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CB info

Discussion in 'Ham Radio - CB - Trail Communications' started by amigodana, May 23, 2010.

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  1. amigodana

    amigodana Active Member

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    I am still new on here but I noticed no decent info on CB's so here you go.

    First, the radio - Picking which radio you want is like choosing between McDonald's or Burger King, each brand has good points and bad points.

    My personnel opinion would be cobra, which is also the one I use, a Cobra 29 LTD Chrome. You also have Ranger which is an excellent radio. And then each brand also has things such as weather band or sideband. Its your choice what you need!!!

    What you need to know about the radio is that it needs to be tuned. A stock radio only broadcasts on approx. 4 watts of power, which gives you limited distance on reaching out and touching someone ( it can be tuned up to 20 watts of power) . And receiving is horrible, for the old timers who remember the dial type TV'S, it is basically the same principle. But, you will need a CB tech to go inside the radio to adjust it (For those who say to get one of those noise filters, forget it, it only masks the problem and decreases the quality of your radio) . To a CB shop it is called "Power Tuning" or "peak and tune" the radio. Just type in "CB shop" on your internet search and you will come up with hundreds of them. The charge to do this is reasonable enough to wonder why you don't do it. After all when you are that far from civilization you need to be able to talk at as great a distance as you can, right? Price is any where from 20$ to 100$ depending on the shop. So call around. My radio can talk up to 30 miles away and I can hear you 40 miles away and that's during bad weather. If you think you can do it yourself here is a link for info,( http://www.cbcintl.com/tmreps.htm )But if you really want to get out just find you a linear to attach to your radio, then look out. But that's a different story!!!!!!

    Next is the antenna and as I have stated before it is like choosing between McDonald's or Burger King.

    But lets start with choosing between fiberglass or steel whip. I have found that when traveling thru trees or your local fast food restaurant you want something that flex's better so as not to tear it off your truck. And the steel whip, believe me, saved me many a problems.

    Placement, I have noticed, is a big issue. Now if your only interested in looking cool, well then put it anywhere you want. But if your like me and you need it too work right, well there is only one choice for all automobiles and that is on the roof in the center. You have to remember, you will have noise coming from your alternator, fuel pump, ignition, and many other sources. So as I stated the best place is on the roof, the furthest point in any direction which is also the center.

    Myself I use a little Wilson steel whip antenna.

    Then you will have too adjust the antenna to get the proper SWR's.

    The manufacturer tries to make you believe that assembling the antenna and mounting it is all that is "necessary". The instructions on the package say pretty much "for optimal performance antenna may be tuned using Radio Shack model # blah blah blah SWR/power meter" It doesn't say anything about if the SWR is too high it will cook your radio. Optimal performance is what you want, but you don't need a Radio Shack meter. Any SWR meter that is designed for the frequency range you are tuning will work.

    What is SWR? SWR is Standing-Wave-Ratio. In English that means the ratio of your transmitter's driven power compared to the power reflected back down the feedline by the antenna. If the SWR is too high (too much power being reflected back into the radio) you are not getting full power out of the antenna and eventually you will most likely fry the final amplifier in your radio. Example: A radio is producing 50 watts of power. The antenna is so far out of tune that 30 watts are being reflected back into the radio, you're actually only getting 20 watts out of the antenna. 30 watts is a lot of power to reflect down a feedline!!!!!!!! It won't take long to smoke your radio. I saw that SWR a couple of weeks ago on one of the Sheriff's deputy's radio. Luckily he didn't fry it.

    What is tuning? Every frequency has a certain electrical length. Tuning is simply matching the antenna's electrical length to the frequency range it will be used on. That doesn't mean that if you have a Cobra CB and a perfectly tuned antenna and then change to a Midland CB you have to re-tune the antenna. Some people have that belief. The antenna doesn't know what kind of radio it's hooked to. All it knows is what frequency it's tuned to. You can change radios 20 times a week and as long as you operate in the same frequency range you don't have to re-tune.

    For CB'ers. CB's by law are only permitted to produce 4 watts of RF(radio frequency) energy. So be careful. If your antenna is not correctly tuned you may be driving 4 watts of power, reflecting 3 watts which means you are actually only getting 1 watt of power out of the antenna. 1 watt on CB freq isn't much. Chances are you won't cook your radio due to the low power being reflected, but you won't be able to talk very far and an out of tune antenna also affects reception.

