Quote: Does anyone know how long a coax run can be? I have a 32' class A and was thinking of running from a CB up front, out the firewall, then maybe try to find some way to get up on top. Just trying to figure out how to not drill any holes. Or at least only one. Any suggestions will be greatly appreciated.
I have a 29' and I ran my coax from under the dash, along the frame and up the ladder and mounted the antenna to the ladder. Works fine. Another 6' or so shouldn't be a problem.
no matter what system you run .... ground it. some thing as simple as attaching a ground wire to your cb case then to a ground will drop swr of .5 or so.
i use a 102'' whip with 9 feet of r58 coax. highest swr is 1.2 on channel 20 and .01 on channel 1 and .5 on channel 40. i have antennae grounded cb case gounded.
jim91303-Are we talking MNGP antenna's? So you think I should ground the radio itself? Shouldn't it be grounded from the black wire in the power cord? The black wire on my radio's power cord is attached directly to my inverter's 12v ground coming directly off the house battery. Are you saying I should run another ground wire off that to the bracket of the radio and another to the antenna mount? Firestik says do not attempt to attach a ground to the antenna itself. There is only one copper wire coming off the special NGP coax. The wire exterior sheathing on the special coax is the counterpoise and should never make ground.
DAS26miles wrote: jim91303-Are we talking MNGP antenna's? So you think I should ground the radio itself? Shouldn't it be grounded from the black wire in the power cord?
Grounding the radio case to the chassis is always good practice. Do not ground the Firesik NGP antenna and do not do anything else to it that Firestik did not tell you to do. That antenna is an odd duck and you must follow the directions that came with it.
There is ground and then there is RF ground. At 27MHz, the CB operating frequency, the small amounts of inductance and capacitance in all wires and other structures play a huge role in how well "grounded" your radio really is. The black wire in the power cord is too long and too skinny to provide a real, low impedance, ground for the radio at its operating frequency. You need a very short, very fat, connection from the radio chassis to the vehicle chassis if you want to truly ground it. Ideally you would use a piece of flat braided copper strapping at least an inch wide and no more than six inches long to get a good ground between radio and vehicle chassis. The thinner and longer you make that connection the less effective it becomes.
It's worse than that though. Even if you have an ideal ground strap between radio and vehicle you are really only "grounded" at that one particular point on the chassis. The chassis itself will not be at a uniform potential at 27MHz because just like any other conducting structure it has its own internal inductance and capacitance.
If you are getting good SWR readings on your antenna and are getting good range on transmit and receive then whatever ground you currently have is fine, even if it is only the transceiver's power lead. If you are getting poor results then a better chassis ground might help but it is not a miracle and will not compensate for serious problems in your antenna.
A good ground for a CB is to use the flat metal bracket that screws onto the CB chassis and screw it onto the metal dash of the truck, removing the paint from the bracket under all the screw heads and remove the plastic washers from the mount hardware so the screws touch the metal bracket directly. I also ran a seperate flat braid ground strap from a chassis screw on the back of the CB to truck sheetmetal nearby, again removing the paint under the screw heads and using 'star' washers to ensure a good metal to metal contact. If an amp is involved, ground the chassis of the amp and CB together as well.
Your home made wood bracket for the CB does look very nice. You did some nice work to it. You probly need more ground than what you have though.
They do make the metal quick-release slide brackets for CB's that are very easy to take the CB in and out. If you use one, connect the wiring direct to the CB though, instead of going through the sliding contacts on the quick release assembly.
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