Sequoia Aircraft Corporation F.8L Falco, Construction Manual

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F.8L Falco Construction Manual 14–2 Revision 4, March 1, 2002
If only one communications antenna is installed, it should be this antenna since the radio waves
from unicom radio antennas are vertically polarized to a greater extent than other
communications (ATC, FSS, tower, ground, etc.).
Materials required:
1 RST Ferrite-foil Antenna Kit
1 UG88 (male) BNC Connector
1 UG89 (female) BNC Connector
25’ RG58 Coaxial Cable (includes 3’ extra)
No. 2 Communications Antenna Installation
See Drawings No. 160 and 161. The No. 2 VHF communications antenna is identical to the No.
1 COM antenna described above; however, this antenna is installed in the left wing and no cable
connectors are required for the coaxial cable.
The center of the antenna should be installed 120mm outboard of wing station No. 10. The
elements are run parallel to the spar to stations 9 and 12, and then the elements are run aft along
the two ribs. The elements should run diagonally along the rib; that is, from the top of the wing
at the aft face of the spar to the bottom of the wing at the aft end of the antenna elements.
Details of the installation of this antenna are shown in Chapter 24 “Wing Assembly”.
The purpose of running the elements diagonally down-and-aft is to make the antenna as vertical
as possible within the wing. VHF communications radio waves are vertically polarized, some
more than others depending on the transmitter antenna. A similar antenna (designed by Radio
Systems Technology) was used in the wing of the Bellanca Viking, and it was found that the
communications antenna in the wing worked well when talking to everyone except unicom, and
the range with unicom was limited to about 20 miles.
The coaxial cable should be run at right angles to the element down the spar aft face, then
forward through the spar just under the upper spar cap to the wing leading edge strip (still at right
angles to the antenna elements), and then along the leading edge strip to the cockpit and the
radio. See “special considerations in wiring” if wing tip strobes are used.
Because a metal pitot tube line will interfere with the operation of the antenna, a nylon line
should be used. The wiring for the wing tip lights should be run along the leading edge of the
wing. The usual method of installation is to drill a small hole in the wing rib gusset just aft of the
forwardmost vertical brace, and run the wiring through this hole.
As with the No. 1 COM antenna, the antenna elements, ferrite balun assembly, solder joints and
coaxial cables must be firmly attached to the wooden structure with epoxy and fiberglass cloth to
prevent airframe vibration from affecting the antenna.
Materials required.
1 RST Ferrite-Foil Antenna Kit
17’ RG58 Coaxial Cable (includes 3-1/2’ extra)