Topband: ADC Overload from MW transmitters

[Tom W8JI]

> I'm still of the opinion --right or wrong-- that there will *always* be
> hams using analog technology that will be able to out-hear anyone using an
> SDR (even DDS) to copy very weak CW signals at the low end of 160. *But I
> have an open mind.* I think it was Barry N1EU that disagreed with me on
> that (I think he has an Anan DDS SDR). But we need people like him that
> drive us to investigate SDR further. :-)

I think it depends on the individual. If an individual has the mental 
ability to "process" noise out of the signal, external filtering and "noise 
reduction" won't mean nearly as much. Some people I've operated with are 
better than I am, some the same, and many others just cannot hear the 
signals unless they are crystal clear.

I'm poor at SSB, but good at tone.

My first experience with this was when a group of people came over to pick 
me up to go to the Cincinnati hamfest. I was working VK's on 160 (using a 
modified SX101) through heavy noise, copying the callsigns fairly easy, but 
no one else could even tell there were signals.

Another case was at Dayton, when MFJ was demonstrating a DSP. I could hear 
the signals the same with or without the DSP, and people walking up were 
marveling. Others walking up couldn't hear the difference.

When a human is part of the decoding system, results will vary.

A similar thing is true for results at different stations, when we talk 
about overload. One size does not fit all applications. I see now where the 
one station's comments about a bunch of modest signals overloading an SDR 
kicked off the "popular folklore" rebuttal, but 1500 watt transmitters into 
antennas less than 2 wavelengths from an RX antenna are not the same as 
something far out of band one or more miles away.

We have to read carefully, and not mix cases.   :)

73 Tom