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peak will form at the frequency set on the FREQUENCY control. The more the
selectivity is increased, the more pronounced the peak will become. This peak
may be preferred for CW operation when extra audio is needed and low frequency
signals are not a problem. Because circuit gain rises in the LOW PASS mode, the
input audio level may need to be reduced to prevent over driving the filter. Gain
on frequencies below the set frequency will drop as selectivity is increased.
Therefore, when using the LOW PASS mode for SSB, the SELECTIVITY control
should not be set beyond the 2 o'clock position.
HIGH PASS:
HIGH PASS mode is set by turning the Function Selector to HIGH PASS (HP). To
remove unwanted low audio frequencies, set the SELECTIVITY and
FREQUENCY controls for the desired response.
AUXILIARY FILTER OPERATION
PEAK:
To set the auxiliary filter in the peak mode, simply push the FUNCTION button to
the IN position. Set the SELECTIVITY control to about center range and adjust
the FREQUENCY control to the desired signal. Adjust SELECTIVITY and
FREQUENCY controls alternately for the best signal and the desired bandwidth.
In the peak mode, the auxiliary filter can be used to further enhance the primary
filter operation. It can be used to obtain very narrow bandwidths with good skirt
selectivity and little ringing when the primary filter is in the peak mode, or to limit
the bandwidth when the primary filter is in the NOTCH, LOW PASS, or HIGH
PASS mode. NOTE: When using both filters in the PEAK mode with narrow
bandwidths, the best skirt selectivity and least attenuation will be obtained by
setting both the auxiliary and primary filter frequency controls to the same center
frequency. This can easily be done by first peaking the desired signal with the
auxiliary FREQUENCY control and then peaking it with the FREQUENCY control
on the main filter.
NOTCH:
NOTCH mode on the auxiliary filter is set by pushing the FUNCTION button to the
OUT position with the primary filter in any mode. Set the SELECTIVITY control
about center range and adjust the FREQUENCY control to remove the unwanted
signal. SELECTIVITY and FREQUENCY should be adjusted alternately.
Remember at high selectivity on NOTCH, the NOTCH frequency is difficult to
locate and the FREQUENCY control must be tuned very carefully. The auxiliary
notch filter is used to remove an unwanted signal in the passband of the primary
filter. It can remove a heterodyne from SSB or AM signal when the primary filter is
set to PEAK, LOW PASS, or HIGH PASS mode. It can also be used to notch out
an adjacent CW signal which is too close to be removed by peaking the filters.