    Mobile Antennas:

    How do I tune a CB antenna?

    Simple. From the beginning. Mount the antenna as near the middle of the roof of your vehicle as possible. This will give the antenna a nice even ground plane. Route the cable to the radio-avoid pinching it or running it next to electrical wires. The SWR meter can be installed anywhere between the transceiver and the antenna. Most mobile antennas have only one connection point. The easiest setup is to have the SWR meter directly after the radio.

    Radio-SWR meter-antenna. Easy as that. Make sure the SWR meter is designed to work on the frequency range of 26-27 MHz. Hook it all up and pick a channel. I generally start on CH 20. Key the mic and watch the SWR...where's it at? Is it over 1:5:1? If it is, then go to CH 40, key the mic again..what is the reading? Remember it. Then go to CH 1, key the mic and check the reading. If the SWR reading is higher on CH 40 than it is on CH 1, the whip needs to be shortened. If the SWR reading is higher on CH 1 than it is on CH 40 the whip needs to be lengthened.

    Easy way to remember that-Higher on the upper, shorten If the SWR is higher on the upper frequency, shorten the whip. Vice versa if it's the other way.

    Adjusting the whip takes a little time & patience. No matter which way you're tuning it, do it in small increments, approx 1/4 inch at a time. After each adjustment recheck the SWR on CH 1 & 40 until you find your correct tune. Ideally you should be able to get 4 watts driven with about 1/2 watt reflected. Equals about 1:5:1.

    Now just have fun...
     
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  3. amigodana

    amigodana Active Member

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    more important info

    Let me add some more to this.

    Things Every CB'er Should Know

    * 1. Every industry has its bottom dwellers. We cannot protect you from them. Consumers who make decisions based strictly on price, or on what someone says instead of what they can do, will often fall prey to the bottom dwellers.


    * 2. Beware of information from "experts" (real or self-proclaimed). There is antenna theory and there is antenna reality. We have yet to see a vehicle that simulates a lab. While theory is a good starting place...experience is invaluable when it comes to real problems. The knowledge gained from the best book on theory will not necessarily produce the best antenna design.


    * 3. Some "experts" may "claim" 5/8 wave mobile antennas are not possible because they would need to be 23 feet high. They are wrong! Physical length and ground wave performance are not the same. If you ever hear someone make that claim, ask them how a handheld CB can have a 1/4 wave antenna 8 inches long and mobile 1/4 wave antennas can be anywhere from 12-60 inches long in spite of the fact that a physical 1/4 wave is 108 inches.


    * 4 .Never key up or attempt to operate your CB without a working antenna or "dummy load" (non-radiating antenna simulating device) connected to the radios antenna jack, unless you have extra money to buy another radio, or know a good repairman.


    * 5. All mobile and base transmitting antennas need counter-poise, more commonly called ground plane. The antenna is the reactive unit, the ground plane is the reflective unit. Neither is more important than the other. In mobile installations with standard antenna systems, the vehicle metal (body, frame, etc.) acts as the ground plane. In "no-ground-plane" systems, the coax shield is used for counterpoise.


    * 6. Most, but not all, manufacturers pre-tune their mobile antennas on a test bench. To protect your radio's circuitry and achieve optimum performance, mobile transmitting antennas (CB, cell phone, amateur, etc.) need to be tuned on the vehicle.


    * 7. Before transmitting, you should check your antenna system for shorts or opens. If you have continuity between the center pin of the connector and the outer threaded housing, you may have a short. Don't transmit! If you do not find continuity between the center pin of the coax and the antenna base, you have an open. Fix it. (See "Testing Continuity") Exceptions: Some base loaded antennas use a center tap design and there will be continuity from ground to center conductor. Also, Firestik "No Ground Plane" antenna kits will have coaxial center pin to ground continuity.


    * 8. SWR that pegs the needle on all channels almost always indicates a short in your antenna system. Do not attempt to tune the antenna until the short is fixed. Operating with high SWR will probably damage your CB's internal circuits.


    * 9. Make sure that the antenna you are using is the right antenna for your application. Don't use a TV antenna or an AM/FM antenna for your CB. Do not operate your CB without an antenna or dummy load.


