Hello!
I have been thinking my K2's filters. I worked EARTTY today. Look for
the following pictures. K4GMF is transmitting around 1000Hz. There is an
unnecessary extra audio peak around 2.5 to 2.8kHz
http://ugly.blerp.org/~oh6kxl/350Hzfilter.jpghttp://ugly.blerp.org/~oh6kxl/350Hzfilter2.jpgWhen tuning so that RTTY signal is between the 500Hz and 1000Hz you can
see the extra signal has bigger shift than the original! Same phenomenom
is visible in all filters.
Next picture tells you what is the filter response with no audible or
visible rtty signal.
http://ugly.blerp.org/~oh6kxl/350Hzfilter_no_signals.jpg From where this unwanted audio peak about 1.6kHz up from actual
transmission frequency is coming from?
- K2's rx is generating it?
- My Sound Blaster is generating it?
- My cables are generating it? (PC is opto-coupled and galvanically
isolated from K2)
I have done my filter adjusments with this gMFSK software.
Rolf Moberg
oh6kxl
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