High SWR troubleshooting

[RookieRooster]

Hello, I have a Cobra 29LX with a four foot FireStik on my 2017 F-350 (Its aluminum) I grounded my antenna to my trucks bed. My SWR readings on all the channels are above three. I have tried multiple antennas, all FireStiks. In the pictures, does the cable look like a good quality coax? The bracket is a pretty good quality one. What could be causing the high SWR's? Please let me know if you need more pictures. All suggestions are highly appreciated.

I can't seem to load a picture of the bracket mount, i'll keep trying.

 

[prcguy]

The ground plane is way insufficient at CB frequencies and it will never tune up. You only have a thin stick of metal about 5ft long as a ground plane on that bed rack. You can try a no ground plane Firestick mount, those will sometimes allow you to tune the antenna up.

Hello, I have a Cobra 29LX with a four foot FireStik on my 2017 F-350 (Its aluminum) I grounded my antenna to my trucks bed. My SWR readings on all the channels are above three. I have tried multiple antennas, all FireStiks. In the pictures, does the cable look like a good quality coax? The bracket is a pretty good quality one. What could be causing the high SWR's? Please let me know if you need more pictures. All suggestions are highly appreciated.

 

[RookieRooster]

The ground plane is way insufficient at CB frequencies and it will never tune up. You only have a thin stick of metal about 5ft long as a ground plane on that bed rack. You can try a no ground plane Firestick mount, those will sometimes allow you to tune the antenna up.

Thanks, do you recomend a NGP set up?

 

[prcguy]

I think its worth a try but it still may not tune up perfect. Relocating the antenna so it has much more sheet metal under it is another option.

Thanks, do you recomend a NGP set up?

 

[slowmover]

Take it off the rack altogether.

A BREEDLOVE Antenna Mount (permanent) is how to do it. Cab roof. 4” Puck or CB Ball for a Tall antenna or a 4” NMO mount for a Short antenna.

A VERY tall antenna in a stake bed pocket is another route.

I use 14’ on a semi as total antenna height. And AT LEAST a 5’ antenna to get there. I’ve a big puck mount to go on my Ram near roof center. And a whole slew of antennas of different lengths to cover both town & country.

You can try adding RF Bonds with what you have:

Mobile Install

but it won’t ever be as good as a quality roof-mounted antenna.

IMO, there’s not much point to having a CB Radio if the antenna (system) isn’t up to the job. That’s what matters.

A cheap radio with a great antenna system will walk all over a $$$$ radio with a total crap antenna system (what you have). It’s not even close.

Start from a fresh perspective. Installing a clean DC Power System and a quality Antenna System are not that hard, even if the subject is new.

It will need some reading and some list-making. Supply and maybe some tools. But you won’t have to re-invent anything. It’s a known set of problems to solve.

The pains I’ve gone to with modern semi tractors (big ones) you won’t have to get involved with. And you’ll have something better if you do it right.

I want (and work towards) always getting the most I possibly can from a radio. The radio must have clean 12V and best antenna mount + coax installed if the rest of my gear is to pull those faintest radio signals into clarity.

Mobile CB is harder than it was in 1978. So’s everything else.

But when it comes to on-road problems, there is just no substitute for having heard that far earlier than others. Choices. Some things known only two miles ahead can’t be acted upon. At twelve miles — or farther — they can.

Upgrading your truck with a permanent mount antenna is that road. Hear, and be heard.

 

[mmckenna]

When I was young, I tried mounting a CB antenna on the headache rack like that. Never was able to get it to tune up correctly.

A No Ground Plane may give you a low SWR reading, but the radiation pattern may be all wonky due to the headache rack under it providing a partial ground plane. It may be just fine for short range use, but antennas really like to have a ground plane under them.

While I know it's unpopular for some, doing a permanent mount dead center of the cab roof will give you a really good ground plane and much better performance.

 

[RookieRooster]

When I was young, I tried mounting a CB antenna on the headache rack like that. Never was able to get it to tune up correctly.

A No Ground Plane may give you a low SWR reading, but the radiation pattern may be all wonky due to the headache rack under it providing a partial ground plane. It may be just fine for short range use, but antennas really like to have a ground plane under them.

