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Section 16
ASTRO OPTION DESCRIPTION
16-1 INTRODUCTION
The ASTRO Option extends the standard functions
of the R2670 to provide an all-in-one servicing
instrument for ASTRO digital radio systems.
16-2 BASIC OPERATION
The R2670 with ASTRO Option can emulate the
same digital environment used by ASTRO radios in
private mode. This capability allows the analyzer to
interoperate with conventional ASTRO radios.
Standard test equipment is unable to decipher
private audio transmissions from ASTRO radios
because the audio signals are converted from their
native analog format to a digital, ciphered
representation prior to transmission.
An ASTRO digital radio provides for both clear
and privacy voice and data. When operated in
privacy mode, the radio scrambles communications
prior to their transmission. Only intended
subscribers, with compatible hardware plus
matching security keys, can decipher the message.
In this way, users of a system can be partitioned
into groups, each with their own security key. The
R2670 with ASTRO Option will accept an external
operating key from any compatible key loader.
In its ASTRO mode, the R2670 provides display
screens for monitoring bit error rate characteristics
of a radio under test and also generates bit error rate
test patterns to support this mode of operation.
The R2670 with ASTRO Option, provides a clear
scope display of baseband signals, either the input
to the vocoder (generate mode) or the output from
the vocoder (monitor mode).
16-3 TEST CONSIDERATIONS
ASTRO digital radio systems encrypted
communications have a need to maintain even
higher standards on RF signal quality than normal
FM radio systems. Encryption subjects the ASTRO
signals to additional processing. In order to work
reliably, the radios must be tuned to preserve
critical factors such as operating frequency
response and transmitter deviation. Individual test
meters and generators compound the effects of
multiple RF paths and wirelines in the test
environment, resulting in degraded signals and less
accurate measurements.
Operating in secure or standard mode, the R2670
with ASTRO Option bundles a wide assortment of
sophisticated test features in a single instrument.
16-4 SPECIAL TERMS
The following list contains brief definitions of
special terms that are used in association with
ASTRO radios and test equipment:
Algorithm - In secure systems, an algorithm is a
distinct method for translating clear information
(input) to a secure version of the information
(output). The same algorithm is used to interpret
the message. ASTRO systems use the following
algorithms:
DVP-XL
DES-XL
DVI-XL
BER Test - In generate mode, the analyzer
modulates the RF carrier with Bit Error Rate test
pattern to test the radio receiver. This BER test
pattern consists of a free running, unframed
pseudo-random bit pattern. In monitor mode, the
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