"Jeff Liebermann" wrote in message
...
I'll make it really simple for you. FM is "hi-fi", while AM is noisy
"no-fi". Don't you want to be cool strutting down the street with
your iPhone watching HDTV with 7.1 sound? It wouldn't do to have it
sound like the typical AM broadcast station. For decent quality, you
gotta have FM.

FM is not inherently any more 'hi-fi' than AM. Fidelity is a product of
bandwidth, not modulation type. AM is not even so susceptible to noise as
the frequency goes up, since the energy of the noise pulses goes down
logarithmically as frequency goes up. AM is used for aeronautical
communications very successfully for several reasons, one of which is the
LACK of 'capture effect'. There are still some frequencies where AM will be
more susceptible to interference than FM, but FM would still suffer, for
instance the segment between 1330-1400 MHz which is the natural frequency of
Hydrogen (lots of that around).

On Jul 15, 4:30 pm, Jeff Liebermann wrote:

Radium hath wroth:

The problem with AM audio is that the ultimate signal to noise ratio
isn't very good. AM is noisy at any signal strength. The noise never
really goes away. On the other foot, FM is noisy with very weak
signals, but becomes very quiet once the limiter starts to work.
That's why FM is preferred for music and why analog AM broadcasting
sounds marginal at any signal level.

AFAIK, the main issue with AM is that it is much more vulnerable to
magnetic disruptions than FM. That is why when you are listening to
the AM radio at home and someone turns on the microwave-oven, you here
those odd sounds on the receiver.

Also, if there is a solar prominence you can hear the resulting
magnetic disruptions on an AM radio receiver. They sound scary and
enjoyable at the same time.

Nope. For decent quality sound you need audio that is uncompressed PCM
[similar to CDs and WAVE files] with a sample rate of at least 44.1
KHz and a bit-resolution of at least 16-bit. Or the analog equivalent.

I thought you didn't like digital? You only gave me a choice of AM or
FM. Now, you want digital.

It depends, if I can find the analog-equivalent of 44.1 KHz-sample-
rate, 16-bit-resolution digital audio, that just as good.

If I a limited to only AM or FM for analog audio, I choose AM because
I like the sounds generated by solar prominences and other RF magnetic
disruptions.

Ironically, for video, I prefer FM. Yup, video signals on FM carriers
instead of AM carrier. The Y-luminance signal should be broadcasted on
an FM carrier. That's the analog video I like.

With compression and
proper coding, you can pickup quite a bit of efficiency, at the
expense of sounding like you're gargling ball bearings.

Disgusting! I hate most forms of digital audio compression. For me,
either keep it uncompressed or use WMA compression. All non-WMA
digital audio compressions below 320 kbps sound like stinky human
fart. Or an angry infant foaming at the mouth.

Not too bad a
tradeoff for voice. Really awful for music.

Awful for both. The only digital audio compression I like is WMA.
The sounds resulting from WMA compression sort of make me think of
those RF electronic telecommunication devices used in The Bourne
Identity. That movie features some really awesome devices that make
those interesting sounds - for example, when the main character is
getting his hand screened. I also associated these sounds with the
electronic telecommunication devices used by the Soviet Union. Soviet
Union has got some really psychedelic sounds in their electronics. You
know, those fancy dial-up modems tones?

Fortunately, none of the
broadcasters or cellular carriers use raw CD data, mostly because it's
not compressed.

All digital audio compression formats other than WMA, stink badly!!

Here are my rules for digital audio:

A. Whether compressed or not, the audio must be monaural and with a
sample-rate of at least 44.1 kHz.

B. The only compression allowed is WMA. No other compression format is
permitted.

C. In its uncompressed form, the audio must have a bit-resolution of
at least 16-bit

D. If compression is used, then the sample-rate of the compressed and
the uncompressed version of the audio must be the same.

