Vectronics VEC-821K - Manual (Page 22)

VEC-821K Instruction Manual Super CW Filter Kit
No Speaker Audio:
No speaker audio can be a symptom of a bad S W 1, a broken wire or a bad C9.
Check the voltage from the 9-volt battery. A broken wire at the audio input to the
filter could attribute to no speaker audio. The audio amplifier chip (U3) could
also be defective.
If technical assistance or factory repair is desired, please refer to the warranty
instructions on the inside front cover.
THEORY OF OPERATION AND SPECIFICATIONS
Circuit Description:
The VEC-821K uses two UA747 operational amplifier integrated circuits to form
four low Q cascaded stages with no insertion loss. This results in a very narrow
bandwidth and extremely high skirt rejection with minimal audible ringing,
making good signal copying possible. The center frequency is between 750-800
hertz. The filter also has an LM380 Audio Amplifier which can drive
an 8 ohm speaker or headphones.
Specifications:
Bandwidth: ......................................... 80 Hz, 110 Hz, 180 Hz (switch selectable)
Skirt Rejection:.................................... At least 60dB down 1 octave from center
frequency for 80 Hz. bandwidth.
Center Frequency:.............................. 750-800 Hz
Insertion Loss: ................................... None
Power Required: ................................ 9-volts DC; 9-volt battery
PCB Dimensions: ............................... 2" x 3"
ENCLOSURE
Vectronics has designed a matching enclosure just for your VEC-821K Super
CW Filter Kit. The matching enclosure is an all metal box which includes
knobs, hardware, decals, and rubber feet. The Vectronics model number for the
matching enclosure is VEC-82 1KC.