Peak N Tune Myth

Discussion in 'CB Radio Forum' started by delta5, Oct 15, 2014.

  1. delta5

    delta5 Road Train Member

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    [​IMG] The Myth of Peaking [​IMG]
    It doesn't take too long before a new CB'er begins to yearn for more. More power, louder modulation, stronger signal, greater distance. The reasons for this are as much psychological as they are technical. Practically speaking, more power allows you to work the more distant stations, which is an advantage if DX'ing is in your blood. Also, when playing in that proverbial sandbox that is the CB experience, like in many other competitions in life, people tend to look up to and respect those who excel at their vocations, and display traits which are head and shoulders above their peers. Likewise then, those same people feel that the stronger they become, the more they will be respected. Power as a sign of status as it were.
    Whatever the underlying reasons, one of the most sought after modifications that CB'ers look for, in their grand quest to be king of the block, is the "peak job". On the surface, this seems straightforward enough. Take a stock FCC legal 4 watt radio, and "boost" the power output to some higher value. After all, more power output translates to the transmission of a stronger signal and more range right? To a point this is true, but it doesn't happen without some tradeoffs. These ramifications of the peak job are not always fully understood by the technically challenged CB'er. Many of these people become confused and can be easily misled by the many inflated claims made by those unscrupulous "Screwdriver Technicians", who are looking only to make a fast buck, and who work hard to promote radio myths in order to separate the unsuspecting CB'er from his disposable income.
    In this article, I will attempt to explain why simply peaking a CB radio is not really a good value for the money.
    Let's first look at signal strength and how it relates to actual transmitter power.
    It would be prudent at this point, to mention a unit of relative measurement which relates to this subject. Many people have heard of the term "db". db is short for "decibel", which is a unit of power relative to a standard reference. Radio people refer to "db's" fairly regularly. The common "S" (for signal) meter, which is standard equipment on most radios, indicates numeric values which are comprised of 6 db increments until "S9", and then read in straight db afterward. The difference between any 2 "S" units is therefore a difference of 6 db, for any signal under "S9". A station giving you an "S8" reading on the S-meter is 6 db stronger than someone giving you an "S7". This, of course, assumes an accurate and linear "S" meter, which most CB's do not have. But for the sake of a discussion, lets assume that they do for now.
    So what does this all, mean? Not much yet until you understand the other side of the equation. That is, what it will take in transmit power to raise that all-important signal reading. On the transmitter side of the equation, every time that you double your power, you increase your output signal by 3 db, or 1/2 of an "S" unit more on another station's "S" meter. That means that if you want to go from say, an "S7" to an "S8", you would have to double your power twice. For someone running a 4 watt CB, that equates to raising the carrier power to 16 watts. And that's just to move one "S" unit. Expanding on this further, lets look at another example. Say that you want to go from an "S7" to an "S9". You would now have to increase 12db (6db per "S" unit), which is the equivalent of going from a stock 4 watt CB, and then turning on a 65 watt amplifier. The steps in wattage get even larger from there. If you are already running 100 watts, and you want to jump 2 "S" units, you'd have to jump up to over 1600 watts (average NOT peak) to achieve it. You're into serious power at this point.
    Ok, now you hopefully get an idea about what is required in the process of raising your signal level. So now let's look at what a typical FCC legal CB is capable of producing in both power and modulation. Power and modulation are in a balanced relationship in an AM radio. If you raise the carrier power, without a proportionate increase in modulator power, you lose modulation percentage, and vice versa.
