Remember easy & cheap 1st, hardest and expensive last.

With the antenna system you have coax, a stud mount, an antenna, and the antenna ground. A final factor is the antenna placement itself.

Check them out in this order – ground, antenna, stud mount, coax and placement.

Try moving the coax or grab the antenna bracket.  If the SWR fluctuates you have a ground problem.

The SWR should be below a 2.0 and not fluctuate more than .1 up or down when moving the coax or grabbing the bracket. In other words 1.9-2.1 of fluctuation is ok. Remember, paint and primer are your enemy. Pinched or melted coax jacket is not good- replace it.

Spin the antenna in a circular direction and check the SWR. Look for serious fluctuation or a spike. If it exhibits either replace it and same for the stud mount is screws into.

Ground is a consideration and tends to be the problem much of the time. For example, the antenna mount must be bolted to clean metal with no paint or primer. The structure the mount is bolted to must also connect to the chassis and make an electrical connection.

A good example of this is a tool box. Most people mount the tool box on top of the bed rail only after sandwiching rubber between the bed rails and tool box. Now you have paint, primer and rubber preventing the electrical connection. I advise drilling two holes, one at each end of the tool box. Clean the contact surface (the area the self tapper’s head will contact) to bare metal. Insert one on each side. This will ground the tool box to the truck.

Most people make the same mistake at the antenna mount itself. Four bolts holding the mount in place will not ground the bracket. Either clean the contact surface (the area the bolt’s head will contact) or drill a fifth small hole and insert a self tapper in place. The self tapper screw will bite into the tool box and ground the bracket.

The point is that the entire path must ground not just the antenna mount for example and don’t even consider ground wires. At 27 MHz ground runs on top of the wire no through it. It tapers off quickly within a foot or two. If using a ground wire, use a basket weave type material with much surface area and make it as short as possible. I use base coax, strip the shield out, flatten it, and apply heat shrink to clean it up.

If none of the above resolves your problem and you can’t find a local professional that can resolve your issue, bring it to us. We will resolve your issue.

Please call for an appointment before showing up as we may be booked for the day.

We can service your equipment – read more

The outer material is usually copper, and it is anywhere from 70 to 95% coverage. The higher the percent, the more surface area coverage. 95 to 100% is optimal shielding. There are two types of dielectric (the material that separates the center conductor from the out shielding), polyvinyl and polyfoam. Poly foam has more flexibility than polyvinyl. Therefore, many customers prefer the poly foam over the polyvinyl. It’s easier to bend and installation is a little easier.

Polyvinyl is superior in its ability to withstand higher temperatures and hard compressions. Next is the center conductor. There are two types of center conductors. The solid wire and a multi-strand wire. High quality coax will have many strands making up the center conductor. The material will usually be copper.

Coax can be terminated with terminals or a PL-259 connector. PL-259′s of high quality are coated in either nickel or silver. Amphenol and Astatic are two of the best brands on the market.

Coax cable for transmitters is 50 and 75 ohm impedances. A single antenna system must use 50 Ohm (RG58) coax and will normally be 18 feet long. Dual antenna systems must use 75 Ohm (RG59) coax cable and will normally be 18 feet to each antenna. The coax types can not be interchanged. RG58 must be used for a single and RG59 must be used in dual antenna system configurations only.

The length of the coax to be used is controversial only because most people have not educated themselves concerning this matter. At 27 MHz 18 feet of coax is the correct length and will provide for minimal loss with an optimal SWR match. When using other lengths a phase shift will occur causing a loss in Db gain even if the SWR matches. This means that the carrier is either lost in the form of heat or the coax cable itself acts as part of the antenna lowering the Db gain. Stay with the 18 foot rule.

You may operate CB radios within the territorial limits of the fifty United States, the District of Columbia, and the Caribbean and Pacific Insular areas (“U.S.”). You may also operate your CB radio on or over any other area of the world, except within the territorial limits of areas where radio-communications are regulated by another agency of the U.S. or within the territorial limits of any foreign government. You may also be permitted to use your CB radio in Canada subject to the rules of Industry Canada. Travelers to the U.S. may operate CB radios within the U.S. as long as the unit is FCC certificated.

