CB radio installation... and aerial mounting

[diggerdave]

So, I had a weekend free last weekend and the weather was ok so I carried out some jobs. I fixed my intermittent reverse light (new gearbox switch for £9-99 from Ebay), engine oil and filter (4500 miles since the last one... I left it a bit long!) and a new fuel filter.

BUT the most important job was to fit my new CB radio before my next laning trip. This is a Thunderpole T-1000. Its a very basic set, which hopefully makes it suitable for a noob like me who doesn't know much about CBs. My usual laning partner has bought the same in the hope that we can troubleshoot together if need be!:

Having spent a bit of time trial fitting the set, there was only one logical place for it to go in the LC90 and that was in front of the gearsticks. There is a slight 'tray' shape moulded into the trim right in front of the levers that would be ideal. In my case a previous owner had mounted a 'mystery object' there leaving me with two existing screw holes:

The trouble is that the 'tray' is actually a bit awkward. I really wanted to be able to tilt the CB upwards so that the display and controls pointed upwards. That required removing the 'pocket' type trim that lies below the ashtray, to allow the rear of the CB radio to tilt down...

...and making a raised 'shelf'' out of a block of scrap wood. I covered it with old car seat material using a staple gun - it's mostly hidden so it doesn't need to be a perfectly finished job! (any material or paint would do but I like the car seat material as it gives it more of a factory look, at a casual glance anyway). Here's the wooden block screwed into position from underneath the gearstick trim, with the CB radio mount screwed into the wooden block in turn. It looks a bit ugly in front of the gearstick trim with the 'pocket' trim removed, but all that will be hidden by the CB radio:

I decided to hardwire the CB radio into the battery as this is recommended on some forums to minimise the chance of electrical interference. I don't know if that's an old wives tale, but I'd rather have my two 12v lighter sockets free anyway and it wasn't hard to do. I ran the positive and negative wires above the pedals (later cable tying them up out of the way) and out through the rubber boot in the bulkhead that is just above and to the right of the accelerator pedal and into the engine bay (it's the black and red wires):

Getting the wires through the rubber boot is a bit of a fiddle. I daresay a bit of bent coathanger wire would help, but luckily I had a handy pair of... er... thingies I have no idea what they're called, but you get the idea. When you squeeze them together they lock in position, gripping the wire:

Then it was a quick trip to Halfrauds to pay an eye-watering price for a couple of yellow ring terminals (8mm holes), which I just crimped on to the ends of the wires (there will be letters! Yes I know soldering is better but I'm really, really crap at it and it's only a CB radio). The power wire is supplied with a fused link, so no need to worry about that. The positive terminal screwed onto the positive clamp, and the negative terminal screwed onto the bodywork as an earth, visible screwed onto the inner wing behind the fusebox (spot the two yellow ring terminals):

BTW I don't know much about vehicle electrics although this seems a simple job. If I have done anything stoopid there, please let me know (nicely!).

And that's it... one CB radio installed. Of course, it's only half the job. Installing the aerial and checking the SWR is a separate job that I'll add soon once I get the chance to take a finished picture of the aerial in the light, but for now here's the CB radio in position:

 

[StarCruiser]

Looks ok to me. . Just as long as the fuse is as close to the battery as possible then job's a good un. Don't transmit without your antenna connected. SWR in the antenna before you use it which will be dependent on where you site the antenna. Plenty of metal round it is good for a ground plane.

 

[Shayne]

Reminds me i never put a fuse in my CB power feed Rich what size would you recommend ? i need one for the fog light which will be coming off the battery to and i've no paperwork for either anymore to suggest what fuse .

I managed to get my smaller CB in the cubby Dave after cutting the bottom and most of the sides of the plastic away which was a scary process given my first cb died before i ever got it working . The new one fits tidy though even if it still doesn't work

 

[Towpack]

I nice neat job well done. Check wether the antenna is a 'radialless' or a ground plane type which will dictate it's performance on different areas of the vehicle. The thingies you mention are Artery Forceps by the way. I have a couple of pairs for fishing, very handy.

 

[StarCruiser]

Depends on cable size Shayne. 10A for the Fog lamp and you'll probably get by with a 10A for the CB as they are limited to 4watts. 1.5 flex minimum really.

 

[diggerdave]

To complete the story, here's my aerial mounting.

Aerial placement is a tricky issue. It needs to be as high as possible and, usually, needs to have metal-metal contact as your vehicle structure acts as a groundplane (which is essential to make your aerial work correctly). I decided to go for a gutter mount - other options are to drill the roof of the vehicle or to use a magnetic mount.

