Con+ systems

[vince48]

Greetings,
is it common that DMR systems with no control channel being used in a Con+ interstate system?
There is one system that I monitor and I just can't find the control channel on any of the (20 sites) frequencies listed

Vincent

 

[SCPD]

Vincent the system up here (OR, WA, ID and northern CA) has its voice channels but the control channels are on 6.25khz steps. Try searching with 6.25khz steps and see if you can find any strong DMR signals. Just remember that SLOT 1 is the control data and SLOT 2 is still a valid voice frequency.

 

[Voyager]

Sounds like a Linked Capacity Plus system. Check and see if there are any data bursts at all on any of the frequencies.
(they are usually spaced out in time to the degree of X minutes)

 

[vince48]

yes, tried 6.25k spacing.... no control channel. tries all the frequencies from all sites and in 6.25k spacing.
Yes, this is a linked capacity plus system (Con+), but I thought all Con+ systems use a control channel?

 

[Voyager]

Yes, this is a linked capacity plus system (Con+), but I thought all Con+ systems use a control channel?

Linked Capacity Plus (Cap+) is not the same as Connect Plus (Con+).

And yes, Connect Plus systems use a constant control channel.

 

[EricCottrell]

Hello,

I have seen Con+ systems that are a mixture of licensed and auctioned (old paging/radiotelephone frequencies). If it is UHF, then it could be a mixture of UHF, UHF auctioned, and UHF T Band.

The reason could be that control channels are considered a constant transmission, so need a more exclusive frequency allocation.

73 Eric

 

[vince48]

Thanks Eric. what would be your suggestion to find the control channel(s)?

 

[Voyager]

Search the band using whatever device you are using to receive. Look for one with the same System ID if you're using something that shows that.

Keep in mind if it's Linked Capacity Plus you will not find a constant data control channel.

 

[EricCottrell]

Hello,

Usually finding the voice frequencies or Cap+ frequencies are the problem since they are not continuous.

I search the band looking for signals. It is easier with a spectrum display, but I have done it using the search function on regular receivers.

UHF in Boston and some other Metro areas are harder since 450 to 455 MHz, 460 to 465 MHz, and the first 3 MHz of the T band allocations have to be search. I have to search 470 to 473 and 482 to 485 MHz in Boston. I usually search each segment separately.

If the system is UHF, I would search 454 to 455 first as that is a block of auctioned frequencies.

73 Eric

 

[vince48]

Ok, Thanks Eric and Voyager

vince48

 

[Voyager]

One thing I like to do every so often is scan the band looking for digital signals. I note the Color code, System/Site ID, and TG. That makes it much easier to later on review a system for additional channels.

 

[vince48]

I tried that also, but I was using the frequencies from RR database form my area. the frequencies according to RR are " confirmed "

 

[SCPD]

One thing I like to do every so often is scan the band looking for digital signals. I note the Color code, System/Site ID, and TG. That makes it much easier to later on review a system for additional channels.

Also scan the old federal UHF frequencies... there's some interesting DMR there...

 

[vince48]

ok nickcarr, will try that also. I ended up scanning the frequencies from RR database, seem to work. But this system is a mixed Cap+ and Con+

 

[Voyager]

But this system is a mixed Cap+ and Con+

No such animal unless they are linked externally.

What makes you think it's a Con+ at all?

Currently, there are four Motorola MotoTRBO system types:

1. Conventional
2. Connect Plus
3. Capacity Plus (single site)
4. Linked Capacity Plus (multi-site)

 

[vince48]

No such animal unless they are linked externally.

What makes you think it's a Con+ at all?

Currently, there are four Motorola MotoTRBO system types:

1. Conventional
2. Connect Plus
3. Capacity Plus (single site)
4. Linked Capacity Plus (multi-site)

because DSD+ VC event log says some frequencies are Con+ and some are Cap+

 

[RayAir]

because DSD+ VC event log says some frequencies are Con+ and some are Cap+

You're probably receiving a Con+ channel and an area Cap+ might be using the freq too.

I ran into that once when trying to monitor a Cap+ rest channel and a Con+ was overriding it with data bursts.

 

[natedawg1604]

After messing around with all these DMR-related protocols for a while via DSD+, I've come to appreciate the P-25 protocol an awful lot more. The explicit & continuous messages makes it trivial to determine (with 100% certainly) what system/site a particular frequency belongs to. Even when a frequency is used in multiple sites spread some distance apart, you can always tell which site you are monitoring based on the WACN, NAC, System ID and so forth. IMO this was a great design concept, one would have thought it would have been used in more protocols...

 

[vince48]

You're probably receiving a Con+ channel and an area Cap+ might be using the freq too.

I ran into that once when trying to monitor a Cap+ rest channel and a Con+ was overriding it with data bursts.

RayAir

I think you are correct. thanks for the insight.

vince48

 

[Voyager]

You're probably receiving a Con+ channel and an area Cap+ might be using the freq too.

I ran into that once when trying to monitor a Cap+ rest channel and a Con+ was overriding it with data bursts.

I've seen the same. And sometimes the format type simply does not change in DSD+. I usually stop and restart it to make sure the info is not 'cached'.

WRT the frequencies in question, are they the same System ID?

Also "fun" when you have 3 or 4 DMR systems on the same frequency.