I have made an unfortunate discovery. I don't know if this is just my KX3 or is more generally applicable, but: when I run WSPR with my KX3, the frequency stability is inadequate to get good results on transmit. I discovered this by transmitting with 1.0 watts with the KX3 and then the K3, using the same antenna, and looking at the reports on the WSPRNet database. I immediately suspected something, because the K3 was being heard by 5x as many stations as the KX3.
I then listened to the K3's WSPR transmissions on the KX3 and vice versa, using just a piece of shorted coax for an antenna to cut the signal level down to about S9. WSPR users will know that the graphical representation of each received signal runs horizontally across the display, with time on the horizontal axis and frequency on the vertical. When the K3 transmits, the line is a nice straight level stripe, as it should be. But when the KX3 transmits, it has a pronounced downward swoop of as much as 10 hz over the first 45 seconds or so. As a result, most receiving stations are unable to decode the KX3's transmission. Listening in the shack at a signal level of S9, the K3 can decode less than half of the KX3's transmissions. KX3 frequency stability on receive seems fine, as evidenced by nice level lines on the graph. BTW I tried two different computers driving the KX3 on transmit, but got identical results on both. The frequency stability requirements both of WSPR and JT65 are considerable. WSPR transmits 4-frequency FSK, with the tones separated by only 1.5 hz. The whole bandwidth is 6 hz. The exact tx frequency is not crucial, but the transmitter has to pick a frequency and stay there. I got my KX3 partly to use on digital modes, and I have an important test of a portable antenna coming up for which the KX3 would be perfect. However, at the moment this problem is standing in the way. I'm hoping that there's a simple fix. 73, Tony KT0NY -- http://www.isb.edu/faculty/facultydir.aspx?ddlFaculty=352 ______________________________________________________________ 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
