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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.





  • Size: 5-1/2” L x 2-7/8” W x 7/8” H (14 cm x 7.3 cm x 2.2 cm). Height not including feet or knobs.
  • Internal Power: 9V battery
  • External Power: 7-14 V (8 V min. recommended)
  • Current Drain: 10 mA minimum volume to 100 mA full volume, typical.
  • Functions: Low pass plus two levels of bandpass with tunable center frequency in bandpass mode.









Q: Is the AF1 compatible with radios other than Elecraft radios?

A: Yes, the features and connections will work with most any QRP radio that needs more filtering at the audio level.

Q: Should I consider adding an AF1 to a older, tube type radio or perhaps a simple new radio?

A: Yes, the AF1 will add additional audio filtering to any radio that needs it.  It can inject new life into any older radio.



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