[Elecraft] K-3 Noisy Receiver?

[Don Wilhelm]

Dick,

I believe you are mis-interpreting the data.  This is the response of 
the receiver to a broadband source.  Is the fact that this is from a 
noise generator confusing you?  We are displaying the capability and 
shape of the receiver response, and it has nothing to do with the fact 
that the source is broadband noise.  Look at the broadband noise source 
as if it were a LOT of signals, all of the same amplitude but of 
slightly different frequencies, so close together that you cannot tell 
where one ends and the other starts.
Within the receiver passband,  the ideal is 0 (all other levels are 
referenced to that), and outside the passband there would ideally be no 
response at all (a very large negative number) - that would indicate a 
perfect filter with infinite skirt slope and a perfectly flat top.

The K3 has nearly the ideal response within the passband (all zeros) 
while the MP varies a little bit (this is normal for a filter).
Outside the passband - take the 3100 Hz point for example - the lowest 
response is better.  Here the MP had a response only 42 dB below the 
maximum in-passband response while the K3 had a response that is 67 dB 
lower than the peak within the passband.  So, out of the passband (and 
at this point), the K3 is 27 dB more quiet than the MP.

73,
Don W3FPR

RLVZ at aol.com wrote:
> Interesting data but what am I missing here?  "Note the K3 audio  amplifier 
> is the cleanest hands down".  Looking at the data below, doesn't  it show 
> that in the 22 audio ranges from 50-3200hz that the MP has a  lower noise 
> level in 12 out of 20 ranges and is about identical in  most of the others?  
> Doesn't a lower negative number = a lower noise  level?  
>  
>   
>