Setting up a CB antenna in a daycab 2017 Cascadia.

Absolutely, and a short braided strap is preferred to a long ground wire.

 

Two miles is better than most modern trucks, but horrible compared to what a good set up can do with just a 4 watt radio.

 

You'll probably be disappointed with your range with a 3 foot antenna. A 4 foot antenna is usually recommended. Of course the longer the antenna the further you should be able to talk.

 

Question; why only a 3 footer…… enquiry minds would like to know …..

 

Okay, I had a hunch you were working in construction or something similar. A longer antenna isn't really necessary, especially if you're okay with the range that you get with your radio. Before I retired I was a flat bedder hauling pallets for many years. I had to drive on a mile of rough gravel road and cross a busy railroad track several times a day to the shop from the oil highway. My favorite antenna was the hustler fg27s.

FG27S - Hustler Steel Center Load CB Antenna

In fact I bought 3 of them, they were only $22 each at the time. I bought the extra one as a spare, and put the second antenna on my bosses truck. He never did say thanks or offer to pay for the antenna.. hmmm. Anyway my antenna broke off after about 8 years of abuse and the other antenna is still on my ex bosses truck. I've always preferred steel antennas over fibreglass.

 

You are correct on having the antenna as high as you can get it. The professional guys claim you need at least 2/3 of the antenna above tallest point of the vehicle. That's the reason you can probably get away with a 5 to 7 foot long antenna mounted lower, like the back of the sleeper. Some guys have had good results and some not so good by mounting the antenna on the back of the cab. I would encourage you to experiment with the antennas and see what the results are.
In simple terms, antennas are based on 1/2 wave lengths which is 17 feet for the 27mhz cb band, simple math is 468 divided by 27.205 (ch 20) = 17.2 feet. The thing to remember is that a mobile antenna is only a 1/4 wave antenna. So that means for the antenna to be efficient (efficient is the key word we are looking for), the antenna needs to be 8.5 feet long. That's why the 102 inch antennas work so well, if you have a good RF ground (referred to as ground plane) that makes up the other electrical 1/2 of the antenna system. So the physical 1/4 wave antenna plus the electrical 1/4 wave equals 1/2 wave length. The problem is that a 102 inch antenna isn't very practical on a big truck for obvious reasons. Of course some guys get away with mounting them on the trucks cat walk. So how do you make a 3 or 4 foot antenna act like a 1/4 wave antenna?, well they wind the wire around the fibreglass antenna to make the shorter antenna act like a 102 inch antenna. So you can see that means more windings on the 3 foot antenna versus the 4 foot antenna. The bad part about that is, when you sends lots of RF power to the antenna, the wires wound tight together introduce heat, which is a waste of energy. Not very efficient compared to having an antenna long enough that needs no windings, like the 102 inch antenna. That is why I mentioned using at least a 4 foot antenna, anything shorter doesn't perform very well. Also another rule of thumb is to have the coil mounted towards the top of the antenna, they call that top loaded. Much more efficient design than just wrapping wire around the whole antenna length.
I wouldn't recommend a magnet mount antenna on top of your truck, mainly if you catch a low tree branch, well obviously that isn't good. The thing about mag mount antennas is that they either work or they don't. I've used them over the years and they are okay if you have no other choice. The big thing is you always need to remove them and wipe the dirt and moisture off the magnet base once in awhile, plus they can leave rings on the paint job over time. So more maintenance required.