CB comunications help needed

[scaltura]

hi guys

i see that a lot of folk have CB's fitted in their vans , this is something on my list of to do's

could someone give me some help in the way of what i need for the full set up ?

thanks

[andisnewsyncro]

You need a radio and an antenna with a suitable mount for your van, that's about it

There's lots of good suppliers out there, I found this place particularly helpful http://www.truck-king.co.uk/store/home.php?cat=422

[Red Westie]

And
SWR meter or access too, in order to set aerial length for the outgoing signal output.

Just need a fused live connection and good earth point. A mounting point for the rig and somewhere for the aerial, gutter or mag mount (mounting bracket or magnetic based aerial)

Martin

[andisnewsyncro]

Forgot about a meter, but if you're anywhere near me you're welcome to borrow mine

[scaltura]

thanks guys

something to chew over

[elsid]

I had a sort out the other day and found my old gear, 2 rigs (AM and FM) 3 twigs (DV27,dial a match and Firestick) SWR meter, dummy load and a mag mount I made for the boot of my TR7 V8 convertible. I will make a mount to stick the FM rig in the van and see what happens.
Sid

[Mocki]

Fitting a CB to a T25

The fitting of the CB itself is purely personal choice.
Many of the modern radios are of the correct size to fit in the dash where the ash tray should live, which is the tidiest in my opinion.
As for the connections, straight to the fuse box, or onto the leisure battery, your choice. Do not connect to the Broadcast radio power cables.
Remember tidy cables rarely cause problems RED to +12vdc black to -12vdc. Remember that VW -12vdc is brown, NOT black.

Siting the Antenna

Ideally the antenna should be sited in the electrical center of the vehicle, but unless you have a panel van, this isn’t going to be possible.
HiTops and pop tops have fiberglass roofs, and radio doesn’t “see” fiberglass, it is nonexistent so drilling the roof, or bolting to the fiberglass is not an option, it simply won’t work. The antenna mounting must be electrically connected to the metal body.
Most T25 owners opt for a gutter mounting, which ensures a solid and well grounded connection to the bodywork. If you have “syncro2 or LT” style mirrors you can opt for a mirror mounting bracket, but you will have to remove or bypass the rubber mounting from the mirror arm to get your electrical connection to ground.
Either gutter or mirror mounting should be on the RHS or off side of the vehicle, keeping the antenna in the center of the road, and thus away from low tree branches and other obstacles on the nearside of the road.
Gutter mounting.

If you can buy a stainless steel gutter bracket, rather than a cast alloy one, the stainless brackets are much stronger and more robust.
The gutter bracket should be sited on the gutter just behind the front door, inline with the “B” pillar on later model vans (85 onwards) as the door gives less clearance at the gutter on the later vans and the mount will foul the door top. Early vans should be ok at the front corner of the front door, at the “A” pillar.
Ensure the grub screws penetrate the paint and sealer as they bite into the gutter ( you can paint of seal this over after installation) as you need this ground connection to be good. Once the mounting has been securely connected to the body the coax needs routing into the cab, and the easiest most effective way to do this is via the front lower edge of the door, at the end of the gutter strip that runs down the window screen, and into the cab just above the top hinge of the door, up and under the dash, making sure the coax cannot be snagged by the feet of the driver of passenger. Safe tidy cabling is the way to go.

Tuning and SWR

Most antenna systems these days are “pre-tuned” and require little of no tuning.
However if you have access to a SWR meter, it is best to check. Should you need to make any adjustments, the procedure is

1. Connect the SWR meter to the CB, via a “patch lead” and then the antenna to the SWR meter.
2. Set the “FWD-REV” switch on the meter to “FWD” select ch40 and transmit by pressing the microphone PTT switch.
3. Simutaniusly turn the |SET\ control to the infinity mark at the right hand side of the meter scale,
4. Release the PTT stop transmitting
5. Move the |FWD-REV” switch to the “REV” position, and transmit again, the needle on the scale should now read ideally below “2” but anything below “3” is ok.

Select channel 01 and repeat steps 2-5 and compare readings, should you need to adjust the length of the antenna, these are the simple rules.
If the SWR is high on a high channel (40) and lower on a low channel (1) shorten the antenna
If the SWR is higher on the low channel, and lower on the high channel lengthen the antenna.
Only move the tunable section 3mm at a time checking with steps 2-5 each time.

SWR is Standing wave ratio, in layman’s terms, the amount of “feedback| of transmitted power trying to return down the coax to the radio reflected by an ill tuned antenna.
All but professional mobile antennas will be electrically 9ft long, but physically much shorter ( the difference being made up with a loading coil or spring at the base or center of the antenna – the longer the antenna is physically the better. Coils are inefficient, so the less of that 9ft that is coiled up the better.
antenna

[scaltura]

^^^^