The use of wireless devices has become very common in many companies
and homes in recent years. Bluetooth =99 connected computer
peripherals,
cell phones, wireless LAN links and cordless phones all depend upon
antennas to make a connection. Often the antenna is inside the device
and is invisible, but if an external antenna is used, perhaps to
increase the range of the connection, it needs a cable to connect it
to the device. Both antennas and their feeder cables are prone to
damage. This is particularly true if any part of the system is
located
outdoors. Fault finding these systems can be more difficult than say
testing a DC system like an electric door bell. This is because the
loss of the cable varies with frequency. It may be perfectly
connected
when tested with an ohmmeter, but still show a high loss when
transmitting power at a frequency of Gigahertz or two, like some of
the systems mentioned above. Measurement of the match of the antenna
and the cable loss are part of the answer. This article explains what
is involved, and how they are measured with a dual directional
coupler.
For details see:
http://www.satori-technology.com/do***ents/Using_a_dual_di=
rectional_coupler.pdf
