[Elecraft] K3 & ADAT ADT-200A by HB9CBU

[John A. McCabe]

Hi Guy's

Thanks for the interesting discussion on the state of the art in SDR 
technology. This discussion does raise a few questions in my mind that I 
would like to ask. To me it is a question of the theoretical as opposed 
to the practical. Does it really matter if a receiver can hold up to a 
80db over 9 signal 2 Khz away or is this just a theoretical exercise? 
Would not the transmitted Phase Noise, IMD, and perhaps key clicks be 
the limiting factor or am I wrong about this?

Is there is a point of no return where increased close in dynamic range 
no long matters because modern transmitters simply can not or do not 
transmit a signal that clean. If so, then has the K3 and the Perseus 
reached that point of no return and the question of which one has a 
better close in dynamic range is more of a theoretical then a practical 
exercise.

I would think that with very strong signals (like 80 db over 9), the 
more important number from a practical point of view would be at wider 
spacings, as I would want to know if the receiver would hold up when I 
move away from the phase noise and IMD of the transmitted signal. I have 
a neighbor ham that I receive a very strong signal from. It would be 
impossible to operate 2 Khz from him regardless of receiver performance, 
but I do operate on CW while he is on SSB on the same band using the K3 
and I do not hear a thing. In my case, wide spacing performance is 
important to me, and is a concern that I have when considering 
purchasing a Windows based SDR. When I see wide spaced numbers of 
117-123, compared to the 140db plus of the K3, I feel that the wider 
spaced number are the more critical numbers to look at, or am I wrong 
about that?

73,

John, KD8K