Don: The TX crystal filter is ahead of the IPA and HPA stages and while a narrower filter may help a bit, the real source of almost all transmitted 3rd, 5th, 7th, 9th etc. order IMD products is the power stages.
Jack K8ZOA On 7/15/2012 9:12 AM, gold...@charter.net wrote: > Hi Jack, > > So I think what you are telling me is that the IPA is after the DSP and > that obvioulsy any inperfections in this circuit and the final amp are > what creates the IMD products. > > Is that another reason that the tx filter is 2.7 or 2.8 wide at the > skirts to act as a wall to prevent this from getting out on the air > compared to using a 3.0 wide filter. > > Thanks > Don > > ~73 > Don > KD8NNU > > > On Sun, Jul 15, 2012 at 8:51 AM, Jack Smith wrote: > >> Don: >> >> Not so at all - whilst the low level SSB generated by the K3's DSP may >> be close to theoretically perfect, intermodulation products produced >> by the K3's IPA and final amplifier stages are present in quantity and >> are the limiting factor. >> >> Jack K8ZOA >> >> >> On 7/15/2012 8:02 AM, gold...@charter.net wrote: >>> Being a SDR there is really no suppressed carrier as the carrier is >>> never created only the sideband for the mode selected. So unless >>> you >>> have signficant splatter there should not be an IMD problem with a >>> K3. >>> >>> Again assuming no splatter and a properly functioning radio. >>> >>> This is no analog radio and all TX is based on the DSP first and then >>> the TX filter last. >>> >>> ~73 >>> Don >>> KD8NNU >>> >>> >>> On Sun, Jul 15, 2012 at 7:34 AM, Geoffrey Mackenzie-Kennedy wrote: >>> >>>> Dave, >>>> >>>> To add to the replies which you have received, the width of your USB >>>> signal should also include those intermodulation products which >>>> appear >>>> at frequencies less than that of the suppressed carrier frequency, >>>> i.e. in the LSB region. If you tuned your K3 to 14.225 MHz, these >>>> IMD >>>> products would fall outside of your General Class portion of the >>>> band >>>> and could create interference. To be safe I would suggest that you >>>> do >>>> not operate your K3 in USB mode below 14.228 kHz. >>>> >>>> In Europe the top end of our 80m allocation is 3.800 MHz, and some >>>> European hams operate LSB on or very close to 3.800 MHz. This >>>> practice has caused some non-amateur users operating just above >>>> 3.800 >>>> MHz to complain about interference from amateur IMD products. >>>> Fortunately those complaints which I have heard are still at the >>>> "muttering" stage. >>>> >>>> 73, >>>> Geoff >>>> LX2AO >>>> >>>> >>>> On July 14, 2012 at 10:39 PM, David Guernsey wrote: >>>> >>>> >>>>> If I tune my K3 to 14.225 MHz will I be in the General Class >>>>> portion >>>>> of the 20 meter band, or do I have to allow for the width of my USB >>>>> signal when I transmit? >>>> >>>> ______________________________________________________________ >>>> 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 >>> ______________________________________________________________ >>> 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 >>> >> >> ______________________________________________________________ >> 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 > ______________________________________________________________ > 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 > ______________________________________________________________ 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
