[Elecraft] Resonant speaker for CW

[Fred Jensen]

Maybe this is the science behind the old trick of putting your 
headphones on the desk facing upward to copy weak signals in noise.  
I've never really understood the reason except that high frequencies 
[noise] tend to be very directional from a transducer and dissipate 
rapidly, while lower frequencies are not directional.  At any rate, I 
know it works.

During my adventures in SE Asia long ago, we used turbine generators.  
They were 400 Hz, ran on JP4, and were light [two troops could easily 
carry them], but also important, their noise was very high pitched and 
could be muffled easily with a few sandbags.  The LF rumble of a 10 KVA 
trailer-mounted MB-5 diesel generator [~1,500 kg] couldn't be muffled at 
all.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County