[Elecraft] RX Test (long)

[Joe Subich, W4TV]

> But these "artifacts", at least in my observation, are only 
> present when a signal is present. If they are there when only 
> noise is being received, they are below the extremely low out 
> of band noise level.

I see 7.8 and 12 KHz products clearly at about 10 dB above the 
stopband noise with no signal present.  They get much stronger 
with signals present and additional products appear.  Even 
though the maximum level is still 60 dB below the listening 
level, they are still clearly above the "masking" level and 
they will be audible to someone with normal hearing with 
"full range" headphones and/or speaker. 

73, 

   ... Joe, W4TV 
 
 




> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Julian, G4ILO
> Sent: Saturday, January 09, 2010 5:11 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] RX Test (long)
> 
> 
> 
> 
> 
> Joe Subich, W4TV-4 wrote:
> > 
> > 
> > Here is the genesis of the complaint that the K3 is more
> > fatiguing than other receivers.  The out of band noise 
> > (noise above 5 KHz) in the K3 is, as you say, at least 60 dB 
> > below the peak audio level (actually, I measure it at more 
> > than 90dB down above 5 KHz).  However, the stopband also has 
> > many leakage products (DAC artifacts) in the stopband some 
> > of which are as much as 50 dB ABOVE the noise floor.  
> > 
> > While these products are well below the desired audio in the
> > passband, they are "in the clear" as far a local noise.  
> > This requires the ear/brain system to subconsciously work 
> > to reject (filter) the undesired discrete frequency products. 
> > 
> > 
> 
> But these "artifacts", at least in my observation, are only 
> present when a signal is present. If they are there when only 
> noise is being received, they are below the extremely low out 
> of band noise level. Therefore, whilst I can see that they 
> could contribute to unpleasant or tiring sounding audio for 
> those blessed with acute hearing, I can't see that they would 
> result in the receiver sounding noisy.
> 
> -----
> Julian, G4ILO. K2 #392  K3 #222.
> * G4ILO's Shack - http://www.g4ilo.com
> * KComm - http://www.g4ilo.com/kcomm.html
> * KTune - http://www.g4ilo.com/ktune.html
> 
> -- 
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