Buying an off the shelf rig is the quick way of getting a signal out on 27Mhz and suits anybody returning or just starting out but what about going that extra mile and building your own CB radio?
With the core of CB technology set in decades old stone there’s more than enough freely available information on the circuitry to make it possible. Add to that the chance to take shortcuts by using some of the available (done for you) modules, that can be configured and used in the project.
That said your going to need a good knowledge of electronics to pull it off, along with some specialized types of test equipment to tune the CB radio once its finished.
How Pretty Does It Need To Be?
Building a simple RF transmitter to produce a signal in the 27MHz band is easy enough but aim to produce a rig with at least the basic 40 channels and its going to need a few controls attached to the circuitry to operate it properly.
Getting the rig looking anywhere near a mass produced one is going to be a battle not just in time taken but also extra cost. Then again if your not bothered about its prettiness, the CB can be fitted into a generic metal box cheaply enough.
Ive always found a huge division between people who turn out home made electronic equipment. Some constructors go to massive pains to get the outward look just right with a solid produced radio on the inside, while others are only interested how the radio performs and would happily squeeze it into any old piece of Tupperware, provided it fixes all the controls down 🙂
Usually for convenience and because I’m a little impatient the second type of home brew constructor pretty much sums me up.
So Much More
The limits on what the CB can do are only set by the amount of effort your willing to put in. Taking away all the added functions and getting down the bare bones of a CB radio leaves you with its frequency coverage, power output and operating modes.
If you can get your head around the extra electronics needed a fully synthesized radio is the better option. That doesn’t mean a standard rotary channel selector won’t do the job perfectly, its just a transmitter that can be set by frequency as opposed to channel is a lot more flexible.
Sticking with a low power output if your going to the trouble of building a CB does seem like a step backward, just keep in mind your countries laws, possible interference to your neighbors and other CB user before shoehorning a 1kw linear in the same box as your CB radio.
The thing with adding internal RF power to a CB is the way you have to supply it with juice. A shop bought CB’s power section is only designed to deal with the basic legal output (with a little wiggle room) and the linear has to be powered from outside the rig.
With you own design you can build up the power supply circuit to a level that will handle a linear and do away with having to used one externally.
Keep in mind though that adding a decent sized RF linear section is going to increase the overall dimensions of the radio. No matter how much you work on the linear its components still have to be laid out in a certain way and its going to need some kind of heat sink to stop it (and the CB) from frying.
The more operating modes you cram into the home brew CB, the more complicated the design and construction will be.
Fitting full sideband does require a lot more circuitry (and setting up) than plumping for either AM of FM modes and a whole new set of controls over those needed for basic CB functions.
This is where the project falls down a bit because the cost of building even a straight 40 channel FM CB radio from scratch is going to dwarf the outlay on a new ready made model.
You’ve got to be building the CB for the joy or challenge as from a money point of view its an expensive way of way of getting a signal out on 27 MHz.
Your Homemade CB And The Law
Even if by some chance you build your CB to work within the legal power output (why?), its still going to fall foul of the restrictions put on CB equipment type.
CB’s are produced to operate within the license agreement terms and unless you by some remote chance get a home brew set approved its never going to be legal for use on 27Mhz.