10
This section describes the operating procedure for best results with the
ANC-4.
When the unit is connected as shown in Figure 3, locally generated noise
can be cancelled, in many cases completely. The controls and switches
should be manipulated as follows: (Refer to Figure 1).
1. Use your receiver “S” meter as a noise level indicator.
2. Set the NOISE PHASE control initially fully CCW and turn the NOISE
GAIN control fully CCW. Set the PHASE RANGE pushbutton “IN” to
the A position, and the FREQ RANGE pushbutton “IN” to the LO
position for frequencies below 20 MHz, or release it to the “OUT” or
HIGH position for frequencies above 20 MHz. (See "adjusting for
Minimum Noise" in Section 3 for further discussion.)
3. Slowly increase the NOISE GAIN control clockwise until a change,
increase or decrease, in the “S” meter reading is just noted.
4. Now adjust the NOISE PHASE control until a null is noted on the “S”
meter.
5. Alternately adjust the NOISE GAIN and NOISE PHASE controls until
the best null is obtained. If interaction due to hand capacitance is noted,
ground the case of the ANC-4 to your system ground.
6. If a good null cannot be obtained with the PHASE RANGE pushbutton
in the A (in) position, release the pushbutton to the B position and
readjust. A null should be obtained in one of the two PHASE RANGE
switch positions. Remember that the “right” switch position is that which
gives the best null.
7. For the deepest noise nulls, it may be necessary to change the noise
antenna polarity (horizontal or vertical) to be the same as that of the main
antenna.
8. When changing bands, it will probably be necessary to readjust the
network to reduce the noise on the new band. Normally, the adjustment
will hold over a frequency range of several kilohertz without requiring
readjustment. So if you adjust the noise cancellation in any one ham band,
it will generally hold throughout that band. However, different noise
sources may be present in different parts of the same band, so that some
readjustment may be required if this occurs.
9. If a null cannot be obtained using the noise antenna supplied with the
unit, you may have to install an external noise antenna. SECTION 2,
ADJUSTING FOR MINIMUM NOISE provides a test which will
determine if adequate noise is being provided by the noise antenna.
SECTION 3, NOISE ANTENNA gives some hints for an external noise
antenna and where it should be physically located.
The ANC-4 can be used as an active antenna. The NOISE GAIN control can then
be used to provide amplification of the signals received by the antenna.
ACTIVE ANTENNA
SECTION 5
OPERATION
LOCAL NOISE
