SDS100/SDS200: Missing DMRT3 Transmissions

[dazza0768]

I've noticed my SDS100 has been missing Tier 3 transmissions when I'm scanning a T3 system alongside others.

I am scanning a few OFT systems, 2 CAP+ systems and the said DMRT3 system.

When scanning all of them it will pick up the OFT and CAP+ alright but it will only pickup on the T3 system at the very start of a transmission, not halfway through which is making it miss ALOT.

I have only noticed this when I turned a 2nd scanner on the T3 system.

The SDS100 does hear all transmissions when held on the T3 systems. Only misses them when scanning and its going on and off the system.

Does T3 have some sort of activation data at the start of transmissions which opens squelch?

 

[enosjones]

So idk if u have dsdplus or not but , we have been struggling with the dmr tier 3 systems when it comes to uniden. We have found that if we cut the LCNs in half it seems to do better on the unidens, for example if one lcn is 500 u put in 250 as the lcn for the uniden for that same channel. It seems to accept it and do somewhat better..it also eliminates the 2 frequency lcn , for example 857.5625 lcn 500 and 857.5625 lcn 501 if u do 250 as the lcn it covers both, therefore it doesn't miss as many transmissions

 

[dazza0768]

So idk if u have dsdplus or not but , we have been struggling with the dmr tier 3 systems when it comes to uniden. We have found that if we cut the LCNs in half it seems to do better on the unidens, for example if one lcn is 500 u put in 250 as the lcn for the uniden for that same channel. It seems to accept it and do somewhat better..it also eliminates the 2 frequency lcn , for example 857.5625 lcn 500 and 857.5625 lcn 501 if u do 250 as the lcn it covers both, therefore it doesn't miss as many transmissions

Ah righto. Fortunately I live in a country that has a full government database of frequencies and their LCNs listed online so I have them on tap so I dont have that problem.

Bare in mind I missed some details out, we have T3 in many different areas of the radio spectrum and im specifically listening to a frequency near 164.mhz.

The site I am listening to is also roughly 70miles as the crow flies from me but I am using a mast amp. I have an RSSI of 50 and 0 digital error.


I have just adjusted the system hold time to 2 seconds which has actually helped, it now stops on more transmissions but with waiting on site for 2 seconds it does slow the scan down and now I'm missing more on other sites.

 

[Ubbe]

I have an RSSI of 50 and 0 digital error.
I have just adjusted the system hold time to 2 seconds which has actually helped

If you use 3 sec or even 4 sec it will work even better. As enosjones mentions Uniden struggles with DT3. As I remember it used to work fine until Uniden added a feature, I believe it was RAS, and after that it has been a hit or miss if it detects a call or not from the control channel datastream. I hope they can fix that in coming firmware upgrades.

/Ubbe

 

[dazza0768]

If you use 3 sec or even 4 sec it will work even better. As enosjones mentions Uniden struggles with DT3. As I remember it used to work fine until Uniden added a feature, I believe it was RAS, and after that it has been a hit or miss if it detects a call or not from the control channel datastream. I hope they can fix that in coming firmware upgrades.

/Ubbe

Cheers. It picks up all calls now with 2 seconds.

What is RAS?

As for firmware, I have a USDS model and we haven't seen an update since forever.
I've never seen one in my ownership atleast.

 

[slicerwizard]

Does T3 have some sort of activation data at the start of transmissions which opens squelch?

All trunking system control channels send channel grant messages at the start of voice calls. Radios and scanners use those messages to tune to the voice channels.

Trunking systems also periodically send late entry messages during voice calls; radios and scanners that missed the channel grant messages use these late entry messages to belatedly tune to the voice channels. However, on many TIII systems, those late entry messages are sent much less frequently than they are on Cap+/Con+/NEXEDGE/P25 control channels, making it easy for a scanning receiver to miss them. Extending the dwell/hold time on a TIII system makes it far more likely that late entry messages will be seen while scanning multiple systems.

 

[ka3jjz]

If you use 3 sec or even 4 sec it will work even better. As enosjones mentions Uniden struggles with DT3. As I remember it used to work fine until Uniden added a feature, I believe it was RAS, and after that it has been a hit or miss if it detects a call or not from the control channel datastream. I hope they can fix that in coming firmware upgrades.

/Ubbe

A very useful tip, one that I will add to the wiki for future reference

Mike

 

[Rahmengo]

Ah righto. Fortunately I live in a country that has a full government database of frequencies and their LCNs listed online so I have them on tap so I dont have that problem.

Hi dazza - are you in Australia? If so, is that government database the ACMA register? If so, I wasn't aware it included the LCNs.

 

[Ubbe]

However, on many TIII systems, those late entry messages are sent much less frequently than they are on Cap+/Con+/NEXEDGE/P25 control channels

I think I looked at a Hytera program instruction and the default time to periodically send out late entry TG info where 10 sec. Then you'll really appreciate a Whistler scanner doing its voice channel trunking.

/Ubbe

 

[dazza0768]

Hi dazza - are you in Australia? If so, is that government database the ACMA register? If so, I wasn't aware it included the LCNs.

Not quite. I'm in New Zealand.
We have an online database called RSM (Radio Spectrum Management) and the channel numbers of the frequencies in the database are actually the LCNs for all Tier 3. It does not work for any other modes that I know of.

Perhaps the Ozzy ones have channel numbers which might also be the LCNs?

 

[JoeBearcat]

Something to remember: There are Logical Channel Numbers (LCNs) and Logical Slot Numbers (LSNs).

They are not interchangeable.

If the list includes duplicate frequency entries, you are probably looking at a LSN list. LCNs only list the same frequency once (unless a system is for some reason using the same frequency twice).

IOW: If you see this:
LCN 1 851.0125
LCN 2 851.0125
LCN 3 852.7375
LCN 4 852.7375

... then you are looking at a list of slot numbers despite the "LCN" tag. To convert LSN to LCN, divide by two and round up if it ends in .5.

Not everyone uses the same terms the same way.

 

[dazza0768]

Something to remember: There are Logical Channel Numbers (LCNs) and Logical Slot Numbers (LSNs).

They are not interchangeable.

If the list includes duplicate frequency entries, you are probably looking at a LSN list. LCNs only list the same frequency once (unless a system is for some reason using the same frequency twice).

IOW: If you see this:
LCN 1 851.0125
LCN 2 851.0125
LCN 3 852.7375
LCN 4 852.7375

... then you are looking at a list of slot numbers despite the "LCN" tag. To convert LSN to LCN, divide by two and round up if it ends in .5.

Not everyone uses the same terms the same way.

Its ok, I know the difference but thanks anyway.

We have both LCNs and LSNs listed.