Mobile Gearmotor Antenna Build
I have fielded many enquires from fellow hams asking what type of materials are used in the construction of one of my antennas, whether it be one of my gearmotor antennas like the one in the photo, or possibly one of my monobander antenna systems.
The gearmotor antenna in the photo is composed of all the materials that you would wish for a a well designed and built gearmotor antenna, and the list includes..... various grades of stainless-steel, various grades of high-tensile aluminum, bearing bronze, white Delrin, black Delrin, Lexan, beryllium copper, fiberglass, tinned buss wire, stainless-steel fasteners, sealed ball bearings, Pitman gearmotor, stainless steel all-thread drive screw, and various other sundries not listed here.
When I begin working on a design for a new antenna, and in the case of the gearmotor antenna shown here, materials are front and center on my mind.
Being that I wanted the finished antenna to be as light as possible and to keep the weight down, my design called for the use of a combination of high-tensile aluminum and stainless-steel.
I selected and used grade 304 stainless-steel to build the lower mast, with 316 stainless-steel used for the antenna coupler at the bottom of the mast, as grade 316 stainless-steel has the extra strength required to keep the antenna securely fastened to the mating coupler on my mobile while going down the road.
For building the upper mast coil housing, I selected 6061 T6 high-tensile thin-wall aluminum that has the strength required to house the 3" coil with included whip and cap-hat, yet very light keeping the overall weight of the antenna assembly down.
The use of aluminum for the upper mast coil housing if left un-finished by itself would in short order look unsightly as aluminum oxidizes quickly.
The solution was simple, being a machinist and familiar with the various finishes available for aluminum, I decided to go with a chrome plated finish for the upper mast that houses the coil.
I am fortunate to have a specialty shop located nearby that specializes in applying chrome on aluminum, and they applied the chrome plated finish to the upper mast of my 10-80 meter gearmotor antenna.
Almost 4 years later, and with a lot of hard use the antenna looks as good as the day I finished building it, with no wear to be seen on the external surface of the upper mast assembly where the weather cover travels when changing bands.
Mind you the design did allow for clearance between the black Delrin trim ring at the bottom of the Lexan weather cover and the chromed upper mast assembly.
Oh...did I mention that the complete antenna minus the whip weighs in at 6 pounds all total, without compromising on the materials used in its construction.
The best place in Canada, the US, and the UK for finding the materials you require for that next project is Metal Supermarkets.
I find them to be a valuable resource for all my material needs.
If you don't have one near you, then its as simple as ordering the materials you need from their on line store.
Metal Supermarkets is the world’s largest supplier of small quantity metals and if they don't have it in stock, they will source and order it for you.
Check it out.
Click on the photo for a closer look.....
HF antenna installs....