[RTTY] PSK and waterfall - some more

[Bill Coleman]

On Feb 14, 2007, at 1:41 PM, Phil Cooper wrote:

> HOWEVER............. I will still stand by the fact that a 600  
> watts PSK
> signal will drown a lot of the waterfall.
> I have seen how bright a 600 watt trace will be, and it clearly  
> wipes out
> any chance of seeing close signals.

That's not just a property of PSK, but of any mode. A weak signal in  
the midst of several strong stations will be hard to copy. That's why  
many receiver specifications deal with close-in dynamic range and  
blocking. Good receivers can be really close to strong signals  
without losing their ability to hear weak ones.

Part of the problem with PSK is that users are encouraged to run wide  
filters and use the waterfall display for tuning. Their rig  
essentially stays fixed on one frequency. If you want to hear weak  
signals, you must use the narrowest possible filters you can, in  
order to block out as much nearly QRM as possible.

> I do concur that 10 watts overdriven will be bad, same as any  
> signal, and I
> do feel that a lot of PSK'ers do not understand this.

A couple of RTTY contests ago, I remember spending a minute or two  
trying to call a station, and he kept coming back to stations I  
couldn't hear.

Turned out, I was actually decoding an IMD product from his  
transmitter, because it was being grossly overdriven. He was actually  
about 1.5 kHz up the band. When I called him there, he came right back.

Overdriven transmitters aren't the sole province of PSK. It can  
happen with any audio signal we feed into our transmitters.

> Yes, I agree, PSK could indeed be a great mode for DX, but my  
> experience has
> been that there are simply too many folk using it without any  
> consideration
> of what needs to be set up.

I was working the ARRL CW this weekend at the NQ4I M/M. I deleted a  
lot of packet spots for some good DX -- many of which would have been  
new multipliers for us -- because they were on PSK and not CW. Bummer.


Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901