    A stock, out of the box CB is normally set to run at around 4 watts of carrier power (per FCC rules). Experience has shown me that the most carrier power that a typical radio can be made to produce by alignment only, in most cases, is in the range of 6 to 10 watts. Since it takes an increase to at least 16 watts of power to jump the 6 db necessary to gain just 1 "S" unit increase, you can see that typical CB radios fall far short in "peaking" potential. Increasing the power from 4 to 6 watts will hardly be noticed on the other end
    The other (and very important) factor to consider is modulation. Modulation is what actually carries your voice. Modulation is rated in terms of percentage, and can also be be referred to as "peak" power. A 100% modulated AM signal will have a peak power of 4 times the carrier power in watts. This means that a stock CB running 100% modulation on a 4 watt carrier will have a peak power of 16 watts. CB transmitters are designed to be able to handle the extra peak power contained in the modulation. But when you "peak tune" a radio to put out more carrier power, there is often not enough extra "headroom" left to fully modulate the new power level to 100%. The result is a lower peak modulation level along with the accompanied clipping distortion. Many so-called "CB doctors" try to compensate for the lower modulation level by removing the modulation limiter. By doing this, you allow the modulator to increase its level of audio drive up to the point of modulator clipping and saturation. While this can make you sound louder to a point, this capacity is not infinite and when the modulator reaches the saturation point, the audio wave flat tops and produces audio harmonics and other distortion. This is what is commonly called "splatter", and is responsible for much of the bleed over that is heard on the channels.
    Also, for a high level modulation scheme, (Most AM-only radios) you need to produce an equivalent of 50% of your R.F. carrier power, in audio watts for the modulator to 100% modulate the R.F. carrier. This means that for a 4 watt R.F. carrier, you need 2 watts (1 watt per sideband) of clean audio power. Most CB radios employ an audio amp chip which produces no more than about 3 watts of audio before distortion starts to set in. So you can't properly 100% modulate an R.F. carrier over about 6 watts without incurring distortion.
    For a regulator modulated radio (Most newer AM/SSB radios), the peak power that the modulation can achieve has to be less than or equal to the maximum peak power that the transmitter strip can produce, at the full operating voltage, in order to maintain 100%. Most modern SSB radios can produce SSB and peak power levels in the 18 to 21 watt range. Remember that in order to 100% modulate a 4 watt carrier, you need to be able to reach 16 watts (4X4=16). For a 5 watt carrier, that means you need to peak at 20 watts (5X4=20). For 6 watts of carrier, you need to be able to reach 24 watts peak (6X4=24), and so on. Since most radios are limited to around 20 watts peak, you can not support more than about 5 watts of carrier, before you start losing peak modulation percentage.
    Another factor to consider is the future. When the result of the "peaking" job fails to produce the results which were originally anticipated (and it will!), the owner will then seek out additional power enhancements. This usually means springing for a power amplifier. Most modern transistorized amplifiers can be driven to their full rated carrier output (peak rated power divided by 4) with as little as 1.5 watts of drive power. Driving an amplifier like this with a "peaked" and "clipped" radio running a distorted 6 watts output is a recipe ripe for disaster. It will not sound good, and eventually the owner will have to get the radio "detuned" again, so that it will work properly with the amplifier.
    So you can see that there is very little benefit to be gained by peaking, and a lot to lose. Other than falling short of the high signal goal, peaking a radio can also place more strain on the transmit final transistor which can lead to premature failure. My advice; don't do it! Save the money and buy a better antenna system. A good quality antenna can achieve signal improvements which will be at least as effective as those from a "peak" job, and usually quite a bit better. A better antenna will also improve your receive performance as well as your transmit signal.
     
