Like Fred my hearing loss is associated to my military career, from
standing near V2 and other large rocket firings at WSPG and a 4'
lanyard firing of a 120 mm AA gun, to the firing of very adjacent
155mm howitzers, and other very loud noises etc.
However when later doing very weak signal detection, while operating
2M EME, I discovered, by accident and experience, that, good passive
external sound prevention, could easily be obtained with just good
headphone earmuffs. Even an "old fashioned ringer" bell telephone,
at my elbow, couldn't be heard. I also found that my sweet spot
audio frequency was about 400 Hz, with no ringing, even with an Autek
1A external audio filter, cranked down to about 25 Hz BW. The
cheapest RS headphones (Nova 10), also had a mechanical resonance at
about 400 Hz. When all was aligned up at the 400 Hz sweet spot, the
signal just seemed to jump out of the noise ! Easily 10 to 20 dB
below the residual noise level, very comparable to what today is
claimed by JT65 and other digital techniques .
Chuck, W7CS
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com
