[TenTec] Purpose of 250 Hz 8 pole filters

[Steve Hunt]

Many, many years ago I was involved in the design of a "survivable" 
military ComSat system that would provide a low bit-rate channel under 
heavy jamming conditions. We set ourselves the target that it should do 
as well as a good CW operator under the same S/No conditions. That meant 
we had to "measure" the performance of the CW operator.

We took 3 very experienced operators - the sort that copy 25wpm random 5 
letter groups whilst doing the Times cryptic crossword at the same time 
(I'm not kidding). We gave them the best receivers available at the 
time, equipped with a vast array of filters.

I was fascinated as a young engineer to see that they never used the 
narrowest filters, however poor the S/No. They rarely went below 1KHz. I 
guess they had some pretty narrowband stuff going on in their heads :) 
And by the way, the set a pretty tough target to beat!

Steve G3TXQ