SDRTrunk and CC/VC

[AngWay]

Hello everyone hope your summer is going well mine is hot!!. I have some questions that i want to ask just so i can maybe understand some things better i am a complete newbie to all of this so please understand, But i'm using SDRTrunk to listen to my local police and EMS the only control channels i can pick up in my area are 152.6825 and 161.800, i have 2 RTL-SDR V4 dongles and if i set one dongle to the 152 CC whenever i get traffic it shows the traffic on a 161 channel i thought that the dongles could only do 2.4mhz of bandwidth how is it receiving voice channels in the 161mhz if one dongle is on the 152 CC?

And if park a dongle on the 161 CC i get traffic on the 150 freqs it just don't make sense to me. Also if i set one dongle to 151CC and one dongle to 161CC would that be ok or would i need a 3rd dongle if i have 2 dongles on 2 different control channels? Also the 152 and 161 control channels are about a 30 minutes drive from one another so would i miss some traffic if i'm only locking onto one CC or would it matter?

Thank you all very much in advance for your responses and God bless!.

 

[maus92]

If you look carefully, the voice traffic is being received on the second dongle that is not locked to a control channel. A third dongle may or may not increase the number of talk groups received.

 

[AngWay]

If you look carefully, the voice traffic is being received on the second dongle that is not locked to a control channel. A third dongle may or may not increase the number of talk groups received.

but a dongle can only do 2.4 mhz and two dongles could do 4.8mhz how is a dongle locked onto a CC able to reach a VC in the 160s mhz range? also i noticed if i lock one dongle onto 152 and one dongle onto 161 both dongles are receiving the same traffic just on different voice channels meaning dongle 1 on 152CC is receiving traffic on a 160s voice channel and dongle 2 on the 161CC is receiving a voice channel on the 150s voice channel.

 

[maus92]

The dongle locked on the cch at 151 is not receiving the voice traffic; a second dongle that is not locked to a specific channel is free to be assigned to any channel. If that second dongle is locked to a control channel at 161.000, it can theoretically receive a voice channel between ~159.000 to 163.000, depending on other traffic that is also being received at the same time. In a multicast system like STARS, two sites may be transmitting the same talk group, but on traffic channels assigned to those sites.

 

[RMason]

From your other threads, it looks like these are the sites you are monitoring:

2 (2)	013 (D)	Honaker	Buchanan	152.6825c	152.7125c	161.875	162.000
2 (2)	017 (11)	Oakwood	Buchanan	152.8175c	161.800c

In this example, there are two ranges of frequencies used:

1. 152.6825, 152.7125, 152.8175 - All of these frequencies fit within the 2.4Mhz bandwidth of a single dongle
2. 161.800, 161.875, 162.000 - All of these frequencies fit within the 2.4Mhz bandwidth of a single dongle

These two frequency ranges can be covered by 2 dongles. Using SDRTrunk, a single dongle can cover multiple control channels and voice channels within a 2.4 MHz bandwidth. SDRTrunk handles the complexities of monitoring the control channel and assigning the voice channel to the appropriate dongle. It does a rather good job of optimizing use of the dongle resources.

In this case, dongle 1 can monitor the 152.*Mhz control channel for the Honker site. When there is a channel grant (voice traffic), SDRTrunk steers the appropriate dongle to the voice channel. Dongle 1 will handle the voice channels in the 152Mhz range; Dongle 2 will handle the voice channels in the 162Mhz range.

Simultaneously, dongle 2 can monitor the 161.*Mhz control channel for the Oakwood site. When there is a channel grant (voice traffic) on this site, SDRTrunk steers dongle 1 to the voice channel in the 152.*Mhz range.

Since the Honiker and Oakwood sites are close to each other, it is likely a talkgroup will be affiliated with both sites. But there is no guarantee that all talk groups will be carried on both sites. You will need to log what talkgroups are carried on each site. You can enable Duplicate Call Detection in SDRTrunk to detect duplicate calls on the same talkgroup.

