CB radio installation... and aerial mounting

[uHu]

I mounted on the spare wheel carrier and because the cb does work , sort of , i think maybe i need to raise the bracket so the antenna is entirely above the roof line .

The antenna on the spare wheel carrier is rather less than ideal, as it is normally not properly grounded. Grounding is much more tricky, and crucial, for radio waves than for normal electric current (AC or DC). The carrier will act partly as an antenna, and partly as ground, depending on several continually varying factors. Not a good situation at all, and a much bigger factor than above or below the roof line. If you insist on using the spare wheel carrier as an antenna mount, you would have to put a wide ground strap at each hinge, connecting the carrier to the car body. For radio waves, it's the surface area of the strap which counts rather than the square, so a wide, thin, braided copper strap is good. Otherwise, an antenna mount through the roof is normally the best, and if done properly, with quality parts and a PH-neutral sealant, it would last as long as any other part of your car.

 

[Shayne]

I think your assuming i have a swing out carrier uHu but the collie spare sits on a carrier bolted to the back door so its more or less a part of the trucks body . While setting up i tested continuity between the carrier and the actual body (inside the jack locker) and found it to be good so welded my flexible antenna bracket to it .

I think my trouble is caused by the radio actually being able to see part of the antenna


I do appreciate your advice though , if raising the antenna doesn't solve my problems i will have to rethink the whole thing so thanks for taking the time to reply .

And well done Dave , sorry for the thread jack !

 

[clivehorridge]

While we're on the subject of mounting locations (if I may) I have mine mounted on one of the antenna mounting brackets on my ARB front bumper.

Whilst this place may not be as ideal as a roof mount (electronically) its far more practical given the overhanging trees and branches that are typical on most of my "laning" routes.

Is it such a bad place on an 80 considering how far the antenna is from the main body of the truck? The ARB bar is at least 300mm forward of the grill and we all know how long the bonnets are on the 80s.

My CB works (of a fashion) but I would have expected it to be better. It seems plagued with interference when on but not in use, it's not others talking, but a very annoying background crackling that makes me just want to shut the volume right down, which kinda defeats the object somewhat.

I have the squelch activated but I don't really know anything about these things, I was hoping I would be able to communicate with Shayne and Chas when they're here, over maybe 1/2 km but that 's impossible. If were in convoy, then sometimes it's OK but mostly I only hear Chas with clarity.

Maybe I should get it set up professionally.

 

[Jon Wildsmith]

Shayne substitute back door for wheel carrier in uHu comments - your back door is on hinges and may not be very well connected to the rest of the truck for RF purposes. Measuring DC resistance between the mount or door and the body of the truck doesn't tell you if there will be a good connection for RF unfortunately but you can fairly safely assume it's not great.

Clive do you only get the crackling when the engine is running, or do you have to be on the move? You may have something generating interference, or a bad connection or your bumper may not be very well connected for RF purposes. You might also want to think about using a strap like uHu described for the bonnet.

 

[clivehorridge]

Shayne substitute back door for wheel carrier in uHu comments - your back door is on hinges and may not be very well connected to the rest of the truck for RF purposes. Measuring DC resistance between the mount or door and the body of the truck doesn't tell you if there will be a good connection for RF unfortunately but you can fairly safely assume it's not great.

Clive do you only get the crackling when the engine is running, or do you have to be on the move? You may have something generating interference, or a bad connection or your bumper may not be very well connected for RF purposes. You might also want to think about using a strap like uHu described for the bonnet.

Thanks Jon, do you mean a strap between the chassis and the ARB? I can check / clean the Antenna mount to the ARB OK, and fit a strap if that may improve things.

The crackling comes when it feels like and goes away the same, it lasts about 5-10 minutes and occurs every 5-10 minutes too. There seems to be no pattern to it in terms of driving, or engine off.

And it doesn't sound engine related like the whizz we used to get in the old days from an unsupressed petrol engine on a MW radio.

 

[Shayne]

I get the principal of it John , hinges nor door catch are proper solid connections and an earth strap would give me a permanent ground

 

[Towpack]

I get interference on 10m (which is adjacent to CB frequencies) from some LED bulbs in the vehicle when they're in use.
I'm not that clued up on CB specific antennas but those available for amateur radio frequencies usually specify if a good ground plane is necessary i.e., for centre roof mounting etc or not meaning it can be fitted virtually anywhere on the vehicle. If no such guidance comes with the CB antenna you're using then i guess it's just trial and error. Irrespective of wether a good ground plane is required or not a good ground (earth) is required at each end of the coax outer conductor.

 

[Jon Wildsmith]

Thanks Jon, do you mean a strap between the chassis and the ARB? I can check / clean the Antenna mount to the ARB OK, and fit a strap if that may improve things.

The crackling comes when it feels like and goes away the same, it lasts about 5-10 minutes and occurs every 5-10 minutes too. There seems to be no pattern to it in terms of driving, or engine off.

And it doesn't sound engine related like the whizz we used to get in the old days from an unsupressed petrol engine on a MW radio.