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  3. Powder Joints

    Powder Joints Subjective Prognosticator

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    Try as I might but I really could not find anything to argue with in your post, but I tried.
    Kind of supports my tuning with a HP scope and my R2200 monitor, Tune to flat, then back it down to a nice pretty sine wave, at thats it. That's is all that radio is capable of.

    The last radio I worked on the hack removed 3 of the slugs completely, jumped out the clippers, stretched the choke coils, turned the voltage to max on the final. My neighbor description was it started smoking right after it was peeked, The picture on the scope is when I was thru. Deadkey about 2 watts peak at just under 8. Once again loud and clear.
    Cost him 75.00 bucks to have his radio trashed. I do not think most shops would have repaired it. About 3 hours (including digging thru old radios for parts).

    The receiver was misaligned also, preselector section was screwed up, 3mv to start, finished at at .7mv, ok for a cb.
     
    Last edited: Oct 15, 2014
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  4. mike5511

    mike5511 Road Train Member

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    And yet I'll bet you ham boys tune on every radio you have..............:yes2557:

    SOME of you ham guys are like the typical redneck. You stereotype a whole class of folks with your endless, negative comments about CB shops. Turbo-T little joke is a good example. Yes there are some folks out there that have no business taking the covers off of a radio. But there are still some very good technicians out there that know what they are doing and provide a great service to the very few of us still using a CB. If you think you can change CB by your constant ragging on anything a truck driver might do to his radio, you are wrong. Others are gonna hear those guys and some of them will always want "one of those big radios" like the other guy has. The Mexican skip and the idiots that shoot skip on 19 are a much bigger problem than a driver that is a little over modulated IMHO. I don't care if it is radios, stereos, cars or anything with a motor, there will always be those experimenting and trying to "hotrod" them to make them perform better. And all the whining some of you do about it ain't gonna change it. There is hardly a thread started on here that doesn't get hi-jacked by the hams and end up bashing CB.........I know it isn't going to change. You guys will gripe about CB shops forever and the CB shops will keep doing what they do forever............(Yes it would be better if nobody ever took the covers off of their radio or ran a amp.....maybe........but that's a pipe dream fellows and it never has been reality and never will be!.......I don't care how many stories you post about the FCC, or how many CB shops you file complaints on with the FCC it ain't gonna change.)
     
    Last edited: Oct 16, 2014
  5. Gadfly

    Gadfly Medium Load Member

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    Actually, you are wrong. The typical ham buys a radio, installs it and runs it the way it came from the factory. There is no REASON for the so-called 'peak and tune' crap. Think about it. You buy a new car, right? You expect it to run well the day you bought it. Do you start snipping this, clipping that, destroying the emissions controls, tampering with this, tinkering with that. Do you take it to a shop and get it butchered & pay EXTRA money for it after you've paid so much for it to start with? The auto companies DO know what they are doing, and their products do what they are designed to do within the law. So do the CB builders.

    First of all, You are NOT going to get some magic increase in performance with these "peak and tune" jobs. Vilify the hams all you like, many, not all, CB shops are scalpers who take advantage of people's ignorance of electronics in order to make a killing on the uninformed. Even if the radios were "detuned" as goes the CB myth of Peak & Tune, the advantage of increasing the power---even DOUBLING it--is minute!!!! Doubling the power will not significantly increase the average received signal at the other end. The "hams" did not make this up; it comes from the Electronics Engineering community--you know, the ones who likely built our radios--ham and CB alike.

    I don't "modify" radios. I make *some* repairs. My IC706 MKIIG was installed 9 years ago AS purchased from the factory. Should it need alignment, I may do that and ONLY to return it to its designed specs. NO "peak & tune, snip and clip" in search of some magical and unattainable power and modulation goal. But then I have big fingers and small eyes anymore, and the bifocals just aren't up to the task. So it would likely go to the Icom service center. These multiband radios cost in excess of $1100 apiece!:biggrin_2556: Only a fool would start snipping and a-clippin' on one of these!!!!!:biggrin_25523:


    GF
     
  6. Outlaw CB

    Outlaw CB Light Load Member

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    gadfly "Actually, you are wrong. The typical ham buys a radio, installs it and runs it the way it came from the factory."

    You know, I think gadfly you just hit the nail on the head as to my attraction to CB so long ago. That is, the ability to talk about whatever subject that comes to mind without worrying about rules is not the main reason. Nor did my efforts to become an Extra stem from any desire to be involved with the crowd of morons on 14.2 coming out of San Francisco in the 80's. I had WWII Vets in the 70+ WPM crowd as Elmer's in the 1960's. To a man every one had shacks full of gear from transceivers to meters and various test gear, outside various antennas, which they built themselves. All had their trusty and coveted pair of ARRL Handbooks circa 1958,59. Eventually so did I due to the kindness of one of them. From the 60's to the end of the 70's I think I built about every project in the book including the quarter gallon 2C39 moon-bounce project. Ham was about building and constructing, mastering RF Engineering, finding new ways to turn junk from a hardware store and the Local (now defunct) Lafayette store into yet another astounding performer in the HF bands or elsewhere. By the late 80's through 90's I was really getting bummed out by the new generation of store bought operators who were no more than operators with a license to talk within the rules. It was not only the burpers and kerchunkers in Phoenix who burned me out on 2 meters, it was the never ending signal and weather reports sans any form of conversation of any level or any interesting subject. I was similarly bored out of my mind by the mindless 10-10 crowd on 28.4.

