> >I have a set of 572Bs for sale for $70 shipped in the lower 48.
> These are at
> >least 90% emission (600 watts out on 40 meters in my SB-200). Or
> will trade
> >them even for a ten tec model 288 1800 hz filter for the
> Paragon. The tubes
> >are American made.
> >
> // In the 1930s, Bell labs found that a male voice needs 2700Hz of
> bandwidth for optimal intelligibility. Narrower bandwidths will work
> acceptably with a female voice. I use a pair of TS-930S filters to
> achieve a 2700Hz bandwidth in my TS-440S.
>
> cheers, Lane
>
> - R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
Indeed, even restricting the bandwidth of a voice signal to 2000 Hz has been
shown to reduce intelligibility by more than 50%. In this case, however,
intelligibilty is nearly always measured by the listener's ability to
distinguish between words that sound alike. (Do a web search on the
Diagnostic Rhyme Test.) Tests conducted more recently indicate that if the
restriction in bandwidth also eliminates an interfering SSB signal then
intellibibility may actually increase in certain subjects. Psychoacoustic
research indicates that some people have extreme difficulty dealing with the
off-pitch syllabic rate of an interfering SSB voice signal. If you know what
you're listening for (like your name or your callsign) then you're less
likely to miss it if the interference is reduced/removed.
More importantly, if the offending SSB signal is S9 and the desired signal
is S2 then the 1800 Hz filter can reduce the AGC pumping effects caused by
the operator just up the band. In these cases intelligibility may increase
dramatically.
Remember, Rich, not everyone can turn on a "tetrode with handles" when the
going gets rough.
Regards,
Doug, K4DSP
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