    * 10. Transmitting antennas are sensitive to objects in their "near field of radiation." Tune your antennas in an open area. Never tune inside or next to a building, near or under trees, near or under power lines, and never with a person holding or standing next to the antenna. Try to simulate normal operating conditions.


    * 11. If you mount two or more antennas close to each other, you will alter the transmission patterns of each one. The affect may be either positive or negative. We recommend that a minimum of 12" exist between your CB antenna and other types of antennas.


    * 12. Your radio cannot tell one component from another. As far as the radio is concerned, the coax, stud mount, mounting bracket, antenna and vehicle is ONE unit. Don't be too quick to fault your antenna until you are sure that all of the other components have been given equal consideration.


    * 13. Of all antennas returned to Firestik for warranty service, 75% show no signs of being tuned to the vehicle. All antennas should be checked prior to use. Most will require some adjustment. Less than 3% of all returned antennas have actual performance causing problems. Of those, half of the problems are user or installer created. High SWR and other performance problems are 20 times more likely to be caused by bad coax, bad connections, shorted mounts, poor installation location or faulty test meters.


    * 14. In almost every instance, once you get the same SWR reading on channels 1 and 40, further antenna tuning will not improve the readings. If the SWR is still over 2:1, you have other problems to conquer. Exception: There are rare occasions when the ground plane is so small or large that the system is way out of phase (especially with high-performance antennas). If you have high SWR on all channels and have confirmed that you have no opens or shorts in the feedline, try making a small tuning adjustment in the antenna. There are times when the SWR will drop equally across all channels under unusual ground plane conditions. If you find this to be the case, carefully adjust the antenna.


    * 15. SWR that is high on all channels (over 2:1 but not pegging the needle) after the antenna has been tuned usually indicates insufficient ground plane, ungrounded antenna mount or that a coax cable problem exists.


    * 16. The doors, mirrors, spare tire racks, luggage racks, etc. on many vehicles are insulated from a good ground with nylon or rubber bushings. This also stands true for fiberglass vehicles. Make sure that your antenna mount is grounded, even if it entails running a ground wire to the vehicle chassis. Bad hard ground at the mount generally equates to less than optimum performance. Exception: No ground plane antenna kits do not require a grounded mount.


    * 17. If you are hearing whining noises from your radio while your vehicle is running, it is probably due to "dirty power" being supplied to the radio. Under dash power may be more convenient, but the "cleanest" power will be found by running the radio's power leads straight to the battery.


    * 18. You can never buy coax cable that is too good for your system. Never compromise quality for cost when purchasing coax. Your best bet is to stick with coax that has a stranded center conductor and 90% or higher shielding.


    * 19. Most manufacturers of high performance antennas recommend a specific length of coax cable. If your antenna manufacturer suggests a specific length, give priority to that recommendation.


    * 20. If your ground plane is good, your mount grounded and, your antenna favorably located, coax length rarely becomes an issue. But, if one or more mismatches occur, you may find high SWR. This can often be corrected by using 18 feet lengths of high quality coax.


    * 21. Excess coax between your radio and antenna mount should never be wound into a circular coil of less than 12" in diameter. Doing so can cause system problems. Your best option for handling excess coax is to serpentine the cable into a 12 to 18 inch yarn-like skein. Secure the skein in the center with a wire tie and tuck it away.


    * 22. Single antenna installations require coax with approximately 50 ohm's of resistance (RG-58/U, RG-58 A/U or RG-8X). Dual antenna installations require the use of 72 ohm cable (RG-59/U or RG-59 A/U).


    * 23. Coaxial cables with foam (polyfoam) center conductor insulation should be your last choice for use on mobile (vehicle) installations. Even though it will work initially, it has limited life and does not stand up to the conditions encountered in the mobile environment. Choose coax with polyvinyl insulation when doing mobile installs.


    * 24. Coax cables should never be cut and spliced together like common electrical wire. Line losses will occur.


    * 25. Coaxial cable with holes in the outer insulation, severe bends, or door, trunk or hood caused pinches will cause performance problems. Treat your coax with care.


    * 26. If you live in an area where rain and/or sleet is common, wipe your antenna down with a rag that has been coated with WD-40, Armor-All, Pledge, light oil, etc. This trick prevents ice build up that can overload and cause your antenna to break. In an emergency use butter, cooking oil or anything else that will repel water.


