Over the years, I have owned and operated most of the gearmotor antennas available in the market place. I have always been disappointed with the limiting size of the coil in these antennas, due to the limitations of the mast size.
For some time I have been working out a design that would allow me to circumvent this problem. After a lot of thought, I came up with the idea for a design that utilized a coil that would have a two diameter coil, the upper section could be of any diameter, and the lower smaller section of the coil including the mast housing would be capable of supporting the complete antenna, This also would allow for the antenna to be much lighter in weight than the typical 3" diameter gearmotor antenna.

                                                   Ths link gives you a look at some of the antennas that I build

                                                      http://www.jerryclement.ca/MachineShop/Antenna-Werks/

 I have built a prototype, and it is proving to be what I have always wanted in a gearmotor antenna, an antenna that does not limit the size of the coil that can be utilized in its construction. I built this antenna with a 3 inch coil, although the design allows for a larger coil if desired. Still, the design is sound, and the design that I came up with, is capable of using a much larger diameter coil with the same results. The antenna as finished weighs in at 6 pounds making it one of the lightest weight gearmotor antennas in this class.

Its been a while since I have got as much satisfaction out of one of my projects, as I have got from building this antenna.
Everything, from my earliest thoughts on what I had in mind for a new antenna design, to the actual designing & building of this antenna has progressed without a glitch. With the antenna now mounted on my mobile, the antenna performs as I imagined that it could. This antenna with its one of a kind coil assembly is proving to be a very good design, and the 3 inch coil with the smaller 1.250" diameter tail section of the coil is wonderful to see in operation. The coil is rock solid with no side to side motion, when extended in the 80 meter position, and will handle the biggest whips with a included caphat with ease.

Of course, it goes without saying that the antenna that resides on your vehicle is only half of a successfully designed antenna system. In my case, my mobile has a body that sits on a frame that required bonding to eliminate noise and increase the ground-plane beneath my antenna. This in turn increased the performance of my overall antenna system. This also took a fair amount of time, and to accomplish this, I used 1 inch wide tinned copper flat braided ground straps with eyelets at either end to bond the various components of my mobile together. It is important that you use flat braided strapping and not round wire for bonding, as RF travels on the surface rather than through the wire, therefore flat braid has more current carrying capacity due to its larger flat surface.

It is important that you keep all of the ground straps as short as possible, and do take care when drilling holes in the body, so that you do not drill in-to any existing electrical harnesses that may not be visible. I used quality stainless steel fasteners along with stainless steel serrated washers for attaching the ground straps throughout my mobile.
So, don?t forget that your antenna is only one half of a dipole, and in the case of a mobile antenna, the missing half is the vehicle and its capacitance to the ground under the vehicle. The single biggest factor with respect to efficiency for any mobile and especially on 80 meters is ground loss, so maximizing this half of the antenna system is essential, and this is accomplished through bonding.

Communications Mobile Radio Stack

As you can see, I have it covered when it comes to navigation with my mobile, as I am running three different mapping devices, that consist of from left to right, my Garmin Nuvi running City Navigator mapping with a built in fm traffic transceiver, that keeps me up to date as to the happenings on all controlled highways, as well as reading out all up coming roadways, safety cameras, and the posted speed on any controlled roadways.

My Garmin Montana is next in line to the right, and I have it paired with the SCS Tracker located just beneath it. The SCS Tracker is a HF APRS Robust Packet TNC that is paired with the Kenwood TS-480HX and listening on the top end of the 30 meter band, the band used for HF APRS across the world. Once the SCS Tracker has decoded robust packets that it is hearing via the TS-480HX, the tracker then sends this information to the Garmin Montana where the beaconing HF stations are placed on the map as seen in this photo. The SCS Tracker is proving to be a wonderful TNC that keeps me connected with the APRS network from anywhere I may travel while mobile. I also run APRSIS/32 on my netbook in conjunction with the SCS Tracker allowing me to keyboard message with HF APRS Stations located across across North America.

The device on the far right, is my Kenwood Geosat 6, that is also used for displaying beaconing ham stations on the map, and I enjoy the fact that it runs in portrait mode. Again, I have it covered in spades, when it comes to mapping for the roads I am going down, and as to what is happening around my position, as I explore southern Alberta.