    I just do not consider this to be the definition of a 'ham', i.e., buying and using the latest model and talking being the end all of the hobby. I went for my Extra for one reason only, to be able to legally design and build microwave gear and experiment in new areas. It was the early influence of Elmer's who from the 1930's on had to design and build if they wished to communicate on the bands that made the hobby so interesting. In effect a new breed of 'explorers' as seen by the first words on this Wiki page:

    http://en.wikipedia.org/wiki/History_of_amateur_radio

    "Throughout the history of amateur radio, amateur radio enthusiasts have made significant contributions to science, engineering, industry, and social services. Research by amateur radio operators has founded new industries,[SUP][1][/SUP] built economies,[SUP][2][/SUP] empowered nations,[SUP][3][/SUP] and saved lives[SUP][4][/SUP] in times of emergency."

    What you describe gadfly is diametrically opposite to this spirit, and portraying those who like to experiment and attempt to improve their stations in a negative light would indicate to me you are nothing more than a 'licensed radio operator' who is void of the founding spirit of 'ham'. Which it would appear is more evident in these CB'ers who like to alter and toy with their gear than all the 'hams' who spend so much time looking down upon and talking down to those of lesser breed, 'CB'ers'. I'm sorry to say but I have said it here before, it boggles my mind so many 'hams' devote their time to putting down CB and this spirit of experimentation on a CB forum on a truck drivers website instead of inhabiting 'ham' forums. So very strange. This 'spirit' of experimentalism as it were appears to me to still be alive in these CB'ers so tell me. What happened to all you 'hams' out here? Where are the 'Elmer's' I so fondly remember? I can only hope they are in the next dimension still doing what they loved so much while they inhabited this one.
     
  7. Ridgeline

    Ridgeline Road Train Member

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    I find it rather amusing how many people defend these cb techs when you look at what they do and the equipment they use.

    If it wasn't for us ham people, they would never have had those watt meters, those all in one service thingies or know how to clip and peak any cb,

    Actually they wouldn't have cbs at all ...
     
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  8. Outlaw CB

    Outlaw CB Light Load Member

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    Can you provide references to back up your claims that hams invented watt meters, 'service thingies', 'the know how to clip and peak', and CB's? A very large number of electronic engineers and inventors managed to live their entire lives having never once held a ticket. Seems to me if it were not for inventors, engineers, and various companies building radios there would be no modern hams. Those would be the ones who merely buy new radios and never look inside, only use them.
     
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  9. Ridgeline

    Ridgeline Road Train Member

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    A lot of people, engineers, inventors and so on were doing it to make money, the hobby provided a specific need to created a market to fill their needs. It was clear by the late 30's that there was not just a small market but one that was rich in knowledge that ended up serving the country during the war, out of that war came an idea of a citizen radio service which was not just created out of thin air but it was something that hams themselves were involved with getting started. It came from the idea of serving the community which came from the ham community and the start up of the cold war.

    Where do you think Lafayette radio stores came from - the ham market.

    Radio Shack was the same thing.

    Allied

    Olson

    That said, I never said invented, I said that they would never have had watt meters and other service things that are common today. It is something that a common CB'er would never have know about if it wasn't for hams. the same goes for the radios itself, without a market that was created by hams, companies like Johnson (who made ceramic components), SBE (who made commercial radios), Multi-Elmac (who made garage door openers) and others who supplied the ham market would have never gotten involved with CBs.

    So the funny thing is that people don't realise the importance of hams when it come to CB history, most think that it just came out of the sky magically.
     
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  10. EZX1100

    EZX1100 Road Train Member

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    piqued and tuned
     
  11. hayseed

    hayseed Light Load Member

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    Well, I have to disagree to a certain degree. While you do want your car to run well like the day you bought it...................Almost all of the car makers do not give us all of the potential from the engines and transmissions when they are sold. Thus the "programmer-tuner" market. Since you can have your car "peaked and tuned" with a new programmer does this make it "crap"?? While a radio may be fine straight from the box, it doesn't hurt to have it checked and adjusted if need be. While I agree that some of the shops don't have a clue, some do. You can find quotes on forums all day long about new radios that have to be returned for warranty repairs for not working properly.
     
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