    * 27. When tuning your antenna(s), make sure that you do so with the vehicle doors, hood and trunk closed. If left open, they can cause inaccurate SWR readings. Try to simulate actual operating conditions.


    * 28. Mobile antennas, for best performance, should have no less than 60% of their overall length above the vehicles roof line. For co-phased antennas to perform optimally, the space between the top 60% of the two antennas needs to be unobstructed.


    * 29. Remember, all transmitting antennas need ground plane (counterpoise). Base antennas, much like "no ground plane" antennas, build it in. Do not use mobile antennas for base station applications unless you know how to build your own ground plane.


    * 30. If you are installing a single antenna on one side or the other of your vehicle, best on-the-road performance will be realized if the antenna is on the passenger side of the vehicle (Passenger cars and light trucks) Large trucks or vehicles pulling large trailers should put the antenna on the drivers side to avoid the signal from being blocked by the trailer and to keep from hitting road side trees.


    * 31. Co-phased (dual) antenna installations create a radiation pattern that favors communication directly in front and back of the vehicle. This is why co-phase systems are popular with people who do a lot of highway driving. Co-phase antennas must be center or top loaded. Top loaded antennas are the best.


    * 32. Some people believe that co-phased antennas must be separated by a minimum of nine (9) feet. We have successfully used co-phase antenna systems with spacing as little as four (4) feet. Space alters the pattern and not always negatively. Each vehicle will be different.


    * 33. Co-phase antennas can improve performance on vehicles that lack good ground plane characteristics (fiberglass motorhomes, trucks, etc.). Instead of using available metal to reflect the radiated energy, the antennas use each others field.


    * 34. When tuning co-phased antennas (dual), it is best to adjust both antennas an equal amount to maintain equality in their individual resonant frequency.


    * 35. On a co-phase system, if you try to tune each antenna independently using RG-58 type coax and then connect them to the co-phasing harness, you will almost always find that they will appear electrically short as a set. We recommend that you first assemble the entire system. Take all measurements and make all adjustments with both antennas in place.


    * 36. If you are experiencing SWR that is high across the entire band and have eliminated shorts, opens, groundless mounts and coax as potential problems, suspect lack of ground plane. Try adding a spring or quick disconnect to the antenna base. In some cases, the repositioning of the antenna relevant to available ground plane will solve the problem.


    * 37. One of the greatest benefits of the FS series (patented tunable tip) antenna is noted when there is lack of available ground plane. If the tuning screw reaches its "maximum out" position before satisfactory SWR is realized, a common 1/4-20 threaded bolt or screw of a longer length can be used to replace the supplied tuning screw. If the vinyl cap is too short to remain in place, the user can disregard it or clip a hole in the top for the longer screw to pass through.


    * 38. In rare instances, like antennas mounted in the middle of a metal van roof, excess ground plane can cause a problem. This usually shows up as high SWR across the band. In these cases, a tunable tip antenna may not be the best choice. The reason being, the antenna is too long and the tunable tip cannot adjust down far enough (see line 40). If you suspect this, an antenna that wire can be removed from will usually fit the bill (i.e. KW or RP series).


    * 39. There may be situations when a tunable tip will bottom out before optimum tuning is achieved. If this happens, try removing the knurled jam nut and finger tighten the tuning screw against the o-ring. If still too long, remove the tuning screw altogether. If total removal causes the antenna to go short, cut the tuning screw in half and re-insert it into the tuning extender and re-test. The following items on the FS Series "tunable tip" antennas, when removed, will have an effect on SWR (in order from least effect to most effect). O-ring, jam nut, tuning screw mass (cutting off length), vinyl cap, tuning screw complete.


    * 40. The vinyl cap on any "tunable tip" Firestik antennas is optional. However, your antenna needs to be tuned as it will be used . . . with or without the tip.


    * 41. Magnetic mounts should be used in temporary situations only. If you leave them in the same spot for a long period, the paint will not age like that of the uncovered areas and/or moisture will be trapped between the mount and vehicle causing rust or discoloration. Periodically lift the magnet and gently clean off the underside of the magnet and the vehicle surface.


