Mixed Mode Operation

[Rlahey]

Can someone explain to me in how mixed mode works? I understand the concept, transmit on analog or P25 and the repeater will take in either signal modulation... but on the transmit side of the repeater, how does it simultaneously transmit analog and P25, so either user can hear the transmission?

 

[GTR8000]

but on the transmit side of the repeater, how does it simultaneously transmit analog and P25, so either user can hear the transmission?

Simple...it doesn't. One or the other. Whichever modulation comes in is what goes out.

 

[mrsvensven]

You can use it a few different ways depending on how the depending on how the radios are programmed.

I know of a town that wanted to take advantage of the better range of p25 but wasn't quite used to the digital sound, so they programmed all their portable radios to receive mixed mode and transmit in digital. Their dispatcher and mobile radios were programmed to transmit analog and receive mixed mide. So everyone could hear each other, but one conversation could be half digital and half analog. This department eventually switched to all digital.

You can so program one group of users to transmit and receive analog only, and a second group to digital only. This way you can have two different groups sharing one repeater and they can't hear each other. The problem is that they will still "walk on" each other if the two groups try to talk at the same time.

Some sales people will tell you that if you are a long-time analog user switching to P25 that you can use mixed mode to keep the ability to talk to your neighbors who have analog-only radios. This sounds good on paper but never actually works. You will end up with the analog-only user calling you and you hear them and respond back in P25, but they can't hear your p25 and there will just be confusion.

 

[PACNWDude]

Great explanation above. I inherited a system that was as described above and eventually converted everything to digital only. Many end users thought I was a "miracle worker" as the audio was considerably better in digital mode. I have this same problem for many Trbo sites where an analog channel is used to pass MDC ID's, and end users complain that that one channel always sounds worse than the others. On Trbo Motorola equipment, this was even a licensed option, and people paid for it, based on sales people pushing the advantages, which are more like a nightmare for those administering the system.

 

[ecps92]

first one in, is the first/same one out

Simple...it doesn't. One or the other. Whichever modulation comes in is what goes out.