Using a narrow filter in the 9 mhz IF eliminates the RTTY signal from
the passband. A wide filter >2100 hz makes it audible.
You can use a narrow filter in the 6.4 mhz IF and make the RTTY signal
audible by turning the PBT knob to about 3 o'clock. Usually I just use a
wide filter.
I have a TT Model 216 digital filter in my Omni V.9 in Greece, and it
works great. Someday I will get one for my Omni VI+ in the USA. If you
want to use a narrow filter on RTTY, the 216 is the way to go.
I wanted to use FSK with my Omni's so I can set the sound card output
level for PSK31 and not have to adjust it for AFSK.
Jim N4AL
Mark Erbaugh wrote:
I'm trying to set up my Omni VI (opt 3) for the upcoming RTTY contest. I
have 250 and 500 Hz filters in both IFs. The 9 MHz filters are centered for
CW.
What the difference in using a narrow filter in the 9 MHz IF vs the 6 MHz
IF. I do realize that I can center the passband of the 6 MHz with the PBT
adjustment. Would performance improve if I cascaded filters using a 250 in
each IF. Since I'm can use AFSK that should be possible, I just won't be
using "standard" RTTY tones.
I understand that if I want to use FSK, I'd have to use the 6 MHz filter and
offset it with PBT. The passband of the 9 MHz filter is not going to pass
standard RTTY tones.
Also, what are the other pros and cons of using FSK vs AFSK? I realize that
with AFSK, I have to worry about the computer audio level and that it
probably takes a little more horsepower from the computer / soundcard to
generage the AFSK tone, but is there anything else to consider?
73,
Mark
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