And we can look at it going the other way. I can
run my FT-817 with its 5 watt signal for a lot
less money than my friend Jim can operate his
kilowatt. If the band is open The difference
between my 5 watt signal and his 1000 watt signal
is 2 or three S units at the far end of the
circuit. Not enough to be really noticeable. If
the band is closed, nobody is talking long
distance, the band is closed. Now when conditions
are marginal he has a decided advantage. Right
now I am happy burning a kilowatt of power
purchased from the electric company every 15 hours
while he gets about 20 minutes operating time for
his station for the same dollars.

--
73 es cul

wb3fup
a Salty Bear

"Ian White, G3SEK" wrote in
message news
Reg Edwards wrote:
Suppose when he's using 100 watts you can hear
only 25% of words (or
morse characters). So you can't copy him.

If he doubles power to 200 watts you will still
read only 40% of what
he says. So you still can't copy.

If he doubles power again to 400 watts you will
be able to copy 60% of
what he says. You will still be in big trouble.

At 800 watts 80% of words (or characters) will
be OK but it's not solid
copy. Requests to repeat will be common.

At 1600 watts 99% of words (or characters) will
be OK and that's solid
enough.

There are many assumptions in the foregoing
crude analysis. But as many
have experienced it is typical.


Typical for a machine, but not for a human
being. For humans, "copying"
very weak speech or Morse is mostly about
*understanding* it as
language.

In conversational speech, we don't always hear
every word. Our minds are
remarkably good at filling in gaps by using the
broader context of the
whole sentence. Even if you don't hear a word
clearly, you can hear a
word was there and your mind will automatically
make a good guess, based
on what we did hear before and after. It happens
all the time, in
conversations both on and off the air, and you
don't even notice
yourself doing it.

It's more obvious when copying Morse, where we
more often fill in
individual letters, but sometimes also whole
words. We make very clever
guesses about what the letter could have been,
based on what we did
manage to hear.

Often there is a threshold effect. Below that
threshold, you can hear
quite a lot but it doesn't make sense as
language. Just above the
threshold, it clicks into context and you can
understand a whole
stretch... and then maybe we lose it again.

It's also like listening to a language we only
"half" know. That doesn't
mean we understand a certain percentage of
individual words, as a
machine might. The way it really works with
human beings, we're suddenly
delighted to find ourselves understanding whole
sentences... and then,
just as suddenly, we lose it again completely.

The exceptions are for certain key items like a
callsign, name, QTH or
contest exchange. These items come one by one
(without context) and must
be logged with 100% accuracy, so then it's
rather more mechanical like
Reg describes. But even for key words like
phonetics, there is a
threshold between hearing a sound, and that
sound resolving itself into
a recognisable word.

As any DXer knows, the threshold between
"getting it" and "losing it"
can indeed be as little as 1dB. The more serious
you are about working
right down to that threshold, the more that last
1dB matters.


--
73 from Ian G3SEK 'In Practice'
columnist for RadCom (RSGB)
Editor, 'The VHF/UHF
DX Book'
http://www.ifwtech.co.uk/g3sek