NXU-2B Operations Manual
8-5
Interoperability Now!
Can I change the vocoder on the NXU-2B?
Yes. This is the voice compression method used to convert the audio signal into a digital format.
There are times when the user may want or need higher voice quality or transparency to certain
kinds of signaling tones. The VOCODER (Voice Compression) command allows the selection
of different vocoders, albeit at the expense of network bandwidth.
Can I pass modem tones over the voice port of the NXU-2B?
Some types of modem tones (such as FSK) will work if you select one of the higher bit rate
vocoders, such as VOCODER 4 or VOCODER 5. Complex modem waveforms (such as 56K
modem data) will not pass no matter what vocoder is selected. Pilot tone, keying tones, and other
similar signaling tones will work properly with the 24, 32, and 64 Kbps vocoders.
In general data should be sent via the RS-232 port.
I've connected my radio to the NXU-2B, I have the levels turned all the way up, and can still
barely hear the audio. What's wrong?
The NXU-2B uses balanced audio on the input. If, instead of connecting to both balanced input
lines, you connect your audio to one audio input and ground, you'll get the effect described above.
There is enough leakage in the transformer to get some audio through, but it won't work properly.
The solution is to ground one side of the NXU-2B balanced input.
I've connected my radio to the NXU-2B, and it works, but the audio sounds very "tinny" and
doesn't have much bass.
Make sure you haven't used the discriminator output, which is sometimes available on FM
receivers and transceivers. Discriminator audio is pre-emphasized, and there is no de-emphasis
circuitry in the NXU-2B. You'll need to use your regular audio output instead.
I've connected the NXU-2B to my computer serial port as described in Section 0 of the NXU-
2B manual, but I can't put the NXU-2B into Command Mode as described in 3.4.1. What do
I do now?
First, you need to make sure that you have the flow control set to 'None' in the serial port
configuration menu of your terminal program. Second, you must follow the instructions in
Section 3.4.1 exactly. Wait 10 seconds and then type three plus signs +++ and nothing else. If
you type more than three plus signs the procedure won't work. Wait a few seconds and try again.
In addition, the three plus signs must be typed within a one second period in order to be
recognized.
I've configured my terminal program and followed the procedure exactly, and I still can't get
the 'OK' prompt telling me that the NXU-2B is in Command Mode. Now what?
If the NXU-2B has been configured previously and the baud rate was changed to something other
than the factory default of 9600 then you'll need to set your terminal program to use the new baud
rate in order to enter the Command Mode.
Summary of Contents for NXU-2B
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