I think I know the answer to this question but is it possible to have 2 Kenwood NX Portables programmed on a simplex channel but also be NXDN Digital quality without going through a Nexedge repeater?
Yes.
NXDN will run in simplex mode just fine. I'm using it on 350+ Kenwood NX-410 and NX-900's at work.
You don't need a repeater to run NXDN.
Kenwood NexEdge, their version of NXDN comes in two flavors:
NXDN Narrow which uses a 12.5KHz channel and does just under 9600 baud data rate.
NXDN Very Narrow which uses 6.25KHz channel and does just under 4800 baud data rate.
Either one will work just fine for what you want. NXDN narrow works a bit better if you are running data across your radio as there is more throughput. NXDN Very Narrow might give you a bit more range.
---very important----
NXDN Narrow and NXDN Very Narrow are NOT compatible, you -must- have the radios set to one or the other. Having them set differently will result in them not decoding each others transmissions.
You don't need to set a RAN code. You can leave it set at zero, which is equivalent to having carrier squelch on an analog channel.
You can also set the "Channel Type" to "mixed" mode, which will allow it to receive analog and NXDN mode. TX mode is whatever you set it to, either NXDN or Analog. You'll still be able to choose Narrow for your analog side and have the choice of Narrow or Very Narrow on the NXDN side. Might be useful to set it up this way so you can still hear analog calls.
Setting up the audio equalizer under the NXDN window "General 2" tab can help the audio quality quite a bit.
-Set the "Function type" to Enhanced. The settings you need will be based on your preference, but there are some good guidelines I can provide if you'd like.
For a "Quiet" environment:
RX Low Cut = unchecked
RX Auto Gain = Off
RX Audio Equalizer = flat
RX Noise Suppressor = checked
TX Auto Gain = On
TX Audio Equalizer = Flat
TX Mic Sense 0dB
Don't pass judgement on the audio quality until you've made sure it's set up right. If it's set up wrong for your environment, it can really sound crappy. Setting it up correctly will give you really good audio.
As for the licensing/emission designation, you do need to get that correct on your FCC license. The NXDN narrow and NXDN Very Narrow will fall inside the normal narrow band analog/FM envelope that you are probably licensed for, so it's unlikely you'd cause any issues to others. You do need to make sure you are not going to annoy others. Another analog radio user will get very tired of having to listen to the digital noise on their radio. It would make you very unpopular.
Let me know if you have any other questions. I've set up hundreds of these radios and have been really happy with the performance.