We've had quite a few questions about broadcast-band reception on the KX3 (0.5-1.7 MHz) and how the KXAT3 ATU helps in this range.
The KXAT3 option module includes some extra elements that reconfigure its ATU L-network as a preselector for the AM broadcast band. This helps reject receive image responses in the broadcast band. The center frequency of the ATU's preselector automatically tracks the VFO. We optimized the preselector for use with typical HF antennas, which appear very reactive in the AM broadcast band. You could of course use a tuned antenna for this range as well. We now have some preliminary performance measurements. With the ATU installed, a 500-kHz signal comes up about 23 dB in amplitude, and the third-harmonic image drops by about 40 dB. This is typical for the lower portion of the band. Harmonic image rejection will get even better as you go higher in the broadcast band, because at some point the 160-meter low-pass filter starts rolling off. At the high end of the broadcast band, the 160-meter band-pass filter is also kicked in. Recent firmware changes allow the KX3 to receive down to 310 kHz, although the high-pass filter, which protects the PIN diodes in the T/ R switch, causes increasing attenuation as you tune lower. 73, Wayne N6KR ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
