Introduction: VHF Scanner Antenna
Here is an Antenna that i made in my free time and thought that this would be useful to some readers as i found no such instructables given. This antenna that I've made is cable of receiving frequency ranging between 107Mhz to 146Mhz. Its quite easy to increase the range by increasing the length of the areal or decreasing it.
I actually made this antenna to receive aircraft band or air-band. The frequency they use is from 108Mhz to 146Mhz. Thus this antenna will work as a charm if used for the purpose above or one can always use it for different frequency like amateur radio and will work just fine.
Step 1: Raw Materials
The things that you will need for assembly of this antennae are as follow:-
1. Aluminum sheet
2. Aluminum rods 5mm in dia 4.5 feet long (for preparation of this antennae and may vary according to frequency used).
3. A steel glass
4. L clamps (which can be made by the same Aluminum sheet)
5.Nuts and bolts
6.Antennae socket (bolt type). I found it from an old booster amp from a TV.
7. Wires, Hot glue and mseal
Step 2: Cutting the Plate and Fixing Nuts and Bolts
Now after the Aluminum sheet are cut in the form of an arrow as shown in the picture, drill a hole in the center for the antenna socket to comfortably fit.
Now drill four more holes just at the sides of the antenna hole for the screws to fit as shown in the picture. Drill more holes for the aluminum tubes that will be fixed later for the array of stick. Add the four nuts and bolts on the four holes that were made one by one as shown in the diagram.
After the small base has been added it should be noted that the two holes should be perpendicular aligned with each so that the aluminum tube can easily pass these holes.
Step 3: Adding the Antenna Socket
Now as our main base of the antenna has been finalised, it is time to put the antenna socket to its position. Now bring on the small square cut of the aluminum plate and fix on the protruding bolts as shown in the figure. This will work as a firm fixture to hold the antenna socket in place firmly.
Notice that in total three bolts are used to fix the antenna socket base. It will ensure that the base plate for the antenna will not move around.
Step 4: Preparing the Amended Steel Glass
Now as our main base structure has complete, it is time for the glass that was cut to be installed with the L shape plate that was cut. This will actually work as a main base support for the vertical aluminum rod as well as a water proof insulator for the antenna socket.
Now fix the L shaped clamps to the bottom half of the cut glass and drill a hole at the center of the glass for the aluminum rod to pass through it.
Step 5: Wiring the Socket and Applying Hot Glue
Now add the glass to the base of the Aluminum plate and fix the remaining nut and bolts to hold the glass as shown. Now bring on the aluminum rod 5mm and slip it through the steel glass from the top. Then by using a mseal or hotglue close the gaps between the rod and the glass. It should be remembered in mind that the aluminum rod should not at all touch the steel glass. If it does then the whole thing will get earthed and the antenna will be a failure. Therefore i would recommend you to add insulation tapes on the aluminum rod by marking the exact contact point and then by using a non conductive material like mseal seal the aluminum tube. This steel glass not only maintains the straightness of the rod but also it will help the rod to stay vertical.
Then finally bolt on the remaining 3 aluminum tubes to the base with the nut and bent the arrow heads to an angle of 45 degrees as to maintain its antenna structure and the design.
Step 6: Final Projection for Completion
After the bent are done to the aluminum plates for the rods. Now will be the time to bent the bottom part of the base for holding the antenna on a mast and to mount in on a roof or any other suitable place.
In my case i have simply screwed two screws to the base with the mast and hosted at the top of my rented house.
The feed can be taken out by using a co-axle cable connected to the socket and it may be brought to the sack.
And finally the antenna is ready to receive the VHF frequencies that will be around in the air.