DMR vs P25

[hill]

FDMA is 2 talkpaths, literally right beside each other, with virtually no separation, right?

No that is TDMA

 

[RRR]

Negative..
Frequency Division is dividing the frequency in half, using one half of the frequency for the voice.
TDMA is using the entire width of the frequency, but alternating it back and forth, IE; Time division.
I ask again, is there any real use of dividing a frequency via FDMA, and successfully using both halves at once, for voice, like TDMA does? Or can data be used on the other "half" of the width?
If so, how would you even program that on KPG111 or D1N?

 

[slicerwizard]

While all this technical stuff is interesting to me and others here, an example of real life DMR unacceptable performance in my area is interesting.
The county sheriff agency converted to DMR awhile back and the had nothing but trouble with voice clarity and range. The radio techs worked on it for months but the sheriff had so many complaints from staff and examples of public safety being compromised that he ordered everything back to analog and it remains there today.

Had a local shop manage to put up a DMR system with the RX filters swapped between channels (filter A on channel B, filter B on channel A). RX sensitivity was down by something like 30+ dB. Symptoms exactly as you describe above.

Techs swore for weeks that everything was set up properly and "That's just how DMR works."

Finally took a demo of a portable DMR radio at the base of the tower (which was on decent high ground) working another portable on simplex at at least two to three times the system's pitiful range to light fires under everyone's butts.

Good times.

 

[slicerwizard]

Negative..
Frequency Division is dividing the frequency in half, using one half of the frequency for the voice.
TDMA is using the entire width of the frequency, but alternating it back and forth, IE; Time division.
I ask again, is there any real use of dividing a frequency via FDMA, and successfully using both halves at once, for voice, like TDMA does? Or can data be used on the other "half" of the width?
If so, how would you even program that on KPG111 or D1N?

Negative. FDMA is using separate RF carriers for separate information streams, such as voice calls.

TDMA is using a single RF carrier to transmit two or more information streams.

FDMA has nothing to do with "dividing a frequency".

 

[nd5y]

FDMA is 2 talkpaths, literally right beside each other, with virtually no separation, right?

No. It only means each talk path is on a different RF channel.

 

[nd5y]

No that is TDMA

No. TDMA is mutiple talk paths on the same RF channel on different time slots.