Carl R. Stevenson wrote:

Mike,

Sounds to me like you were experiencing front end overload in your
receiver ... when the signal exceeds the dynamic range of your receiver,
all sorts of things happen and the signal can appear to be MUCH wider
than it actually is.

To verify this, turn off the preamp (if you have one), and switch in about
20 dB of attenuation before the front end of the receiver and see if it
all gets better ...

Will do. Thanks Carl. The other users wer complaining about it too, but
they could have been experiencing the same problem.

- Mike KB3EIA -

Bill Sohl wrote:
"Mike Coslo" wrote in message
...

The question kind of states it. I suppose that the BW might be wider as
the speed increases.

The reason I ask is that on 3580 tonight, we're all sitting there fat,
dumb, and happy, when W1AW starts it's CW broadcast. And it's some 700
kHz wide!!! And now I'd swear it's almost 3kHz wide. That's like SSB!!!


Did you mean 700Hz wide (you typed 700kHz).

Yikes! Yep that was 700 Hz. A 700 kHz signal would be something indeed!
I see I misspelled Morse too......

Just got a new computer, and was probably too excited last night! 8^)

- Mike KB3EIA -

"Mike Coslo" wrote

The question kind of states it. I suppose that the BW might be wider as
the speed increases.

There are three different bandwidths that come into play. They are
"necessary bandwidth", "effective (or actual) bandwidth", and "apparent
bandwidth"

Necessary bandwidth in hertz for copying a morse signal is defined as Bn=BK
where B is modulation rate measured in Baud, and K is an overall numerical
factor which depends on the allowable signal distortion. The commonly used
values of K are 3 for non-fading paths, 5 for fading paths, and 8 for
fading/multipath smearing. From the formula you can see that higher speeds
(Baud) require more bandwidth, just as you supposed. The nominal "necessary
bandwidth" presumed for CW is 100Hz which is based on 25WPM (20 Baud) over a
fading path (B=20, K=5). Quite honestly, "necessary bandwidth" is primarily
an academic exercise and planners tool, as it ignores some practical 'real
world' issues and doesn't answer the question raised in your subject line.

Effective bandwidth is an actual on-the-air measurement of the width of the
signal at some designated level, most commonly -60dB referenced to the peak.
To understand what is being measured, you need to recognize that Morse is
sent as an amplitude modulated carrier (AM) and that it contains sidebands.
Like any AM signal, those sidebands extend nominally plus/minus the carrier
at the frequency of the modulation, or BW=2M. Modulation of this signal
contains two components.

The first component is the baud rate of the actual on/off keying (see
"necessary bandwidth" above). Were it only for this component, measured CW
signals would be very narrow, 100Hz, and dependent totally on keying speed.

The second modulation component is related to the rise time of the radiated
signal. Fast rise times (where the RF envelope resembles a square wave)
generate signals rich in harmonics and as these harmonics mix with the
primary signal and each other in the transmitter stages, they produce sum
and difference signals which become part of the sidebands of the radiated
signal. The sharper the rise time and the more non-linear the transmitter
stages, the more energy there is in the harmonics, and thus the bandwidth is
wider (as measured at -60dB skirt points). Controlling this component of
bandwidth can take the form of regulating the rise time (shaping in the
keying circuit) and ovoiding overdriving of transmitter circuits.

The third kind of bandwidth is "apparent bandwidth". This bandwidth is
determined by the effective bandwidth (see above) AND the performance of the
receiver environment. If a receiver were "perfect", then effective and
apparent bandwidth would be equal (the receiver would perfectly reproduce
the desired signal in the form it arrived at its antenna and would reject
the effects of all non-target signals present.)

But receivers aren't perfect (well, maybe my Sherwood equipped R4C is
close). Extremely loud signals (your neighbor 3 doors away) will sound
("apparent") several hundred kHz wide, because your receivers AGC will pump,
RF and IF stages will be overloaded, and the faster he sends the worse it
will be. I'm giving the obvious extreme example, but just to make the
point. Many times just some reasonable adjustments of your receiver such as
turning off noise blankers, reducing the preamp level, or turning your
antenna will reduce the apparent bandwidth down in line with the actual
bandwidth of the transmitted signal.

73, de Hans, K0HB

"Dan/W4NTI" w4nti@get rid of this mindspring.com wrote in message thlink.net...
"Bert Craig" wrote in message
om...
Mike Coslo wrote in message
t...
The question kind of states it. I suppose that the BW might be wider as
the speed increases.

Mike, I believe the bandwidth actually decreases as the speed increases.

The reason I ask is that on 3580 tonight, we're all sitting there fat,
dumb, and happy, when W1AW starts it's CW broadcast. And it's some 700
kHz wide!!! And now I'd swear it's almost 3kHz wide. That's like SSB!!!

Needless to say, their strong signal was pretty tough on all us 5 and
ten watters. you could get most of a message through, but it took a lt
of the fun out of it.

Bummer, hope it was just a one-time anomaly.

What the heck , over?

- Mike KB3EIA -

73 de Bert
WA2SI

A one time anomaly????? W1AW is a bulletin station. Been there, on or
about for 90 years.

Dan/W4NTI

Geez Dan, I thought it might've been a malfunction at W1AW...hence the
"anomaly" statement.

73 de Bert
WA2SI

Mike Coslo wrote:

The question kind of states it. I suppose that the BW might be wider
as the speed increases.

CW code signals are around 100Hz wide, IIRC.



The reason I ask is that on 3580 tonight, we're all sitting there fat,
dumb, and happy, when W1AW starts it's CW broadcast. And it's some 700
kHz wide!!! And now I'd swear it's almost 3kHz wide. That's like SSB!!!

