wave-whip and “ground-plane” antennas with an attached cable which may be
used for this purpose. Two such antennas are required for use with diversity
receivers. Other types of antennas may be needed for unusual applications, such
as operating at extreme ranges of 500 feet (150 m) or more. Vega offers a high-
gain log-periodic antenna that covers the complete operating-frequency range of
the R-662 receiver. UHF TV antennas (with appropriate matching transformers)
are often used for this purpose. A wide-bandwidth “corner reflector” antenna
works well in this application. UHF communications antennas are also sometimes
used for specialized requirements. However, such antennas are usually narrow
band and must be modified to function properly in the 494 to 608 MHz and 614
to 806 MHz ranges. Contact the Vega factory or your sales representative for
assistance in selecting antennas for unusual applications.
No matter what type of antenna is used, care must be used in positioning and
mounting. In all cases, a clear and unobstructed line-of-sight path between the
receiving antenna and the transmitter is required. The receiving antenna may be
concealed behind fabric, thin plastic, acoustic tile, and thin plywood without
significantly affecting performance. However, close proximity to metallic objects
such as furniture, lighting fixtures, scaffolding, electrical cables, metal structural
members, aluminum window frames, and equipment cabinets must be avoided.
Whip and dipole antennas require at least a 5-inch (0.1-m) minimum spacing
from metal surfaces. Other types of antennas may require greater spacings. The
radiation pattern of these antennas is much larger than the antenna itself.
Consequently, even objects well off to one side of the line-of-sight path can
distort the antenna pattern, affecting performance. Also often overlooked are the
effects of using metal brackets for physical mounting of the receiving antenna.
Vega's magnetic-mount and ground-plane antennas are designed to mount on a
flat metal plate and on an antenna mast, respectively, but many types of antennas
are not. The manufacturer's recommendations should be followed when using
Yagis and other types of specialized antennas.
The use of long cables connecting the antenna to the receiver is strongly
discouraged. At UHF frequencies, the signal loss in the cable rapidly builds up
and can seriously degrade operating range.
Assembly of Lemo Microphone Connector
Slide threaded clamp, then collet, over the end of the cable; the slotted end of the
collet faces away from the cable end.
Strip approximately 1/2 inch (12 mm) of outer insulation. Open a small hole in
the shield where the outer insulation has been stripped; work the center
conductor(s) through the small hole in the shield.
Strip the center conductor(s) approximately 1/8 inch (3 mm). Tin the center
conductor(s); also tin the end of the shield.
Solder a 3/4-inch (18-mm) piece of 24-gauge bus wire into pin 4 of the insert.
Bend the bus so it comes out of the center of the insert in the direction of the
cable.
Position the mic cable so the center conductor(s) will slip into their respective
pins. Solder the shield to the bus; trim away any excess shield. Solder the center
conductors into their respective pins.
On those mics where pins 1 and 3 are tied together, use 24-gauge bus wire
between the pins. This forms a bar to which the center conductor is soldered.
UHF Wireless-Microphone Bodypack Transmitter
7