I've been warned that the gutter mount will be vulnerable to low-hanging trees when laning. To (hopefully) avoid that problem I also bought a quick-release bayonet fitting so I can quickly take it off if the lane is tight. The gutter mount is metal but it does feel a bit fragile. Here's the gutter mount and the bayonet fitting (which just screws into the mount at one end and the aerial at the other):

Two (very small and rather brittle-looking) allen bolts hold the mount to the gutter. Its apparently important that these contact bare metal so I ground the paint off the contact points in the gutter channel (with a dremel tool and mini grindstone). You can just about see the nearest spot in this photo. I did this on Sunday and there's already a bloom of rust, which I'll have to cover with waxoyl or grease:

The quick release could be an achilles heel. It's about 3" long and is completely inflexible, unlike the aerial above it. It could make it more likely for the whole mount to be ripped off by trees. Time will tell:

And here's the finished installation. You can see that the cable just goes in through the rear window. The window seal is really soft and there's plenty of space so the co-axial cable isn't stressed at all. Hopefully it won't leak as it is to the rear of the window. The cable runs inside the vehicle a little untidily at the moment, but I've got some sticky cable clips:

The supplied cable is 4m long which is fine for my SWB, but might be a bit tight if you have a LWB (you can buy extensions). All that remains is to plug it into the back of the CB radio. BUT you must check the SWR ('standing wave ratio') with an SWR meter first otherwise you risk damaging the CB when you first transmit. I didn't take any photos of that process but it's pretty simple and there are loads of instruction on the internet . As it happens, my SWR was near perfect from the get-go, but you may need to tune your aerial if it's not by adjusting its length. It sounds fairly straightforward.

I don't know anyone local enough to test it, but I've heard other people's transmissions and it appears to work! All the transmissions I have heard have been very crackly and intermittent, but I think its because they're almost out of range (the nearest motoway to me is at least ten miles away, and the transmissions have been largely on channel 19 - the trucker's channel). I'll get the chance to test it in a couple of weekend's time

 

[clivehorridge]

Unless you already have, of course, it's worth checking what channels are for what use.

Certain channels (I'm led to believe) should not be transmitted on, only for receiving, emergency calls and whatnot.

Wouldn't want you to be upsetting folks or getting into trouble.

 

[MarkW]

I had that exact same mount and yes it is fragile despite being metal, snagging a tree snapped it in half

 

[Shayne]

Well done it sound like a winner to me , mines bloody rubbish and i have no will to do anything about it because i have nobody to test it with .

 

[diggerdave]

Unless you already have, of course, it's worth checking what channels are for what use.

Certain channels (I'm led to believe) should not be transmitted on, only for receiving, emergency calls and whatnot.

Wouldn't want you to be upsetting folks or getting into trouble.

As far as I understand it - and perhaps any experienced UK CBers can chip in to confirm this? - everything is very relaxed in the UK:

Channel 9 is the unofficial emergency channel. Unlike the US (so I understand), nobody actually monitors it.

Channel 19 is the trucker's/motorway channel and just seems to consist of people talking over each other

Channel 14 is the 'calling channel'. I think that's an enthusiast's thing - making contact at as great a distance as possible.

Supposedly there is a 'young farmer's channel' but I'm not sure what it is.

From the conversations I've hear there is no CB talk, just plain speech. It sounds as though no-one uses 10 codes or gives it all the 'breaker, breaker' type thing. Also (I read on a US forum) 'good buddy' is a no-no these days, having aquired strongly homo-erotic overtones since the '70s (when it just meant 'mate'). The advice was only use it if you mean it!

 

[diggerdave]

I had that exact same mount and yes it is fragile despite being metal, snagging a tree snapped it in half

Yes, I'm like a German vegetarian... I fear the wurst.

You can get heftier gutter mounts apparently, but I might just drill the roof and go for a central mounting at the rear if it comes to it.

 

[diggerdave]

Well done it sound like a winner to me , mines bloody rubbish and i have no will to do anything about it because i have nobody to test it with .

You're a bit too far away mate!

My mate David ( who was into CB in the 70s and 80s) told me to just go onto a motorway and randomly say 'radio check!' into the microphone. He said that loads of people would reply and you could check how you (and they) came through.

He tried it several times on the M1 yesterday and no-one replied...

 

[Shayne]

It's a handy tip for when i do get around to messing with it but i wouldn't be surprised if even the Rubber Duck probably uses facebook instead nowadays

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 .