E. If compression is used, the only thing that should be decreased is
the bit-resolution. The sample-rate must remain unchanged

Let's say a song that was originally recorded in stereo is given to
me. The song must to be converted to mono* via the following steps:

1. Record audio from CD [or other stereo audio source] into Wavelab,
Adobe Audition [or other audio software] into a file. For simplicity
let's call this file "Track1.wav"

2. Make a copy of Track1.wav and save the copy as "Track1B.wav"

3. Open Track1.wav and reduce the gain of its audio by 77.5%

4. Convert Track1.wav to monaural audio

5. Save Track.1

6. Open Track1B.wav and reduce its audio gain by 50%

7. Invert the phase of the left channel of Track1B.wav

8. Convert Track1B.wav to mono

9. Save Track1B.wav

10. Create a new stereo wave file whose bit-resolution is 16-bit and
sample rate is 44.1 kHz. For simplicity let's call this file
"untitled.wav"

11. Copy and paste the audio of Track1.wav into the left channel of
untitled.wav

12. Copy and paste the audio of Track1B.wave into the right channel of
untitled.wav

13. Convert untitled.wav to mono

14. Save untitled.wav

*Songs that were originally-recorded in stereo need to be converted to
mono via the above 14 steps because different sounds are recorded
differently in the L and R channels. The audio that is originally
panned to the center is significantly louder than the audio whose
phase is different in the left & right channels. This is why I reduce
the loudness of non-inverted stereo audio file by 77.5% [before
converting it to mono].

In the stereo file whose left channel has its phase inverted, I
decrease the loudness only by 50% and then convert it to mono. Usually
-- the lead vocals, bass, and percussion are recorded identically in
both the left and right channels. The piano, chorus, guitar, and synth
pads are usually recorded differently in the left and right channel.

"Brenda Ann" hath wroth:

"Jeff Liebermann" wrote in message
.. .
I'll make it really simple for you. FM is "hi-fi", while AM is noisy
"no-fi". Don't you want to be cool strutting down the street with
your iPhone watching HDTV with 7.1 sound? It wouldn't do to have it
sound like the typical AM broadcast station. For decent quality, you
gotta have FM.

FM is not inherently any more 'hi-fi' than AM.

FM was invented by Edwin Armstrong specifically to eliminate the noise
problems of AM broadcasting. What I think you might be referring to
is the huge ****ing match between Armstrong and John Carson over
whether FM was any better than FM in the 1930's. The consensus is
that very narrow band FM isn't that much better than AM (of equal
occupied bandwidth), but wide band FM (as used in broadcast FM and TV)
is far better than AM for just about everything.
http://fecha.org/armstrong.htm

Fidelity is a product of
bandwidth, not modulation type.

Correct. Actually, it's also a function of modulation linearity
(distortion and intermod) and encoding method (dynamic range), but I
don't wanna slither down that diversion. Pretend I didn't mention it.

AM is not even so susceptible to noise as
the frequency goes up, since the energy of the noise pulses goes down
logarithmically as frequency goes up.

If you're thinking of impulse noise, you're mostly correct. However,
there are plenty of other sources of AM noise available. For example,
the typical VHF aircraft radio requires substantial filtering of the
magneto to avoid hash. Same with any onboard motor. If you've ever
tried to install a TV (VSB is a form of AM) in a vehicle, you'll also
find that ignition and motor noise can be a problem.

Also, your statement isn't quite right. I think what you meant to say
is that as the frequency increases, the energy produced by an impulse
source, in a given bandwidth, goes down. Even that's not accurate as
I have a fluorescent lamp calibrated noise source that's quite noisy
well into the GHz range.

AM is used for aeronautical
communications very successfully for several reasons, one of which is the
LACK of 'capture effect'.

The FAA, FCC, and various manufactories have tried to move aircraft
radios away from AM and towards FM several times in the past 30 year
or so. They failed mostly due to international WRC reluctance to swap
out expensive radios. It took literally forever to get GPS receivers
TSO approved and about 15 years for nav/com radios to go from 50KHz to
25KHz channel spacing, and that was just the FAA. Where else can you
find an industry, where progress is somewhat retarded by a regulatory
agency of the federal government?