It might seem so if your receiver was in SSB mode. A narrowband signal
will still be
heard throughout the passband of a filter set for a wideband mode.
Also, if you were in CW receive mode instead, the receiver's AGC will
make the
attenuation of that filter's side skirts seem worse. What would be 10dB
down without
AGC will look like only say 3dB if the AGC is enabled. Especially as
you mentioned
(below) that w1aw was a strong signal.



Needless to say, their strong signal was pretty tough on all us 5 and
ten watters. you could get most of a message through, but it took a lt
of the fun out of it.

In article , Mike Coslo
writes:

How did you determine the bandwidth?

On the waterfall display, you can look at the BW pretty directly. A good
psk31 signal doesn't take up a whole lot of space, maybe 40 hz.

A Morse signal set up for optimal BW at 50 wpm takes up about 200 Hz.

This CW signal had spikes on the end that extended almost 400 hz on
each side. It ripped into the PSK signal and wiped it out. When it got
really bad, everyone just gave up.

Key clicks. Could be caused by a problem at Newington, or by a problem at the
receiver end.

And now I'd swear it's almost 3kHz wide. That's like SSB!!!

Yep. Such a bandwidth would require extremely "hard" keying, though. Or a
modulated carrier.

Needless to say, their strong signal was pretty tough on all us 5 and
ten watters. you could get most of a message through, but it took a lt
of the fun out of it.

Was the AGC on?

Both on and off. I often have to turn it off when a strong signal
desenses the reciever and I'm working a weak station.

But did you also turn down the RF gain and turn up the AF? Or kick in an
attenuator?

What WK3C posted earlier is correct - if a strong signal overloads your
receiver, its bandwidth may appear to be wider than it really is. If someone is
running PSK31 using the usual SSB-rig-feeding-a-soundcard approach, overload of
the receiver is a real possibility.

What was your setup?

Your modulated carrier thing may just be a big clue. When the signal
ended up putting spikes over the whole section of the band, I removed
the connection to the computer to listen to the signal. It sounded
pretty strange. I'll have to check what the signal again to see what it
sounds like on ssb or even AM.

Sure.

btw, W1AW's 80m CW freq is advertised as 3581.5 IIRC.

Oddly enough, last night I was "reading the mail" from W1AW on 40 meters while
packing up some parts I sold. Signal was very clean on my Southgate Type 7. I'm
not sure of the exact time, but the transmission ended with "END OF 35 WPM" ;-)


But in these K1MAN days, it would be a good idea for ARRL to keep a
good clean signal, and not do the eqivelant of K1MAN - that is to just
start the transmission and stomp all over everyone else nearby.

The transmitters at W1AW are all Harris "professional grade" transceivers, one
for each band plus a spare. Computer controlled from the main console, no
adjustments needed to the rig itself. But even Harris stuff can have problems.

Separate antennas for each band, too - the 80/75 antenna is a cage dipole
between two of the towers. 80 feet up if it's a foot.

I'll tune down to 80 tonight if I get the chance and see how W1AW sounds.

73 de Jim, N2EY

Mike,

You're received a number of good answers. As for measuring bandwidth, I've
used exactly two receivers that would be suitable for accurate measurement,
and I couldn't afford either of them. With stability measured in 10 to the
9th power and accuracy at 10 to the 8th, these little babes were well over
$50,000 in the mid 90s. LOL. Oh, and that doesn't include the cost of the
IF spectrum analyser that was connected to one of them, nor any other costs
such as calibrated antennas.

As stated, the rise and fall times of the waveform determine the bandwidth;
often the receiver can deceive you as to what the bandwidth is.

Of course, it is possible there may have been a problem at W1AW.

73 from Rochester, NY
Jim AA2QA

"Mike Coslo" wrote in message
...
The question kind of states it. I suppose that the BW might be wider as
the speed increases.

The reason I ask is that on 3580 tonight, we're all sitting there fat,
dumb, and happy, when W1AW starts it's CW broadcast. And it's some 700
kHz wide!!! And now I'd swear it's almost 3kHz wide. That's like SSB!!!

Needless to say, their strong signal was pretty tough on all us 5 and
ten watters. you could get most of a message through, but it took a lt
of the fun out of it.

What the heck , over?

- Mike KB3EIA -



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In article k.net,
"Dan/W4NTI" w4nti@get rid of this mindspring.com writes:

W1AW is a bulletin station. Been there, on or
about for 90 years.

Actually about 66 years (1938). In all that time there have been only three
main rigs - the original rackpanel jobs, the 1960s ones installed about the
time the "new" Hq building went up, and the Harris setup from the mid-90s
renovations. Something like 25-30 years of service per setup.

Trivia Quiz:

There was an ARRL HQ station before W1AW. What was its callsign?

There's a second callsign for the ARRL lab. What is/was it?

73 de Jim, N2EY

On Sat, 03 Jan 2004 20:21:22 GMT, KØHB wrote:

Effective bandwidth is an actual on-the-air measurement of the width of the
signal at some designated level, most commonly -60dB referenced to the peak.

IIRC the accepted standard for measuring occupied bandwidth is -26
dB, which includes 99% of the signal.

--
73 de K2ASP - Phil Kane

N2EY wrote:

Trivia Quiz:

There was an ARRL HQ station before W1AW. What was its callsign?

W1MK, I think located near Brainard Field, Hartford.

There's a second callsign for the ARRL lab. What is/was it?

Memory fails...

Dave K8MN