Theoretically FSK should be cleaner than AFSK. With the latter you can get the following spurious signals:
- Incompletely-suppressed carrier - Unwanted sideband - Audio harmonics of the AFSK tones None of those unwanted signals occur with true FSK. With either FSK or AFSK you can get switching transients when transitioning from one frequency to the other. If you just use two free-running oscillators, there will be horrible transients as you switch from one to the other. The K3 apparently uses phase-continuous switching, which eliminates that problem. However you really should transition gradually from one frequency to the other to limit the transmitted bandwidth. I believe the K3 addresses that problem by running the FSK signal through the 2.7 kHz crystal filter. Al N1AL On Sun, 2010-06-13 at 14:24 -0700, Fred Jensen wrote: > N1JM wrote: > > In real world operating, has anyone really experienced a difference or > > could > > tell a difference? > > If AFSK is working right, I don't think it is possible to tell the > difference between it and FSK by listening [unless the two audio tones > aren't clean sine waves]. I think the real difference between FSK and > AFSK is that the interface in FSK has some hardware involved but is > pretty straight forward in MMTTY config, while AFSK requires only a > couple of audio cables but you have to make sure the K3 Pitch and MMTTY > mark frequency are set to the same values. > > 73, > > Fred K6DGW > - Northern California Contest Club > - CU in the 2010 Cal QSO Party 2-3 Oct 2010 > - www.cqp.org > > ______________________________________________________________ > 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
