Topband: SDR Mythbusters - ADC Overload myths debunked...

[Tom W8JI]

> The opinion expressed in the Flexradio editorial about noise blankers 
> being
> completely harmless, is not an opinion, it is even false.
>

It really isn't an accurate or factual technical article. It is a sales 
brochure meant to enforce the love each of us have for a particular system, 
in this case the magic of SDR. You might as well read an MFJ advertisement 
for technical accuracy, watch a year old VW diesel commercial, or listen to 
a politician of any party telling us how they will fix everything. It is all 
sales and stoking people's emotions or existing opinions, with just enough 
truth woven in to avoid prison.

Oddly, the K3 Elecraft is largely SDR. It is an SDR receiver with a standard 
analog front end as a frequency converter with roofing filter. IMO, the 
worse part of the K3 is the SDR part.

Try this test. Poll users who work very weak CW signals routinely in all 
sorts of station environments, just the general population of weak signal CW 
DXers.  Ask them if analog detection is better for pulling a weak signal 
below noise floor out of noise, or if a DSP detection system is better.  The 
results are always that DSP detection systems are viewed unfavorably over 
good analog systems by significant number of people.

The limits of this case are digging weak signals, that are at or below 
noise, out of the noise.

There is always a certain loss of dynamics to me, when I listen to any SDR. 
It has been this way for me with any SDR or DSP detection radio. Something 
my ear depends on to know the difference between a signal below noise and 
just noise without signal is lost in every single DSP detection system I 
listen to. It melts the signal into the noise with a distortion.

We did a blind A-B test (I have audio lines that bring every receiver to a 
jack ). It is easy to tune two receivers to the same signal, and have 
someone else switch the lines.

People who cannot copy below noise signals seem to not notice this effect.

73 Tom