>
>> >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.
>
// May
>Remember, Rich, not everyone can turn on a "tetrode with handles" when the
>going gets rough.
>
// And that turned out to be the problem. When I ran a tetrode with
handles to get over jammers, I found that the jammers quickly learned to
jam only the station I was trying to talk to since jamming the "Plywood
Box" successfully was somewhat less than likely. The workaround was for
me to telephone the person who was being jammed, leave the VOX on and the
RX Audio gain on 0 at both ends, then carry on the simulcast conversation
as if the jammers were not being heard -- which was assuredly the case
with both Audio Gain controls at "0". The jammers eventually realized
that they were not being heard by the jamees and went away with their
tails between their legs.
cheers, Doug
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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