 

[dave3825]

You created 2 dummy channels. One set to 152.6975 mhz, and the other set to 161.9375 mhz.


One dongle will handle everything within reach in the 152 range. Control channels. Green freqs.
One dongle will handle everything within reach in the 161 range. Control and or voice channels. Blue freqs





Based on what's listed in the database, third dongle is not needed. If you start seeing messages about no tuner available then they are using freqs not listed in the database.


Max traffic channels can be increased on each site.




If your getting duplicate calls, you are monitoring two different sites.

Try going into preferences and turn on duplicate call detection.

 

[AngWay]

The dongle locked on the cch at 151 is not receiving the voice traffic; a second dongle that is not locked to a specific channel is free to be assigned to any channel. If that second dongle is locked to a control channel at 161.000, it can theoretically receive a voice channel between ~159.000 to 163.000, depending on other traffic that is also being received at the same time. In a multicast system like STARS, two sites may be transmitting the same talk group, but on traffic channels assigned to those sites.

ok but isn't 152.6825 to 161.800 to big for one or even two dongles to handle i was always told each dongle can only handle 2.4mhz and like i said if i lock both dongles to each control channel they both are bringing in the same traffic just backwards for example when i have one dongle locked onto control channel 161.800 and one dongle locked onto control channel 152.6825 when the traffic comes through the dongle locked onto CC 161 shows the traffic around 152 and the dongle locked onto CC 152.6825 shows traffic around the 161 and both outputs of traffic are identical. thats the part i just ain't getting,

 

[RMason]

How are you determining: (a screen shot would be helpful)
"When the traffic comes through the dongle locked onto CC 161 shows the traffic around 152 and the dongle locked onto CC 152.6825 shows traffic around the 161"

The dongle locked on to the 161Mhz CC will receive the channel grant and steer the traffic at 152Mhz to the other dongle.
Likewise, the dongle locked to 152Mhz CC will receive the channel grant and steer the traffic around 161Mhz to the other dongle

Each dongle will stay locked on the control channel and receive voice channels within its 2.4Mhz bandwidth.

 

[dave3825]

ok but isn't 152.6825 to 161.800 to big for one or even two dongles to handle

Yes. The rtl sdr dongle does close to 2.4mhz

when i have one dongle locked onto control channel 161.800 and one dongle locked onto control channel 152.6825 when the traffic comes through the dongle locked onto CC 161 shows the traffic around 152 and the dongle locked onto CC 152.6825 shows traffic around the 161 and both outputs of traffic are identical. thats the part i just ain't getting,

Somehow you are reading it wrong. You cant view what's locked, and see the calls window, that shows you the active freqs, at the same time.

 

[AngWay]

From your other threads, it looks like these are the sites you are monitoring:

2 (2)	013 (D)	Honaker	Buchanan	152.6825c	152.7125c	161.875	162.000
2 (2)	017 (11)	Oakwood	Buchanan	152.8175c	161.800c

In this example, there are two ranges of frequencies used:

1. 152.6825, 152.7125, 152.8175 - All of these frequencies fit within the 2.4Mhz bandwidth of a single dongle
2. 161.800, 161.875, 162.000 - All of these frequencies fit within the 2.4Mhz bandwidth of a single dongle

These two frequency ranges can be covered by 2 dongles. Using SDRTrunk, a single dongle can cover multiple control channels and voice channels within a 2.4 MHz bandwidth. SDRTrunk handles the complexities of monitoring the control channel and assigning the voice channel to the appropriate dongle. It does a rather good job of optimizing use of the dongle resources.

In this case, dongle 1 can monitor the 152.*Mhz control channel for the Honker site. When there is a channel grant (voice traffic), SDRTrunk steers the appropriate dongle to the voice channel. Dongle 1 will handle the voice channels in the 152Mhz range; Dongle 2 will handle the voice channels in the 162Mhz range.

