[Amps] Getting rid of blower noise

[Bill Fuqua]

Unlike the situation where you are trying to null out the noise in a small 
confined environment such as a ear phone, the noise sources in the 
amplifier and the possible locations of reception of the noise have many 
path length differences and multiple frequencies. You may find a location 
for the microphone in one location that works to null out some noise but 
not noise from the other locations. Also, it is not phase shifting that 
would be required but time delay or linear phase shift with frequency.

73
Bill wa4lav


At 10:52 AM 2/20/2007 -0700, mail at jimforsyth.com wrote:
>The nice thing about this design is that the microphone is apparently
>only needed to get things started. Once you have everything set up for
>dead silence the microphone is not picking anything up so I guess you
>could unplug it and move the tripod out of the way.
>
>Jim, AF6O
>
>*** Seriously (yeah right), you need a condenser microphone on a tripod
>3
>feet from the affront of your amp.  A mic amplifier, a phase shifting
>network, an audio power amplifier and speakers all bolted into the amp
>rack
>next to the RF power amp...
>
>When at full power adjust the phase shifting network until the amp is
>silent.  Total BOSE system for your amp.  It would probably neutralize
>choke
>talk and everything.  Dead silence.
>
>
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