Am I receiving Simulcast? Or not?

[gfoust8]

My BCD536HP appears to be receiving very well, however I cannot determine if I am receiving Simulcast or not. I am in Cape May County New Jersey and I do see the following pop up on my screen,

"New Jersey Interoperability Communications System, Cape May County Simulcast." But the squelch never opens on that. There are also a few more which say simulcast and the squelch does not open.

On Sentinel Cape May County Simulcast is listed with just a series of frequencies when opened. I believe these are the frequencies utilized for Talkgroups.

My bottom line question is am I missing some communications on "Simulcast"?? Or do I need to get a SDS200 to find out?

Thank You in Advance,
Greg

 

[Whiskey3JMC]

My bottom line question is am I missing some communications on "Simulcast"??

Most likely, yes. I've run a 436HP, 536HP & an SDS100 over the years on this very system as well as many neighboring simulcast systems. The former two missed & locked up on comms but my SDS100 never misses a beat on simulcast. There are a number of workarounds mentioned here but they work in very few instances. It's all relative to your location between two or more simulcasting sites

 

[Hit_Factor]

The system label probably comes from your FL or the database, not the actual signal being received.

Squelch doesn't really apply to digital systems in a similar manner to analog signals. There are enough ones and zeros to decode or there isn't. I have oversimplified a bit, and I'm sure others will chime in here.

 

[gfoust8]

I did HOLD on the SYSTEM and I notice every time the Simulcast label appears DAT is showing above. I suspect this indicates that a Control Channel is being received and there is no transmission in progress.
Does that sound like what is happening?

 

[gfoust8]

I tried an exercise. I created a Favorites list for NJICS and deleted all frequencies except for those labeled "Cape May County Simulcast".

When running a scan on that favorites list all transmissions appeared as normal with no issues.

 

[maus92]

Trying to guess what you actually did, but it *sounds* like you created a list of frequencies and scanned them conventionally. This suggests a programming issue in Sentinel.

 

[gfoust8]

In the Favorites list I created, I maintained all of the Talkgroup IDs Systems etc and deleted all frequencies except the ones under the heading simulcast.

 

[WA0CBW]

All frequencies in a simulcast system are the same.
BB

 

[natedawg1604]

All frequencies in a simulcast system are the same.
BB

Not only that, there is nothing in the P25 data packets (i.e a status bit/flag) broadcast on the CC identifying a system as simulcast. Usually it's listed in the RR database as such. If not, a big clue is looking for tower locations in ULS that share the same frequencies within the same county.

 

[gfoust8]

I am not getting garbled transmissions nor am I getting drop outs. So unless there are completely missing transmissions I suspect I am not having any problems.

 

[wtp]

it can happen that you could get nothing for some time.
i sent another PM.

 

[maus92]

I am not getting garbled transmissions nor am I getting drop outs. So unless there are completely missing transmissions I suspect I am not having any problems.

How would you know if you were or were not missing transmissions? Do you have another reliable source to compare - like a subscriber? Can you post a screenshot of your Frequencies tab of your Site List? It should look something like this (note that I edited out all irrelevant sites and traffic channels, leaving only the control channels for the Cape May site.)



FWIW, I use a 536 on a P25P2 simulcast site in my office. It does a pretty good job, but it will occasionally miss transmissions - particularly one in progress. Its performance is very much dependent on location wrt tower infrastructure.

Also, are there really 4 alternate control channels for this site? That would be unusual for a Moto system; usually it's 1 or 3.

 

[maus92]

I did HOLD on the SYSTEM and I notice every time the Simulcast label appears DAT is showing above. I suspect this indicates that a Control Channel is being received and there is no transmission in progress.
Does that sound like what is happening?

When you HOLD on a system using a Uniden scanner, the radio will regularly leave the control channel to perform internal housekeeping tasks. When you see DAT, that indicates the cch is being received and decoding. The "Simulcast" in your display is simply the label assigned to the Cape May site, and is user configurable. The 536 is not detecting / identifying the signal as simulcast per se.

 

[gary123]

Electronically simulcast signals are identical to regular signals. Think of the system as a single light flashing on and off slowly. If there is only one light then you have no problems watching it flash on and off. A simulcast system would be the same as seeing 2 lights both flashing on and off. The lights should be synchronized so watching them is not a issue. What confuses the scanner is that the lights are not quite synchronized one starts flashing before the other. This confuses you as this is annoying. Thats why scanners have trouble handling simulcast.

This is a simplification. The flashing is happening at the speed of light and distance to and from the sites plays a roll but you get the general idea.

 

[nessnet]

Lots of good explanations here, so joining a bit late....

In the days of analogue TV and FM radio, there was a thing called multipath interreference. (snow on the TV, dad on the roof adjusting the antenna - tweaking the rabbit ears kinda stuff...)

Multipath is simply more than one signal being received by a receiver. Think of that mega TV tower sending out radio waves. Ideally, the waves are coming directly to you from the tower. But, hills, buildings etc, reflect these waves also. So you were getting these reflections too, but just a bit delayed. Yes, the speed of light is fast, but the extra time the wave traveled, caused it to be delayed, just a bit.

Simulcast is basically the same concept. Remember, simulcast is towers all on the same frequency. So, you have a radio getting multiple signals that are not all the exact same timing because the distance to you is different with each signal.

This is why the SDS radios came into existence. Because they use software to discriminate, the software can compensate for these delays.