CB MythBusters

1) My transmit sounds distorted locally, but it clears up when the signal gets further out.

Unless the person you are talking to over the CB is sitting a few feet from your antenna this is not correct. If you start with a distorted signal you end with a distorted signal. The atmosphere does not work miracles on your CB signal to clean up distorted transmit audio. Unless the receiver is within "rock throwing distance" of the transmitting antenna, if it sounds distorted locally it will sound distorted out in the distance.


2) Pouring salt in the ground around the base of your antenna will help you get out better.

Pouring salt in the ground will increase the soil conductivity in the immediate area of the antenna, but you would have to saturate the ground surrounding the antenna with salt for hundreds of yards to make any noticeable difference. There are many papers on this subject, so I'll just keep my answer short and to the point. The higher your antenna is above ground the less influence near field ground loss will affect your signal. If you can get the base of your CB antenna 75 feet or more above ground (about 2 wavelengths at 27 MHz), pouring salt in the ground around the antenna will not make any difference. At 36 feet the difference if any will be so small no one will notice.

If the base of the antenna is on the ground then near field ground losses will be significant. Burying a large number of 1/4 wave ground radials around the base of the antenna will help your transmission in this instance, but you will get a much bigger bang for the buck on the CB band by raising your antenna as high possible. A 5/8 wave ground plane antenna with the base of the antenna starting at 72 feet is an amazing performer on the CB band.


3) Trimming the length of my coax will lower my SWR.

Wrong. Trimming the length of your coax will trick your SWR meter and you in to believing your SWR is lower. SWR is the ratio of the impedance of your coax to the impedance of the antenna. Standard CB coax is rated at 50 ohms. It has a 50 ohm impedance regardless of whether it is 3 feet long or 1000 feet long. To get a Standing Wave Ration of "1 : 1" both the antenna and the coax must have an impedance of 50 ohms. If the antenna has an impedance of 100 ohms and the coax has an impedance of 50 ohms then your SWR is 2:1, or put another way the impedance of the antenna is twice the impedance of the coax. Likewise an antenna impedance of 25 ohms and a coax impedance of 50 ohms is STILL a 2:1 SWR because the coax impedance is twice the impedance of the antenna.
Changing the length of the coax will neither change the impedance of the coax, nor will it change the impedance of the antenna. It will trick your SWR meter in to a false reading.. In reality the impedance mismatch between the antenna and the coax will remain, and so will the accompanying power loss. It does not matter whether you have a Bird SWR meter or a Radio Shack SWR meter. SWR meters are not perfect, and they can be fooled.
If you can change the SWR reading on your SWR meter by changing the length of the coax then you can be sure of only one thing. You do not have a 1:1 impedance match between your antenna and your coax.



4) Whistling in your mic is bad for the tubes in an RF amplifier.

Not really, but tuning up your amplifier ten times a day is. If you repeatedly whistled for long durations of time you may shorten the life of your amps tubes, but one quick whistle should not hurt a thing provided you are not over driving your amp.



5) You can get a approximate idea of total output watts using this mathematical equation.

Voltage X Amperage - ( yes minus ) the efficiency of the tube or transistor ..( pill ) = Apx. wattage
so your good buddy says he has a 4 pill that does 1000 watts in his mobile, OK look at the fuse, lets say its a 100 Amp fuse, now fuses are normally rated at 15% more than the designed operating amperage, if it was any closer it would blow all the time on peeks. so 100 Amps - 15% = 85 amps. so the voltage of the vehicle is 13.8 Vdc . 13.8 Vdc X 85Amps = 1173 total maximum watts, now you have to subtract the efficiency of the transistors, remember they make heat when they work and this heat is not free, so a 2SC2879 is Approximately 65% efficient so 1173W - 65% = 762.45, in a perfect world with the entire linear circuit being perfect, this 762.45 is the ABSOLUTE max power obtainable, you also need to remember that the bias and relay and fan are all also taking power in the form of watts from that original 1173 watt number so the actual number is even lower. Again if your watt meter is saying more, look for a new watt meter.



6) IF your antenna feed point is not plus or minus J zero, you cannot get a accurate SWR reading from ANY SWR meter no matter how expensive.

Your plus or minus J zero number is the reading of inductance and capacitance



7) A properly modulated, non overdriven carrier will grow 4 times over dead key.

ie. dead key 4 watts, modulate 100% properly and it should grow to 16 watts PEP,

dead key 4 watts and modulate 200% properly and it should grow to 64 watts PEP.

Percent of modulation is what makes you loud, not watts.