[Elecraft] K3: listening to both rcvrs

[Joe Subich, W4TV]

> So the reduction in SNR (assuming equal noise power) is
> 3.01 dB, not 6 dB.

That's the best case if the noise power is equal.  If the 
"other" receiver has higher noise power (wider bandwidth, 
more interfering signals, etc.) the S/N reduction is greater. 
Even 3 dB reduction in S/N is a big hit if the DX Station 
you're trying to hear is at or just below the noise level. 

It would be a shame to turn a top performing radio into a 
mid-pack device by mixing the audio - because of some old 
wife's tail.  Let those who want mixing do it externally 
so it doesn't impose a S/N penalty otherwise.



> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Kok Chen
> Sent: Sunday, November 16, 2008 5:10 PM
> To: Elecraft Reflector
> Subject: Re: [Elecraft] K3: listening to both rcvrs
> 
> 
> 
> On Nov 16, 2008, at 1:52 PM, Joe Subich, W4TV wrote:
> > Assuming equal volume settings and equal bandwidths in the two
> > receivers, the S/N will degrade by 6 dB (twice the noise voltage).
> 
> Unless the noise is correlated, the probability density
> function from  
> summing two random variables causes variances (noise power), not the  
> standard deviations (noise amplitude), to add.  So the reduction in  
> SNR (assuming equal noise power) is 3.01 dB, not 6 dB.
> 
> 73
> Chen, W7AY
> 
> _______________________________________________
> Elecraft mailing list
> Post to: Elecraft at mailman.qth.net
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft    
> 
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com