A 1:1 Balanced Balun

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Going from an 'unbalanced' transmission line...to a 'balanced' antenna, both of which having an impedance of 75 ohms...one needs to construct a 1:1 balun...in order to 'balance' the 'unbalanced' transmission line.

This balun will then let the full amount of the FM transmitted signal, coming from the transmitter...to 'fully radiate out of the coax' and into the open half wave dipole antenna rods.

Thus a home-made 1:1 Balun is needed for the Open Half Wave Dipole Antenna (a 75 ohm impedance antenna) using an RG-59 (a 75 ohm impedance transmission line) coaxial cable. The finished balun is then placed in between the 'feed point' of the antenna and the end of the transmission line going to the antenna. Below is a step-by-step method on how to construct it.

Begin with 4 inches of a 1 inch diameter PVC plastic tubing...as shown in the picture to the right.

Next, take a 1/4 inch drill bit and drill two 'slanted' holes...approximately 1/2 inch inward from each end...as shown in the picture to the left. These two slanted holes will keep the coaxial cable from making sharp bends...once it is passed though the two holes.

When you have determined the total length of your coax cable (RG-59),...that is...from the transmitter to the antenna, take the 'antenna' end of the coax and pass it through one of the slanted holes on the 4 inch PCV. Leave it come out about 26 inches...as shown in the picture to the right.

Go ahead and make 5 complete turns with the coax cable, around the 1" diameter PVC.

Make sure that one hand is always kept on the coil wrappings...so it will not become un-wrapped. Try and keep all turns as tight as possible...as shown in the picture to the left.

Take a roll of electrical tape, and while holding the coax good and tight around the plastic form, begin to tape it securely down...as shown in the picture to the right. Make sure you keep a constant pressure on the tape...that is...always keeping it slightly stretched, as you make your turns with the tape over the balun. This 'stretching' method makes a better seal. Yes, it will help keep the wraps secure...while prevention exposure of the balun to dirt and moisture.

Now, apply a second application of the electrical tape to the overall coax and PVC....making sure that you keep the tape slightly stretched, while making your wraps. This second wrapping of electrical tape will prevent movement of ALL of the transmission line on the PVC.

The coax cable on the left side of the balun (as shown in the above picture) will be cut to within 2 inches, and then soldered directly to the 'feed point' on the dipole antenna. The coax cable on the right side of the balun goes directly to the FM transmitter.

A close-up picture shows how the finished balun should look like. Notice the tape looks like it was 'shrink wrapped' around the coax...simular to using 'heat shrink' tubing? Yes, when 'stretching' the tape as you apply your wraps around the balun,

the tape will appear as though it was 'heat shrinked' over the coaxial cable. This, in effect, makes a perfect and 'well-sealed' job. Most of my uses with electrical tape is done this way. Most electrical tapes have that elastic capability of 'stretching'.

The picture below shows exactly where the balun is placed, in relation to the transmission line and antenna.

You will then use electrical tape to secure the balun to the antenna mast. Once that is done, you have finished making a good homemade...

There you have it, my friends. If you keep patience by your side...this project will come out very successful ! ! !