the insulated wire connected to the location on the circuit labeled
INPUT
.
Apply the negative side of the audio signal to the insulated wire
connected to the location on the circuit board labeled
GND
. Please refer
to the "Parts Placement" section, Figure 1 for the location of both points
on the circuit board.
Next, connect the
POSITIVE
lead of the external speaker to the end of
the insulated wire connected to the location on the circuit board labeled
SPKR
. Connect the
NEGATIVE
lead of the external speaker to the point
labeled
GND
on the circuit board. Again please refer to the "Parts
Placement" section Figure 1 for the location of the point labeled
GND
on
the circuit board.
Next, turn the receiver volume all the way down, then clip the 9-volt
battery to battery snap. Set SW1 to the far left position. Now turn the
receiver up slightly so you can hear the received signals on the external
speaker. The signal you are listening to is the "raw" or "unfiltered" signal.
Using the tuning knob on the radio, find a CW signal. A good place to
find CW signals is in the Amateur Radio bands. Once you find a CW
signal, switch SW1 to the 110 filter cutoff. The 110 position is the third
from the left. When you switch to the 110 cutoff, you will notice that the
signal sounds cleaner than before. You can now fine tune the radio
tuning knob for the best received signal. If using a communications
receiver or scanner with a BFO control, use this control to fine tune the
received CW signal. If the receiver or scanner you are using does not
have a BFO control, it will be very difficult trying to tune the signal in
properly. If the signal you are trying to receive is in a "pile up", then try
the 80 hertz filter cutoff. Then fine tune the receiver to "pull out" the
desired signal.
Operation with an Amateur Radio transceiver is basically the same, but
you would use either LSB, (Lower Side Band) or CW mode. All other
connections are the same.
IN CASE OF DIFFICULTY
No Signal Filtering:
A newly constructed filter that fails to work upon initial power up,
generally requires a very close and careful inspection of all work. Please
go back through all steps of assembly and inspection, referring to the
"Parts Placement" Figure 1. Most of the time there will be a part that is
not installed or not installed properly, a wrong value part in place of
another, or a broken part. A close inspection at this point may reveal
some accidental mistake(s).
Intermittent Filter Operation:
A filter that operates intermittently may have poor solder connections, a
problem with broken wires, or a low voltage power source. Self-
