Looking for a little advice as I get my CB up and running in my new, old truck. I had a 2001 Screw with this set up and it worked fairly well but I am hoping for a little more range with this truck. It's a 96 F350 CCLB and I want to mount the antenna (8 foot whip) on the plate on the toolbox between the two sides - toolbox doors open from the side. I know it will mean the bottom of the antenna is about 18" from the roof and I suppose I could build a bracket to raise the base up while still attaching it to that plate. Will it really make that much of a difference? I'll route the cable up to it and add a ground strap to the frame. Any other considerations? The CB is a Cobra 148 GLT ST and someone has tinkered with it some - not really sure all that has been done to the guts. Thanks for any help.

 

i have no leg to stand on, but i was thinking about building a headache rack and putting a mount centered on that. then i remembered the parking garage at work. 7'2" clearance. good luck.

 

Yeah, that's a little low. My whip is on a spring mount so it will bend way over. Not sure that my truck is under 7'2" anyway. It's that bottom 18" that I am trying to determine if it will really mess up my receiving/SWRs. I'm sure someone "expert" will know.

 

Put a K40 in the center of the roof,you won't regret it.I use K40[s exclusivly and even with a fairly cheap but well tuned radio with a D104M6B mic I could easily talk back and forth with a base station 30+ miles away.

 

I'm probably a little late for the OP's benefit, but for others:

Mounting on that toolbox will make the antenna almost useless. For two reasons.

1) There's almost no grounding contact between the toolbox and the rest of the truck, because of the side rail covers. The piffling little screws holding the toolbox to the bed just won't cut it.

2) There's not enough flat surface there to form an effective ground plane. Even if you managed to properly ground the toolbox, you need a good ground plane to get good range.

The best places for an antenna are either in the middle of the roof, or a corner of the hood.

-blaine

 

A CB whip is usually 102" long (234/27.5MHz = 8.509 feet*12 inches = 102 inches). That is 1/4 wave length on the CB band. Properly installed this can be the best antenna from an efficiency stand point. Anything shorter uses inductance to make up for the electrical length - there is resistance and other losses in gaining the inductance that take away from the efficiency.

Low impedance grounds are important.

Radiation patterns will favor the direction of the most metal. If you mount the antenna at the rear drivers side stake hole in the bed rail the radiation pattern will favor towards the front passenger side corner. In practice I don't think you would ever notice unless you were trying to talk to a real weak station and had a parking lot or field you could turn around in that was out in the open (no buildings or light poles that can affect the signal strength). I'd be curious as to what the results of that test would be... may have to try that some time and watch a signal on my analyzer.

In general, antennas radiate the most energy (and are the most sensitive to receive) at the feed point - the base. When you transmit that is where the most current is. As it travels up the antenna more and more of the energy has radiated off = less current 3/4 the way up than at 1/4.

I just came across this page, pretty good information. Check out figure 15-13 (just past half way, close to the bottom third of the page). The top half of the red line is the current distribution of your antenna, the bottom half is made up within the ground plane.

 

Very good write up...or from the bottom side - as a rule of thumb you always want to mount the longest antenna as high as poosible attached to the largest sheet of metal possible. I keep that in mind when mounting an antenna, but I pretty much only use mine to talk between trucks when 4wheeling and I don't need much distance.

Since my 4 foot Firestick only reaches about 2 feet above the cab...is it worth the money to have the cb tuned at a cb shop? I did the normal swr tuning but will I gain much if they optimize the amplifiers?

 

I'd be surprised if ANYONE could "optimize" a set of finals...

What MOST CB shops do on a "peak and tune" is to remove the audio input "limiter" so that the audio section can overdrive the finals. That makes the meter move further, but it also makes the audio sound like crap. It's the effective equivalent to turning up your stereo till it distorts and blows up. You can add bigger finals, but you're still driving them with a crap signal. And by the time you've spent that kind of money, you could have bought something better or bigger.

SWR tuning will get you the biggest bang for the buck.

27MHz (aka 11meters) Amplitude Modulation (AM) is absolutely LOUSY for either distance or signal quality, especially during this time in the solar cycle (A Solar Maximum). You're not going to get more than 3-5 miles out of it without either a full-wave/full-ground antenna, or a really BIG linear amplifier (or both). It is the nature of the beast, and the nature of having an electrically charged atmosphere.

If distance is what you're looking for, and you're not trying to talk to random strangers (as you would be on the freeway with a CB) then consider 450-MHz FMRS radios. They're in a better signal band for propagation, and are FM, so they actually transmit legible sound. You can buy a nice pair (or three) for the same money that you spend on a high-quality CB rig + antenna tuning + linear.

-blaine

 

a wilson 1000 or 5000 is the best ...look up thomas distributing they have about the best prices and shipping