The next two photos shows the phase relationships as the tone transitions from mark to space. The butterfly filter maintains a perfect out of phase relationship using the AFSK, single filter, data mode. With the dual filter, the phase relationship is sometimes in phase and then transistions to an out of phase condition. The phase non-coherence can cause a distortion in the data symbol and increase the bit error rate.
The bottom line is. If your using an external RTTY box like a PK-232, KAM or even RTTY decode software, use the AFSK (single filter) and not the FSK (dual filter). http://elecraft.365791.n2.nabble.com/file/n6757028/rtty_afsk.bmp http://elecraft.365791.n2.nabble.com/file/n6757028/rtty_fsk.bmp ----- Jack WA9FVP Willco Electronics -- View this message in context: http://elecraft.365791.n2.nabble.com/RTTY-FILter-tp6756724p6757028.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ 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
