Coax Calculator
Discussion in 'CB Radio Forum' started by mike5511, Jul 5, 2021.
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If i see one againg ill pass on a link..mike5511 Thanks this. -
Coax Length = 492 x VF/freq. If length is 14.7 feet, then cut coax to around14.8 1/2 inches. Take .7 x 12 = 8.4 inches.
So 492x.66 (66% VF for 58/u coax) equals 324.72, divided by 27.205 mhz (channel 20), equals 11.9ft long. That a why some tech's say 12 feet of coax is close enough.
I use RG213 coax with 66% Velocity Factor for my base antennas. So for a simple example, if the length for channel 20 was 12ft long, you would add another 12ft to get 1 wavelength, a total of 24ft. . Then keep adding 12ft to reach your antenna. Now you have to use every other 1/2 wavelength number. The problem is that if your 1/2 wavelength coax is 4ft short from reaching your antenna, you will have a lot of excess coax because you need to cut it at the next 1/2 wavelength. Also in this example, you would need to use a 1/2 wavelength 12ft jumper cable between the radio and swr meter, instead of the usual 3 ft jumper.
I just found this website that will explain it better.
RadioMods coax length pageLast edited: Jul 27, 2021
mike5511 Thanks this. -
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Found this one while surfin youtube..
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Another about le
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Oxbow Thanks this.
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No im sayin that a mfj was used in the vid but useing the 35 would be able to do the same as mfj..You would have to use the screen that shows all the swr/resistances and resonance screen..
The 35 will not allow you to just calibrate the for the null of coax by useing an open/short/load....Not that i asked rig expert but according to the dx engineering site where i got my o/s/l its says for the 55 and up.. -
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