NXU-2B Operations Manual
6-3
Interoperability Now!
listening to transmissions from the NXU-2B/donor radio) increase the TX delay of NXU-2B
analog interface connected to that donor radio.
Explanation: When a radio user initiates a transmit sequence for a trunked radio, that user
depresses the PTT switch on the radio, which sends a signal to the system’s trunking controller,
asking to be assigned to a free (not currently busy) channel. The trunking controller sends a signal
back to the user’s radio that automatically sets the radio to a free channel, and signals this to the
radio user by tone called a
channel acquisition tone
or simply a
go-ahead
tone. The trunked
system radio user is trained to not begin talking until this tone is heard.
RX Audio Delay must be increased if initial syllables are clipped on incoming audio of a Radio
Channel; see below. If you are using a cross-connected radio channel and additional increases in
TX Audio Delay have no effect on missed first syllables in the field radio, then it may be
necessary to increase the RX Audio Delay in that cross-connected Radio Channel. An uncommon
but possible condition.
6.1.5
RX Audio Delay
Delay in the RX audio occurs by processing the COR detection immediately but holding the
incoming audio in a buffer and spooling it out after the set delay time. This resolves the
(uncommon) condition for a Radio Channel where the COR indication or detection occurs late
and initial incoming syllables are therefore clipped.
The NXU-2B is designed to prevent this as well as practical, through proper design of the various
COR Detection algorithms and by including a minimum RX Audio Delay for VOX & VMR
modes, but additional delay can be added if needed.
6.2
Radio Interface Using Customer-Designed Radio Cables
For customers who plan to create their own radio interface cables, JPS strongly recommends
using the Unterminated Radio Cable, JPS P/N 5961-291115. This shielded cable includes the
D15 end of the cable that plugs directly into the NXU-2B rear analog port, along with the small
PCB found in other JPS cables – this circuitry has a variety of variable attenuating, terminating
and DC-blocking components; essentially everything that JPS Systems Engineers have deemed
necessary to interface any of the several hundred types of radios they have created custom cables
for. This seven-pin cable is unterminated on the radio side, allowing radio specific portion of the
he Application Notes for this cable, like all other JPS Custom Radio Cables Application Notes,
contains information to help in the cable design and, in particular, explains how to determine
which of the various configuration options is best (e.g. how to decide how to choose between the
COR options of VOX, VMR, or Hardware COR).
Note: Older versions of the Unterminated Radio Cable Application Notes relate to its
use with the ACU-1000 or ACU-T gateways. All relevant information applies also to
the NXU-2B.
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