Be sure to hold onto your hat when [email protected] decides to expell some gas.
" wrote in
ups.com:
From: on Tues, Oct 3 2006 3:25 pm
wrote:
From: Nada Tapu on Sat, Sep 30 2006 2:23 pm
On Fri, 29 Sep 2006 20:56:08 -0400, wrote:
Amateur radio is the ONLY radio service still using
morse radiotelegraphy for communications purposes.
So what? Amateurs choose the mode they want to use. What is wrong with
choosing Morse Code and HF operation?
Now, now, Jimmie, you are assigning some "blame" on a plain
and simple factual statement: "Amateur radio is the ONLY
[US] radio service still using morse radiotelegraphy for
communications purposes."
What I wrote is a plain and simple fact.
You seem to be in denial, unable to accept a plain and simple
fact. Your problem, not mine.
Some may say the Morse Code *test* is outmoded. But you are saying the
*use* of Morse Code is outmoded!
Yes, in every other radio service except amateur.
You seem to be in denial, unable to accept a plain and simple
fact. Your problem, not mine.
FM broadcasting is the only radio service that uses stereo multiplex FM
- is it outmoded?
There is NO SUCH THING as "stereo multiplex FM" mode.
FM broadcasting is NOT the "only radio service" using stereophonic
audio modulation. Stereophonic audio modulation is NOT required
by FM band broadcasters. Those broadcasters MAY use stereophonic
audio OR they may use monophonic audio plus a SUBCARRIER separate
audio channel OR they may use stereophonic audio PLUS the
subcarrier audio. The term "multiplex" applies to SEPARATE
information sources, not stereophonic audio. All of that is
very much in use today.
DTV (Digital TeleVision) broadcasting carries QUADRAPHONIC audio
(optional, may be monophonic or stereophonic) with or without
extra separate audio subchannels, with or without audio text
("Teletext") accompanying the video. That is very much in use
today and for the foreseeable future of American TV broadcasting.
Some AM broadcasters are still using the Motorola C-QUAM system
for stereophonic broadcasting where each stereo "channel" takes
one of the two DSB sidebands. While that system works well,
the AM broadcasting listener market has NOT received it well
enough to warrant more than a few broadcasters adopting it or
any similar AM stereophonic system. It appears to be on the
way out due to listener non-acceptance.
"Shortwave" broadcasting is still "testing" Radio Mondial
system which is capable of stereophonic audio transmission.
Technically the system works very well. The increased cost
of receivers and the general downturn in world interest in
"shortwave" broadcasting might result in a future
discontinuance. Note: What was once "shortwave" radio
broadcasting is increasingly shifting over to satellite
relay and VoIP dissemination rather than maintaining the
HF transmitters; program content remains the same.
The International Civil Airways VOR (Very high frequency
Omnidirectional radio Range) system ground stations ALWAYS
broadcast with a subcarrier (9.96 KHz) that is FMed with
the reference magnetic azimuth bearing phase. The RF
output is amplitude modulated with 30% AM so that any
receiver can determine its magnetic bearing to the ground
station by comparing the demodulated reference phase with
the main AM phase. Relatively simple receiver demod that
was devised in vacuum tube architecture times. In use
since 1955 worldwide, no foreseeable discontinuance in the
future despite wider use of GPS.
Multi-channel (many "multis") using FM was once the choice
of trans-continental microwave radio relay, the linkage
across the USA that made national TV and 'dial-anywhere'
long distance telephony possible. It has been largely
replaced by optical fiber relay using digital multiplexing
of voice and TV channels using digital modulation of laser
light. The longest (to date) fiber-optic relay is the
long, long like between London and Tokyo through the
Mediterranean Sea past Saudi Arabia, India, around
southeast Asia, past the Phillippines. Most of it under
water. Optical "pumping" with a second optical wave-
length is used for amplification to avoid electronic
repeater amplifiers. Such optical pumping (amplification)
is not possible with microwave RF radio relay.
There are many different other examples of "FM"-like
modulations at work daily in HF and on up into the micro-
waves. The most common is the various adaptations of the
common dial-up modem using combinatorial amplitude and
phase modulation of an audio carrier wave. Those are the
"TORs" (Teleprinter Over Radio) used for data
communications in maritime service; voice is done via SSB
and may be simultaneous with the data. This is on-going
in use and for the foreseeable future.
The FIRST HF Single Sideband circuits (since the beginning
of the 1930s) used combinatorial modulations. The 12 KHz
bandwidth was composed of four 3 KHz wide separate one-way
channels. Each 3 KHz (voice bandwidth) channel could carry
up to 6 frequency-shift-modulated teleprinter channels.
The common arrangement worldwide (by both commercial and
government users) was to use two 3 KHz channels solely
for voice/telephony and the remaining two for 8 to 12 TTY
circuits (number dependent on the redundancy required to
overcome selective fading). While those "commercial" SSB
circuits were numerous from the 40s on into the 70s, their
number has dwindled due to better throughput and reliability
from satellite radio relay services.
Was there anything else technical about communications
and/or broadcasting that you wanted to erroneously state?
Whewww. That was a gassy one.
SC
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