    * 42. It is a bad idea to use magnetic mounts and amplifiers together. Magnetic mounts rely on capacitance grounding. This situation can literally cause the paint under the mount to bubble or discolor due to excessive heat build up.


    * 43. On wire-wound antennas that require wire removal for tuning purposes, best overall performance will be achieved by keeping the loose end of the wire pressed down tightly against the wire coil. If you use power amplification on top loaded antennas and do not process the end of the wire load so it can dissipate its heat into other adjacent coils, you can melt the tip of the antenna.


    * 44. Generally speaking, center loaded antennas perform better than base loaded antennas, and top loaded antennas perform better than all. For any given antenna design (base, center or top loaded), the taller the antenna the better. With length comes a wider bandwidth (lower SWR over more channels), more power handling capability and overall performance increases.


    * 45. When ultimate mobile performance is desired, function should be given precedence over mounting location convenience and appearance.


    * 46. Don't confuse SWR with overall performance. You should seek SWR of 2:1 or lower on channel 1 and 40, but keep in mind that best performance may not be found at the lowest SWR readings. For the most part, if you get your SWR below 2:1, on both ends of the band, don't be overly concerned about using meter tricking procedures that bleed off energy.


    * 47. The SWR meters built into CB radios are okay for general readings, but are rarely sensitive and/or accurate enough for fine tuning of antennas. Use them mostly to indicate serious high SWR problems only.


    * 48. Firestik has tested literally hundreds of SWR meters. A large percentage of these have shown to be off by 0.3 to 0.7 when compared to a piece of certified equipment. There is no standard among production meters. However, unless a unit is defective, most will indicate the most serious problems that you might encounter


    * 49. Aside from cost, the type of wire used in or on antennas (copper, silver, aluminum, gold, tinned, etc.) has negligible effect on antenna performance. The antenna must be designed to resonate with the wire type and gauge chosen by the designer. However, larger wire gauges will normally increase the bandwidth and heat dissipation abilities of the antenna.


    * 50. Copper is 55% better than aluminum, 27% better than gold and 578% better than tin insofar as conductivity is concerned. Silver will conduct AC/DC current less than 2.5% more efficiently than copper, but the cost to performance is generally unjustified and any gain, insofar as RF transmission is concerned, is negligible.


    * 51. If devices other than an SWR meter are going to be used between the CB radio and antenna, always tune the antenna system first without that device in line. If SWR is high with the other device in line, you will know where the problem is.


    * 52. In "no ground plane" systems, it is best to choose a system that terminates the coaxial ground at the radio end of the cable. These systems are far less reactive to cable routing errors and will almost always outperform systems that are terminated at the antenna base or antenna end of the coax.


    * 53. Cables and antennas from standard & no-ground plane kits are not interchangeable. The "No Ground Plane" antennas from Firestik have a yellow band near the base.


    * 54. Wire wound antennas with a plastic outer coating will greatly reduce audible RF static when compared to metal whip antennas.


    * 55. If you leave your antenna on your vehicle permanently, remove the rubber o-ring that is found on the threaded base of some antennas. Tighten permanent antennas with a wrench. Add a lock washer if you want.


    * 56. If you use mirror mounts and often find yourself in areas with overhead obstructions, tighten the bolts just enough to keep the antenna vertical at highway speeds. If the antenna contacts something overhead, the mount will rotate on the mirror arm and protect your antenna.


    * 57. If you use long antennas and find that they bend too far back at highway speeds, tilt them forward if possible. When under a wind load, they will end up in a relatively vertical position.


    * 58. On antennas that are topped off with a vinyl tip, make sure that you take your SWR measurements with the tip in place. If you tune your antenna with the tip off and then reinstall the tip, your SWR will change.


    * 59. Without advocating the use of power amplifiers or unauthorized channels, take note that the Firestik II tunable tip antennas have a fairly large metal tip that broadens the bandwidth and dissipates a considerable amount of heat.


    * 60. It is illegal to use power amplifiers with CB radios. It is illegal to "tweak" the radios internal circuits to increase output power. The transmitter power of a legal, FCC certified CB radio is 4 watts AM.


    * 61. If having one antenna for CB/AM/FM is appealing, use a CB antenna and a splitter that allows it to be connected to your AM/FM radio. Devices that let you use your AM/FM antenna for CB use will leave you disappointed.


