Wunder, The KX3 does have high-pass filtering integrated into the T/R switch, like the KX2. But it starts rolling off below the 160 m band. The KX2’s rolloff starts somewhat higher, as you noted.
73, Wayne N6KR > On Aug 11, 2017, at 11:53 AM, Walter Underwood <wun...@wunderwood.org> wrote: > > The KX2 has internal filtering to reject frequencies below 3 MHz. The filter > is 30 dB down at 1.5 MHz, and 56 dB down at 1 MHz. The KX3 does not have that > filtering, probably because it would interfere with performance on 160 m. > > There was some discussion of this a few years ago, including suggestions for > commercial filters. > > http://elecraft.365791.n2.nabble.com/Broadcast-band-interference-td7568427.html > > <http://elecraft.365791.n2.nabble.com/Broadcast-band-interference-td7568427.html> > http://www.digitalhams.net/ForumMsgs/msgsDisp.php?forum=KX3&subject=Broadcast+Band+Interference > > <http://www.digitalhams.net/ForumMsgs/msgsDisp.php?forum=KX3&subject=Broadcast+Band+Interference> > > Contact Elecraft support and they should send you a schematic for a high pass > filter that rejects the AM broadcast band. > > wunder > K6WRU > Walter Underwood > CM87wj > http://observer.wunderwood.org/ (my blog) > >> On Aug 11, 2017, at 11:21 AM, Philip Anderson <phil.ander...@invades.net> >> wrote: >> >> Hi everyone, >> >> I have been using a KX2 as my main rig for most of this year, it works very >> well although the receiver sometimes struggles a bit from my favorite >> portable location right next to the sea, where there's often a large amount >> of very strong signals. >> >> Because of this, recent review comparisons of the KX2 with the KX3 tempted >> me to buy a KX3 mostly for the extra receive performance. Unfortunately, >> when I tried the KX3 from my favorite portable location next to the sea >> yesterday, I had a problem with breakthrough of an AM broadcast station on >> 20m, the only way I could completely eliminate the problem was by turning on >> RX SHIFT, which unfortunately disables the roofing filter (a big reason for >> buying the KX3) and dual watch. >> >> I understand from comments I have read that this issue is an inherent >> weakness of the direct conversion architecture, however - my KX2 never >> suffers from this problem. >> >> So before surrendering to the possibility that I've spent $$$ on a larger >> KX2 with disabled dual watch ;) I thought I'd explore alternatives to using >> the RX SHIFT feature. >> >> Since I've never had this problem with my KX2, and since that radio does not >> have the RX SHIFT feature, I'm assuming that for some hardware reason, the >> problem of AM broadcast breakthrough is not expected on the KX2. >> >> Does anyone know what the difference between the two is? I suspect that the >> KX2 has a more severe high pass filter, in which case a 3Mhz high pass >> filter in the KX3 aerial lead might help sort out everything above top band. >> >> Has anyone tried that? >> >> Has anyone found any other solutions? >> >> Phil G4PWO >> ______________________________________________________________ >> 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 >> Message delivered to wun...@wunderwood.org > > ______________________________________________________________ > 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 > Message delivered to n...@elecraft.com ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com