On Fri, Feb 1, 2013 at 5:12 AM, Billy Cox <aa4nu@ix.netcom.com> wrote:
> Sorry, I disagree, as the ability of the Orion
> platform to switch in the 1.8 verses ~3.0 of
> the FT5K, would ADD value to the overall chain.
>
> The narrower 1.8 would reduce even more of the
> other non-desired strong signals off frequency
> that the 3.0 of the FT5K could do nothing about.
>
> That is/was Wayne's key question below, and is
> not an option offered by the FT5K, agree?
>
>
I agree, but only for signals that are s9+. The threshold for adc overload
depends on the circuit but is typically 15 to 35dB above s9. Any signal
less than that is easily handled by dsp alone.
I think there's some confusion in this thread because several of us were
responding directly to that linked video where the roofing filter clearly
doesn't matter.
But to go back to the OP's orignal question, yes a 1.8Khz roofing filter
instead of a 3.0Khz roofing filter can make a difference, but it's a small
difference. You also need to consider that a slightly off-channel STRONG
ssb signal is more than likely to have wide sidebands/splatter and rf
actually in your desired 1.8Khz passband and there's nothing you can do to
filter that out except rotate your antenna. Yes, if the off-channel STRONG
signal is clean, than the narrower ssb roofing filter can help. Narrower
roofing filters are generally more effective in cw.
73,
Barry N1EU
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