The cause of this is likely to be straightforward. One of our software engineers is looking into it. Once we have the fix in place, we hope to get a KX2 to Rob for retesting.
A temporary workaround (if needed due to QRM) is to use 450 instead of 500 Hz, etc. Wayne N6KR ---- http://www.elecraft.com > On Aug 1, 2017, at 4:25 AM, John Reilly <[email protected]> wrote: > > John, N0TA, forwarded this question to me about why I listed the KX2 close-in > dynamic range at 3 kHz rather than the more typical 2 kHz. Some radios have > limitations that make a measurement at 2-kHz impossible or invalid. If a > valid measurement cannot be made at 2 kHz, then it is made at some wider > spacing, such as 3, 4 or 5 kHz. Typically if a measurement cannot be made at > 2 kHz, it is because of filter leakage. When a test is made at 2-KHz, for > example, the third-order intermodulation products are 2-kHz below the lower > frequency test tone and 2-kHz above the higher frequency test tone. If the > radio cannot reject the test tone that is 2-kHz away, then it is impossible > to measure the third-order distortion product. > > In the case of the KX2, I could measure the low side distortion product at 2 > kHz with no problem using the standard 500-Hz filter bandwidth. On the other > hand, when measuring the distortion product on the high side, the filter in > the KX2 does not reject the test tone that is 2 kHz away. Two different KX2 > radios were tested, and both showed this identical anomaly. If one reads the > ARRL report on the KX2, you will see that the reviewer mentioned the filter > leakage when tuned above a strong signal. > > Here are the odd details on the KX2 filter leakage. If the filter bandwidth > is 500, 400, 300, 200 or 100 Hz, filter leakage makes the measurement at 2 > kHz impossible. On the other hand, if the filter bandwidth is 550, 450, 350, > 250, 150 or 50 Hz, then the measurement can be made. The League chose to > publish a 2-kHz dynamic range in QST even though the measurement cannot be > made on the high side with the standardized 500-Hz filter bandwidth (or any > even bandwidth value). Note: Both the League and I only publish the LOWER of > the two measurements. Let’s say the low side dynamic range of some radio is > 95 dB and the high side is 90 dB. Both the League and I publish the lower > worse-case 90 dB number. In the case of the KX2, I couldn’t pick the lower of > the two readings since no measurement is possible when using the standard > 500-Hz filter. > > Since the 2-kHz dynamic range value could not be made with the standard > filter bandwidth at 2 kHz, but could be made at a 3-kHz signal spacing, I > published that data. It may be of interest that the 2-kHz dynamic range > number with the non-standard 450-Hz bandwidth was only 1 dB worse than the > 3-kHz value. The point of listing the 3-kHz value, or any other radio with a > non-2 kHz listing is to point out the radio has a limitation in its filter > performance. > > My long form report on the KX2, available in PDF format, goes into detail > about this issue, and has data on the two radios I tested, listed by serial > number. > > At this point, Elecraft does not know why the KX2 behaves this way, or > whether there is a possible firmware fix. > > Rob Sherwood > NC0B > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
