[Elecraft] Bridging L-R of stereo Line Out for single channel diversity RTTY

[Jack Smith]

Classically, in ye olde days of mechanical printers, diversity combing 
was done post detection in the modem. Two receivers feeding two modems, 
and the detector outputs of the two modems were combined with a 
switching device that selected the output with the best SNR.

With CW, the operator's wet-ware can separate the two channels and 
perform a version of best channel selection.

Jack K8ZOA

On 2/18/2013 6:15 PM, conwell at aracnet.com wrote:
> I'm wondering if diversity receive might help with RTTY decoding, to 
> reduce deep fades.
>
> I shorted together the left and right channels from the Line Out jack 
> on the back of the K3, and fed them to right input of computer sound 
> card.  (The left input of sound card is connected to a TS-850, for SO2R.)
>
> I was concerned that bridging the two audio channels in this way would 
> cause the diversity separation in the headphones to be lost (e.g., 
> when operating CW, and having the bridged audio line for RTTY decoding 
> still connected).  But the headphones seem to still work as before, 
> with separate channels audible, L-R.  I'm guessing there's a buffer 
> amplifier that feeds the rear panel line out jack, so that shorting 
> those channels doesn't effectively short the other audio L/R outputs 
> (e.g., headphones).
>
> Does anyone know for sure?  'Anyone see a downside to this approach?
>
> (I recognize I might be trading one problem for another: instead of 
> QSB in one channel, I now might sometimes have the L- and R-channels 
> equal in amplitude and out of phase, leading to a nil combined signal 
> for the decoder at odd intervals.  But that seems a low probability.)
>
> Tnx,
>
> /Bill, K2PO
>
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