Well, it finally warmed up enough so I can get back outside and work on my Cb antenna mount for my Pickup (2007.5 GMC Sierra). I have a 3' Firestick II, Cobra WX75ST, and 9' of coax (firestick firering). Since I periodically use a ladder rack and a camper a middle of the roof mount isn't an option, nor is installing the antenna on the bed rails. The place that makes the most since is at the hood/fender junction on the drivers side (accross from radio antenna). At present I see an SWR of 1.4 on Channel 20, SWR of 2.5 on channel's 1 and 40, and SWR's less than 2.0 from channels 8-34.

I tried making a better mount and run a 2' ground strap (4ga) to the main ground point in the engine compartment where the motor grounds to the firewall. Doing this made no change in the SWR's. Anyhow, I want to try and improve the SWR on the higher and lower chanels and wonder which would have more effect. 1) Change the antenna to a 4' or 5' firestick to get more elevation above the roof line? Or 2) change the coax to 18' instead of 9'? Thanks

My bet is on the coax length. What did the back of the package say, it was pre-tuned for what, rg-58, 18 feet right? 1.4 is not terribly bad at all, it should be within acceptable limits. The 2.5 is a little high, but it’s probably one of those things that bug you.

Firestik's are, IMHO, one of the best bang for your buck fiberglass antennas. I have 2 5 footers, I only run 1, the other is for show, looks better with 2. I run mini-8 18 foot from my CB, can usually get it tuned down to bout 1.2 or so on channel 19.

I don't know how experienced you are with tuning antennas, as I’m just an greenhorn, but as you know the roof line, position on body (ground plane) all make a difference. I have found out you need to do this with the doors closed and nothing around for good 50 feet (building, trees, power lines, poles) for the best readings. So I like an open parking lot like Wally World.

SWR is an acronym for Standing Wave Ratio, which means, in laymans terms, how efficient your antenna is for a given frequency. It is a ratio of output wattage vs reflected wattage. I use a watt meter that allows me to directly measure output wattage and then compare it to reflected wattage (the # that makes the SWR climb).

With that said, IMHO, coax length plays a very, very small part in efficiency. The closer an antenna is mounted to any metal that will reflect radio waves, the shorter it must be.

An example.........

I use a stainless whip on a bottom loaded antenna. I use the same radio in 100 different pieces of equipment.

Ideally, in the center of the roof, with no metal in line of sight, the whip is trimmed to 44".

Same antenna on the front fender, opposite the AM/FM, and the antenna length needs trimmed to 43".

Same antenna at the leading edge of the bed, 4 inches from the cab, requires a 40" antenna

6" from the cab, 42" antenna.

Put a crossbed tool box on, 39" antenna.


So..... Never is the antenna longer than ideal length, but the antenna must be shortened 'til tuned in any other location.

Read this http://www.firestik.com/Tech_Docs/swr-intro.htm

and this http://www.firestik.com/Tech_Docs/Setting_SWR.htm.

I would start with 18' of coax. If there is no change, then go with a 4' firestick or try a different antennae. I use a wilson trucker 5000 that works really good for me.
Grounding the mount was a good start.
I have noticed different coax styles (firewire - 18'length) work differently with different length antennaes.

I would start with 18' of coax. If there is no change, then go with a 4' firestick or try a different antennae. I use a wilson trucker 5000 that works really good for me.
Grounding the mount was a good start.
I have noticed different coax styles (firewire - 18'length) work differently with different length antennaes.
I'd suggest reading the two pages I linked above. Wire length is a minute factor and the actual physical length of the antenna is different than the electrical length of the antenna.

Read this, too. http://www.firestik.com/Tech_Docs/63Things.htm Especially 13 and 15.

I agree with above. The antenna needs to be tuned. You can not expect to achieve perfect results, either. The best you can hope for is a good compromise.

I agree with above. The antenna needs to be tuned. You can not expect to achieve perfect results, either. The best you can hope for is a good compromise.
Using my Bird Watt meter, I can achieve less than 1/2 of 0.1 watt reflected on channel 20, which translates to 1:1 swr. That's all the better resolution the meter has to display. It requires common sense in installing the antenna in the best compromise position(aestheticly) and tuning with patience.
Even though Firestik makes a quality product, I can get the best tunes from a bottom loaded antenna (I use a hybrid Larsen/Motorola antenna).

It's a hybrid because Motorola doesn't make a load coil for the Spectrum series antenna lower than 30mhz (Cb is around 28mhz) and Larsen's whip is too delicate for a bunch of construction workers. So.........Motorola whip and spring on a Larsen load coil. Our low band construction radios are at 31.5 Mhz, hence all my learned knowledge on antennae and their placement.

I've run a Wilson Silver Load and a firestik 2 on my truck both with 9 foot of cable and 18 foot of cable cable length made no difference unless the extra cable was looped. Both are fairly easy to tune as long as you are patient and willing to run back and forth for adjustments. Read the above mentioned articles, tuning is done on channels 1 and 40 with the idea of making them as close to each other as possible and as close to 1 as possible, getting to below 1 with a top load is nearly impossible. Once you have those tuned close together, you will note that 20 falls right into place. Good luck.

I'd suggest reading the two pages I linked above. Wire length is a minute factor and the actual physical length of the antenna is different than the electrical length of the antenna.

Read this, too. http://www.firestik.com/Tech_Docs/63Things.htm Especially 13 and 15.

Very informative!
I know from personal experience that using standard 18' length of coax helps with getting low swr's. I changed the the coax on my wife's jeep (just wanted to try different style of firewire) and original 3' firestick antennae would not get low enough swr's. A 4' worked great, but was not condusive with her parking in the garage with the longer antennae. Had to go back to original setup and no problems.

Just bought a cb for the first time in 20 years. It's a Ranger and I first set it up with a 3 ft Firestik. That didn't get it so I now have a 2' Halfbreed bottom load and the swr is virtually 1.1 I couldn't get it below 2 1/2.1 with the Firestik. The mount is on the frt the same as Sowilson. Just got it all together today so we'll see how it goes

I've found that grounding the base of the antenna solidly makes a difference. If you are creating a mount longer than about 4-5 inches between the antenna base and the mounting point, you sometimes end up with problems trying to peak for best SWR, especially if the grounding via the coax shield is iffy. A short heavy ground strap from the base of the antenna to a body panel can help. Short antennas tend to interact more with nearby body elements like the roof pillars since all the energy comes in about level with them in this sort of installation. Getting a longer stick can sometimes help.

All of this talk rekindled an interest of mine. I am now studying to get my HAM license. I never realized there was so much info. Gives you a better understanding of how everything works together and be able to communicate without the need of excess power.

Sounds like you've already added the ground braid. You should be able to move the antennas proximity to the pillar and see some VSWR change. A minor adjustment to the front may be all your looking for.