You might be better off putting a strap from the body to the bumper rather than from the chassis. You can buy the braided straps for this ready made with fixings on the end suitable for putting a bolt through. The bonnet needs a good RF connection as well because it is so close to the antenna and you want to use it as part of the ground plane. Of course you might add straps in both cases but discover the biggest problem is much simpler e.g. faulty cable

For your crackling I would have a think about if any electronic devices could fit the pattern you mention. What none standard electrical parts or devices do you have on your truck? Could be something daft like an ipad used for navigation is cycling through charging and not charging the battery and the 12v to USB converter you're using makes RF noise under load.

 

[Chas]

My CB works (of a fashion) but I would have expected it to be better. It seems plagued with interference when on but not in use, it's not others talking, but a very annoying background crackling that makes me just want to shut the volume right down, which kinda defeats the object somewhat.

I have the squelch activated but I don't really know anything about these things, I was hoping I would be able to communicate with Shayne and Chas when they're here, over maybe 1/2 km but that 's impossible. If were in convoy, then sometimes it's OK but mostly I only hear Chas with clarity.

Maybe I should get it set up professionally.

I've just remembered I used to get interference from my HID headlights on my previous CB but since I bought my current one, a President Johnston, I don't get it anymore so maybe it's the CB you have

 

[clivehorridge]

Thanks again Jon, now I think I understand the gist of the "ground plane" concept, I'll try a strap to the bonnet and see if that makes a difference.

Of course, there are a lot of other reasons that could account for it.

As Chas said above, I'm running HID headlamps, and as you mentioned, I've got numerous USB chargers for phone, iPad, camera and the like.

I do know of a guy who fits CBs for a living. Maybe I should try to contact him because otherwise I'm going to go round and round in circles, methinks.

 

[StarCruiser]

Sounds like a plan Clive. I've seen an antenna set up like yours with two heavy straps down to the chassis bolts. I can see that they would be better (and neater) coming from the bodywork in front of the radiator and through the grille. A strap to the bonnet at the hinges also makes sense. Some good info on this thread here.

 

[clivehorridge]

Sounds like a plan Clive. I've seen an antenna set up like yours with two heavy straps down to the chassis bolts. I can see that they would be better (and neater) coming from the bodywork in front of the radiator and through the grille. A strap to the bonnet at the hinges also makes sense. Some good info on this thread here.

Absolutely, Rich.

If Shayne thinks he knows nothing about CB, then he's probably forgotten more than I have ever known about it!

Jon's been very helpful in a practical sense and many others in a more technical sense.

I'm lost with the numbers and the acronyms, I'm afraid, but some simple practical guidance might get me there!

Thanks Dave for the thread and everyone for contributing.

 

[diggerdave]

SO I tested my newly installed CB radio this weekend laning in the North York Moors. My mate and I had both fitted the same model at the same time and were keen to test them in convoy.

Everything is working perfectly! CBs are a huge step up from hand held radios in at least three ways:
- The speaker is in a fixed place, so no matter how clumsily you've stowed the handset you can always here what people say
- The volume is louder and the reception clearer, presumably because of the greater wattage of the transmitter. There was none of the crackling and interference and slurring that we used to get with the (admittedly cheap) walkie-talkies we used to use
- The range is better. We estimated around 5 miles, but that's in the up and down topography of the Moors

Even my gutter mounted aerial seems to have survived some moderately tight tree-lined lanes around the Esk Valley!

After just one laning trip we are wondering why we didn't do this a long time ago...

 

[diggerdave]

P.s thanks to everyone who chipped in with advice above

 

[clivehorridge]

P.s thanks to everyone who chipped in with advice above

Good to know you're efforts weren't in vain Dave.

5 miles? I'm lucky if I get 1 mile range with mine, I must get it checked to see if I've got the right set-up

 

[diggerdave]

If I was to guess, I'd say that it's a height issue Clive. My aerial is vulnerable mounted on my gutter, no doubt about it, but it is high and unobstructed by bodywork. My mate mounted his on the roll-bar/ladder rack of his pick-up so that's nice and high too.

I'm seriously considering drilling the roof (in the centre at the rear) to try to protect the aerial a bit while keeping it high...

 

[LC80tim]

I've got a mag mount that just sticks to middle of roof, it has a rubber cover to stop scratching and works perfectly with no direct connection to body? The thing is like a limpit takes the bashing from overhead trees and doesn't move a bit, if needed I can just take it off and put in car ( if I can persuade it to let go of the roof lol )

 

[clivehorridge]

You could be right. Mines mounted on the top of my ARB front bumper, so the tip of the antenna is barely above roof level, although there's no immediate bodywork above the mounting part of the antenna.

 

[Shayne]

We have the same antenna and we both mounted it low Clive , it seems unlikely we both set it up wrong don't you think .

 

[clivehorridge]

We have the same antenna and we both mounted it low Clive , it seems unlikely we both set it up wrong don't you think .

Sure, but you know we didn't enjoy 5 mile range did we. It seemed to me that if you were further than 500 m away, we had problems...

And of course, Bill no mates by myself, I can't test it out...