Control Channels

[xrorx]

What are ALL the reasons a trunk system would change control channels?

 

[n5ims]

What are ALL the reasons a trunk system would change control channels?

* A repeater broke.
* A repeater needed maintenance done.
* System policy stated to rotate control channel frequencies to allow a repeater to move from 100% continuous duty to a more typical 20 - 25% duty cycle.
* System issues due to interference (or other issues) on a control channel frequency.
* A repeater was repaired.
* A repeater's maintenance completed.
* Interference issues corrected.

These aren't likely but you did say "ALL" reasons
* System manager wanted to change control channel frequency.
* Agency discovered that the current CC frequency wasn't licensed for CC emission mode.
* Somebody mistakenly commanded system to change CC frequency.
* Coding error caused system to change CC frequency.
* Shoot out at the repeater site caused the CC repeater to fail, causing the system to switch channels to remain operational.

 

[talviar]

You left out a really good one. . . . .

Transmit Combiner for the port the Control Channel connects to has failed. . . . That seems to be a culprit on my system a lot- The CC rolls to a transmitter that has a TX cavity issue with the circulator on the combiner causing the circulator to over heat, and the transmitter starts getting reflected power. Controller receives an error and pulls the channel off line.

 

[KevinC]

You left out a really good one. . . . .

Transmit Combiner for the port the Control Channel connects to has failed. . . . That seems to be a culprit on my system a lot- The CC rolls to a transmitter that has a TX cavity issue with the circulator on the combiner causing the circulator to over heat, and the transmitter starts getting reflected power. Controller receives an error and pulls the channel off line.

You must have GTR8000's in an ESS rack.

I'm not a big fan of the ceramic cavity combiners myself.

 

[xrorx]

Thanks guys for the education.

 

[talviar]

You must have GTR8000's in an ESS rack.

I'm not a big fan of the ceramic cavity combiners myself.

MSF5000's running @ 150W output
Old style external combiner. 7 Channel combiner takes up a lot of rack space.

 

[fourthhorseman]

* A repeater broke.

* Shoot out at the repeater site caused the CC repeater to fail, causing the system to switch channels to remain operational.

Almost spilled my morning DD hazelnut I chuckled so hard when I read this...

 

[rescue161]

On a system with more than one controller, if there are too many errors on the first controller, then the system will switch to the other one, which will cause the control channel to switch.

System admins SMT or switch disabling channels.

 

[whyohmean]

Combiner failures

You left out a really good one. . . . .

Transmit Combiner for the port the Control Channel connects to has failed. . . . That seems to be a culprit on my system a lot- The CC rolls to a transmitter that has a TX cavity issue with the circulator on the combiner causing the circulator to over heat, and the transmitter starts getting reflected power. Controller receives an error and pulls the channel off line.

I came across this old thread trying to research some new VHF trunking combiners. The symptom you describe is exactly what we have experiences MULTIPLE times on our 6 site/6 channel system with 100W radios. The isolator DL burns up (100W) and several cavities have apparently arced. No evidence of lightning strikes anywhere. Running tuning rod in/out several passes will clear it up for a short spell, but it always comes back. Have to send in to have copper fingers replaced.
Curious as to what brand you are using and see these issues on. I don't want to outright badmouth the manufacturer of ours. Perhaps others are seeing similar problems.

 

[dlwtrunked]

* A repeater broke.
*...
* System policy stated to rotate control channel frequencies to allow a repeater to move from 100% continuous duty to a more typical 20 - 25% duty cycle.
...
QUOTE]

That is the main reason.

 

[Project25_MASTR]

* A repeater broke.
*...
* System policy stated to rotate control channel frequencies to allow a repeater to move from 100% continuous duty to a more typical 20 - 25% duty cycle.
...
QUOTE]

That is the main reason.

Not so common these days with newer systems. Quantars for example, can handle 100% duty for years. Aside from the SCM's failing or the unit going out of alignment (typically won't happen if it's got a 10 MHz reference or receives annual to semi-annual PMs) the primary culprits are the fans which cool the PA or the fan which cools the PS. Not like some other designs.

Most current P25 systems don't rotate often. I have my Connect Plus system set to rotate daily...since I've had issues with the PS on the MTR3000's and I know a guy running Smartnet system who's had a MSF5000 as the control channel since 1997...it's only been down for 2 hours in that time span (he's averaging a PM every decade).

 

[mdsxfire]

Not so common these days with newer systems. Quantars for example, can handle 100% duty for years. Aside from the SCM's failing or the unit going out of alignment (typically won't happen if it's got a 10 MHz reference or receives annual to semi-annual PMs) the primary culprits are the fans which cool the PA or the fan which cools the PS. Not like some other designs.



Most current P25 systems don't rotate often. I have my Connect Plus system set to rotate daily...since I've had issues with the PS on the MTR3000's and I know a guy running Smartnet system who's had a MSF5000 as the control channel since 1997...it's only been down for 2 hours in that time span (he's averaging a PM every decade).

Very late to this thread but my question is my county system list every channel as a primary or alt control channel does that mean they always change or just that any channel can be a control? And does a scanner or a unication pager automatically switch as long as all channels listed are programmed in?


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[Project25_MASTR]

Very late to this thread but my question is my county system list every channel as a primary or alt control channel does that mean they always change or just that any channel can be a control? And does a scanner or a unication pager automatically switch as long as all channels listed are programmed in?


Sent from my iPhone using Tapatalk

Means it’s a Harris system.

But what it means is any channel can be a control channel. Not knowing a ton of the physical equipment layout it’s difficult to really try and say why Harris makes every channel control capable but you may see this as common place as they are not know for wide area systems and instead focus on simulcast.

With the scanner, you’ll want all of the listed control and alternates. With the Unication, there should be a control channel scan feature which will scan for an active control channel broadcasting the SID of interest. Control channel scan shouldn’t be used with the Unication in a multi-site system as it makes it more difficult to steer the pager to the site of interest.


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[mdsxfire]

Means it’s a Harris system.

But what it means is any channel can be a control channel. Not knowing a ton of the physical equipment layout it’s difficult to really try and say why Harris makes every channel control capable but you may see this as common place as they are not know for wide area systems and instead focus on simulcast.

With the scanner, you’ll want all of the listed control and alternates. With the Unication, there should be a control channel scan feature which will scan for an active control channel broadcasting the SID of interest. Control channel scan shouldn’t be used with the Unication in a multi-site system as it makes it more difficult to steer the pager to the site of interest.


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Thank you, yes Harris system I think about 15 different towers all simulcast. Tried 2 different scanners both did horrible with LSM and when I could hold control channel they missed a lot of traffic! Waiting for the phase 2 update for the unication since I heard they work great on these systems. I would much rather pay more for something that works, hopefully the phase 2 comes out soon


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