaker audio as the unmute function for the speaker are a bit sluggish in SDS100, you will never hear a pulsating carrier that you can hear like a machine gun in a 536 scanner, the SDS100 indicates on the display that it receives something but there's no audio, so it will mask some of the audio problem in the beginning of a transmission but the delay problem can be heard at the end of analog transmissions as the last syllable often are muted.

/Ubbe

 

[Mongerbl82]

Hey K9JRF or W3JMC maybe you can help me understand this I have a scanner that on multiple frequencies around 1:50 450 and up in 800 MHz bands that stops and produces a modem dial up sound would either one of y'all know what that RF is??

 

[Ubbe]

Enable the recording function and let it record that sound for 5-10sec and then post here. Maybe you will have to zip the wave file first. Otherwise it would almost impossible to tell what it is you hear.

/Ubbe

 

[Mongerbl82]

Ok