>>>>> "Matt" == Matt Zilmer <mzil...@roadrunner.com> writes:
Matt> Hi Pf,
Matt> Most tone modes operate at an offset from carrier frequency, so that
Matt> the audio frequencies of interest are more or less cenetered in the
Matt> filter passband. I believe the JTx modes are already in the 1200 to
Matt> 1500 Hz range so no offset is required.
Hi Matt,
actually, I'm seeing JT9 stations transmitting at 3400 Hz, and who knows
if there are some even above that. JT65+JT9 uses quite a wide receive
window.
Matt> The crystal filter being used only restricts the bandwidth of the RX
Matt> chain (1st IF). The DSP imposes its own audio filtering on the
Matt> baseband, and that's what you're seeing as rolloff below ~300 and
Matt> above ~3500 Hz.
Yes, and that was what I wanted to know. I've read in this mailing list
that the DSP limits the audio at 4 kHz. I'm seeing it roll off at little
above 3400. The low end rolls off at around 300, so I'm getting an audio
passband of ~3100 Hz. I wonder if this is normal, or if there's
something else I can tweak in the settings.
Pf
--
Pierfrancesco Caci, ik5pvx
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