Home |
Search |
Today's Posts |
#11
|
|||
|
|||
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 |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
shortwv | Shortwave | |||
178 English-language HF Broadcasts audible in NE US | Shortwave | |||
Amateur Radio Newslineâ„¢ Report 1402 Â June 25, 2004 | Shortwave | |||
Amateur Radio Newslineâ„¢ Report 1402 Â June 25, 2004 | General | |||
214 English-language HF Broadcasts audible in NE US (09-APR-04) | Shortwave |