    * 62. On a budget? Buy a cheap radio and a good antenna. Aside from added bells and whistles, all CB's are FCC regulated to transmit no more than 4 watts of power. A good antenna on an inexpensive radio will almost always outperform a bad antenna on an expensive radio.


    * 63. Beware of the wire wound mobile antennas mentioned in ads that claim them to be "full-wave" or "wave and a half". At best, you are being deceived by the misleading association of wire length to actual performance characteristics. Wire length, for all intents and purposes, is irrelevant. With "very" few exceptions, antennas must function as a 1/4 wave or 5/8 wave to be useful on mobile installations. For example, Firestik and Firestik II antennas between 2 foot and 5 foot have a radiation pattern similar to a 5/8 wave reference antenna. However, wire lengths range from 20 feet to 32 feet (0.6 to 0.9 of a full wave length). If wire length was relevant, each antenna would need 22.5 feet of wire.

    How to Pick a CB Radio


    So you've decided to get a CB radio for your vehicle? Great! Now comes the tricky part. There is a wide range of radios on the market, and they come with a dizzying number of options. To decide which radio will best suit your needs, you'll need to keep these considerations in mind.

    The universal FCC transmission limitation

    You may be surprised to learn that all CB radios, regardless of size or price, have exactly the same transmission power out of the box. This even playing field is a result of the Federal Communications Commission's 4-watt power restriction for all CB radios. While it's possible to have your CB radio "peaked and tuned" after purchase (a process by which a radio technician adjusts the radio to achieve additional transmission range), all CB radios are shipped with exactly the same transmission wattage. With the transmission power a constant factor, choosing a CB radio becomes an exercise in determining what features are most important to you.

    Common CB radio features

    CB radios range in price between $50, which will get you a bare-bones radio, and $200, which buys you a fully loaded, top-of-the-line model. Carefully evaluating which features you'll use the most will allow you to get the most value from your radio. Some common CB features are explained below:

    *
    Backlit displays. If you'll be operating your CB regularly at night, you should consider a backlit display. As the name implies, this feature illuminates the entire CB display for easy operation in dark conditions.
    *
    Weather capabilities. Features that allow users to receive real-time weather updates are some of the most popular add-ons for CBs. Some models even issue severe weather alerts when the CB radio is turned off.
    *
    Channel scanning. If you'll be using your CB primarily for recreational purposes, channel scanning is a great feature to have. Channel scanning allows you to automatically scan all available CB channels for activity, ensuring you'll know of anything happening on the airwaves.
    *
    Public address (PA) capabilities. With the addition of an external PA speaker, this feature allows you to use the radio and handset as a public address system. With the speaker mounted outside the vehicle (often underneath the hood) the system can be used to address large groups and is both a useful and an entertaining feature.
    *
    Single Side Band (SSB). Found on higher-end radios, SSB allows you to make use of the frequencies both above and below each standard CB channel. Without getting too technical, this feature makes use of a smaller frequency spectrum and provides two significant benefits: access to 80 additional channels and the ability to legally transmit at 12 watts of power without needing a FCC license. While the additional transmission power is extremely attractive to some users, remember that only other SSB users can receive your SSB signal and respond to you. Luckily, all SSB radios support standard AM-mode operations to allow for communications with non-SSB CB users. For more information about how SSB works, read Bruce Clark's explanations.
    *
    RF (Radio Frequency) gain. This feature allows the radio operator to filter transmissions being received according to signal strength. It's extremely useful for isolating a weak signal amid a barrage of stronger transmissions, or to block out background noise when communicating with someone nearby.
    *
    Built-in meters. Many higher-end radios include a meter that displays transmission and reception strength, as well as Standing Wave Radio (SWR) antenna readings. While built-in SWR meters aren't nearly as accurate as stand-alone meters, they are useful for quickly identifying potential antenna problems.


    Radio size considerations

    One important radio feature that is often overlooked is size. CB radios range in size from small, hand-held units to large, full-chassis units. It's important to consider where your radio will be mounted and to pick a CB that will fit conveniently within the space. For example, Jeep and off-road vehicle owners usually have little room in their cabs and tend to use smaller radios; RV and large-truck owners with ample room have a much wider spectrum of radios to choose from.