Simultaneously, dongle 2 can monitor the 161.*Mhz control channel for the Oakwood site. When there is a channel grant (voice traffic) on this site, SDRTrunk steers dongle 1 to the voice channel in the 152.*Mhz range.

Since the Honiker and Oakwood sites are close to each other, it is likely a talkgroup will be affiliated with both sites. But there is no guarantee that all talk groups will be carried on both sites. You will need to log what talkgroups are carried on each site. You can enable Duplicate Call Detection in SDRTrunk to detect duplicate calls on the same talkgroup.

ohhh ok i gotch there the way i was seeing it was the honaker site being 152 to 162 i was thinking that was the cc and vc for that one site so the 161 and 162 channels fall into the 161.800 control channel now that makes more sense to me.. and u said a single dongle can cover multiple control channels dose that mean i can set both the 152.6825 control channel and the 161.800 control channel to one dongle? and leave the 2nd dongle free?

 

[RMason]

dose that mean i can set both the 152.6825 control channel and the 161.800 control channel to one dongle

No. This exceeds the 2.4Mhz range of the dongle. One dongle needs to be used for 152.6825; another for the 161.8Mhz. One dongle cannot receive both simultaneously.

Two dongles are required to cover this range.

1. 152.6825, 152.7125, 152.8175 - All of these frequencies fit within the 2.4Mhz bandwidth the 1st dongle
2. 161.800, 161.875, 162.000 - All of these frequencies fit within the 2.4Mhz bandwidth of the 2nd dongle

 

[AngWay]

Yes. The rtl sdr dongle does close to 2.4mhz



Somehow you are reading it wrong. You cant view what's locked, and see the calls window, that shows you the active freqs, at the same time.

alright thanks for the duplicate call setting i didn't know about that and mine was off. but what is still happening is if i turn on only the 161.800 control channel and a call comes across the call will be in the 152mhz range and if i only turn on the 152.6925 control channel the call comes over on the 161 mhz range and that's what is confusing if i turn both control channels on to each separate dongle then it will still show that with the duplicate calls.

 

[AngWay]

How are you determining: (a screen shot would be helpful)
"When the traffic comes through the dongle locked onto CC 161 shows the traffic around 152 and the dongle locked onto CC 152.6825 shows traffic around the 161"

The dongle locked on to the 161Mhz CC will receive the channel grant and steer the traffic at 152Mhz to the other dongle.
Likewise, the dongle locked to 152Mhz CC will receive the channel grant and steer the traffic around 161Mhz to the other dongle

Each dongle will stay locked on the control channel and receive voice channels within its 2.4Mhz bandwidth.

i'll try to get a screenshot as soon as i can

 

[AngWay]

Yes. The rtl sdr dongle does close to 2.4mhz



Somehow you are reading it wrong. You cant view what's locked, and see the calls window, that shows you the active freqs, at the same time.

alright thanks for the duplicate call setting i didn't know about that and mine was off.

You created 2 dummy channels. One set to 152.6975 mhz, and the other set to 161.9375 mhz.


One dongle will handle everything within reach in the 152 range. Control channels. Green freqs.
One dongle will handle everything within reach in the 161 range. Control and or voice channels. Blue freqs


View attachment 164341


Based on what's listed in the database, third dongle is not needed. If you start seeing messages about no tuner available then they are using freqs not listed in the database.


Max traffic channels can be increased on each site.

View attachment 164342


If your getting duplicate calls, you are monitoring two different sites.

Try going into preferences and turn on duplicate call detection.

View attachment 164339

also i see on yours under frequencies u have 4 freqs in there is that the control channel and the voice channels or is it just control channels and alternate control channels? my system is C4FM do i need to put all mine in or just the one control channel?

 

[dave3825]

Your scanning 2 sites so it will show duplicates.

A dongle set to a cc of 152.xxx is not tuning to any channels in the 160.xxx.

