[Elecraft] Elecraft] Audio/noise diversity/phasing question

[Fred C. Jensen]

I used Bose noise cancelling phones in the 90's while doing around 250K miles a year on United.  They cut the steady aircraft noise nicely, mainly the higher pitched part, not so good on the LF rumble.  It seemed the steady higher frequencies were responsible for the headaches.  On my radio, they were ineffective with IF atmospheric static, and almost ineffective against power line noise.

I'd guess that much of the LF rumble was conducted thru my body rather than through the air.

Full disclosure: My hearing was already severely compromised, the higher frequency steady noise was weakly audible to me without the phones and absent with them.  However, it apparently still gave me headaches on transcontinental flights without the phones.

Fred K6DGW
Sparks NV

phil anderson <aldenmcduffie at sunflower.com> wrote:
>HI JERRY, 
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>You may be thinking of the Bose Noise Cancelling Headphones. These operate at audio and an extra microphone is added to each earbud to pick up background audio in your hamshack or workplace. I'm guessing that the signal from one of these added microphone earbuds is then inverted; and, in turn each earbud adds the signal from its extra microphone to the audio signal from the phone's audio output. In that way, the external noise is cancelled when listening to both phones. 
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>One way one might utilize this process in diversity mode using two radio receivers within one radio - like in a K3 or K3s - is to offset receiver B from receiver A, such that receiver B is only receiving noise. Then sum the inversion of that in an external audio circuit with the output of receiver A to receive just the CW signal generated by receiver A. This in effect would cancel the noise from each receiver similarly to that with the Bose. 
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>Right now I'm using the K3 in diversity mode by receiving RXB via the AUX input (with a Beverage antenna) and RXA via ANT1 port (with a SteppIR vertical) and letting the K3 process the audio in its native diversity mode. To this I'm also utilizing the APF feature. It's an easy guess that this beats out the scheme described above. However, if might simply be fun to try the adhoc method. 73, Uncle Phil, W0XI, Lawrence, KS. 
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>----- Original Message -----
>
>From: ae4pb at carolinaheli.com 
>To: Elecraft at mailman.qth.net 
>Sent: Thursday, August 13, 2015 11:31:53 AM 
>Subject: [Elecraft] Audio/noise diversity/phasing question 
>
>I've read where a received signal is split into two signal paths, the noise 
>is somehow shifted 180 degrees (not sure how without affecting the desired 
>signal), the two signals are fed to your headset, one to each side, somehow 
>our brains then perceive the signal to POP out of the noise. Does this apply 
>to the K3/S ? I'm very interested in anything that effectively results in a 
>higher signal to noise. 
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>
>Thanks in advance. 
>
>Jerry Moore, Future K3S owner 5Sept2015 
>
>AE4PB 
>
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