    Summary

    Despite the large number of CBs available, selecting an appropriate radio is fairly straightforward as long as you consider which features will best suit your needs. As a radio's transmission performance is primarily a result of the external antenna, which is purchased separately, that shouldn't be a factor when deciding among various models.

    When choosing a CB radio and its corresponding features, it’s important to focus on how and where the CB will be used. Specific vehicle owners tend to want different features in a CB radio:

    * Pick-Up CB Radios : Most Pick-up trucks are generally large enough to accommodate mid to full sized CB radios, although radios of all sizes are commonly used. An ANL is an important feature to have as engine noise can be an issue in larger trucks.

    * Car CB Radios : Most cars have limited cab space and the vehicle is often used for day-to-day life. This makes radio size an important factor in passenger vehicles. Small radios that take up little space, as well as radios that don't require intrusive and complicated installations are popular with passenger vehicle owners. CB radios such as the Midland 75-822 are popular with car owners.

    * Semi-Truck CB Radios : Professional drivers tend to want full-featured CB radio as they are a crucial communication tool on the road. As such, a good after-market radio “peak and tune” to boost performance is often important. The Cobra 29 LTD series is one of the most popular CB radios among professional drivers.

    * Jeep CB Radios: Off-road drivers usually have smaller vehicle cabs and tend to choose compact CB radios due to space constraints. The Uniden 510XL and Cobra 75 WX ST are both popular choice with off-road drivers due to their compact size.

    * RV CB Radios : RV owners traditionally have ample cab space that can accommodate large CB radios. Popular features with RV owners include weather channel capabilities as well as front-mounted speakers for convenient in-dash installation. The Cobra 18 WX ST II and Uniden Bearcat 538W are both popular with RV owners.
     
  4. amigodana

    amigodana Active Member

    Joined:
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    City, State:
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    Year, Model & Trim Level:
    98 Exp 2WD conv. to 4WD
    Cb modification

    Here is the link for pics

    http://cbradiomagazine.com/March%202007/Cobra%2029%20LTD%20Super%20Modulation%20Modification.htm

    The Cobra 29 LTD super modulation modification

    It's one of the most popular modifications to have done to your CB radio. You'll often hear people say on the radio that their Cobra 29 LTD has had a "swing mod" or "Super mod" done to it. On ebay people often will tell you that the radio they are selling has had a swing modification done to it to make it a "screamer".

    So what exactly IS the famous "super modulation" modification?

    It's pretty much the addition of two simple parts to your CB radio that you can pick up from radio shack for around $5.

    Wow! A modification to my radio that costs $5 and will give my loud modulation? Yep.

    Now this modification is not for everyone, and it does require a little soldering, But if you have an old Cobra 29 LTD or Cobra 25 LTD laying around it's a fun modification to learn.

    The first thing to know about this modification is that you don't need a special "kit" to do it. Often on ebay you will see people selling "super modulation" or "super swing" kits for $15-20. Although the kits will work, they aren't necessary. You can get all of the parts you need for this mod at Radio shack.

    As mentioned there are different variations of this modification. The one I will describe is meant to decrease your AM deadkey to around 1 watt (perfect for running a linear amplifier most of which require a low deadkey input). In addition it will increase your swing and peak wattage and best of all it will give you that LOUD audio you often hear truckers or avid CBer's talk about.

    Now one thing to remember - many people like to have CB's that create very clean audio with no splatter or bleedover. Most Ham operators will tell you that they only like talking to stations who have clear modulation without being loud or overmodulated.

    Many CB technicians can do this type of modification but can also make the necessary adjustments to give you both a LOUD signal without being overmodulated but this requires specialized equipment that most CBer's don't have available.

    Do not do this modification if you are someone who wants clean, clear modulation. Doing this modification to your radio may cause your radio to have bleedover into speakers, neighbors TV's etc.

    And now for the warning:

    WARNING: Modifying your CB radio is illegal. I don't promote it or condone it. I'm merely providing information. In addition I make no guarantee to the validity of any of this info. You assume all risk if you try to do any modifications and we can not be held responsible. I'm not a CB technician so this information is being provided by an amateur unskilled individual. Proceed at your own risk.

    Okay - now that we've explained that let's continue.

