Rotating CCs

[James]

I was wondering how many cels rotate control freqs. I live in Columbia, so I mostly monitor Rich. and Lex. Simulcast. Since the change from Killian-Palmetto, which never rotated, now the Rich switches from 868.0375 to 868.5375, and Lex. 860.2625 to 860.8875 so often I have to allocate four channels in each bank just for these towers.
I'm curious, I used to have 50 ccs in a bank, and was pretty confident I could travel most of the state and be covered.

Jim

 

[Curfew]

Jim, i would say the majority of them in SC county wide change over. Whenever this happens, i search 851-869 mhz and find where they are and punch it in place of the old one. When it changes again, i punch the old one back in.

Im sure others will kick in on this. John.

 

[jeffmulter]

>> I was wondering how many cels rotate control freqs.

All of them ... under the wrong conditions. If the control frequencies not specifically set to rotate at a certain time, changes will still occur anytime there is interference to the control frequency from another system sharing the same frequency.

Besides band enhancements affecting the control channel, there is also the issue of 800 users. As the number of agencies on 800 MHz increases, so do the number of trunked sites and the amount of interference. Under favorable circumstances, that interference may be originating from out-of-state.

>> Jim, i would say the majority of them in SC county wide change over. Whenever this happens, i search 851-869 mhz and find where they are and punch it in place of the old one. When it changes again, i punch the old one back in.

If you are using a scanner with control-channel-only scanning, there should be no need to manually search for the control channel. Just enter the primary and secondary control frequencies (up to 4), and let the scanner I-D which frequency is in use for control data.

If the control channels are unknown, just enter all the frequencies assigned to the particular system or site.

 

[Caesar]

I have 3 banks for my area, 1 for richland system, 1 for lexington system and 1 for all the control and alternate control channels

 

[brian]

Generally speaking (which means this doesn't hold true in all situations), a Smartzone system's control channels won't rotate. A Smartnet system's control channels will rotate. I'm not an expert on this, so this may be completely incorrect. I'm sure others who are more knowledgeable will correct me if necessary.

My understanding is that when programming a subscriber radio for a Smartzone system, one has to program in each possible active control channel frequency, but radios are limited in the number of available memory slots. I think it used to be 32 control channel frequencies, maybe now it's more like 64 (or more). For a system like Palmetto 800, with 62 sites, each with a primary control channel and at least one alternate, that's as many as 124 possible frequencies (some sites "advertise" more than one alternate according to trunker, and there is some frequency duplication state-wide, so that number is approximate). If the control channel for each site rotated among 3 or 4 frequencies, that's a lot more frequencies to program (200+).

In a Smartnet system, you're allowed to program up to 4 control channel frequencies for each system. So those rotate on a more regular basis. Examples of Smartnet systems in SC would be Florence, Charleston City, Horry County, Sumter County, Beaufort County and many Business SMR systems. Charleston County is actually a simulcast single-site Smartzone system. Asheville NC is upgrading their Smartnet system to a Smartzone system right now.

Based on my observations in the Upstate, the control channels on Palmetto 800 sites don't change often. Paris Mountain changes more frequently than the others, maybe once a month for a day or less at a time, and I think that's due to interference. When Motorola is testing a site, they can also manually change the control channel.

Hope that helps.

Brian

 

[bpalmer]

Down here in the Lowcountry the Beaufort County TRS rotates through 4 channels. As I recall a number of years ago the reason given was to prevent any one repeater from taking the abuse of transmitting all the time.


i suppose the repeater are built better now-a-days. But even with a major refit a few years back, they kept the same concept.

 

[James]

Thanks for the replies.
I have been using a pro96 for the past few years. The best setup for me until recently was to narrow down all the PRIMARY ccs to 50 for each bank. Bank 0, containing 150 municipal PD and SD tgs. Bank 1, 150 SCHP, SLED tgs. Bank3, Fire/EMS. etc.
Here in Cola the main sites were Killian, and Palmetto, and as I stated earlier, monitoring for years, they never rotated ccs.
I was taking for granted that other sites would probably not swith ccs, and could travel the state and not miss much. I found this to be true over the past few years.
When the Lex and Rich simulcast was implemented the ccs for Rich especially, started switching several times a day. Lex not quite so often, usually at night only.
The remaining banks I use for LE VHF, UHF, Ft Jackson/Gordon etc.
Am looking for feedback from others who know, or have noticed frequent rotations in their areas.
Thanks again, Jim

 

[Caesar]

when i use unitracker i will notice the data feed will die on the main control ch and the scanner will search until it hits one of the alt controls, but the few times i have seen it, it doesn't do it for long...