Cannot hear CMPD

[Reedrosa]

I am using a BCD436HP. It scans every system I have programmed but in the last week has stopped picking up any activity on the CMPD system. Has anything changed or is anyone else having issues?

 

[trumpetman]

What division(s) are you trying to monitor? Are you hearing any other law traffic in Mecklenburg County like Sheriff or one of the town PDs?

 

[Reedrosa]

I reset my radio and now it appears to be working. Not sure what happened. I just started using Sentinel and like I said it worked fine until about a week ago. I don't seem to be hearing much traffic on their system but at least it is stopping on some talk groups now.

 

[hamstang]

I reset my radio and now it appears to be working. Not sure what happened. I just started using Sentinel and like I said it worked fine until about a week ago. I don't seem to be hearing much traffic on their system but at least it is stopping on some talk groups now.

Guessing the simulcast issue affects your BCD436HP. Uniden SDS 100 and 200 scanners work well with the Charlotte UASI system.

 

[Reedrosa]

Just started reading about the SDS scanners. After resetting mine and uploading my sentinel favorites again it is working. Not sure what happened but thanks for the responses.

 

[tradecraft6f]

MOTO XTS5000 OR APX,BENDIX KING

 

[BryanTheRed]

Unication G5 also works well with UASI.

 

[Reedrosa]

Can someone give me a brief 2 or 3 sentence explanation of the simulcast issue and why the other scanner mentioned work better on CMPD?

 

[trumpetman]

Simulcast is the transmission of the same signal from multiple sites at the same time. The Mecklenburg simulcast uses 9 towers to cover the county. When a scanner can receive more than one site it struggles to differentiate and decode the multiple digital signals that are all arriving a few milliseconds apart. A work around for this is to use a highly directional antenna and point it towards one tower to try and decrease the chances of hearing multiple towers at the same time. You can also get lucky and live close to a tower and use attenuation or a smaller antenna. Both of these are only effective in stationary situations though.

The Uniden SDS scanners use I/Q demodulation similar to commercial radios so they tend to handle simulcast distortion much better. You can read a little more in depth on the wiki page linked below.

Simulcast Distortion - The RadioReference Wiki

wiki.radioreference.com

 

[brian]

Simulcast is the transmission of the same signal from multiple sites at the same time. The Mecklenburg simulcast uses 9 towers to cover the county. When a scanner can receive more than one site it struggles to differentiate and decode the multiple digital signals that are all arriving a few milliseconds apart.

All of this is quite true, but I think it's important to stress that simulcast distortion occurs when the same signal is transmitted from multiple sites on the same frequencies at the same time.

I think many people confuse the term "simulcast" when it is applies to multiple sites transmitting the same signal on different frequencies at the same time. This scenario can accurately be called "simulcast", some people refer to this as "multicast." But this scenario does not cause scanners trouble with decoding. It's when a single "site" (to mean a specific set of frequencies) is broadcast from multiple tower locations at the same time.

A system such as NC VIPER has many tower sites, and many of those sites carry signals from talkgroups at the same time. But the vast majority of VIPER sites are single-tower sites and are not "simulcast." There are a few exceptions, one being in Gaston County.

 

[dave3825]

If your scanner was scanning those systems without issue, and now as of a week ago your having trouble with one system, it might not be simulcast but also could be. Where do you usually use the scanner, I mean where was it receiving good? Did anything change like rearranging items in your home?