    What you will need for this modification is two parts from radio shack -

    1) 220uf (16-25 volt) electrolytic capacitor (the 470uf version will also work and people have also used a 1000uf version)

    2) 33ohm, 68ohm or 100 ohm (1/4 to 1/2 watt) resistor (ohm resistance determines deadkey, more ohms=lower deadkey)

    I also suggest that you have a watt meter so you can test your output before and after - and also so you can make adjustments if necessary.

    Now - different value resistors offer different resistance, so I can't tell you exactly which resistor will be perfect for your installation. Some resistors will give you a 1 watt deadkey, some will give you a 2 watt deadkey. A pack of a couple costs $0.99 so you might as well buy a couple different values and that way you can experiment if you first choice doesn't work out.

    Next thing you will need to do is to remove the screws for the top and bottom covers on your radio.

    Now we will go step by step

    1) Flip your radio upside down so the speaker is facing up.

    2) Remove the bottom cover (be careful, your speaker is attached to the cover and the connection wires run to your PC board so don't pull it up abruptly, gently lift it off and lay it to the side so the wires aren't being pulled.)

    3) Now you should be looking at the component side of the PC board. You will see that the board has a lot of small labels on it in white lettering. Look toward the rear of the radio and locate JP36.

    4) Once you have located JP36 you will need to remove it. To do this you will need to flip the radio over, remove the top cover, and unsolder each end of the jumper on the solder side of the PC board.

    To locate the ends of the jumper on the solder side see the picture below.

    5) Once the jumper is removed you can fit the legs of your electrolytic capacitor into the empty holes. (VERY IMPORTANT NOTE: The electrolytic capacitor has a NEGATIVE and POSITIVE SIDE to it. When installing make sure the negative side is installed closest to the back of the radio.)

    If you do not install the capacitor with the negative side facing the finals or rear of the radio it will blow your radio.

    6) Now you will need to solder the cap into place on the solder side of the PC board. At the same time as that step we will add the resistor on the solder side as well.

    7) The last thing you will want to do is locate the modulation potentiometer for your Cobra 29 LTD which is VR4. Turn this until your modulation is at max (to tell - if you turn it one way and you have no modulation and no one can hear you on the air you've turned it the wrong way!)

    8) Some people recommend adjusting L14 for maximum power, but in most cases after doing the modification your swing should be better than before and your radio much louder so trying to squeeze a couple of extra watts is not my recommendation.

    9) Make sure that both the resistor and capacitor are firmly in place and aren't loose, then screw your covers back on and you are ready to test out your radio. (A watt meter is needed to see the results of course.

    Many people do this modification because most amplifiers like deadkey input of 1-2 watts and most stock radios have output of 3-4 watts (not a good combo if you want your amp to last a long time).

    Some people want to be able to turn the power down for running an amplifier and then turn it back up to run without one. There is a way to do this and add variable power to your Cobra 29.

    Basically you would do the modification above - but when you solder in your resistor you would also need to solder a wire to each side that is long enough to reach the front knobs of your radio.

    Find the back side of your RF gain knob - it will have two wires coming off of it. Clip those wires and then strip a small section off of each and solder them together.

    Now you shouldn't have any wires running to your RF gain knob.

    Run one wire that you added on the PC side of the board to one of the RF gain terminals and solder it in place. Then run the other wire to the other terminal and solder it in place. Make sure to use the same terminals that the original RF gain wires used.

    Once done your RF gain will now control your variable power. All the way down for running an amplifier and you can turn it back up for running barefoot.

    Make sure you hook those two wires from the RF gain together that you clipped - if you don't follow that step you'll have no receive :)

    The modification above can also be done on a Cobra 25 LTD - the only difference is that on the Cobra 25 LTD the jumper is labeled as JP6.
     
  5. amigodana

    amigodana Active Member

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    Ok

    i guess not
     
  6. amigodana

    amigodana Active Member

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  7. amigodana

    amigodana Active Member

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  8. amigodana

    amigodana Active Member

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  9. 94fourdoor

    94fourdoor Active Member

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    Seriously, thank you. This is a freakin AWESOME wealth of info on some things that I have been thinking about since I recently started getting into C.B.'ing. Please keep giving us tips and tricks as you come across them! Thank you again!:salute:
     
  10. ncranchero

    ncranchero Co-moderator Staff Member Moderator Elite Explorer

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    X2 ! Excellent posts. Thanks!
     

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