I listen to a mix of VHF aircraft AM channels and FM ham and public
safety channels on my scanner almost constantly. It's easy to
recognize the AM stations by their uniformly crappy audio.

Most domestic ground to ground airport traffic is now all FM, as is
military ground to ground and ground to air. The reason is that it's
difficult to find a decent AM aircraft band walkie talkie. So, they
use commercial FM radios. The only AM walkie talkies are used by
experimental aviation and ultralights, some of which do not have much
of an electrical system that can handle the grossly inefficient AM
transmitters.

Also, nobody really cares about the "capture effect" as the tower
usually has multiple receiver sites and can generally deal with
simultaneous transmit collisions. However, they do care about the
heterodynes produced by simultaneous transmissions, which obliterate
both transmissions. With FM, they could use commercial receiver
voting systems and largely eliminate the problem.

There are still some frequencies where AM will be
more susceptible to interference than FM, but FM would still suffer, for
instance the segment between 1330-1400 MHz which is the natural frequency of
Hydrogen (lots of that around).

If my AM or FM receiver is sensitive enough to hear something in the
"water hole", it would be attached to a very big dish antenna.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Radium hath wroth:

AFAIK, the main issue with AM is that it is much more vulnerable to
magnetic disruptions than FM.

Wrong. Take a magnet, any magnet. Wave it around your AM or FM
radio. Hear anything different? You won't. Therefore, forget about
magnetic disturbances. The main issue with AM is susceptibility to
pulsed noise, as found in motors, fans, auto engines, and computahs.
FM doesn't have as bad a problem because the limiter in the receiver
clips everything to the same level, thus reducing the effect.

That is why when you are listening to
the AM radio at home and someone turns on the microwave-oven, you here
those odd sounds on the receiver.

No. Microwave ovens operate at 2400Mhz. AM broadcast operates at
1MHz. No way there's going to be any interference there. However,
the microwave oven may have a fan or CPU that runs the display, that
belches garbage at 1MHz. I just tried mine and there's a tiny bit of
buzz coming from the display section when I shove an AM radio right up
to the display. If that's what you're hearing, I would test it with a
different microwave oven. If only yours has the problem, I suggest
you consider a replacement.

Also, if there is a solar prominence you can hear the resulting
magnetic disruptions on an AM radio receiver. They sound scary and
enjoyable at the same time.

You can also hear lightning storms. In the US, most of those are in
the south east of the country. Nothing like interference from 3000
miles away. Lightning detectors operate in the 25-50KHz region.
Incidentally, there are about 8 million lightning hits per day, which
is why the noise sounds almost continuous.

(chomp...)

Sorry, my time is up. Please insert $0.25 for the next 3 minutes.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

In rec.radio.amateur.antenna Jeff Liebermann wrote:
Radium hath wroth:

AFAIK, the main issue with AM is that it is much more vulnerable to
magnetic disruptions than FM.

Wrong. Take a magnet, any magnet. Wave it around your AM or FM
radio. Hear anything different? You won't. Therefore, forget about
magnetic disturbances. The main issue with AM is susceptibility to
pulsed noise, as found in motors, fans, auto engines, and computahs.
FM doesn't have as bad a problem because the limiter in the receiver
clips everything to the same level, thus reducing the effect.

That is why when you are listening to
the AM radio at home and someone turns on the microwave-oven, you here
those odd sounds on the receiver.

No. Microwave ovens operate at 2400Mhz. AM broadcast operates at
1MHz. No way there's going to be any interference there. However,
the microwave oven may have a fan or CPU that runs the display, that
belches garbage at 1MHz. I just tried mine and there's a tiny bit of
buzz coming from the display section when I shove an AM radio right up
to the display. If that's what you're hearing, I would test it with a
different microwave oven. If only yours has the problem, I suggest
you consider a replacement.

