How to Make an Omnidirectional TV Antenna?

The first thing to build something is the materials and tools. One of the virtues of this antenna is that it needs a few and “simple” things:

Coaxial cable

There is a reason why it is an omnidirectional antenna with coaxial: P
In the example shown, cable type RG213 has been used.
This cable was chosen (10mm section) for its rigidity since it
must be straight in vertical (more or less).

N female connector

We will use a female N-type of the panel or chassis mounting. We will use any of the 2 existing models. In the first images, one of the types is shown. In the final assembly, one of the chassis mounting types is shown.

PVC tube

The mission of this tube is to protect and give rigidity to our antenna.
Specifically, one of 15mm inner diameter has been used
(it will be worthless, depending on the chosen cable.)

Tools :

Another fundamental element. We will not need more than:

Cutter or Blade

To slice the coaxial Maya. It may also be necessary a
cutting pliers cut the internal coaxial conductor
(depends on the cable used).

Soldering iron and tin

Necessary to fix the cable to the N connector

Mountain range

To cut the PVC pipe.

Construction :

Once the material and tools were assembled, we proceeded to build the antenna. As we said, 6 steps would suffice.

Step 1: Stripping the cable first thing we should do is to strip the coaxial cable to regular 40mm sections. We just have to cut the outer insulation and the Maya. Each time we cut a section of 40mm, it is best to take it out of the cable to work more comfortably. We must achieve 4 + 1 or 8 + 1 sections depending on how big we want our Omni.
Step 2: Welding the cable so we will now proceed to solder the inner coaxial cable to N.Step 3: Welding the decoupler to do build the decoupler, we will weld a 40mm section to the N chassis and once it is properly fixed we will cut it until it is exactly 30mm.
Step 4: Introducing the first phase-shifting element introduce a 40mm section and adjust it to 60mm of the phase shifter.
Step 5: Assembly of all elements will have to introduce the pieces of 40mm with a spacing of about 60mm (depending on the frequency we want to tune). Once introduced all the desired phase shifters (4 or 8) we will leave a 60mm piece of internal cable and cut the excess. Resuming: Decoupler (30mm) + Air piece (60mm) + Phase shifter (40mm) + …. + Phase shifter (40mm) + Outdoor piece (60mm). The antenna will measure about 49cm in case you have chosen to use four decouplers or 90cm if you prefer eight decouplers.
Step 6: Fitting the protective tubeNow we only have to introduce the antenna in the PVC tube that we previously cut to size. To fix the N to the tube, you can use different methods (glue Loctite or similar is a good help). If the connector used is the one of the through type and the tube is of 155mm of internal diameter it will adjust olgadamente being very firm (and aesthetic: P). It will also have to plug the upper part of the tube.

And now We have our antenna ready to use.

Annex, coaxial omnidirectional mini antenna :

Once this antenna was built and having modified the USR cards, we found ourselves in need of some kind of small and manageable antenna to use in the cards when they were in a portable and we did not want to hold an antenna with their pigtail. As we had leftover pigtail cable (M43, whose single-core thread and therefore quite rigid), we did a test scaling the design of this antenna. The construction of this antenna is even simpler. We will need a connector (SMA male for cable in our case), a piece of coaxial cable (better semirigid), cutter, soldering iron, and pliers.

The construction of this antenna is even simpler. We will need a connector (SMA male for cable in our case), a piece of coaxial cable (better semirigid), cutter, welder, and pliers (or better crimper).
In this case, as we want a portable antenna, we will only create two radiant elements. Therefore the composition will be: 30mm unpeeled cable (uncoupler) Half-wave (+/- 60mm) of cable without Maya, the first radiator element 40mm (half-wave multiplied by the cable speed factor, 0.66) of whole cable (phase shifter) And finally, another half-wave (+/- 60mm) of bare wire8only the core) as the second radiator element
We only need to place the connector on the antenna. In our case, we use SMA crimp males. To place them you have to leave a millimeter of the soul in the air and about 10mm of the mesh without protector (the connector has some brief but clear explanations).
And we have our minantena ready. The results of the measurements tell us that we achieved better signal with this small antenna than with the original interior antenna of the card. That is, in this case, the polarization will be vertical, not as with the internal antenna that has a very slight polarization.