[Lowfer] " XR " HSCW experiment tonite on 186.100 KHz

[JD]

>>>Curiousity has me wondering just how much information could
>>>be conveyed at the rate of 1200 wpm when a lowFER signal
>>>peaks above the noise ??

In principle, almost none outside the immediate neighborhood.  In practice, 
even less.

Remember, Andy, "the noise" is not some quantity that's the same for every 
mode.  The higher the data rate, the broader the transmission bandwidth; 
thus, the broader the receive noise bandwidth will have to be also, and the 
harder it is for a miniscule LowFER signal to ever peak above it at all! 
The statistical chances of overcoming the noise grow smaller and the time 
intervals during which it can happen grow shorter.  Even at conventional CW 
speeds, one is already well into the area of diminishing returns so far as 
data throughput per day is concerned (compared to lower speed, narrow band 
modes).  Over any substantial distance, you have to wait a very long time 
for a good enough opening to occur to copy anything at all.

That's one limitation in principle.  In practice, there's another, and it's 
a biggie: if your LF antenna has any efficiency at all, it is too limited in 
bandwidth to transmit a signal that wide in the first place.  That's why I 
said the chances in practice are even less than "almost" none.

Consider 12 wpm Morse.  A continuous string of dits would comprise a 10 Hz 
square wave imposing itself as 100% amplitude modulation on your carrier. 
To maintain anything resembling a square shape to the envelope (required for 
distinct detection of the on/off states) it is necessary to transmit the 
first few odd harmonics of the 10 Hz fundamental frequency.  The third and 
fifth are sufficient--but that still means crucial sidebands exist as far as 
+ and - 50 Hz from the carrier, which is why 100 Hz is a reasonable 
bandwidth specification for a carefully shaped 12 wpm CW signal.  Multiply 
the data rate times 100, and your signal will be 10 kHz wide!  It wouldn't 
make it through your antenna without serious envelope distortion and group 
delay problems...not to mention, you might need to move down in frequency a 
bit to keep sideband products within the band if you somehow did broaden the 
antenna response enough. :)

As a rough approximation of what high speed CW would do to your coverage 
area, imagine transmitting music in AM mode over your LowFER and seeing just 
how far away you can decipher unfamiliar lyrics on an AM radio.  The range 
will be a tiny fraction of what you achieve with CW, let alone QRSS. 
Antenna bandwidth is the main reason spread spectrum techniques have never 
caught on among LowFERs, too.

John