Two voice paths in a 25 kHz channel

[12Kbps]

Hello All, Please post your thoughts and opinions on this thought. In order to comply with the upcoming equivalent efficiency requirement one must have two voice paths in a 25 kHz channel. Also for data 19.2 kbps per 25 kHz channel. The rules pertain to efficiency NOT bandwidth. Does anyone know of either multiplexing two astro streams over a 25 kHz channel (9600 bps X 2= 19.2 kbps) or a vocoder/box to achieve two voice paths in a 25 kHz channel? Thanks in advance.

[FMROB]

I think that only transmitters and/or protocol in the 6.25 khz will allow you to do this. I don't believe astro is at that level yet, only 12.5 khz. I don't believe that you can make two 12.5 channels out of a 25 channel, the centers are off, and you will have interference issues with adjacent channel. I might be wrong, - Rob

[tvsjr]

The current narrowbanding requirements are 12.5KHz per talk path, which ASTRO will do as will standard 2.5KHz deviation analog. If you're talking about the as yet undated plan to go to 2 talk paths per 12.5KHz, you can do this with TRBO (2-slot TDMA), NexEdge/NXDN/IDAS (FDMA, 6.25KHz talk path), or P25 Phase 2/ASTRO25 X2.

Could you clarify your question a bit?

[12Kbps]

It seems to me after looking around and reading between the lines one MAY be allowed a 25khz wide channel as long as one meets equivalent efficiency requirements, meaning two voice paths in a 25khz channel.The mandate dictates efficiency NOT bandwidth. For example using a wideband digital emission designator and running two voice channels within the digital stream thus technically meeting equivalent efficiency requirements. Then again I may be wrong.

[escomm]

If I understand what you're saying, sounds like you're correct. Tetra meets narrowband equivalency requirements even though it's a 25KHz carrier. Tetra flies because you get 4 paths in that 25KHz carrier, i.e. 6.25KHz equivalency

[tvsjr]

Correct, it's all about efficiency.

The 1/1/2013 narrowbanding mandate is 1 voice path per 12.5KHz. Single-path 12.5KHz (narrowband analog, P25 Phase 1, etc.) or 2-path 25KHz meets the spec.

The next narrowbanding mandate, whenever it might be scheduled, is 1 voice path per 6.25KHz. Single-path 6.25KHz (NXDN/IDAS), Two-path 12.5KHz, four-path 25KHz (OpenSky, supposedly) all meets the spec.

[12Kbps]

Now onto my next thought. If one were to take a securenet equipped msf5000 (25khz wide) and come up with a way to "tunnel" two voice paths WITHIN the securenet stream, would that technically meet the equivalent efficiency requirement?

[tvsjr]

I don't know. The better question is - why? This will require custom infrastructure and custom subscriber units, with zero support. Upgrade to TRBO or P25 and call it a day.

[desperado]

Not to mention that if it's not off the shelf, it's not going to be type accepted and therefor non-compliant.
Look at the emission designators and see if there is even one that applies t what you are doing. Again, if there is nothing to file on the license paperwork, the license will get canceled Jan 1, 2013