Primer for Ham radio part two

This guest post is by Michael C and entry in our non-fiction writing contest .

Single Side Band (SSB) transmission is available on higher end CB radios and of course, in ham radios that support the mode. Think of the “mirrored sine wave” cut in half. That half of the signal uses less than half as much power. Also, lets get rid of the carrier so that if there is no sound, even though you are keyed up, there is no signal. All CB radios transmit at 4 Watts of power (per FCC regulation) but on side band that amounts to 12 Watts since the “average” of the sine wave (for a half height signal) is used. Radios that have SSB have a choice of USB or LSB (Upper/Lower Side Band) which does allow for double the number of channels for CB’s. Ham radios don’t have near as much of a channel crunch with thousands of options.

SSB is really a “person to person” mode because both operators must “fine tune” their radio to each other. It goes something like this; first radio operator gives a count of ten and the second operator twists the fine tune knob until the first operator does not sound like a chip monk and not like “Jabba the hut” either. The second operator then gives a count of ten while the first operator tunes in. A third operator cannot participate since he can only tune in to one or the other operator, then the other operator sounds like a chip monk or “Jabba the hut”. The third operator also sounds odd to BOTH of the first operators since neither is tuned in to him/her.

FM

The circuits that made radios better, more reliable, also allowed higher frequencies to be used. Electronics allowed the signals to be manipulated in ways not done before. The FM (Frequency Modulation) transmission mode varies the “frequency” of the wave with change in sound.

fm wave1 300x220 Primer for Ham radio part two

I’ll use FM stereo radio (88-108 MHz) as an example. It works like this – start with a base line frequency like 100.1 FM then add the audio count (20-20,000 Hertz) to the base (100.1+20,000=100.12) to get a transmit frequency.

The right channel (radios are south paws) of the stereo signal is subtracted from the base and transmitted separately. There is no stereo mode for ham radio. FM broadcasts have very high fidelity compared to AM broadcasts. Lightning does not make FM crackle like it does AM. This is because lightning cannot affect the frequency, only the amplitude or power.

An early problem was FM drift in which the FM signal “drifted” out of frequency – PLL (Phase Locked Loop) circuits corrected this. In fact most ham radios have digital tuning. FM transmission is the dominant method for frequencies above 29 MHz. You’ll also notice something nice about the FM signal – it’s constant strength. The power (amplitude) does not change like AM does. AM transmissions are low frequency which means big waves and big antennas.

The big waves can travel a long distance as “ground waves”. The AM waves can “circle the globe” by reflection off the ionosphere which occurs mainly at night. Sky wave bouncing is an interesting subject in itself but since most people are going to start as a tech – all of the bands that you will be allowed on are “line of sight” bands. You would have to become a General (ham license) to operate on HF bands then you would already know about bouncing your signal.

This contest will end on December 16 2012 – prizes include:

  • First Place winner will receive a Go Berkey Kit valued at $150.
  • Second Place: $100 Cash.
  • Third Place: $50 Cash.

Well what are you waiting for – email your entries today. But please read the rules first… thumbs up Primer for Ham radio part two

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Comments

  1. Keep ‘em coming!

  2. Since I’m the techie geek guy, I’d like to add a little to the Sideband and FM discussions. If you look at Part one of this series you will see a nice representation of the carrier signal, the signal to be transmitted, and the combined signal that is produced when the mixing or modulation takes place. In AM, there are actually 2 copies of the combined signal, since the modulation (Fm) signal is both added to and subtracted from the carrier (Fc). So in the frequency spectrum you would see the carrier with a copy of the modulated signal above it (the upper sideband) and another mirror image copy of the modulated signal below it (the lower sideband; therefore, three distinct signals are sent in an AM transmission, which can also be called Double Sideband (DSB). Since the carrier contains no information except a reference point for the frequency, it can be easily discarded, sending only the two modulated frequencies containing information. This is known as Double Sideband Suppressed Carrier (DSB/SC). Since we are not wasting power on the carrier, this power ends up in the sidebands, making them 50% stronger from a power perspective. Since DSBSC still sends two copies of the information, we are wasting spectrum (channel space) and power to transmit redundant information. Eventually techniques were created to eliminate either the upper or lower side band, allowing only one copy to be sent as Single Sideband Suppressed Carrier (SSB/SC), now commonly referred to as Upper Sideband (USB) and Lower Sideband (LSB) and is a standard transmission mode on nearly all HF radios in the last 30 years or more. Since AM or DSB divided the power between the carrier and the two sidebands, eliminating the carrier and one of the sidebands allows all of the power to be used on just the remaining sideband, effectively tripling its power.

    SSB is not merely a “person to person” mode and is used in radio networks with dozens or hundreds of participants. Networks generally have a network control station who calls the net into operation, so generally all participants will tune to that station. As other participants in the net work communicate, it is sometimes necessary for you to slightly re-tune the radio to make them more understandable. Most modern HF radios take care of this with a Receiver Incremental Tuning (RIT) knob that allows slight tuning changes in the receiver without changing the transmitter frequency.

