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Old 04-05-2010, 17:35   #16
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Quote:
Originally Posted by kb79 View Post
alright, i've been playing with my rig and have a question that i'm sure is stupid and easily found elsewhere, but i'm apparently too dumb to find it:
Oh come on, you've got to be pulling our legs.....
The basic answers are in the links provided in earlier posts....
Trying to teach an entire class on radiowaves, modulation, etc. is well beyond the possibilities of an on-line discussion board.....and that is why you were given the links to the info that you need/desire.....
PLEASE read them.....

Now, the above was my first reaction to your recent post......and as I write this I'm having another thought......
Perhaps the above will be interpted as harsh???? and maybe that would leave you thinking this was a bad idea????
And, since that is not my intention.....here's my second thoughts...


ALL MF/HF Maritime voice comms are USB (Upper SideBand)......

If you had read the link USCG HF Voice
you would've seen the frequencies and mode (USB), are listed quite clearly.....(and if you follow further links to MF/HF Maritime frequencies, you'd find them easily....)
Quote:
4426, 8764, 13089 kHz (USB)0430Z1030Z8764, 13089, 17314 kHz (USB)1630Z2230Z
And, for maritime WeFax and Text (SITOR), these links also show the mode to use (USB) and details on how to tune-in these signals....as well as further links to WeFax and Text decoding software and/or receiving equipment manufactures, etc....
NWS Radiofax
Quote:
See tables below for abbreviated versions of radiofax broadcast schedules. Assigned frequencies shown, for carrier frequency subtract 1.9 kHz. Typically dedicated radiofax receivers use assigned frequencies, while receivers or transceivers, connected to external recorders or PC's, are operated in the upper sideband (USB) mode using carrier frequencies.
http://www.nws.noaa.gov/om/marine/hfsitor.htm
Quote:
Assigned frequencies shown, for carrier frequencies subtract 1.7 kHz. Typically specialized marine communications equipment uses assigned SITOR frequencies while general purpose equipment uses carrier frequencies. Note that stations share common frequencies.
Since I've posted these links before, I'm sure there are some (myself included) that feel I'm wasting my time, but figured I'd spend just a few minutes and make one last effort.....

Typically all HF Ham radio voice comms are USB on 14mhz and up....and LSB on 7.3mhz and below.....(to learn more about ham radio, please use this link www.arrl.org )



Quote:
Originally Posted by kb79 View Post
hat's the difference between USB, LSB, FM, AM and CW modes? if i'm tuned to any specific frequency, i can select any one of these modes, but i don't get it - isn't a frequency a frequency?
The "mode" is the mode of modulation.....and it is the modulation that carriers the information.....
In this specific case, the information is a voice.....(or data that makes up a weather chart or written words....)

If you think of your car radio for a moment, and forget about the IC-735, I think you'll get it....think of either AM of FM....
There are many radio stations transmitting on many different frequencies, and most all have different "information" carried on them (music, voices, etc.).....sometimes you run across (especially on "News Radio" and "Talk Radio" stations) the SAME information (like the same talk show, or the same news broadcast) on many stations at the same time......
USB = Upper SideBand
LSB = Lower SideBand
AM = Amplitude Modulation
FM = Frequency Modulation
CW = Continous Wave



Now, kb79, I realize that this is NOT a very involved technical explanation, but you've been given the resources to learn from and if you're unwilling to do this, that is your choice......


Good luck and fair winds....

John
s/v Annie Laurie


(GOD how much of an idiot do I feel like spending time giving information to someone that is "nameless"!!!!),
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Old 04-05-2010, 19:04   #17
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hey john,

sorry - i think my question may have been a bit poorly worded.

i did read the links, and (i think) understood them. i'm appreciative of the time you (and others) have taken, and i've made an honest effort to digest the information that you've provided. if i'm still missing something obvious... well, my fault not yours. anyhow -

Quote:
Typically all HF Ham radio voice comms are USB on 14mhz and up....and LSB on 7.3mhz and below.....(to learn more about ham radio, please use this link American Radio Relay League | Ham Radio Association and Resources )
my novice interpretation of this statement is that if i'm tuned to, say 14.3mhz, then i'm by definition in the upper side band. i was confused as to how i could then switch to LSB mode yet remain in a frequency range that's designated as USB.

after your reply, i did some research on my own and found a few links. i probably should have done this looking before posting. i'll take that one as my bad. anyhow:

