[CW] 600 Hz Resonant Speaker for CW - Plans

[Sergio R Rubio]

I have a Morse Code Reader MFJ-461, with its 9-volt battery included and 
working OK, for sale. Please let me know.

Sergio KP4L
No. 1 Honor Roll
FOC 1090
----- Original Message ----- 
From: "Jeffrey Herman" <jeffreyh at hawaii.edu>
To: <flymooney at gmail.com>; "CW Reflector" <cw at mailman.qth.net>
Sent: Tuesday, September 01, 2009 7:17 PM
Subject: Re: [CW] 600 Hz Resonant Speaker for CW - Plans


> Great. Well, if it was an April Fools article, I fell for it.
>
> 73, Jeff KH6O
>
> PS: If anyone has an MFJ Morse Tutor you'd like to sell, please let me
> know.
>
>
>
> On Tue, 1 Sep 2009, Patrick wrote:
>
>> Jeffrey Herman wrote:
>> >  I seem to recall an article about a VERY narrow CW mechanical filter,
>> > constructed as such: Take a pair of old headphone "cans", remove the
>> > outer plastic ear cover, then remove the metal diaphram. Using a metal
>> > cutter called a nipper (?), trim the diaphram in such a way that, for
>> > the most part, just a reed appears in the center (the longer the reed,
>> > the lower its resonant frequency, and vice versa). Replace the diaphram
>> > and cover. Now that particular earpiece will only pass signals whose
>> > audio freq'y exactly matches the reed's resonant freq'y.
>> >
>> > One of those "ah-ha" type of simple but effective projects.
>> >
>> > 73, Jeff  KH6O
>>
>> This was from an article in the April 1976 QST. I think this was
>> something for the April Fools issue as the author's name was "Tinh
>> Ehres" (Tin Ears) with a call of WH0OP. I remember reading about it
>> before I was a ham (an Elmer had given me a bunch of old QST's) back in
>> the early 80's. I have the .pdf of it or if you are a member of the
>> ARRL, you can do an article search. The title is "CW Super-Selectivity".
>>
>> Patrick KA4ZNU
>>
>>
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