On Wed, 23 Jul 2003 11:38:14 GMT, "Matthew and Wendy Plante"
wrote:


"Robert Grizzard" wrote in message
...
Matthew and Wendy Plante wrote:
Is CW just FM without an audio signal? So, If I have a FM receiver, can
I
install a CW audio filter and pick up CW. Such as... an IC 207H or BC
780xlt
and a Vectronics CW Audio Filter. Thanks

FM receivers are designed to not respond to amplitude variations. CW is
about as pure an example of "information conveyed by variations in
amplitude" as one is likely to find. To cut to the chase, what you
propose won't work.

That being said, one can send Morse in a format receivable on an FM
receiver, but it'll be MCW rather than CW. Feeding a keyed audio
oscillator into an FM transmitter will produce MCW. The caveat here is
it is legal here in the states only from 50.1 to 54 MHz and above 144.1
MHz.

HTH

de kg7yy
--
The appearance of my E-mail address in any venue does not in and of itself
constitute a solicitation of bulk or commercial E-mail.

I don't want unsolicited commercial E-mail.

So, If I had a receiver capable of AM reception, then a CW filter would
work?


No, with AM reception, you'll just hear the CW signal as a staticky,
hashy sound. You need a receiver with a beat frequency oscillator, a
BFO, to receive CW with a nice tone.

The CW filter has nothing to do with receiving the CW signal, other
than narrowing the bandwidth to cut out interfering signals.

Bob
k5qwg

On Wed, 23 Jul 2003 18:26:21 -0000, (Dave Platt)
wrote:

FM receivers are designed to not respond to amplitude variations. CW is
about as pure an example of "information conveyed by variations in
amplitude" as one is likely to find. To cut to the chase, what you
propose won't work.

Sure it will! Open the squelch up all the way. You'll hear the
background noise from the band and/or the front-end electronics when
there's no carrier being sent. When the OM at the other end keys up,
the FM receiver will lock onto the carrier, and happily demodulate the
(nonexistant) sidebands - it'll go silent. No CW filter needed... in
fact it'd make the noise/silence difference harder to hear.

Admittedly, trying to copy "negative noise" CW is likely to be a real
hassle at first, but I imagine that one can train oneself to do it
(just as one can train oneself to read a book held upside-down).

Hey, it'd be easier to just pick up the mike on an FM rig and say, dah
di dah dit, dah dah di dahhh.

Bob
k5qwg



For _conventional_ CW reception, you need something rather different.

;-)

On Wed, 23 Jul 2003 18:26:21 -0000, (Dave Platt)
wrote:

FM receivers are designed to not respond to amplitude variations. CW is
about as pure an example of "information conveyed by variations in
amplitude" as one is likely to find. To cut to the chase, what you
propose won't work.

Sure it will! Open the squelch up all the way. You'll hear the
background noise from the band and/or the front-end electronics when
there's no carrier being sent. When the OM at the other end keys up,
the FM receiver will lock onto the carrier, and happily demodulate the
(nonexistant) sidebands - it'll go silent. No CW filter needed... in
fact it'd make the noise/silence difference harder to hear.

Admittedly, trying to copy "negative noise" CW is likely to be a real
hassle at first, but I imagine that one can train oneself to do it
(just as one can train oneself to read a book held upside-down).

Hey, it'd be easier to just pick up the mike on an FM rig and say, dah
di dah dit, dah dah di dahhh.

Bob
k5qwg



For _conventional_ CW reception, you need something rather different.

;-)

On Wed, 23 Jul 2003 20:09:30 -0500, Robert Grizzard belch-spoke these
words:

Matthew and Wendy Plante wrote:

So, If I had a receiver capable of AM reception, then a CW filter would
work?

Max and Bob both mentioned a beat frequency oscillator. This is
necessary to hear CW on an AM radio. You might beable to loosely couple
an external oscillator to your AM radio and have it beat against the IF.
The oscillator will want to be 800 Hz either higher or lower in
frequency than your last IF.

