Irritating buzzsaw type sound on EDACS system

[compuscan]

I am listening to an analog EDACS trunking system with 2 different brand scanners. Most times I receive them fine but at least a few times a day, I'll get a digital burst of what's like a buzz saw or digital signal that's very irritating. I usually hear a call out, then a reply and sometimes when I expect a second or third reply, I heard this noise that could be from 3 or 4 seconds to 10 or 15 seconds.

I don't know if it's something to through off scanners or something else but it can make it hard to listen to the radio when it happens. Also when it happens, it can happen off and on 5 or 6 times in a 10 minute windows and then not hear it for a few hours.

I don't know what it is but I don't believe it's analog or digital encryption because it may happen once during a conversation and then only for 5 seconds between a normal conversation. Also the reply that's just seconds after it happens don't mention hearing this noise.

One scanner's a analog trunking scanner and another is a digital trunking scanner made by different manufacturers. I may never know what it is but it's not the little beeps I've heard others talk about that a G-Wiz circuit will fix.

My question is, is their a electronic box or audio software that will connect to the speaker out of the scanner to let normal voice or audio pass to a speaker and mute any digital noise or tones? Some Radio Shack Scanners had a Data Signal Skip on their scanners but it never worked. I'm looking for something similar to this but one that works.

I just want to monitor this trunking system without hearing this awful or irritating sound and I'm sick of having to turn the volume down 5 or 10 times a day when this happens.

 

[WNZT398]

I am listening to an analog EDACS trunking system with 2 different brand scanners. Most times I receive them fine but at least a few times a day, I'll get a digital burst of what's like a buzz saw or digital signal that's very irritating. I usually hear a call out, then a reply and sometimes when I expect a second or third reply, I heard this noise that could be from 3 or 4 seconds to 10 or 15 seconds.

I don't know if it's something to through off scanners or something else but it can make it hard to listen to the radio when it happens. Also when it happens, it can happen off and on 5 or 6 times in a 10 minute windows and then not hear it for a few hours.

I don't know what it is but I don't believe it's analog or digital encryption because it may happen once during a conversation and then only for 5 seconds between a normal conversation. Also the reply that's just seconds after it happens don't mention hearing this noise.

One scanner's a analog trunking scanner and another is a digital trunking scanner made by different manufacturers. I may never know what it is but it's not the little beeps I've heard others talk about that a G-Wiz circuit will fix.

My question is, is their a electronic box or audio software that will connect to the speaker out of the scanner to let normal voice or audio pass to a speaker and mute any digital noise or tones? Some Radio Shack Scanners had a Data Signal Skip on their scanners but it never worked. I'm looking for something similar to this but one that works.

I just want to monitor this trunking system without hearing this awful or irritating sound and I'm sick of having to turn the volume down 5 or 10 times a day when this happens.

If you listen to an EDACS system in a conventional format, you will hear anything that is repeated on that scanned frequency. This includes analog voice calls, digital voice calls (buzzing sound), data calls (buzzing sound), system test calls (buzzing sound) and even system introduced scramble data calls (used to disrupt old conventional scanners). EDACS radios and properly configured (trunk tracker) scanners only allow radio calls to be heard from the speaker. My guess is that you don't have a trunk tracker (EDACS) scanner OR you don't have it configured properly.

 

[GM]

Is this the sound that you are hearing? http://www.w2sjw.com/sounds/EDACS Defeat.mp3

 

[srich10]

Is this the sound that you are hearing? http://www.w2sjw.com/sounds/EDACS Defeat.mp3

If that's the sound you're hearing, that's normal. Same thing happens here in Brevard county on our system. Original intent was to defeat/obfuscate scanner listeners with these false squelch openings that were nothing but this sound. Mildly annoying but comes with the territory of EDACS

 

[SCPD]

We had an analog EDACS up here before the migration to P25 statewide. At the end of transmission the frequency used for the transmission would air a couple of seconds of beep tones to make it harder to monitor in conventional mode before EDACS could be trunked tracked. I believe at sometime the tones were set to mimic the GE "we bring good things to life" theme. The FCC said it constituted music and not allowed to be transmitted. The tones were modified to be generic beeps.

 

[kb4cvn]

Channel Drop Message & Scrambled Data Calls

The three beeps you hear at the end of an EDACS group call is the WORKING CHANNEL ASSIGNMENT drop message.

