The ABF128 is a receive (only) bandpass filter especially designed to improve strong signal handling characteristics of receivers for VHF commercial Airband listening. The AFB128 is suitable not only for AOR receivers, but also for most airband and wideband receivers on the market. The addition of ABF128 will provide additional selectivity, and allow the receiver's circuitry to cope much more easily with strong interfering signals such as Band-2 Stereo or Shortwave broadcast transmissions, which can be manifest in many ways such as "hissing", multi-signal hash and desensitization of the receiver.

The ABF128 will provide additional selectivity (in many situations) to any receiver's "front end" by reducing the multitude of unwanted strong signals from reaching and saturating the receiver's first mixer stage. This results in less interference and improved reception.

This makes the ABF128 suitable for connection to both external antennas and right under the whip antenna of a handheld receiver.

The ABF128 is not an amplifier and will not "boost" signals, however the additional selectivity offered can significantly improve reception in many situations by removing unwanted strong signals which may overload the receiver and reduce it's effectiveness. Band attenuation is very small, due to the excellent in band V.S.W.R. of 2;1 resulting in a loss of only about 4dB.

NOTE: Since this is a blocking filter, it must be removed for normal reception outside the air band.

Alternatively, a second antenna selectable by a common A/B TV antenna switch may be installed, or a single antenna may be fed to a common A/B TV antenna switch, one side connected to the filter which is connected to a TV splitter/combiner, and the other to to the second port on the splitter, the output of which is connected to the scanner.