 

[clivehorridge]

Well done it sound like a winner to me , mines bloody rubbish and i have no will to do anything about it because i have nobody to test it with .

You sound like me Shayne, Billy no-mates

 

[Bert]

I confirm what DiggerDave says. Generally I use mine on the motorway, lot's of chat down my way. Every now and then, just to make sure it still works, I say some stuff like, "Breaker, break. Radio check"......if there is anybody in range, they'll usually answer and let you know how much you're regulating. Wales is where I get the most chatter, but it seems every truck driver uses rigs that way.

 

[diggerdave]

let you know how much you're regulating

Silly question (sorry), but what do you mean exactly? Do you mean there's a way to actually measure signal strength or just that they let you know that they can hear your transmission loud and clear? If there is a way to tell it must be only on more expensive rigs, not my bargain basement one.

 

[Bert]

Silly question (sorry), but what do you mean exactly? Do you mean there's a way to actually measure signal strength or just that they let you know that they can hear your transmission loud and clear? If there is a way to tell it must be only on more expensive rigs, not my bargain basement one.

Hi Dave. I think that most of the time it's the guys with home base units and I believe that they have a meter or something similar and it lets them know how much power you are broadcasting with. 'Modulation' rather than regulation. That was a momentary lapse of reason on my part. My radio has a small power indicator to let me know what sort of strength signal I'm receiving too.

 

[StarCruiser]

It's worth remembering that signal strength is dependent on the power output of the radio (fixed at no more than 4 watts), the losses in the cable (which if you use good quality cable and fittings can be kept to a minimum) and the gain of the antenna. This gives you maximum Effective Radiated Power or ERP. I can't remember if CB is limited to 4 watts radio power or 4 watts ERP).
Edit. In other words, you are stuck with the power that comes out the back of the radio, but you can improve that power by having a good (high gain) antenna and placing it well. Conversely having a lower gain antenna and placing it badly will reduce the transmitted power.

 

[Towpack]

The legal maximum transmitter power into any antenna is 4w. Units with a built in antenna have the maximum ERP pegged at 4w. Since June 2014 the use of AM and SSB modulation (in addition to FM) has been permitted but the max ERP for these modes is 4w and 12w respectively.

 

[diggerdave]

I jus thought I'd add some photos of the missing step above, checking the SWR (standing wave ratio). This is very technical as you can see if you look at the wikipedia entry (https://en.wikipedia.org/wiki/Standing_wave_ratio), but really boils down to the ratio of the power output that actually gets transmitted by your aerial to the amount that gets reflected back. If not enough gets out, it can limit the quality/range of your transmissions or, at worst, fry your CB unit. The key thing is aerial length. Most CB aerials are pre-SWRed, but that only means that they are made for ideal circumstances. The nature of your mounting can affect it, particularly the groundplane, so it is essential to check the SWR after initial set up and after any changes to your aerial mounting (like being ripped off by tree branches, which I anticipate will be happening sooner rather than later!).

The SWR meter needs to be connected between the CB radio and your aerial using a short patch lead. With the radio pulled out from it's mounting, attach one end of the patch lead to the socket on the back of the CB (that the aerial lead normally plugs into) and the other to the 'trans' (i.e. transmitter) socket on the back of the meter:

...then connect the aerial lead (that normally plugs into the back of the CB ) to the 'ant' socket. The SWR meter is now connected in line:

Mine is a cheap combined power and SWR meter - obviously I'm using the SWR function so the right-hand switch is set to 'SWR'. The SWR is first checked in the middle of the 40 UK frequencies, on channel 20.

The first thing to do is set up the meter. With the left hand switch set to 'fwd' (to measure power going forward to the aerial), the PTT button is pressed to transmit (red light on my model of CB shows that it is now transmitting) and the knob is twisted until the needle is at the end of the scale (where 'set' is written)...:

...then the left-hand switch is moved to 'ref' (to measure power REFlected back from the aerial). Some say this should be done with your PTT button continuously pressed. I've tried that way and letting go of the button in between but it doesn't seem to make any difference. Anything less than 1.5 is ideal, 2 is acceptable, but above 3 risks frying your CB radio. Through sheer dumb luck, mine came up pretty good (only just above 0):

The same check should be made on the extremes of the UK frequencies (channel 1 and 40) just to make sure all is well. Only on channel 40 did I get much noticeable reflected power, and even then it was well within the comfort zone:

That's it! My CB is now ready for next weekend's laning trip: