Having the right antenna for your radio station can dramatically change your broadcast signal. I will show you the different types and one which I found to be absolutely amazing for low-power radio stations. Watch to the end and I will show this antenna and how it makes the maximum use out of your FM transmitter signal. Pirate radio stations and professional broadcast radio stations need quality antennas.
FM antennas come in a range of designs and configurations and not just the standard half-wave dipole. While the dipole is commonly used in FM broadcast many radio stations have found better results from some very unorthodox antenna designs.
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Antenna design is not just about gain or polarity. While these do matter, antennas can even affect the down tilt of the radiated signal. Both licensed broadcasters and pirate radio stations with pirate FM transmitters, need to have a good radio antenna setup. Hobby pirate radio stations often need to get the most out of their signal with a good antenna. Later in this video, I will show you that very special FM antenna that not only offers high gain but also tilts the radio Signal down to the horizon. This can turn a small signal into one that seems much stronger. This is because the signal is not lost out to the sky or down into the ground. All of the signal goes out to where you want it. That’s to your listener.
Let's first start with the standard half-wave dipole. This is the industry standard for low and high-power broadcasts. The reason is that this is the easiest antenna to match with additional antennas. Arras can be as little as two and as many as you can fit on a pool. This makes it very versatile and easy to adapt to any power level from low-power community radio stations to high-powered commercial stations. Once set up this antenna array can run for many years without being tested or adjusted. But like all stock standard things, the half-wave dipole offers nothing special. It provides a basic vertically polarised zero gain signal unless in an array of more than one. The additional downside to dipoles is that a lot of the signal is lost into the sky and down to the ground below the antenna.
There are antennas that can offer gain in a single antenna. The examples are a 5/8. or a J-pole. These offer a gain of 3 dB and more. That means a single 5/8 or J-pole can put out twice as much as a half-wave dipole. The 5/8 also lifts up some of the radio signal lost down to the ground because the ground radials tilt the signal upwards. The downside is that if you need even more gain it is extremely difficult if not impossible to match these antennas in an array. It's just not practical because of the ground plains. Also, it can only give vertical polarization like a half-wave dipole and there is still loss of signal into the sky.
The half-wave dipole also suffers from a partial directionality problem because it is side mounted. That means the pole it is mounted on acts like a reflector pointing a sizeable chunk of the radio signal in one direction. This is fine if your antenna is outside of your coverage area pointing in like on a mountain on the side of a city.
If you are broadcasting from the centre of your broadcast area then this is not good. You will want an antenna with an almost perfectly circular radio pattern.
There is another antenna that can do more than one polarity. This is called a circular polarized antenna. This antenna does not actually give all 180 degrees of signal but actually offers a combination of vertical and horizontal polarization.
This is often more than enough because radio receiver antennas are mostly vertical or horizontal or halfway in between like a car bee sting antenna.
This helps to fill in shadow areas, especially in urban broadcast footprints. So if you broadcast to a city then this can be a solution for you.
There, of course, is a downside which this that the antenna not only it does not offer any gain but in most cases has a minus gain meaning that it will radiate less on a plane than a dipole. In many cases, the circular polarized antennas need to be paired with at least one more antenna just to provide zero dB gain or put out the same signal strength as a dipole. You can also just turn up the power you put into a single antenna to compensate for the loss but most stations would opt for the matched pair. If these antenna arrays go out of tune and become slightly mismatched they can even create horrible ripple shadow areas that make moving within the signal footprint really unpleasant as the wave interference result in the signal doubling and halving giving a type of pulse RF signal which is really bad for listening on a car radio. They also suffer the same problem of the dipole that they are side-mounted giving a semi-directional radiation pattern. Pirate radio station transmitter antenna.