Sideband - Wikipedia, the free encyclopedia

Quote:
Transmission in which only one sideband is transmitted is called single-sideband transmission or SSB. SSB is the predominant voice mode on shortwave radio other than shortwave broadcasting. Since the sidebands are mirror images, which sideband is used is a matter of convention. In amateur radio, LSB is traditionally used below 10 MHz and USB is used above 10 MHz.
also found this one:

A Science Odyssey: Radio Transmission: FM vs AM

Quote:
FM radio works the same way that AM radio works. The difference is in how the carrier wave is modulated, or altered. With AM radio, the amplitude, or overall strength, of the signal is varied to incorporate the sound information. With FM, the frequency (the number of times each second that the current changes direction) of the carrier signal is varied.
so, now that i've reexamined your links, and dug into a few of my own, i think i'm learning that the mode (USB, LSB etc.) really has nothing to do with the frequency i'm tuned to and more to do with how that frequency is generated by the transmitter or interpreted by the receiver. fair statement?

also sounds like, depending on frequency, convention dictates one mode vs another, but that there's nothing inherent in any particular frequency that dictates a certain mode. also fair?

in fairness, while plenty of the links you supplied mention which mode a transmission might be in, none of them really directly addressed the actual functional difference between these modes (which was the question i was trying to ask).

anyhow, i appreciate your time and patience.

-krister
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Old 04-05-2010, 20:13   #18
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Hi Krister,

While not necessary to understand the meaning of all the terms, if you are like me, understanding the details helps to figure out how to use it or make it work.

If I understand your questions correctly you are trying to figure out the meaning of the various terms? I will try to explain.

First think of all these as vibrations. Radio waves are electromagnetic vibrations, spoken words are sound or sonic vibrations. The goal of radio is to take the vibrations in the air caused by your voice and convert them into radio waves. This is done in the microphone where vibrations from your voice are first converted into electrical vibrations that are then added to the radio signal that goes out as electromagnetic vibrations. Then when you receive the radio signal the process is reversed and the electrical vibrations are converted back to sound in the speaker.

OK so based on that there are two ways to convert the sound of your voice into electrical signals and add them to a radio wave to transmit.

AM - amplitude modulation. The sonic vibrations of your voice make the radio signal vibrate stronger and weaker. It modulates the strength or amplitude of the radio wave.

FM - frequency modulation. Sonic vibrations make the frequency of the radio wave vibrate faster or slower.

So since the voice vibrations are electrically added to the power of the radio by two ways, changing the frequency or the power (amplitude) it takes a very different kind of circuit to add the voice vibrations to transmit and to get them back out in the receiver.

USB and LSB. This means the power of the radio wave is divided in half so you can use just the top half or bottom half of the wave. Simplistic explanation why to do this, it allows more power to go into the signal.

For various reasons, some technical (it just works better that way) and some because groups or governments agreed to set aside certain radio frequencies for certain uses, AM or FM or USB or LSB may be used for different frequencies or different applications.
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Old 05-05-2010, 08:52   #19
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Quote:
Originally Posted by kb79
...the mode (USB, LSB etc.) really has nothing to do with the frequency i'm tuned to and more to do with how that frequency is generated by the transmitter or interpreted by the receiver. fair statement?

also sounds like, depending on frequency, convention dictates one mode vs another, but that there's nothing inherent in any particular frequency that dictates a certain mode. also fair?
More than fair. You've got it exactly right.
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Old 05-05-2010, 18:57   #20
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Krister,
My apologies if my post from last night came off as abrupt.....(bad day here, yesterday.....my brother in surgery and my best friend's sister having a fatal heart attack...both in one day...)

1) As others have posted here, yes you've got it!!!

2) I forgot to include a few more links that would be helpful....
USCG Freqs http://www.navcen.uscg.gov/marcomms/cgcomms/call.htm
MF/HF Maritime Freqs http://www.navcen.uscg.gov/marcomms/...cy/default.htm



Good luck and fair winds.....

John
s/v Annie Laurie
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Old 22-07-2010, 17:44   #21
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just wanted to resurrect this thread for long enough to say thanks again.

due in large part to the info provided here, i've been able to successfully set up a wefax program (i'm using JVComm 32), download some faxes (just for fun - woohoo! hard to explain that thrill when the digital noise on my radio turns into visual weather info) get my general ham license and set up a winlink account.

if it hadn't been for you guys, i'd still be scratching my head.

so, thanks all.

oh, and no worries, john - looking back, it was a pretty dumb (or at least uninformed) question.
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