Control Channels

[ButchGone]

There's a new regional P25 trs being built in Tennessee. I have noticed on the 800Mhz simulcast sites (there are three of them) the sound of the control channel noise is different on each of them. One sounds more like a grinding, noisy machine. The others sound more similar to the control channels on mixed-mode SmartZone systems. They all share wide area operation and same talkgroups. On the stand alone, 700Mhz IR sites the control channel noise is the same.
Is this common? Before this P25 system went up all control channels from Moto systems sounded the same. Do the CC's that sound different result from the onging testing/build out?
Thanks,
BG..

 

[rdale]

The "grinding" could be a data channel (i.e. MDT)?

 

[radioman2001]

The sound does change based on traffic being handled by the site. A more monotonous sound is the channel at idle, when there is traffic, ie requests for channels etc, the sound changes as the amount of data is being transmitted varies. Other than that, is one if the systems 9600 baud vs 3600 baud?

 

[ButchGone]

It's definately different sounds to the CC's...not dependant on whether there is traffic on the system. I have heard that with the 3600 b channels. And it's not MDT stuff. These are the actual confirmed CC's for the simulcast systems linked together in the regional system. And that's what's so wierd about this, I never have heard different sounding CC's from sites on the same band/same system/same vendor.
Strange.
BG..

 

[wlmr]

It's definately different sounds to the CC's...not dependant on whether there is traffic on the system. I have heard that with the 3600 b channels. And it's not MDT stuff. These are the actual confirmed CC's for the simulcast systems linked together in the regional system. And that's what's so wierd about this, I never have heard different sounding CC's from sites on the same band/same system/same vendor.
Strange.
BG..

The simulcast control channels definitely sound different than single site control channels. They use a different modulation scheme. The difference between the three simulcast sites may be due to their distance from you and how in or out of phase the individual transmitting towers are in relation to your location.

 

[N_Jay]

How are you hearing three different control channels if they are simulcasted?

 

[wlmr]

How are you hearing three different control channels if they are simulcasted?

I read it as meaning he's hearing three different simulcast sites, not three sub-sites from the same simulcast site. Otherwise, you have a very good question!

 

[N_Jay]

Different simulcast areas just like different individual; sites will have different loading and sound different.

 

[WayneH]

If the system is new one of the channels could be broadcasting BERT test patterns for coverage testing.

 

[ButchGone]

One system is a four site simulcast, 800Mhz P25. The other system is a three site simulcast, 800Mhz P25. A four channel 800Mhz stand alone IR site is between these, and the rest are stand alone IR five-channel sites in the 700Mhz range. I'm new to the P25 thing and learning a lot based on listening to it being built out. In addition to the control channels, which sound different, one of the other voice repeater channels on each system is sending data too, but it does not reveal any info when I put scanner in contol channel search mode. I would assume while it's being tweaked I'll hear and see some unusial things?
BG..

 

[WayneH]

I would assume while it's being tweaked I'll hear and see some unusial things?

It's a matter of perspective so I'll just say yes.