A rotary switch on the unit allows you to select a low-pass characteristic with adjustable upper frequency roll-off, or a narrow bandpass characteristic.
The bandpass filter offers two levels of selectivity, and its center frequency may be tuned from about 350 Hz to about 950 Hz.
The low-pass filter is active during bandpass operation, allowing you to further control the upper frequency response.
The output amplifier drives low impedance phones or a small loudspeaker.
Power can be supplied via either an on-board 9-V battery or an external supply. An LED indicates power on/off status.
A: Yes, the features and connections will work with most any QRP radio that needs more filtering at the audio level.
A: Yes, the AF1 will add additional audio filtering to any radio that needs it. It can inject new life into any older radio.