Steve;
There is another "effect" relating to the color
waterfall that I have become aware of as a developer
of PSK31 sofware. Whether the waterfall colors are RGB
or CMY based unlike a greyscale the increments of
signal strength are continuous but may large steps
depending on the number of colors. In most waterfalls
the signal strength is logarthimic.

Let me illustrate the effects, suppose there are 2
stations. The first a QRP station has display strength
of 10 and the second a display strength 20. Thus, 10x
relative difference (remember logarithms). Assume the
noise floor is 3. BTW, 100x or more differences are
very common. This gives the weak station about 7db
above the noise (without heavy math, just about
copyable). OBTW, don't even try for IMD on the weak
station it will be bogus and even the strong station
in this example is suspect, but this is a different
topic for another time.

With a greyscale (usually 256 values) waterfall
display, the signal differences show as intensity
differences just above. Now for color, if we assume, 8
colors for the entire display range say 0-80. First
color 0-10, second 10-20 etc. Ooops..... The lower
signal and noise have the same color....gone!

I have contrived this example a little...but only a
little. I fundamentally do not like a waterfall
particularly color for weak signal work. The solution
is a spectrum display (which I'm adding to our Linux
Kpsk program) available on most PSK programs.

Steve, maybe if everone turns off the squelch and uses
spectrum displays we'll get some of those big gun
scores ;-)

---- 070@yahoogroups.com wrote:

I received six responses to my question on whether

any of you use

the squelch function available in PSK. As expected,

the responses

varied. Two people never use it, while the other

four use it at least

occasionally. Three of those four specifically note

that they turn it

off when working with weak signals, while the fourth

carefully

watches visually for the weak signals.

My conclusion based on this non-scientific sampling

is that the

people who responded to this question understand

what the

squelch function is, when to use it, and most

importantly when

NOT to use it. But I also think that there are many

PSK operators

who do not have this same understanding.

As a dedicated QRP operator, I recognize that my

signal is usually

one of the weaker ones on the waterfall. And I know

that it is

difficult for me to stand out in a pileup. But I

find that there are

many times when I try to respond to the CQ of a very

strong station

and it seems he can't hear me. Even if the other

station is running

100 watts, he's only 13 dB stronger than I

am--that's about 2 S-

units. (Note that antenna gain works both ways,

transmit and

receive, so the only real variables are our

transmitter powers and

our receiver sensitivities and noise levels.)

Last weekend in Delaware there were a few stations

that didn't

respond to my call, even though they were plenty

strong in my

waterfall, and their power levels weren't

drastically more than mine.

Perhaps their noise levels were higher than mine,

but I also

speculate that they may have set their squelches in

a way that

"filtered out" the weaker stations.

From a technical standpoint, I'd like to point out

that PSK acts a

lot more like SSB than it does FM. With FM, there is

a real

threshhold effect--below a certain SNR, there is

virtually no copy,

and just a fraction of a dB higher, there is very

good copy. This

type of modulation is wonderful for squelch, and you

can eliminate

the annoying background noise when there's no signal.

But PSK, like SSB, has a more gradual relationship

between SNR

and performance. Of course there is a large range of

signals that

have virtually perfect copy. But we've all

experienced the ranges of

signals that have varied from 10% copy up to 98%

copy. This is the

tricky range, where a squelch setting may eliminate

a lot of random

letters, but it may also eliminate a weak signal

with only 65%

copy. This level (65% copy) admittedly won't make

for a pleasant

ragchew. But 65% is plenty good enough, with a few

repeats, for a

contest QSO or for DXing.

I don't know of anyone who uses a squelch during SSB

operation,

especially during a contest or while DXing. Yes,

there is static, and

sometimes it's hard to make out the other station.

But we train our

ears and mind to ignore the noise and copy the voice

on the other

end. I think the same principle applies to PSK

operation. By

opening up the squelch a little bit more (or turning

it off

completely), there will be more random or erroneous

characters on-

screen. But just as you can train yourself to HEAR

through the

noise, you can also train yourself to READ through

the noise. And

sometimes that can be the difference between making

the contact

and not.

Let me encourage you to try operating without your

squelch on, or

at least opening it up more than usual. Yes, you

will see some

more garbage characters, but you'll also find that

you will be able

to copy some signals much better. And with a little

practice, I think

you'll find (as I did) that the garbage characters

won't bother you as

much as you think they will.

73,
Steve
W3HF

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