Interferance between two Digital channels on different Time Slots

[salarazad]

Hi everyone,

We have upgraded lately our repeater (SLR5500) from Analog to Digital and now we are on DMM mode and using two Digital channels on this repeater by using different time slots (1 & 2), but with the same color code.

Now the users are complaining that sometimes an interference is occurring between the two channels, so they claim that one of the groups is listening to the other channel on the other time slot of the same repeater, is this possible to happen in such a case?

We have been using the DMM mode for almost two months, so could this also be an issue? since DMM mode is mostly used during the transition period.


My question simply, could interference happen between two digital channels on same repeater (same frequency), with same color code and different time slots; especially that we are using the DMM mode?

Many Thanks
Salar

 

[hill]

Don't you mean DMR and not DMM, as you stated a few times in your post.

 

[KR3LC]

Perhaps they are using the digital equivalent to analog open squelch. Some DMR radios call it promiscuous mode. In this mode they will hear all traffic on a frequency independent of color code or time slot.

 

[IAmSixNine]

As @KR3LC eludes to i would bet there is something in the programming of the talk group or personality that is not set correctly. Have the radio shop that did the conversion (analog to digital) come back out and fix it.

 

[jonwienke]

It's far more likely that the subscriber radios are set to listen to both slots versus the repeater crossing traffic between slots.

 

[mikewazowski]

Don't you mean DMR and not DMM, as you stated a few times in your post.

Dynamic Mixed Mode. Let’s the repeater do analog and digital.

 

[salarazad]

As @KR3LC eludes to i would bet there is something in the programming of the talk group or personality that is not set correctly. Have the radio shop that did the conversion (analog to digital) come back out and fix it.

Actually we did the programming, and we didn't set any group talks, so in the channels configuration the RX list is set to 'None'; could this be the problem?

 

[salarazad]

Don't you mean DMR and not DMM, as you stated a few times in your post.

As mikewazowski mentioned, it is Dynamic Mixed Mode, which lets the repeater to operate on both Analog and Digital at the same time.

 

[jonwienke]

Actually we did the programming, and we didn't set any group talks, so in the channels configuration the RX list is set to 'None'; could this be the problem?

Yes. You need to specify a talkgroup and a slot for TX and RX, or the radio will will wnt to RX anything it hears.

 

[salarazad]

Perhaps they are using the digital equivalent to analog open squelch. Some DMR radios call it promiscuous mode. In this mode they will hear all traffic on a frequency independent of color code or time slot.

I've read about the promiscuous mode and this feature is only available on non commercial radios, but we are using professional commercial radios so this should not be possible on them right?

 

[jonwienke]

If you don't explicitly set a RX slot, it either won't work, or will RX either slot.

 

[salarazad]

Yes. You need to specify a talkgroup and a slot for TX and RX, or the radio will will wnt to RX anything it hears.

We have set the time slots (1 for first channel, and 2 for second channel), but we didn't set a specific talk group, so the talk group option in the channel configuration is set to NONE; could this create a problem? or the time slots should be enough to prevent them from hearing each other?

 

[jonwienke]

Explicitly stating the talkgroup and slot is always better IMO, unless hearing traffic on either slot is something you want..

 

[KK6ZTE]

Explicitly stating the talkgroup and slot is always better IMO, unless hearing traffic on either slot is something you want..

Motorola radios will require you to specify a talkgroup "TX Contact" in order for the radio to work. It's also the only contact the radio listens for--it's not like it goes into carrier squelch.

OP:

I've heard of radios slipping timeslots if there's another repeater on frequency.

Can you narrow down the user complaints?

 

[mikewazowski]

Explicitly stating the talkgroup and slot is always better IMO, unless hearing traffic on either slot is something you want..

Motorola radios can’t be programmed without a slot or group.

 

[jonwienke]

The repeater was specified as Motorola, but I don't see where the same is said of the subscriber units. The mention that the TX contact wasn't programmed might indicate otherwise?

 

[buddrousa]

This is why Commercial Radio was never ment to be DO IT YOURSELF you have to have training and service tools to set up radios properly.

 

[salarazad]

Motorola radios will require you to specify a talkgroup "TX Contact" in order for the radio to work. It's also the only contact the radio listens for--it's not like it goes into carrier squelch.

OP:

I've heard of radios slipping timeslots if there's another repeater on frequency.

Can you narrow down the user complaints?

The user complaint is that it is happening sometimes and not all the time and I also been testing it and not facing any overlap between the two channels, even so we haven't set Talk Groups at the RX side. So it is probable that this interference is happening at some special case, location or time.

 

[clbsquared]

Is the analog side of the repeater still active? Analog radios will here interference from the digital side. Just a guess

 

[mikewazowski]

The user complaint is that it is happening sometimes and not all the time and I also been testing it and not facing any overlap between the two channels, even so we haven't set Talk Groups at the RX side. So it is probable that this interference is happening at some special case, location or time.

What make and model of portable radios are you using?