primary vs alternate control channels

[jimmyo]

I know that primary channels are only required on a trunked system, but does adding alternate channels slow down the scanner?

 

[troymail]

I know that primary channels are only required on a trunked system, but does adding alternate channels slow down the scanner?

It only slows down the finding and lock onto a "new" control channel if the the system switches from the primary control channel. Generally, once the radio locks on a CC, the other frequencies have no affect on the scanning. As always, there are exceptions.

If you program only the main CC, the radio has a better chance to relock is the lock is lost. However, if the system switches to an alternate (or any) system frequency, and you don't have that programmed, the radio will go silent.

It's a trade off.

 

[jimmyo]

Thanks for the info. I think I'll keep the alternates and control channels for all systems.

 

[mmckenna]

Thanks for the info. I think I'll keep the alternates and control channels for all systems.

Since control channels on trunked systems run 24x7, it's very common practice for the control channel to roll on a fixed schedule. Middle of the night is a popular time to do that. The trunked systems are programmed to do this at a set time.
I run a 5 channel trunked 800MHz system. I've set it up to roll the control channel over every night at 1am. This shares the wear and tear on the transmitter and amplifier. I use 4 of the 5 channels as control channels. The 5th channel doesn't share in that rotation, but it is the channel that is used for sending out the FCC call sign. Rules used to be, not sure if they still are, but the lowest channel on the system was the one that the morse code ID was sent out on. This sort of precluded it from being used as a control channel.

Not having all the control channels in your scanner will cause it to stop following the system when/if the rollover happens.

 

[lynxrufus]

does adding alternate channels slow down the scanner?

Yes, at least on my scanner (pro197). When I'm trying to identify radio IDs, I get more IDs when I enter just the primary control channel and no alternates.

Of course, if they would change the control channel to an alternate, I would't get anything.

 

[aps_ak]

Yes, at least on my scanner (pro197). When I'm trying to identify radio IDs, I get more IDs when I enter just the primary control channel and no alternates.

Of course, if they would change the control channel to an alternate, I would't get anything.

These scanners pull radio IDs out of the initial channel grant by the CC. If you have extra channels that the scanner is scanning through and misses that grant, you don't get the radio ID. Minimalism is good in this respect, though my 106 skips over control channels with no signal pretty quick, and takes more time scanning through all the active ones.

 

[rdale]

That's incorrect. Scanners don't scan through other CCs unless there is no signal or if you set it to.

 

[mmckenna]

That's incorrect. Scanners don't scan through other CCs unless there is no signal or if you set it to.

Exactly. A trunk tracking scanner will sit on the control channel and listen, waiting for a channel assignment.

Since I find the trunking control channels on RR.com suspect to accuracy, I'd put all of the frequencies in and let the radio find the active control channel. Once it finds an active control channel, it will sit and wait. Failing to put all the possible control channels in will result in the possibility of it now working if it switches to a control channel that isn't in your radio.

 

[hfxChris]

And of course if you notice errors in the database, you submit corrections so other people can benefit, right?

 

[wtp]

it all depends

my county (charlotte fl) has 4 red cc this one rolls to the next about every 24 hours (11pm or so)
the next county (sarasota fl) has one red and from one to three (depends on the tower ) that red one almost never changes
going north (de soto) added a new channel and that was a new control channel
so your radio would go silent if set to cc only

it is always good to go through a full scan once and a while(25 to 1300 mhz)

 

[jimmyo]

CC Channels first

Now that i've learned so much about CC vs Alt channels. does it matter in what order the channels are in the scanner (Pro-106 using win500). Right now they are not in any specific order.

 

[N8IAA]

Now that i've learned so much about CC vs Alt channels. does it matter in what order the channels are in the scanner (Pro-106 using win500). Right now they are not in any specific order.

No. The scanner will pick up on the CC, and decode from there.
Larry

 

[UPMan]

The accuracy of this entire thread relies on its context being limited to Motorola or APCO 25 trunked systems only. EDACS and LTR systems must have all frequencies entered, and every frequency must be associated with the correct LCN.

 

[hitechRadio]

Since control channels on trunked systems run 24x7, it's very common practice for the control channel to roll on a fixed schedule. Middle of the night is a popular time to do that. The trunked systems are programmed to do this at a set time.
I run a 5 channel trunked 800MHz system. I've set it up to roll the control channel over every night at 1am. This shares the wear and tear on the transmitter and amplifier. I use 4 of the 5 channels as control channels. The 5th channel doesn't share in that rotation, but it is the channel that is used for sending out the FCC call sign. Rules used to be, not sure if they still are, but the lowest channel on the system was the one that the morse code ID was sent out on. This sort of precluded it from being used as a control channel.

Not having all the control channels in your scanner will cause it to stop following the system when/if the rollover happens.

This is the case for Smartnet 3600 analog systems, if it Smartzone Digital P25 9600 the CC never rolls. Unless of course a failure, interfernce or manually commanded to roll be sys admin. Still a safe bet to just go ahead and put in all the freq's in though. To bad they don't have full spectrum scan in the scanners like subscriber units have. Just plop in the sys id, and let the radio scan the entire spectrum for a matching sys id. Maybe they do have that feature not sure if they do. I do not even own a scanner.

 

[troymail]

The accuracy of this entire thread relies on its context being limited to Motorola or APCO 25 trunked systems only. EDACS and LTR systems must have all frequencies entered, and every frequency must be associated with the correct LCN.

Excellent point Paul -- a clear example of one size (answer) doesn't fit all. You need to know (and use) your options.

Case in point -- entering ALL of the frequencies used to work for me (single site Motorola 3600 analog system) but once you get into the newer P25 (Phase 1 or Phase 2) systems - with the known signal/modulation issues- and couple that with a system that has many, many sites with many frequencies, the quality of reception regrades by loading everything. My best results are to create a system/scanlist with on the system's site I want and then only the primary control channel frequency. That way, it sync on the CC is lost (but it hasn't changed) the lock can be more quickly reacquired. There are obvious downsides to this - some have already been stated in this (and other) threads. But I also keep a separate load/scanlist that contains either the single site with all CC frequencies and/or all of that site's frequencies as a fall back. Many possibilities and as they say "your mileage may vary".

 

[SCPD]

So on a P25, phase 1, with 36 frequencies, 3 primary, 9 alternate, 24 stations, just put in the 3 primary and that should do it ? I put in all and have no issues.

 

[troymail]

So on a P25, phase 1, with 36 frequencies, 3 primary, 9 alternate, 24 stations, just put in the 3 primary and that should do it ? I put in all and have no issues.

Load everything - if that works for you then use it.

If you have problems, consider alternatives. It just really depends...... you have to advise of a problem - and then we can offer suggestions.

As mentioned - the situation is different for everyone. Some are ok with whatever they get/hear - others of us are trying to squeeze every drop out of our radios....

 

[UPMan]

You should create 3 sites. In each site put in at least all of the primary and alternate control channel frequencies for that site. Putting in all the voice channels won't hurt (but won't help, either, as the scanner will never use that input information for anything).

 

[troymail]

Putting in all the voice channels won't hurt (but won't help, either, as the scanner will never use that input information for anything

Not sure this is true for several reasons - but one I know for sure is that the data on RR isn't always complete or fully accurate.

 

[eorange]

I run a 5 channel trunked 800MHz system. I've set it up to roll the control channel over every night at 1am. This shares the wear and tear on the transmitter and amplifier.

Really? I'm not doubting you since you sound like you're in the biz, but do CC changes (from what I've seen, around 1 MHz or so) really help extend the equipment life?

I could see there being a more noticeable effect when switching across entire bands.