BCD996XT Control Channel Question

[hiyudurin]

When using a 996xt to monitor a P25 system such as NC VIPER. What's the benefit versus drawbacks of programming all frequencies for a site rather than just the control and alternate frequencies?

 

[Voyager]

The "benefit" is that you use more of the scanner's memory. Aside from that, there is absolutely no benefit. The scanner will still use only the control channels for scanning it.

 

[ofd8001]

While respecting Voyager's opinion, I look at it differently.

Unless you are pressed for memory resources (and a statewide trunk system might do so), I'd program in all of the channels listed for a site. If nothing else, those for the sites you listen to the most or are the most critical for you to receive.

While remote, there is always the potential for a trunked system to use a voice frequency as a control channel, unbeknownst to the the database. If that happens, you will miss comms. If all frequencies are programmed, you won't miss a thing.

If you look how the database for the HP line of scanners is downloaded, this includes all of the frequencies - control channels, alternate control channels and "regular./voice" frequencies. Of course memory isn't as big an issue with the HP line of scanners.

 

[W8RMH]

I don't think your memory will be an issue. I have 120 systems and a bunch of IDs programmed into my BCD996XT and am using less than 20% of the memory.

I have also read where some systems use a fail-safe backup system where all the frequencies are used in conventional mode, however I have never experienced this first hand.

 

[marksmith]

I don't think your memory will be an issue. I have 120 systems and a bunch of IDs programmed into my BCD996XT and am using less than 20% of the memory.

I have also read where some systems use a fail-safe backup system where all the frequencies are used in conventional mode, however I have never experienced this first hand.

Those must be small systems. I don't have anywhere near 120 systems and I am over 20%.

Having said that... total memory will not be the constraint on a 996xt. The main constraint is the number of pieces of data per system of 500. No more than 500 frequencies, talkgroups and RID's per system.

BCD536HP/HP2/996XT/PSR800/396XT/996T

 

[marksmith]

VIPER is a massive system. You will need to enter it to the 996xt as a whole lot of partial systems just to get it into the 996xt and I'm not even considering radio id's. I'd still enter all of the frequencies but enter them as logical systems that are chunks of the overall system. Obviously the stuff that can be broken dow by location is helpful. You would not really save enough by only entering control and alternate frequencies to make much of a difference.

BCD536HP/HP2/996XT/PSR800/396XT/996T

 

[cg]

All you need is the Control Channels. Knowing if the database hase ALL the possible CCs marked as such would be the question.

Trunked systems vary with how many control channels are used. For example, Harris P25 systems can use any system frequency for a CC. Usually though, there are 2-4 programmed in for each site. Some systems never rotate CCs, some do it regularly. I have found that watching Unitrunker during a thunderstorm can show the alternates as electrical crashes are sometimes seen as interference and prompts a CC change.

What your system does is something that either knowing the radio programming or extended monitoring with Unitrunker would determine.

I program in all that I see in a database unless it is something excessive or if I know the info is from a codeplug and is complete.

chris

 

[hiyudurin]

Thanks for all the replies. I travel around the state quite a bit for my job. I have the 996xt installed in my vehicle with a GPS antenna connected. The reason I asked this question is because when I'm traveling, on some sites I hear lots of traffic and when the GPS turns off a particular site and turns on another I get nothing. A lot of times the sites will be in the same county so I know I should get some of the same traffic. I have all control and alternate channels programmed for every VIPER site, I also check the database frequently to make sure everything is programmed correctly. I had the whole VIPER system programmed as a single system but ran into the problem of too many talk groups for the system, so I broke the system down into multiple systems based on the State Highway Patrol troops. I program local agencies within each troop into that troop system. I'm only using 12% of the memory now. I was wondering if I programmed all frequencies for every site would it slow the scanner down and cause me to miss more traffic? Thanks again for all the responses!

 

[marksmith]

Adding all the frequencies should have no impact on the scan speed as its only going to scan control channels.

What you describe in terms of gps changing and then nothing suggests that there are some control channels that might be marked as voice in the database.

The only way to know is to enter them all in. I know you only need the CC and alternates to theoretically receive everything but how do you ever know if you have all of those?

BCD536HP/HP2/996XT/PSR800/396XT/996T

 

[hiyudurin]

I'm gonna try programming all the frequencies and I'll report back my results after my next trip.

 

[Voyager]

While remote, there is always the potential for a trunked system to use a voice frequency as a control channel, unbeknownst to the the database. If that happens, you will miss comms.

