[SFDXA] Presentation for the May SFDXA Meeting

[Randy Shirley]

Howdy DXers,

As I mentioned at the March meeting , we are going to have more 
presentations at the in-person meeting to increase attendance.

We have a terrific and educational presentation, planned for the May 7th 
meeting!  Our member, Carlos N4IS, will be presenting some very special 
speakers that he has been designing and building for many years.  He 
just recently re-started his research on these special speakers, for 
weak signal CW.

When CW signals are very weak, our brains can actually detect these 
signals significantly below the noise.  Then we would use narrow digital 
filters, and in some cases, analog audio peak filters.  The problem is 
that, the more narrow that you make the pass band, the more the filter 
rings.  Ringing is not very good, while listening to high speed CW!

These speakers are VERY narrow in response AND they don't ring!!, like 
the electronic filters do. I was very impressed while visiting Carlos as 
he demonstrated these narrow band speakers.

He has built and tested over 100 designs!



And he has tested over 40 different speaker drivers!



At the presentation, you will be able to hear for yourself the results 
of Carlos's research.  I look forward to a large turnout!

More forthcoming!

Very73,
Randy N4QV
President SFDXA
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