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Sound on some analog channels

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ddpelp

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Any idea what this sound is? I hear it occasionally on some of the Motorola Smartnet analog listening channels thanks
 

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JnglMassiv

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I don't have any specific information but I doubt it's intentional or desireable. It sounds like a malfunction in their end.
 

MMIC

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That is a hallmark sign of a channel in a simulcast cell out of alignment. You probably hear this on some of the channels on the trunked system, but not others. In simulcast, the transmissions from different sites must be very close together in frequency, phase, and amplitude. If any one of these is outside of a certain tolerence, you will hear sounds similar to what you recorded in the sample.

What system is this, out of curiosity?
 
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ddpelp

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wow..

I think you are right. Exactly what I find same sound on two different scanners 9a 785 and 996 ) and only on some freqs. thanks makes me feel better...
 

ddpelp

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Added question

I have been watching the scanner and I note the noise is coming from one freq. Not a CC but one of the set of used freqs. 858.2 .. I wonder do they not hear thaton their euipment? I thuoght about sending a email to the FFC listed contact for this system but half afraid that will not llike being told they have a problem on their system. I am glad I asked the question though and you are right it obviously is their system not my scanners. All others int he 15 freqs sets are fine just when it locks to 858.2
 

N4DES

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You could be out of the designed simulcast overlap area and you hear the alignment issue more than a user that is in the PSAC. Also sounds like the users were able to communicate even though the .wav file was unintelligable to us.
 

ddpelp

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Simulcast?

Question if you have time to teach me something.. What do youmean when using the term simucast for the trunking system? I see the simulcast mentioned on some systems but in the database the system I am listenign to says Primary. I may have apples and oranges but thought I woud see if you can train me <g> tnx
 

N4DES

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Simulcast
Refers to the process of transmitting the same signal from multiple sites.

For public safety communications, this typically means multiple towers configured to transmit the exact same communications, on the exact same frequencies, from multiple towers, resulting in much better coverage of a wide area or area with dense population/buildings.

Retrieved from "http://wiki.radioreference.com/index.php/Simulcast"
 

MMIC

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Yes, the users will be able to hear mis-aligned simulcast issues on their equipment. You can hear similar issues on a couple of systems in the Kansas City, Missouri area, too.

You're probably best not to contact the licensee - you're right that they probably won't appreciate it too much. :)
 

ddpelp

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signal strength?

Is there any chance the strength of the signal can make things worse? Reason is I noticed the freq that seems to be the noisey one has only 2 bars of signal. The best sounding freq is 3 to 4 bars. I thought maybe a better external antenna might reduce this warble sound. Thanks for all the comments and help sure been a learnign experience.
 

NeFire242

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Simulcast Noise

Here is a recording sample of one of the local Motorola Trunking systems near Omaha, and I can hear that flutter or simulcast noise on many transmissions made on the system.
 

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ddpelp

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I hear that on more then one freq in the local trunking system the one I posted at the start of this thread is almost un readable in the voice audio. I guess maybe this problem is more wide spread then I had thought. Some freqs are crystal clear
 

MMIC

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Each channel in the simulcast system must be aligned for phase, frequency, and amplitude - which is why you are seeing some channels that are OK, and others that are not.

Mis-aligned simulcast can cause signal strength degredation on a channel, but so can a number of other factors (differing power output, mis-aligned combiners, interference, etc.).

From what I have seen, simulcast alignment is a neglected aspect of the system and must be performed periodically. There are several factors that can send simulcast out of alignment, so it needs to be checked. Unfortunately, it takes a bit of skill, knowledge, and some expensive equipment to do it. Some places don't, or won't, invest the money in it. But, hey, it's only public safety, right? :roll:
 
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