"Dick Carroll;" wrote:
Floyd Davidson wrote:

So while it is quite possible to make the s/n ratio larger by
increasing the signal, it is equally possible, and sometimes much better
to increase the s/n ratio by lowering the noise. Sometimes it is the
*only* option available.


However, what has to change is the noise power per Hz, and
reducing the bandwidth does not change that.

That *Can't* be correct for all cases.
The total noise appearing in the channel is the sum of that appearing in
every Hz
within the entire channel. A narrow signal such as a radiotelegraph
signal may not
occupy the entire width of the channel. So narrowing the channel width DOES
reduce the noise while preserving the signal and improving the SNR..
Obviously where the signal is as wide as the channel this doesn't work,
but in
ham radio, working CW it sure does. Guaranteed.

DICK, you are not discussing the efficiency of a mode. What you
are arguing is the *operator's* ability to effectively use a mode.

Yet you insist that you are proving something about the mode itself,
rather than the operator and his equipment.

If the operator is effectively utilizing the mode he has chosen,
the bandwidth requirement of the mode is closely matched to the
channel the operator provides.

You are saying that your ineffective use of one mode compared to
your more effective use of another mode proves that it was the
*mode* that was more effective. All you've done is demonstrate
that you don't understand the effective use of radio
communications, the theory behind efficient use of the modes
involved, or what you have observed.


Increasing the signal power has the desired effect. There are
other ways to accomplish that, of course. Reduction of noise by
any means other than reducing the bandwidth (switching from an
omni directional antenna to a directional antenna, for example)
will have the desired effect.


Another example of why his stuff doesn't apply to the real world of ham
radio.
When a ham is working another station he has no control over the power that
station is injecting into the channel. What he can control is the
bandwidth,within limits of course.

DICK, the operator can do any number of things. We should
assume that just for starters the receive operator is correctly
adjusting the bandwidth of the channel to match the bandwidth
being transmitted.

There are *many* other things that can be controlled to change
the effective use of a communications channel. Your suggestion
*reduces* the channel capacity rather than making it more
effective.

If you want more *effective* communications, either increase the
data rate within the existing channel, or if it is already being
used as best that a given mode can provide, increasing the
channel capacity to either 1) allow a higher data rate or 2)
reduce the error rate.

To increase the channel capacity an operator has several
choices. Asking the distant end to increase power is one
possible solution. Another is to use, or adjust, an antenna to
provide an increase SNR, whether by reducing noise or by
increasing the signal, or both.

Within ham radio such situations vary widely, but for CW the sitiation
is pretty well
straightforward. Hams almost always enhance CW signals by reducing the
bandwidth
which raises the SNR.

Only if it was misadjusted to begin with. You aren't making a case
for CW, you're making a case that you are a poor operator.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)