SECTION 1
BRIEF
DESCRIPTION
1
The ANC-4 is an rf device which is designed to provide cancellation of
locally generated noise from signals received by a primary antenna. This
unit is employed right at the antenna connector of the receiver or
transceiver to cancel locally generated noise, such as power line noise,
computer noise, TV-generated interference, etc., before it gets into the
receiver and affects the receiver AGC circuits. This will allow the
reception of signals well below the noise level induced by the local
interference.
To cancel locally generated interference, the interference signal must be
detected and its phase and magnitude adjusted so that it matches the
offending interference, but is 180 degrees out of phase, effectively
cancelling the interference. This scheme is particularly effective at
reducing local power line noise or other locally generated noise types.
This unit may be used with any receiver or transceiver with rf power
output of 250 Watts PEP or less. An rf detector built into the unit
automatically bypasses the network whenever transmit rf is detected.
The unit is NOT designed to be used at the output of a high power linear
power amplifier, but must be installed at the lower rf level of the
transceiver, if transmitting is anticipated. In other words, if you use a
linear amplifier, place the ANC-4 between the transceiver and the linear
amplifier.
Controls are provided on the front panel to allow adjustment of both the
phase and magnitude of the local interference, providing extremely deep
cancellation of the offending interference.
The unit connects between the main station antenna and the receiver
antenna connector. The DC power mating connector for the ANC-4 is
supplied with each unit. UHF (SO-239, which mates with a PL-259 plug)
connectors are used for the outside antenna and the output to the
receiver. A short wire antenna
is
supplied with each unit to act as a noise
pickup antenna.
This
will generally be satisfactory for eliminating
noises generated around the operating position or in the house, but are
generally not large enough to eliminate noises generated outside the
home, such as power line noise. For noises generated outside the home,
we recommend that you mount a small noise dipole (6 feet of wire each
side of center) outside perhaps down in the shrubs or some other area a
foot or two above ground, and broadside to the noise source, such as
parallel to power lines. Feed the noise probe at the center with coaxial
cable, shielded wire or even lampcord and connect it to the NOISE
ANTENNA connector J1, located on the rear of the ANC-4, using an
RCA plug. (Connect the center conductor of shielded wire or one side
of the lampcord to the center pin of the RCA phono plug, and the shield
or other dies of the lampcord to the ground side of the RCA plug.) The
short wire antenna supplied connects to an RCA jack on the rear panel
of the unit. Any noise antenna that works, including combinations of
horizontal and vertically polarized antennas, may be used.
The ANC-4 can be used to cancel ignition noise, alternator whine or
other noise types found in an automobile. To provide sufficient noise
signal to the unit, it may be necessary to run a wire from the NOISE
ANTENNA connector into the engine compartment to act as a noise
pickup. It will probably be necessary to readjust the NOISE PHASE and
NOISE GAIN controls when changing from one band to another, but the
settings should hold over an entire Amateur band.
