Hi all, I am going to describe a problem that I have found recently. Several days ago, I was encouraged by another ham to see aircraft doppler radio reflections. I wired my K3 to Linrad (www.sm5bsz.com) FFT waterfall Linux program. I tuned a spanish broadcast station on 21610 KHz (REE, Radio Exterior de España) just to see a 1KHz line on the waterfall. Soon I discovered aircraft reflections on the screen, but a nasty problem appeard. Aircraft lines on the waterfall were duplicated, as if the broadcast station carrier were a mirror. After some nightmares, headaches and own teories about this behaviour, comenting with other hams, even thinking that long path signal could have hit the aircracft (hi), suspecting that my audio card was a bad one (M-audio Fast Track Pro USB), a final testing with a FT-897 receiver told me that the spurs were generated inside the K3. Investigating further in USB, LSB , CW and DATA RX mode, I see that the problem is not present in USB or LSB modes (very slightly indeed) and is strongly noticeable in CW and DATA modes.
What do cause these spur signals? What is the diference among CW-DATA vs USB-LSB modes? I will appreciate your help. I tried reproducing the problem without depending on aircrafts reflections. I used a home made PIC controlled DDS generator as an "aircraft simulator". It is not a very pure signal cause it has a builtin 40 MHz clock. I has got 50 Hz spaced spurs, so ignore them on the pictures below. You can see the pictures with comments in the following URLs: http://ea1abz.ure.es/cw.jpeg http://ea1abz.ure.es/usb-lsb-data.jpeg Many thanks for your time. 73, Ramiro, EA4NZ (ex-EA1ABZ). ______________________________________________________________ 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
