NXU-2B Operations Manual
6-2
Note: If replacing an NXU-2A with a new NXU-2B, remove the audio crossover
adapter at the rear panel AUDIO/CONTROL connector (assuming one is being used).
This adapter is not needed when using a JPS Radio Interface Cable with an NXU-2B;
the unit will not function properly with it.
6.1.1
RX Audio Input Level
Some minor adjustment may be required, mainly due to radio-to-
radio variations. A way to
make sure the level is adjusted properly is to:
•
Use a companion radio to communicate with the donor radio, speaking into the
microphone in a voice level consistent with standard usage. The Audio Input LED should
flash with voice peaks. Adjust if it never or constantly flashes.
•
Note: The RX (receive) input level values on the NXU-2B Configuration page indicate
the actual level of audio being received. If the incoming level is -12 dBm, the Receive
Input Level should be set to -12dB. This must be understood to know which way to
change the audio level for proper operation. If the NXU-2B, when set to -12 dB, is not
receiving enough audio, the value must be set to a lower number to correspond to the
actual input level. The NXU-2B will then apply additional gain/reduced attenuation.
6.1.2
TX Audio Output Level
The TX (transmit) output level should be set to properly modulate the donor radio transmitter.
Audio coming from the donor radio, when doing a normal voice volume radio count, should be
heard in the companion radio at the same level as received conversations from other radios in the
system (as heard in the companion radio).
Note: Doing the RX level adjustment before setting the TX audio level and verifying it will help
prevent a mutually erroneous condition where a too-low RX audio input is compensated by a
too-high TX audio input on a cross-connected channel. This condition is worsened whenever a
third interface is introduced to the system – its incoming audio will be too low for one of the
mutually-erroneous interfaces and too high for the other.
6.1.3
VOX/VMR Sensitivity
The VOX threshold may benefit from optimization (either more or less sensitive) due to system
variations or user preferences. More sensitive means less audio level must be detected for the
incoming audio to be declared valid. Less sensitive is of course the opposite. Increased sensitivity
makes it more likely that falsing (declaring the input valid when it is not) will occur; decreased
sensitivity increases the potential that valid speech may be missed. Changes may be desired due
to level of static on the channel, quiet talkers, or desire to never miss any audio, even if some
falsing occurs.
6.1.4
TX Audio Delay
If the donor radio is used with a trunked radio system, it may be necessary to adjust the TX
(transmit) Audio Delay. If initial syllables are missing in the RX audio of the field radio (when
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