While I know it's unpopular for some, doing a permanent mount dead center of the cab roof will give you a really good ground plane and much better performance.

Thanks, I just did not want to drill any holes in the truck.

Take it off the rack altogether.

A BREEDLOVE Antenna Mount (permanent) is how to do it. Cab roof. 4” Puck or CB Ball for a Tall antenna or a 4” NMO mount for a Short antenna.

A VERY tall antenna in a stake bed pocket is another route.

I use 14’ on a semi as total antenna height. And AT LEAST a 5’ antenna to get there. I’ve a big puck mount to go on my Ram near roof center. And a whole slew of antennas of different lengths to cover both town & country.

You can try adding RF Bonds with what you have:

Mobile Install

but it won’t ever be as good as a quality roof-mounted antenna.

IMO, there’s not much point to having a CB Radio if the antenna (system) isn’t up to the job. That’s what matters.

A cheap radio with a great antenna system will walk all over a $$$$ radio with a total crap antenna system (what you have). It’s not even close.

Start from a fresh perspective. Installing a clean DC Power System and a quality Antenna System are not that hard, even if the subject is new.

It will need some reading and some list-making. Supply and maybe some tools. But you won’t have to re-invent anything. It’s a known set of problems to solve.

The pains I’ve gone to with modern semi tractors (big ones) you won’t have to get involved with. And you’ll have something better if you do it right.

I want (and work towards) always getting the most I possibly can from a radio. The radio must have clean 12V and best antenna mount + coax installed if the rest of my gear is to pull those faintest radio signals into clarity.

Mobile CB is harder than it was in 1978. So’s everything else.

But when it comes to on-road problems, there is just no substitute for having heard that far earlier than others. Choices. Some things known only two miles ahead can’t be acted upon. At twelve miles — or farther — they can.

Upgrading your truck with a permanent mount antenna is that road. Hear, and be heard.

When you say very tall, how tall do you mean?

 

[FLA727]

I am using a Breedlove Bedrail Mount on my 2015 Silverado and what appears to be the same coax as you are using. My antenna however is a 102" whip and I have the ground wire going from the ground lug of the mount down to the underside of the truck bed. My SWR runs about 1.3 across all the channels.

 

[WB9YBM]

My SWR readings on all the channels are above three. I have tried multiple antennas, all FireStiks. In the pictures, does the cable look like a good quality coax? The bracket is a pretty good quality one. What could be causing the high SWR's? Please let me know if you need more pictures. All suggestions are highly appreciated.

You haven't mentioned much about the coax--by the sounds of it, it's the one thing that has not changed (along with the SWR situation leading me to wonder if that commonality indicates a problem with the coax). Did the coax get pinched someplace (causing an internal break)? Flexed too often at some point (causing the internal wire to break)? Is it the right impedance coax? Internal short anywhere? (To paraphrase Arthur Conan Doyle, After eliminating the obvious, whatever's left--no matter how unusual--is probably the culprit.)

 

[slowmover]

Thanks, I just did not want to drill any holes in the truck.


When you say very tall, how tall do you mean?

As said, what will take it to 14’.

Some use 13’5” as a maximum (big truck clearance minimum).

Truck cab height on mine is 70”To a 13-5 clearance is an antenna at 7’ or a little more.

A PRESIDENT Texas is just over 7’ (tall antenna).

My preferred minimum (5’) reaches to about 11’.

Less than this is “short” (my opinion). See threads regarding Larsen NMO-27 (about 4’).

A permanent antenna mount is an upgrade where the rest of the installation is
top notch.

The factory left more than a dozen “holes” on your vehicle exterior.



.

 

[RookieRooster]

You haven't mentioned much about the coax--by the sounds of it, it's the one thing that has not changed (along with the SWR situation leading me to wonder if that commonality indicates a problem with the coax). Did the coax get pinched someplace (causing an internal break)? Flexed too often at some point (causing the internal wire to break)? Is it the right impedance coax? Internal short anywhere? (To paraphrase Arthur Conan Doyle, After eliminating the obvious, whatever's left--no matter how unusual--is probably the culprit.)

We have checked the coax, thats not the issue. Its brand new and is in perfect condition.