Reason for using 9600 NXDN

[phillmobile]

Hi guys i have looked through many pages here and the internet but i find no technical explanation as to why i would use narrow/9600 if the voice part is still only 4800 within that, is it so that if your sending lots of data like images its faster, Kenwood always seem to be exceptionally vague on the technical things and leave you to figure it out, for example you cant find anywhere the default speed that the gps mic should be set at and had to try various ones and guess.

Cheers
phillmobile

 

[kd4efm]

(1) 9600 is 12.5 bw, 4800 baud is 6.25. (2) GPS serial speed is 4800 AFAIK. Two things in one question. So let's tackle issue one. I am guessing you need to choose narrow, or very narrow. (2) Your other item is GPS. My question to you is, what kenwood radio model. Then we can talk more on the GPS.

kd4efm Evans, sent using TapTALK on my HTC M9

 

[phillmobile]

dont worry about the gps i was just ranting, i was just looking for some information from the experts re what 9600 can do for me that 4800 cant before i deploy a nxdn system for a customer.

 

[mmckenna]

From the NexEdge system planner:

4.1.2 12.5 kHz versus 6.25 kHz?
Some considerations to choose 12.5 kHz (narrow) over 6.25 kHz (very narrow) for the application.

12.5 kHz (narrow) is the preferred mode when the customer requires data applications to work over the radio network,
since the 12.5 kHz mode offers a higher data bandwidth than 6.25 kHz. The over-the-air data rate in 12.5 kHz is 9600 bps,
with a net data rate available for transparent data transmission to be about 3700 bps.

6.25 kHz provides better sensitivity by about 3 dB, which means an increase in coverage.

6.25 kHz over-the-air data rate is 4800 bps, with the net data rate for transparent data transmission is about 1850 bps.The

6.25 kHz bandwidth offers better range and better interference resilience compared to 12.5 kHz.

However, if 6.25 kHz (very narrow) is required on trunking operation, the optional KXK-3 is required, one unit per site, to
guarantee long term frequency stability, synchronize the Control Channel and Traffic Channel frequencies.
The decision whether to use narrow or very narrow bandwidth operation has to be taken system wide. It is not possible to mix 12.5 kHz and 6.25 kHz modes in one system.

 

[slicerwizard]

i was just looking for some information from the experts re what 9600 can do for me that 4800 cant before i deploy a nxdn system for a customer.

If your customer doesn't need the data speed, do them a favour and go with 4800 - I'm sure they'll enjoy the extra range/reliability.

 

[EricCottrell]

Hello,

The NXDN specification also has the option of a higher rate codec with NXDN9600 (12.5KHz). The NXDN9600 systems around here use the regular codec and insert idle frames between the voice frames. I suppose the system could be setup so small amounts of data, like gps positions, could be sent in place of the idle frames.

73 Eric

 

[mmckenna]

Hello,

The NXDN specification also has the option of a higher rate codec with NXDN9600 (12.5KHz). The NXDN9600 systems around here use the regular codec and insert idle frames between the voice frames. I suppose the system could be setup so small amounts of data, like gps positions, could be sent in place of the idle frames.

73 Eric

That's how the NexEdge systems do it. I've got GPS on a few of our radios and it'll stick it right in with the voice traffic.

 

[phillmobile]

Thanks guys, 6.25 it is then, just got to figure out how to get the darned thing to send the gps at the end of transmission not the begining so i dont get 2 seconds of no audio every time they key up.

Phill

 

[kd4efm]

GPS and voice are in the same stream, if your losing voice, they are not waiting for the go ahead.... in trunking not an issue, conventional you can set it up for key up chirp, then talk.

kd4efm Evans, sent using TapTALK on my HTC M9