The highest point of your CB radios antenna must not be more than 20 feet above the highest point of the building or tree on which it is mounted, or 60 feet above the ground.

Rules & Regulations
The FCC rules and regulations for CB radios are codified in Title 47 of the Code of Federal Regulations (CFR). They are initially published in the Federal Register. The FCC does not maintain a database of its rules nor does it print or stock copies of the rules and regulations. That task is performed by the Government Printing Office (GPO). After October 1 of each year, the GPO compiles all the changes, additions, and deletions to the FCC rules and publishes an updated CFR.

The rules for CB radios are provided in text version and in portable document format (PDF) and can be viewed using the Adobe Acrobat Reader.

You can check the Federal Register to review rule changes since October 1, 2004.

1) The base load.
A base load antenna has coil or load at the bottom of the antenna.  Base load antennas  usually have a three to four foot long whip made out of stainless steel. Base loaded antennas have a wave length of 1/4.  A 1/4 wave antenna has an angle of radiation of 45 degrees. Signal radiates off the antenna at all angles and directions but the strongest point is at a 45° angle.

2) The top loaded antenna.
A top loaded antenna is usually fiberglass with copper wire wrapping a round a fiberglass rod loosely until it approaches the top of the antenna.  This is normally the top 6 inches to 1 foot where it is wrapped tight. This tightly wrapped area is the load.  That is why the antenna is called a top loaded antenna. Top loaded antennas have a very low angle of radiation.  Fire stick antennas for example are normally 5/8 wave antennas.  5/8 wave antennas have an angle of radiation of seven degrees from the horizon.  A Tiger SOTT antenna is a 1 1/2 wave length antenna.  Its angle of radiation is lower than seven degrees. As a rule of thumb the higher the wavelength the lower the angle of radiation.

3) The center load antenna.

A center load antenna is called a center load is because the load is at the center of the antenna.  The center load antenna will have a shaft below the coil and a whip above the coil. Center load antennas are also 1/4 wave length antennas.  Therefore, they have an angle of radiation of 45° as well.

There is not an antenna made that is best for all applications. Our recommendation changes depending on the type of auto, preferred mounting location, and required bandwidth.

Generally these are typical recommendations.

Vehicle Type: Car

Mounting location: Roof top  or trunk lip type mount.

Antenna recomended: base load such as the Wilson 5000

Mounting location: Side body

Antenna recomended: Lite weight fiberglass  such as the FL series Firestik. A spring or antenna quick disconnect can be added as a precaution

Mounting location: Bumper (older metal bumpers)

Antenna recomended: 102 inch steel whip, or a 4 to 5 foot fiberglass whip. The SOTT Tiger 1 1/2 wave is an excellent choice for this application.

SWR stands for standing wave ratio. Basically it is a very simple concept. When you transmit a certain amount of the wattage is reflected back into the transceiver. Dammage to the radio will occure If the amount of wattage that is being reflected back into the transceiver is to high.

So the SWR is a measurement of how much signal is going out the antenna, versus how much signal is reflected back into the transceiver. An SWR level of a 3.0 will damage the transmitter. A 2.0 SWR is about an 11% loss and the transmitter of the radio will run hotter as compared to a lower SWR. Amplifiers do not like high SWR’s.
A radio with a built-in amplifier should not normally be used if the SWR is above a 2.0. While they might get away with it the duty cycle on transmit is reduced. The transmitter will warm up much quicker with a higher SWR as compared to a lower SWR.

Let’s talk about setting the SWR’s

All CB antennas are tunable. Antennas that have an easy, often mechanical, tuning device are referred to as a “tunable antenna”. Accordingly, many people think the other antennas are not tunable and so they make no attempt to have the antenna tuned. This is a critical mistake.

