KAF2 Low Noise Audio filter and Real Time Clock for the K2
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Click on each picture for a larger view.
The KAF2 supplements the K2's crystal filters with effective, low-noise audio filtering. It also adds a real-time clock, allowing you to check
the time or date with a tap of the K2's DISPLAY button (details below).
Audio Filter
The KAF2 includes a passive, balanced low-pass filter (LPF) that significantly attenuates splatter, carriers, and wideband I.F. noise above
3 kHz. It's especially useful on quiet bands, with the preamp off, or when using small, low-noise receiving antennas. It completely eliminates the
hiss sometimes heard when using hi-fi headphones. The passband has very low ripple, so the filter has no impact on speech or data signals.
Also included is an active, two-stage, narrow band-pass filter for CW or data use. It can be used in conjunction with the K2's variable-bandwidth
CW filter, providing a significant improvement in skirt selectivity and in noise reduction. The center frequency is tunable over the K2's entire
400-800 Hz CW offset/sidetone range. The -3 dB bandwidth of the cascaded filter sections is about 80 Hz, ideal for digging weak signals out of QRN or QRM, and the Q of both stages is low enough to avoid excessive
ringing. The AFIL switch on the K2 front panel turns the band-pass filter on or off.
Real-Time Clock (RTC)
The real-time clock displays 24-hour time, as well as both MM-DD-YY and DD-MM-YY date formats. Time and date can be easily set using the BAND+
and BAND- switches. The RTC is very convenient for field operation since it eliminates the need to bring a separate clock. The on-board lithium
backup battery will power the clock for up to several years, and can be replaced by removing either the K2's top cover or left side panel.
Price and Availability
The KAF2 is priced at $79.
If possible, please order using our on line order form. (This will avoid overloading Lisa with telephone calls.) Of course please feel free to call us if you prefer to order that way or have questions about the KAF2.
73, Wayne (N6KR) and Eric (WA6HHQ)