(this is a work in progress, check back for updates)
I am a scientist both by nature, and by training, although from the medical field, I got my first Rf burn at 6. And I was hooked!
Over 6 decades later I am still playing.
My goal?
To make it work for everyone, everywhere. And to stop drivers from blowing up very expensive radios and getting fuked by the CB guy.
After I blew up my first tube radio, a Courier (with the business band in it), I learned the hard way, so many times.
I never put together that no matter what radio you have, it’s the other half that makes it work:
THE ANTENNA SYSTEM.
Hey, I was 6, give me a break.
A truck antenna is a monopole. This means the part that’s in the air is one half, the truck is the other half. A very common misconception is the radio has to be matched to the antenna. Nope, the antenna has to be matched to the truck. If the mounting bracket does not have connection to the rest of the ride, you don’t have an antenna. A bad ground is usually the main problem why an antenna won’t tune.
Example: Take a 379, you put on a new bracket, stud and coax and no matter where you test it, from band A to E, channel 1 to 40, you have a 3:1 SWR reading.
WTF
Pick up on the end of the door, and the chances of slop in the hinge is high. It usually means the only ground your antenna is seeing is the door panel and not the complete truck. That ain’t enough metal to make a ground plane. If sometimes the SWR is good then other times not so good, you are relying on the door striker, through dirt and grease to make ground contact. Either run a short ground strap from the door to the door frame (short as possible) or replace the hinge (yeah, that ain’t happening. Talk about it all the time, but low on the priority list).
TUNING TIP: BEFORE YOU START TRIMMING THE WHIP, if you are running high 2s or 3s for SWR on every bank, check that you have continuity from the base of the bracket to the truck. I usually go from bracket to the stack to check for a good ground.
The Antenna was hitting shit so I shortened it.
NO!
This is where we dive into a little technical aspects of antennas.
Wavelength.
Channel 19 is 27.185 MHz. With a little simple division the wavelength is 36’. The actual length of the wave radiating out of the antenna is 36’ oscillating 27.185 million times a second.
Now monopoles are quarter wavelength antennas so that makes our whip in the air part 9’, fact. Now the trick is to make a 3’ antenna look like 9’ and that is done by a coil. Doesn’t matter what style, make, or material, all truck CB antennas have a coil. It goes by a couple of names, but it’s an inductive coil that adds electrical length. The whip still needs to be shortened or lengthened to tune the antenna to it operating frequency though. The reason being: minimum standing wave ratio,SWR,, the ratio between the wave that gets out of the whip versus the wave the gets reflected back into the radio.
The proper length will minimize the refection and maximize the transmission. Think of it as a rope with one end tied to a post.
Wave it up and down a few times and you will see that once the wave hits the post, a portion gets reflected back. Same thing with a radio wave, standing on the line.