On Tue, Sep 27, 2011 at 12:46 PM, Leigh L Klotz Jr WA5ZNU <[email protected]>wrote:
> Interesting point about TX. Why do you suppose you get worse results? On > my rigs, the TX goes through the widest SSB TX filter installed (2.8 KHz for > example) and th sweet spot of 1500Hz ought to be the best for both TX and RX > as it is the same filter. What filter architecture does you rig use? > Crystal filters have both passband ripple (change in attenuation across the passband) and change in group delay (not all frequencies in the passband pass through the filter in the same amount of time). Both of these characteristics introduce distortion. Generally speaking, the wider the filter, the less there is of both of these distortions around a narrow group of frequencies. But there is no guarantee that these distortions are minimized at the center of the passband. They *probably* are hence 1500 Hz for a 3kHz-wide filter is a good guess, but it is *NOT* guaranteed to produce the best results. FWIW, my K2 has its best performance around 800Hz up from the low-frequency inflection point of the filter, i.e. at around 1kHz audio input. I now use Flex radios where the filters are ideally defined in software. They have very consistent behavior no matter what the width or center is of the filter setting and the center of the pass-band is always the best place to put the signal. So I no longer worry about this. -- Brian Lloyd, WB6RQN/J79BPL 3191 Western Dr. Cameron Park, CA 95682 [email protected] +1.767.617.1365 (Dominica) +1.916.877.5067 (USA)
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