Wire-wound antennas (without mechanical tuners), that test electrically long (higher SWR on ch 40), can be tuned by removing wire from the top. Remove the antenna cap, remove one wrap of wire and cut it off. Put the cap back on and recheck the SWR again on ch 40 & ch 1. As long as the SWR is higher on channel 40 continue to cut. Do not cut more than one wrap at a time. If SWR testing indicates the antenna is electrically short (higher SWR on ch 1), test for a ground problem. Touch the antenna bracket while keyed and watch for SWR fluctuation. Do not touch or even get close to the antenna. Move the coax around bending it, again watching for SWR fluctuation. If the SWR fluctuates a ground problem exists and must be corrected before proceeding.
If there was no fluctuation bend the end of the wire straight up the fiberglass shaft and lap it over the very top of the fiberglass shaft. Check the SWR on ch 40 & ch 1. The goal is to reverse the situation so that ch 40 has a higher SWR than ch 1. If ch 40 is higher cut 1/8 inch of wire, put the cap back on and check the SWR on ch 40 & ch 1. Continue with this process until ch 40 & ch 1 are relatively the same.

Wire-wound antennas (with mechanical tuners), that test electrically long (higher SWR on ch 40), can be tuned by adjusting the mechanical device at the top of the antenna. Remove the antenna cap, and adjust the rod down or if threaded turn the device clockwise. Put the cap back on and recheck the SWR again on ch 40 & ch 1. As long as the SWR is higher on channel 40 continue to adjust the rod down or if threaded turn the device clockwise. If SWR testing indicates the antenna is electrically short (higher SWR on ch 1), test for a ground problem. Touch the antenna bracket while keyed and watch for SWR fluctuation. Do not touch or even get close to the antenna. Move the coax around bending it, again watching for SWR fluctuation. If the SWR fluctuates a ground problem exists and must be corrected before proceeding.
If there was no fluctuation adjust the rod up or if threaded turn the device counter-clockwise. Check the SWR on ch 40 & ch 1. Continue with this process until ch 40 & ch 1 are relatively the same.

Solid fiberglass antennas (straight or helical wire impregnated in fiberglass resins) that are electrically too long (higher SWR on ch 40) can be cut shorter with a hacksaw or grinder. Cut only 1/4 of on inch at the most at one time. If the SWR test on one of these antennas indicates that it is electrically short (higher SWR on ch 1), the addition of a spring or quick disconnect (or both) is the only way to correct for the short condition.

Base loaded antennas with wire whips have a set screw (or two) just below the area that the whip is inserted into the loading coil. By loosening up the set screw(s) you are able to slide the whip up or down as required. If the SWR is higher on ch 40 slide the whip down, If the SWR is higher on ch 1 raise the whip.

Setting the antenna SWR with an amplifier can get involved. The antenna SWR is calibrated at the back of the amplifier with the amplifier in line and turned off. Once the antenna is properly tuned the meter is removed and re-installed at the radio with the amplifier in line. The antenna SWR level is then measured with the amp off and then with the amplifier switched on. The SWR level must be at an acceptable level at the radio under all conditions. The conditions are with the amp off on channel 40 and 1 and with the amp turned on, on all power levels of the amplifier on channel 1 and 40. Most shops don’t check the SWR match at the radio with the amplifier turned on. This is a critical mistake. With these steps added the SWR calibration can turn into a multi hour event at times.

High Tech Mobile Communications is a full service repair shop. If you are looking for a radio repair service center that is on top of their game you have found it!

The quality of our work is as good as it gets! It’s a bold statement to make, but a fact you will come to realize by using High Tech Mobile Communications.
All services are warranted and results are guaranteed. Our Technicians are highly trained and have many years of hands on experience.

Specializing in Mobile Communications for Bikes, Cars and Trucks.

Clay Thompson

Owner of High Tech Mobile Communications LLC
(Clays Radio Shop) (Motorcycle-communications.com) (Twowheelradios.com) (Pamperedbutt.com)