In the days before Ericsson purchased GE's Private Radio Systems Division in Lynchburg (Virginia), the channel drop message was a series of 1000 Hz tones which was timed to sound like the “GE Brings Good Things To Life” jingle of that era.

When Ericsson purchased the company, as part of the “rebranding” process, they told the chap (Mr. Alan Hill) who designed the GETC (GE Trunking Card) and all the software that ran it, to ditch the jingle and go to a generic set of tones instead, to avoid any Copyright infringement issues, as the GE jingle was in fact a copyrighted trademark of General Electric. Not Ericsson.


...And NO, the rumor that the FCC mandated the change is incorrect.




The “buzz saw” sound you hear is actually a system diagnostic function, referred to as SCRAMBLED DATA CALLS. This is routinely run a few times an hour to perform an operational status check of each repeater in the system. However, in the pre-EDACS Trunktracker scanner days, when all you could do was scan the frequencies conventionally, you could use this function to annoy the hell out of listeners! I know I used it often…

Back before I took a job at the factory in Lynchburg doing Tech Support (TAC) in the late 90’s, I ran a public safety EDACS system. When I would receive info from the PD that a VIP was going to visit town, or a Grand Jury was issuing arrest warrants, and a ‘door knocking party’ would be commencing soon, I would institute a few anti-scanner measures on the system to discourage listeners, especially the Media. Starting several days prior to an event, I would:

#1 – I would start rotating the CONTROL CHANNEL every hour. Sometime at random, several times an hour.
#2 – I would program the SCRAMBLED DATA CALLS to run continuously, 24/7, activating every few seconds.

It that point I knew to expect the hate and discontent from the local media…


Crude, but effective.

 

[compuscan]

If that's the sound you're hearing, that's normal. Same thing happens here in Brevard county on our system. Original intent was to defeat/obfuscate scanner listeners with these false squelch openings that were nothing but this sound. Mildly annoying but comes with the territory of EDACS

Yes, it sounds very similar.

My question is their any software program or hardware box/audio circuit that will mute this type of sound on an external speaker if you take the audio from the scanner's external speaker output and run it into hardware or software (sound card on a computer for example)? Some type of DSP software?

The software or circuit would mute sounds like noise or tones but pass normal voice. I've seen similar features on scanners in the past to ignore silence on a channel and I believe ICOM's VSC will ignore tones but I haven't scene anything external to add to a radio.

 

[wa8pyr]

Yes, it sounds very similar.

My question is their any software program or hardware box/audio circuit that will mute this type of sound on an external speaker if you take the audio from the scanner's external speaker output and run it into hardware or software (sound card on a computer for example)? Some type of DSP software?

The software or circuit would mute sounds like noise or tones but pass normal voice. I've seen similar features on scanners in the past to ignore silence on a channel and I believe ICOM's VSC will ignore tones but I haven't scene anything external to add to a radio.

When the data call pops up randomly as it usually does, you shouldn't hear it, as it's not announced as a regular group call.

If you're hearing it at the end of a voice call, it's possible that your scanner didn't catch the "working channel drop" tones well enough to realize it was time to start scanning again. We had the same problem locally in some areas where the system wasn't received well.

As far as muting the tones, I suspect a simple mute circuit would have trouble seeing the difference between the data call and a regular voice call, unless the levels are very different; you would have to tweak the mute threshold carefully for it to work right, and even then it might still catch legitimate calls.

 

[compuscan]

It would have to be a little more than a simple circuit that mutes with audio levels. Some audio software have audio pop & click filters or other noise/tone removal filters. I'm not sure exactly how a pop or click filter works but I would guess it mutes a very quick attack signal for a very short time period.

Would the digital signal have factors that could be auto notched out by hardware or HAM radio software?

How about the attack time of the audio signal. The digital signals are more like a square wave and harsh when viewed on a scope while voice is more smooth like a sine wave. Is their software or hardware that can either attenuate or mute a harsh audio signal like that. It would have to have some adjustment to fine tune out the harsh signal while allowing a normal audio signal. May be some HAM DSP software run through a computer sound card?

If the shape and attack time of the signal can't be detected and muted with hardware/software is their some sort of software that could sample the digital signal, detect it in real time and remove it?