JT Asked: >Would an 80/40/30 combo work on a KFL1-4 board?
You could build a KFL1-4 board mostly normally per directions, with band 1 being 40m and band 2 being 30m, and both using the current LP and bandpass filter designs. After that, you could build band 3 as an 80m band, using the component values for 80m that others on this list have developed. So yes, an 40m/30m/80m KFL1-4 is definitely possible. In the as-designed KFL1-4, the each of the two sections or branches of the output low pass filter supports multiple bands. The section that supports 40m and 30m allows the fundamental frequencies of 7 MHz and 10 MHz through, but does not allow the second and higher harmonics of 14 MHz and 20 MHz through. Similarly, the section that supports 20m, 17m, and 15m allows the fundamental frequencies of 14 MHz, 18 MHz, and 21 MHz through, but does not allow the second and higher harmonics of 28 MHz, 36 MHz, and 42 MHz through. This shows why a particular section of the LP filter can NOT serve for multiple bands that are harmonically related. An LP filter that passed both 3.5 MHz and 7 MHz signals for 80m and 40m operations would also allow the second harmonic of 3.5 MHz right on through too. I built my four-band board for the standard 40m/30m/20m/15m bands. I built a two-band board for the 80m and 17m bands. I don't often swap in the two-band filter board, but it's nice to have that capability when desired. Mike / KK5F _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