If you have ever used harmonics to tune a string instrument then you
have heard beat notes in operation. When you pluck the E string on a
guitar while you're touching the string over the fifth fret then pluck
the A string while you're touching it over the seventh, they should both
be vibrating at the same basic frequency. If they're not, you'll hear
the guitar go "woooOOOOWWWWWWOOOOoooowwwwooooOOOOWWWWWWOOOOOOooo oo",

Nice sound effect.

and
the rate at which the "wow"s get louder and softer is the difference in
tuning between the strings. A CW receiver -- or sideband receiver, for
that matter -- does the same thing except at RF instead of at audio
frequencies.

HTH

de kg7yy

On Wed, 23 Jul 2003 20:09:30 -0500, Robert Grizzard belch-spoke these
words:

Matthew and Wendy Plante wrote:

So, If I had a receiver capable of AM reception, then a CW filter would
work?

Max and Bob both mentioned a beat frequency oscillator. This is
necessary to hear CW on an AM radio. You might beable to loosely couple
an external oscillator to your AM radio and have it beat against the IF.
The oscillator will want to be 800 Hz either higher or lower in
frequency than your last IF.

If you have ever used harmonics to tune a string instrument then you
have heard beat notes in operation. When you pluck the E string on a
guitar while you're touching the string over the fifth fret then pluck
the A string while you're touching it over the seventh, they should both
be vibrating at the same basic frequency. If they're not, you'll hear
the guitar go "woooOOOOWWWWWWOOOOoooowwwwooooOOOOWWWWWWOOOOOOooo oo",

Nice sound effect.

and
the rate at which the "wow"s get louder and softer is the difference in
tuning between the strings. A CW receiver -- or sideband receiver, for
that matter -- does the same thing except at RF instead of at audio
frequencies.

HTH

de kg7yy

On Thu, 24 Jul 2003 10:47:21 -0500, Bob Miller belch-spoke these words:

On Wed, 23 Jul 2003 18:26:21 -0000, (Dave Platt)
wrote:

FM receivers are designed to not respond to amplitude variations. CW is
about as pure an example of "information conveyed by variations in
amplitude" as one is likely to find. To cut to the chase, what you
propose won't work.

Sure it will! Open the squelch up all the way. You'll hear the
background noise from the band and/or the front-end electronics when
there's no carrier being sent. When the OM at the other end keys up,
the FM receiver will lock onto the carrier, and happily demodulate the
(nonexistant) sidebands - it'll go silent. No CW filter needed... in
fact it'd make the noise/silence difference harder to hear.

Admittedly, trying to copy "negative noise" CW is likely to be a real
hassle at first, but I imagine that one can train oneself to do it
(just as one can train oneself to read a book held upside-down).

Hey, it'd be easier to just pick up the mike on an FM rig and say, dah
di dah dit, dah dah di dahhh.


I've heard it done. Or hell, try whistling without having the airstream go into the mic.

John

On Thu, 24 Jul 2003 10:47:21 -0500, Bob Miller belch-spoke these words:

On Wed, 23 Jul 2003 18:26:21 -0000, (Dave Platt)
wrote:

FM receivers are designed to not respond to amplitude variations. CW is
about as pure an example of "information conveyed by variations in
amplitude" as one is likely to find. To cut to the chase, what you
propose won't work.

Sure it will! Open the squelch up all the way. You'll hear the
background noise from the band and/or the front-end electronics when
there's no carrier being sent. When the OM at the other end keys up,
the FM receiver will lock onto the carrier, and happily demodulate the
(nonexistant) sidebands - it'll go silent. No CW filter needed... in
fact it'd make the noise/silence difference harder to hear.

Admittedly, trying to copy "negative noise" CW is likely to be a real
hassle at first, but I imagine that one can train oneself to do it
(just as one can train oneself to read a book held upside-down).

Hey, it'd be easier to just pick up the mike on an FM rig and say, dah
di dah dit, dah dah di dahhh.


I've heard it done. Or hell, try whistling without having the airstream go into the mic.

John