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The Elecraft AF1 is a versatile audio filter that can be used with any receiver or transceiver. It can improve intelligibility of CW, phone, or data signals, and is especially well suited to radios that have inadequate I.F. or audio filtering.

The AF1 uses straightforward analog circuitry and no surface-mount components, so it’s an ideal project for first-time kit builders.



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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.

Note: This product is a kit which may involve building the product by selecting individual components, soldering them to the circuit board, winding toroids, installing LEDs and displays, calibrating circuits to meet specified performance levels. 





  • 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.



AF1 Audio Frequency Filter Quantity Price
AF1 AF1 Audio Frequency Filter

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