[CQ-Contest] RE: [AMPS] End to background noise

Nemecek, Joseph F. Joseph.F.Nemecek at twa.com
Mon Oct 20 14:12:49 EDT 1997

If you want the data sheets Morel mentions FAXed to you. Dial
800-446-6212 and enter FAX Code number: 1956.
Joe, K0JN

>From: 	Morel Grunberg[SMTP:morel.grunberg at telrad.co.il]
>Sent: 	Monday, October 20, 1997 2:01 AM
>To: 	'Amplifier reflector'
>Cc: 	'Cq-contest'; 'FT-1000MP list'; 'Ham-equip'; 'Towertalk'; 'Yaesu
>Subject: 	[AMPS] End to background noise
>Few months ago I heard that "Analog Devices" has a new 
>integrated circuit ( SSM-2166 ) who is able to cancel the
>background noise present in an audio signal coming from
>a microphone. 
>After I received the 15-pages data specs & application note
>I discovered that this tiny 14-pin IC can solve my background
>problems coming from the amplifier blower, computer fan, TV
>and radio sound, children cries and a busy street down under 
>my window shack.
>After I've built the circuit and  began the tests, I was astonished
>by the effectiveness of the IC: simply all the background noise
>was attenuated with an average of 35dB down of my voice. The 
>air reports were excellent and all my partners asked me what
>I'm using to cancel the noises, after a short demonstration with
>the unit bypass switch on/off. Now, I can use my processor at
>compression levels much bigger than the previous 3-4 dB I used
>before due to the high background noise with extremely low 
>distortions ( typical 0.1-0.2% ). Absolute no voice alterations or
>any kind of time delays, echo or signal rise/fall timing related
>(as in other products) were found.   
>The unit is quite simple: an IC, 5-6 capacitors, 3-4 resistors and
>5 small variable resistors. The supply is 5Vdc at 15mA or 12-25V
>if a simple 7805 regulator is used. The board can be as small as
>3x4cm and should be placed in a small shielded box.
>Some modifications should be made on the original schematic diagram
>and setting procedure given in the "Analog Devices" application note.
>The unit was tested with Yaesu/Kenwood/Icom transceivers and 
>performed very well with no RF feedbacks. The only difference is
>of course, the microphone connector wiring.
>Few of my local friends built also this small unit with very good
>too. As I've heard, a complete kit and and an assembled kit will be
>available very soon in U.S. Also, an article on this issue will appear
>in "QST" very soon, as I've heard from some U.S. friends. 
>The unit is very useful for SSB contest teams when few operators
>are crying in their microphones at same time creating a stressing
>noisy environment.
>The "Analog Devices" complete documentation can be found on their
>home page ( www.analog.com ) and can be read with Acrobat Reader
>software. If you don't have this program on your computer, you can
>download for free immediately via a link to "Adobat".
>The 15-pages can be received also from Customer Support Hot Line
>automatic fax : 1-800-262-5643.
>73 de Morel, 4X1AD
>FAQ on WWW:               http://www.contesting.com/ampfaq.html
>Submissions:              amps at contesting.com
>Administrative requests:  amps-REQUEST at contesting.com
>Problems:                 owner-amps at contesting.com
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