Re: Antenna cable length?
SWR ,(standing wave ratio) is the ratio between RF power the antenna system can radiate,called "Forward",to the amount of RF power it reflects back to the radio (called reflected). <br />The reflected power is unused,useless,and if enough of it is present, bad for your radio. The principles are the same for all types of transmitters, whether they are CB,VHF,or cell phone. These all transmit RF energy.The differences are the mode (FM,AM,CW ect),and the frequency they operate on. CB is 27MHz,VHF is in the 170MHz area of the spectrum. The only other thing to deal with is line loss. At lower frequencies ,like CB, line loss is less critical than on higher frequencies. VHF marine band is somewhat suceptable to line loss in standard coax cable such as RG-78-U, which is the standard 50ohm coax that comes packaged with most radios,regardless of what type of radio they are.<br />This is because it is cheaper. Line loss should only be of concerne if your VHF rig will have a long run of coax.If over 12feet,I would change it to RG-8U, the thick stuff.The white coax is a marine-grade insulation form of RG58-U,and unless you have a yacht with a tuna tower, it should do just fine. If you mount the antenna close to the radio, or any other electronics, like within 3feet or so, expect it to interfere with that other device.<br />SWR must be checked. And there ARE slight differences in the useable frequency of SWR briges.One designed for CB may allow you to determine there are no shorts in the coax, but the forward and reflected scales will be totally whacky.<br />2 meter ham swr meters are close enough to get fairly acurate readings, but the CB jobby may actually try to radiate some RF on it's own when hooked up to your VHF,and act like a small antenna in itself..Uncool.<br />Best bet is buy one,borrow one, or have it checked by a ham or marine elctronics shop.<br />If you didn't live in MD, I'd check it for you.<br />My callsign is N4ZAW, but I live in Florida.
