[RTTY] Narrow RTTY

[Kok Chen]

On Jan 16, 2006, at 6:15 PM, Bill Turner wrote:

> Just had a long chat with W7AY on 7085 using very narrow RTTY. We
> started out with 170 Hz shift and then went to 23 Hz. I transmitted a
> canned macro (the word TEST repeated 36 times) at 100 watts, then ten
> watts then one watt, using both shifts at each power level.

I had earlier played with Steve WB6RSE using 125 Hz shift (since it  
will fit into a 200 Hz bandwidth if you use the 1.2*shift + baudrate  
equation).  Bill could only go to fixed shifts, so between W6WRT and  
W7AY, we'd only tried 170 Hz and 85 Hz before dropping down to 23 Hz.

Bill was actually transmitting with a 25 Hz shift but receiving me  
with 23 Hz shift.  I was switching my transmission at various times  
between 23 Hz and 25 Hz.

I was doing the receiving end of the test, using 45.45 baud matched  
filters, and a bandpass filter that adjusts to the width of the signal.

Real or HF Simulator signals that exhibit selective fading would be  
more interesting, since I suspect wider shifts will do better.

I didn't notice any observed selective fading with the close tone  
separation.

73
Chen, W7AY