This is not true. The control channels (and alternates) are programmed in the user radios. They cannot use voice channels as control channels. They can only use the pre-defined control channels (Primary and alternates).

Adding the voice channels mean an increased chance the scanner may lock onto a distant trunking system should that one happen to use one of those voice-only channels as a control channel on their system. That means you will no longer be trunking the system you want, but a different one.

There are several reasons for not adding the non-control channels, but no logical reasons to add them. As I mentioned, the user radios only have the control channels (again, Primary and up to 3 Alternate) programmed in them, and like the scanner they use only those to trunk the system.

 

[Voyager]

Adding all the frequencies should have no impact on the scan speed as its only going to scan control channels.

That is not true. Read my last reply. If you have the non-control channels programmed, they are subject to the same evaluation as the control channels. Whether that be a distant system's operation or the one you want to scan cannot be differentiated by the scanner.

So, it's best to program only one ones used on the system you want to monitor so as to avoid issues.

 

[ofd8001]

This is not true. The control channels (and alternates) are programmed in the user radios. They cannot use voice channels as control channels. They can only use the pre-defined control channels (Primary and alternates).

Unless the radios are re-programmed either physically or over the air. Granted this is only a remote possibility, but can't be discounted. Also this is placing great faith that the database is absolutely perfectly accurate.

Adding the voice channels mean an increased chance the scanner may lock onto a distant trunking system should that one happen to use one of those voice-only channels as a control channel on their system. That means you will no longer be trunking the system you want, but a different one.

There are several reasons for not adding the non-control channels, but no logical reasons to add them. As I mentioned, the user radios only have the control channels (again, Primary and up to 3 Alternate) programmed in them, and like the scanner they use only those to trunk the system.

So if this is an issue, why does Uniden download all of the frequencies for sites rather than the primary and alternate control channels and then "push" them to the Sentinel database?

 

[RWPowell2]

Voyager is correct. Programming only the Primary and Alternate Control Channels into a BCD996XT for a P25 System is the more efficient way to scan or search. Memory is not a big issue but it makes database management a lot easier. Control channel assignments are carefully coordinated and rarely change in most systems. In the original Motorola Type I trunking system the control channel did rotate within the channel group. In the old Orange County system the change was made at midnight. But most of the Type I systems are long gone.

 

[JoeyC]

The point that ofd8001 was probably making that the some of you are ignoring is that you are assuming that radioreference has 100% accurate information for all the trunked systems in existence, which is not a true assumption to make. Yes, the ONLY frequencies you need to program for the 996XT to function correctly are the control channels, but not every TRS listed in RR has every system 100% correct. Therefore you are better off programming all listed frequencies for any TRS that is questionable. Unfortunately figuring out which systems in the db are 100% correct can be as frustrating as figuring out which posters in the forum give credible information.

 

[Voyager]

So if this is an issue, why does Uniden download all of the frequencies for sites rather than the primary and alternate control channels and then "push" them to the Sentinel database?

Compatibility with LTR/EDACS, I would guess. Those system types do need all the channels.

I know for a fact the Uniden scanners will only do 'control channel trunking' on P25 systems. On Motorola systems, they will do either, but for the same reasons it's best to enable control channel only and just use the control channels, as it's about 99.99% more common to add a voice channel than it is a control channel. In fact, adding voice channels is something that often happens as systems expand.

 

[ff2sherman]

I have tried Both ways in the scanner 996XT
I will continue to have both to compare. 996P2 and 996XT

 

[marksmith]

The point that ofd8001 was probably making that the some of you are ignoring is that you are assuming that radioreference has 100% accurate information for all the trunked systems in existence, which is not a true assumption to make. Yes, the ONLY frequencies you need to program for the 996XT to function correctly are the control channels, but not every TRS listed in RR has every system 100% correct. Therefore you are better off programming all listed frequencies for any TRS that is questionable. Unfortunately figuring out which systems in the db are 100% correct can be as frustrating as figuring out which posters in the forum give credible information.

This is the rule of thumb I have gone by for years and I can't think of a single time where it ever resulted in a problem of any kind. I suspect Uniden pulls all the frequencies from the database to Sentinal for the same reason. I know of a number of P25 systems that regularly change control channel frequencies

Mark
536/996P2/HP1e/HP2e/996XT/
396XT/PSR800/PRO668/PRO652

 

[Voyager]

Unless you're talking about them reprogramming every radio on the system, they will be limited to four control channels - a primary and up to three alternates.