Also, if there is a solar prominence you can hear the resulting
magnetic disruptions on an AM radio receiver. They sound scary and
enjoyable at the same time.

You can also hear lightning storms. In the US, most of those are in
the south east of the country. Nothing like interference from 3000
miles away. Lightning detectors operate in the 25-50KHz region.
Incidentally, there are about 8 million lightning hits per day, which
is why the noise sounds almost continuous.

(chomp...)

Sorry, my time is up. Please insert $0.25 for the next 3 minutes.

Don't tell him about whistlers.

--
Jim Pennino

Remove .spam.sux to reply.

msg hath wroth:

Jeff Liebermann wrote:

snip
I have a fluorescent lamp calibrated noise source that's quite noisy
well into the GHz range.

Sounds interesting.

Would you please post some details or pointers to references about
constructing and calibrating such an instrument?

Groan. I built it myself from an article in some long lost magazine
perhaps 30 years ago. It's just a 5watt fluorescent tube, with a few
turns of wire wrapped around it going to a broadband CATV amplifier.
One end of the wire coil is terminated at 50 ohms. The other end goes
to the broadband amp. The lamp is powered by a heavily filtered
isolation xformer. Calibration consisted of taking a scope photo of
the output on a spectrum analyzer. Just about any gas discharge tube
will work. Neon, fluorescent, blue or green gas discharge display,
the new compact fluorescent tubes, plasma tube TV, etc.

Most older microwave noise sources use argon filled gas discharge
tubes, but fluorescent will sorta work. The HP 346A (3-18GHz) and
349A (0.4 to 4GHz) noise sources are examples of such gas discharge
tube test noise sources. The manual for the 342A NF test system,
which includes the 349A noise source is at:
ftp://bama.sbc.edu/downloads/hp/342a/342a_349a_service_6.pdf
See section 5.

Some minor notes around Fig 9.24 on Page 207 at:
http://books.google.com/books?id=sNLQmi3ymTYC&pg=PA206&lpg=PA206

I could post some photos, but I really don't want to tear it apart to
take pictures of the guts.

These daze, microwave noise sources use avalanche diodes although just
about any diode with a sharp knee will work. Diodes are more stable,
less fragile, and easier to produce than gas discharge tubes.
http://www.ham-radio.com/sbms/sd/nfsource.htm
http://www.atmmicrowave.com/coax-noise.html

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sun, 15 Jul 2007 16:30:13 -0700, Jeff Liebermann
wrote:


Not really. If you really want weak signal reception, I suggest you
look into SSB (scientific set back) modulation.

what??!! ^^^^^^^^^^^^^^^^^^^


John

In rec.radio.amateur.antenna John Larkin wrote:
On Sun, 15 Jul 2007 16:30:13 -0700, Jeff Liebermann
wrote:


Not really. If you really want weak signal reception, I suggest you
look into SSB (scientific set back) modulation.

what??!! ^^^^^^^^^^^^^^^^^^^

Too subtle for you?

It's called humor.

--
Jim Pennino

Remove .spam.sux to reply.

John Larkin hath wroth:

On Sun, 15 Jul 2007 16:30:13 -0700, Jeff Liebermann
wrote:
Not really. If you really want weak signal reception, I suggest you
look into SSB (scientific set back) modulation.

what??!! ^^^^^^^^^^^^^^^^^^^

Sigh. Nobody here seems to have a sense of humor.
SSB = Single Side Band
Happy now? You sure take the fun out of acronym mutilation.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
If you've ever been hit by lightning, I don't think you'll find it
very boring. With 8 million hits per day, chances are good that
you'll get hit. Ummm... could you step outside for a moment?

Reminds me of an afternoon when I was 600 ft up a 1,000 ft TV tower
climbing on the inside. The tower took a hit and the lightning bolt
followed a aircraft cable hoist line down the inside of the tower. Right
between my legs.