Alien Technology ALR-8780, Interface Manual

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C
HAPTER
4 A
LIEN
R
EADER
P
ROTOCOL
R
EADER
I
NTERFACE
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UIDE
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ONTROL
# 8101938-000 R
EV
05
39
the antenna number specified in the AntennaSequence is always the
transmit antenna. The receive antenna is taken to be the remaining
antenna of the pair.
The ALR-9770 reader recognizes only those antennas that are present
when the reader boots up. If the antenna configuration is changed, the
ALR-9770 must be restarted before it will be aware of the new
configuration.
AntennaSequence Examples
Command
Response >get AntennaSequence
AntennaSequence = 0
To always use antenna 1:
Command
Response
>set AntennaSequence = 1
AntennaSequence = 1
To cycle between
antenna 0 and antenna 1:
Command
Response
>set AntennaSequence = 0, 1
AntennaSequence = 0, 1
To weight antenna 0 more
than antenna 1:
Command
Response
>set AntennaSequence = 0, 0, 0, 1
AntennaSequence = 0, 0, 0, 1
RFAttenuation
9800 | 9780 | 8780 | 9640 | 9774
Alien RFID readers output 1 watt of RF power at each antenna. While this power
is sufficient to provide good penetration and range, these attributes are not
always desireable. If multiple readers are in the same vicinity, their signals may
interfere with each other. Also, in situations where tagged product is close
together, but only on product should be read at a time (a conveyor belt, for
example), then penetrating power and long range are your enemies.
Attenuating RF reduces its power, and there are two ways to do this. The first
method involves placing attenuators inline in the antenna cable. This method is
quick but is not flexible and, more importantly, reduces both the emitted RF
power as well as the return signal from the tag, which is already very weak. This
would impair the reader's ability to detect tags.
The second method uses software-controlled digital attenuation, built into Alien
readers. Using the software-controlled digital attenuation reduces the emitted
power but not the return signal. The RFAttenuation value ranges from 0 (no
attenuation, maximum power) to 160 (maximum attenuation, minimum power), in
increments of 10 - each "decade" representing an additional 1 dB of RF
attenuation.
The default value for RFAttenuation is 0.
RFAttenuation can range from 0 to 160.
Increasing RFAttenuation by 10 reduces RF power by 1 dB.
Changes take effect immediately.