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| What is this sound? http://interceptradio.com/bbs/viewtopic.php?f=26&t=2272 |
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| Author: | Rodentkj [ Wed Aug 20, 2008 5:23 pm ] |
| Post subject: | What is this sound? |
You can hear what I am talking about at the link below. But I've been randomly hearing it for years on the Snohomish TRS. There are a few TG's I hear it on. It sounds like data of some type? The transmission length is random. It will usually last for a few hours and then be gone for a several days. Here are the two TG's of recent. 46192 - SNOCOM ERT (is happening right now) 46064 - SCSO ERT http://www.daronjohnson.com/temp/noise.mp3 |
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| Author: | Rich [ Wed Aug 20, 2008 6:38 pm ] |
| Post subject: | Re: What is this sound? |
Its digitally encrypted audio. Not sure of the flavor (DVP/DVI/DES? -XL?) |
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| Author: | Rodentkj [ Wed Aug 20, 2008 6:47 pm ] |
| Post subject: | Re: What is this sound? |
Ok. That is interesting. So some of the ERT channels are encryped. I did not know that they did this on the Snoho TRS. I wonder what is so secret that they have to encrypt it? |
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| Author: | Rodentkj [ Wed Aug 20, 2008 6:57 pm ] |
| Post subject: | Re: What is this sound? |
So I went out to research a bit about digital encrypted audio and I found this cool site that has audio samples with descriptions. I found what seems to be exactly what I'm hearing. It says it's a Motorola Network Trunking Control Channel This is the website. It has a small audio clip one can listen to. http://www.kb9ukd.com/digital/ 
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| Author: | Rich [ Wed Aug 20, 2008 8:21 pm ] |
| Post subject: | Re: What is this sound? |
It is certainly not any kind of control channel. Listen more closely, they don't sound anywhere near the same. Near the end of the transmission you can clearly hear the digital epilog followed by some sort of analog reverse-burst tone. BTW, it appears to be astro imbe, not DES/DVP/DVI. |
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| Author: | Rodentkj [ Wed Aug 20, 2008 8:32 pm ] |
| Post subject: | Re: What is this sound? |
On my clip, that is actually 3 different transmissions edited to be put together. The clip on the other site is very much like what I hear sometimes on my system on long transmissions. But ya, the clip I included is different. I agree. |
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| Author: | Vizwar [ Thu Aug 21, 2008 8:53 am ] |
| Post subject: | Re: What is this sound? |
The Sno Co system is a mixed mode (analog & digital voice) system. (hybrid?) IMPORTANT: Digital does NOT mean encrytped. Digital transmissions can be decoded by any capable device. Encrypted transmissions can only be decoded by devices with a matching encryption key. ERT should be read as Swat which is probably why those groups aren't analog. I haven't listened to the file yet and assuming it is voice it could be just digital or it could be digital encrypted. A control channel will not lock as one ID on your scanner. Your scanner may display several IDs as they are sent through the control channel though. |
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| Author: | Rodentkj [ Thu Aug 21, 2008 8:56 am ] |
| Post subject: | Re: What is this sound? |
Perhaps it is mixed mode. But the only TG's that I hear this on are the ones I have tagged as ERT. And thanks about the encrypt thing. I had not thought of that. Wish I had a digi scanner. |
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| Author: | bcscanner [ Thu Aug 21, 2008 9:11 am ] |
| Post subject: | Re: What is this sound? |
All the digital comms i've heard on that system are also encrypted. Kind of spoils the surprise of having a dozen ERT guys breaking down your door, when you can hear their every movement before hand. |
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| Author: | Rodentkj [ Thu Aug 21, 2008 9:17 am ] |
| Post subject: | Re: What is this sound? |
I guess I think of ERT as more of a group who goes out and helps people during an emergency situation. Opposed to police activity. |
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| Author: | Mark [ Thu Aug 21, 2008 1:05 pm ] |
| Post subject: | Re: What is this sound? |
In Seattle/King ERT 1 has ways been encrypted. ERT 2 is rarely used, but in the clear and interesting when it is, mostly car-car. |
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| Author: | Vizwar [ Thu Aug 21, 2008 1:07 pm ] |
| Post subject: | Re: What is this sound? |
Rodentkj wrote: I guess I think of ERT as more of a group who goes out and helps people during an emergency situation. Opposed to police activity. You're thinking CERT? Community Emergency Response Team? 'Swat' seems to be looked at as an obsolete or politically incorrect term. ERT and other even more odd/public friendly terms are being tossed around now. |
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| Author: | SpudGunMan [ Thu Aug 21, 2008 1:19 pm ] |
| Post subject: | Re: What is this sound? |
yea sounds close to astro voice, how close is the mp3 to exactly what you heard? its been a while since i heard analog astro voice yours sounded faster encryption however 9600 is the norm now. I could be remembering 3600. had more of a slow churn to the data bits. I will reverse it thru my 996 this evening and see if it will decode it. I do know up north there is some P25 here and there I have picked up showing USBP-Tac but thats on VHF not on trunk. |
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| Author: | Rodentkj [ Thu Aug 21, 2008 1:47 pm ] |
| Post subject: | Re: What is this sound? |
Oddly enough it just started up again on a TG I have tagged as Everett ERT. You can hear it at the link to my live feed listed in my signature. And this link is a pretty long transmission that I just captured unedited. http://www.daronjohnson.com/temp/1.mp3 |
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| Author: | Tidalwave [ Thu Aug 21, 2008 2:44 pm ] |
| Post subject: | Re: What is this sound? |
I would have to say after listening to that last clip that it is definetly digital. Most Probably P25. As to encryption, not sure but I would assume so. |
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