Sorry for the inadvertent premature posting. I'll try again - After I had posted my observations on the behavior of KAT500 "Tune on QSY" option I suggested to an owner of a TS-890S, KAT500, and KPA500 that he should try disabling the QSY option as it might cure his annoying re-tunes during transmit. It did not fix the problem.
After exchanging email with him I have been able to reproduce the problem and I think I understand it. Disabling the "Tune on QSY" options, as previously reported, prevents RF count re-tune but still allows CAT frequency re-tune. It works fine if either one, or the other, is enabled but not when both RF count and CAT can change the KAT500 frequency. With "Tune on QSY" not selected, and FCCS and FCMD at default values, the KAT500 may re-tune during TX. I have captured several events with my data logger and the sequence is the same each time. What happens is that, when TX starts, the KAT500 is using the most recent CAT frequency. If RF count frequency becomes different from CAT frequency then the "last observed frequency" is updated to RF count frequency. Even if this frequency is in a different "bin" than CAT frequency there is no change in tuning solution as that is inhibited by "Tune on QSY" being inactive. All ok so far. Now KAT500 sees the next CAT frequency update and, if it crosses a bin boundary from the RF count frequency, there may be a re-tune. Note that CAT frequency re-tune is not inhibited by clearing the "Tune on QSY" options. The problem is most likely to be seen when the transmit frequency lies at the edge of a bin. My tests used the FT8 nominal frequency of 1840 and 1840/1841 is the boundary between bins 183 and 184. A re-tune was seen at the start and end of every transmission when my TX freq was 1841. These re-tunes moved from bin 184 before TX, to bin 183 at start of TX, and then back to bin 184 at end of TX. The paradox is that the transition to bin 183 tuning solution is triggered by a change of frequency from bin 183 to bin 184. Bottom line is that disabling "Tune on QSY" option does not prevent RF count re-tune if CAT frequency is available to KAT500. Detailed logger data available on request. Andy, k3wyc ______________________________________________________________ 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