A dongle set to a cc of 160.xxx is not tuning to any channels in the 152.xxx.

also i see on yours under frequencies u have 4 freqs in there is that the control channel and the voice channels or is it just control channels and alternate control channels?

Yes, cc and alts for my system..

my system is C4FM do i need to put all mine in or just the one control channel?

II don't have any C4FM so I am honestly not sure. Believe you only set control channels and do not set any voice channels. If I am wrong, someone please correct me.

 

[AngWay]

Your scanning 2 sites so it will show duplicates.

A dongle set to a cc of 152.xxx is not tuning to any channels in the 160.xxx.

A dongle set to a cc of 160.xxx is not tuning to any channels in the 152.xxx.





Yes, cc and alts for my system..


II don't have any C4FM so I am honestly not sure. Believe you only set control channels and do not set any voice channels. If I am wrong, someone please correct me.

right here is some screenshots the first screen shot is with both dongles locked onto each control channel and when i turn off the 161 CC and just leave the 152 on the call is on the 161 freqs the same is happening in the first picture the 152 CC shows calls on the 160 freqs and the 161 cc shows calls in the 152 freqs. i'm just really confused

 

[AngWay]

How are you determining: (a screen shot would be helpful)
"When the traffic comes through the dongle locked onto CC 161 shows the traffic around 152 and the dongle locked onto CC 152.6825 shows traffic around the 161"

The dongle locked on to the 161Mhz CC will receive the channel grant and steer the traffic at 152Mhz to the other dongle.
Likewise, the dongle locked to 152Mhz CC will receive the channel grant and steer the traffic around 161Mhz to the other dongle

Each dongle will stay locked on the control channel and receive voice channels within its 2.4Mhz bandwidth.

like i told @dave3825 right here is some screenshots the first screen shot is with both dongles locked onto each control channel and when i turn off the 161 CC and just leave the 152 on the call is on the 161 freqs the same is happening in the first picture the 152 CC shows calls on the 160 freqs and the 161 cc shows calls in the 152 freqs i'm just really confused

 

[RMason]

Lets focus on only the Honaker site:

From the RR database, the site frequencies for the Honaker site are:

2 (2)

013 (D)

Honaker

Buchanan

152.6825c

152.7125c

161.875

162.000

The site is composed of 4 frequencies - an active control frequency plus voice channels. The Honaker site has 1 active control channel and 3 voice channels.

• Control Channel: Responsible for managing and controlling the site.
• Voice Channels: Used for carrying voice traffic.

For this site, the active control channel is 158.6825. The other three frequencies on this site are used as voice channels.

If you focus on the Honaker site, what you are seeing is the traffic for the call shown is being carried on 161.875. The control channel is 158.6825.

 

[AngWay]

Lets focus on only the Honaker site:

From the RR database, the site frequencies for the Honaker site are:

2 (2)

013 (D)

Honaker

Buchanan

152.6825c

152.7125c

161.875

162.000

The site is composed of 4 frequencies - an active control frequency plus voice channels. The Honaker site has 1 active control channel and 3 voice channels.

• Control Channel: Responsible for managing and controlling the site.
• Voice Channels: Used for carrying voice traffic.

For this site, the active control channel is 158.6825. The other three frequencies on this site are used as voice channels.

If you focus on the Honaker site, what you are seeing is the traffic for the call shown is being carried on 161.875. The control channel is 158.6825.

the control isn't 158.6825 it's 152.6825 u said 158.6825. i'm just confused if it's on CC 152.6825 how is it picking up a voice channel in the 161 mhz isn't each dongle only capable of 2.4mhz?

2 (2)

013 (D)

Honaker

Buchanan

152.6825c

152.7125c

161.875

162.000

 

[RMason]

It may be beneficial to give each channel a unique name in the channels tab of the playlist editor. I believe that this is used to populate the Channel Name column. You may want to use Honker Control instead of Control