    As for FM having more fidelity, this is really not the FM mode (although the problems with AM and noise sources like lightning are correct). Fidelity comes with the amount of information being transmitted in the signal. FM from your local FM station uses a signal range up to about 20,000 Hz (cycles per second) which allows transmission of signals with a wide frequency range (like music), and in the case of an old fart like me, well beyond my hearing range. FM used for ham radio is generally limited to about 2400 Hz, so the fidelity for voice is fine; however, if you were to transmit something like music, you would notice a difference from the commercial FM radio station.

    All in all Michael is giving a good primer for those who want to know more about the hobby and may be ready to take the plunge. The truth is that more people on this forum will get useable information from his articles than my comments, but hopefully it will all come together to get some folks into the hobby.

    • michael c says:

      Thanks OP. I could not have put this in without adding another chapter to the series.

      • michael c,
        NP. The whole point of any of the articles and comments on this blog is to inform and allow questions to be posed. There always seems to be more than enough folks here to jump in both to questions and explain. What you’re doing here is give everyone a look at amateur radio and tell folks what many already sort of know; that they heed communications equipment and skills and informing folks and getting them to act is always a good thing.

      • I am late on this reply but the first contact for me was

        A the first contact on hf was a 5b4ti in Cyprus at that time many years ago on 10m.. on cw… got the QSL card still..

        thatAway…

  3. MountainSurvivor says:

    Fine learning material, Michael. It has been over 30 years since I heard anything about Jabba the Hut so it kind of brings back the good oI’ days. I was once told that my dad decided to put an amplifier on his system, although he knew he should not and why he dare not and, sure enough, his t.v. went kablooey! Where his brains had run off to, nobody ever knew. He tried to get the seller to repair or replace the t.v. but he was out of luck. Good for his ego, bad for his pocketbook. I wonder what will be in your next article…???????????????

  4. Go job Michael And Ohio Prepper.
    Although I seem like Michael is trying to explain a little to much information for a person trying to get into the hobby of ham radio (if that is his intent?). This information is way above a novice class license, even a general class license. ((I will comment more when Michael is finished writing to see where exactly he is taking us with this series)).. This is a pretty big primer for most people not familiar with ham radio to absorb.

    Also Michael a novice can get on Usb on the 10 meter band of HF. 28.300 to 28.500 and the band has been opening sporadically . And the band has been opening to all of the world.

    Some of my friend that only have a novice ticket. Are very excited talking to place like Russia to Japan, England, and All over Europe, S.America.
    So even just to California and he Westerns states and even Alaska, (Alaska is sorta rare from Ohio when the band is not so hot).. And some from them are mobile running only 10 watts USB.
    The new ham’s are very excited having never even talked across the country before. And I am sure you rember the fun and excitement when you worked you first DX contact. Or new state..
    Bring on the next article Michael.. Lets see what you have..

    73
    thatAway

    • michael c says:

      My purpose was to “expose” people to radio principles in general (AM, FM, CB) and ham in particular. You will notice that I don’t reference any book so the explanations have to be more complete then “read book X for details”.

      OP kindly pointed out how complex explanations can get.

      I still remember my first contact – my brother.

      • Actually and amazingly so do I. I don’t remember the call-sign, but the contact was Morse code on 40 meters to Woonsocket, Rhode Island. That was more than 30 years ago, but I don’t remember what I have for breakfast last week.

      • Michael
        I am late on this reply but the first contact for me was
        A the first contact on hf was a 5b4ti in Cyprus at that time many years ago on 10m.. on cw… got the QSL card still..

        And the no book thing is good idea . But Un-Fortunately I think the hams have Look at book and they need to be escorted along the way buy an elmer ( experienced ham as you know )
        Unless you are already into the hobby well tech talk people do not care about.. There so many appliance operators out there and I have even become one due to the complicity of the equipment..
        Just like a car I used to to be able to work on them even into the 70’s

        YA know an Idea is a ham (elmer/prepper/elmer) for the prepper minded folks..
        Mabey that would help any paranoid thought .. But it may already be being done???
        But if you want a legal ticket you will need to get with the Fcc.. sooner or later.. So the gov. knows whom you are..
        they already do if you are on any of these blogs…

        Ya know mabey it already exist but mabey some prepper ham Elmer’s would help..

        Do not know the answer .. It is fun to get some one interested in the hobby and they end up surpassing you..

        The clubs down buy me here in S. Central Ohio have once a month classes for a minimal fee.. like 10 buck for the whole class and 20 buck for he exam.. And they even have used and donated
        study books .. And if a person is nervous.. some club in particular really good at getting em calmed down and passing many of them to there first ticket..

        Gotta go
        thatAway…