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6
ANTENNA OVERVIEW
The BigIR is a vertical antenna that can be adjusted for resonance on the 40, 30, 20, 17, 15, 12, 10
and 6 meter ham bands, including frequencies in between. With the addition of the 80 meter coil accessory,
the BigIR/80 will also provide coverage on 80 and 60 meters, including frequencies in between.
The antenna comprises two primary subsystems:
1. The Element Housing Unit (EHU) contains the stepper motor, copper-beryllium tape and wiring interface.
The optional 80m coil attaches to this unit as well.
2. The Element Support Tubes (EST) provides guidance and protection of the copper-beryllium tape as it
extends or retracts.
With the EST subsystem affixed to the EHU subsystem, the antenna is complete (except for mounting and
radials).
Once the EHU and EST are coupled, under control of the controller unit, the element can be extended
or retracted within the EST. The EST consists of an outer portion of light-weight fiber composites and an in-
ner element-guidance portion of Chlorinated Poly Vinyl Chloride (CPVC). The CPVC portion is where the
tape extends and retracts, and the outer EST portion provides physical support and weather protection for
the inner portion. At the topmost end of the EST, a special rain cap ensures that air can move in and out of
the EST as the tape is retracted or extended, and that rain and moisture is prevented from entering the EST.
If the 80 meter coil accessory has been purchased, it attaches to the EHU and provides a tapped in-
ductor at the EHU feed point allowing the antenna to be made resonant on 80 and 60 meters. The antenna
with that option is designated the BigIR/80. Both the EHU and 80 meter coil accessory are controlled by the
in-station controller unit and each has its own 4-conductor control cable that interfaces with the in-station
control unit.
Once the antenna is mounted and radials have been installed, the user controls the extension and
retraction of the radiator (copper-beryllium tape) by selecting the appropriate controls on the in-station con-
troller. The controller also provides operational modes whereby adjustments to tape-length memory points
can be made to fine tune for best SWR match. The in-station controller can communicate with a transceiver
such that a change in frequency prompts the controller to adjust the tape length automatically, provided you
have the correct interface cable. In addition, the tuning relay accessory can prevent trans-
mitting power to the antenna while it is tuning via the “PTT” port in the back of the controller.
Controller
Control cable
BigIR
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