Building a Better Reception Mousetrap: RF Venue Diversity Fin Antenna

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Generally speaking, wireless receiver antenna systems tend to fall under the “necessary and important, but unexciting” category in live sound equipment, with most sporting a similar spaced diversity pair of antennas. RF Venue, clearly not content with the status quo in reception design, have developed a “better mousetrap” for reception with their Diversity Fin antenna, and it is truly worth getting excited about this piece of technology.

Bucking standard design and operation conventions to provide improved reception and decreased dropouts caused by multi-path interference, the Diversity Fin is capable of preventing wireless signal dropouts that can affect many typical diversity antennas systems, and does so with simple plug-and-play operation. The Diversity Fin can be integrated into most live or installed sound applications for concert venues, conferencing centers, and houses of worship, and is fully compatible with any wireless receiver or antenna distribution system from manufacturers such as Shure, Sennheiser, Audio Technica, or AKG, among many others.

How is it different?

Right out of the gate, the Diversity Fin displays its differences from the norm, consisting of only one antenna with dual BNC outputs. This is in stark contrast to most diversity antennas systems, which are made up of a spaced pair of antennas. Its design consists of a hybrid LDPA (shark-fin)/dipole antenna. The dipole is seated horizontally at 90 degrees on either side of a vertically placed shark-fin antenna. The obvious benefit of the single-antenna design is that the Diversity Fin takes up roughly half the space of a typical LDPA antenna pair, making the antenna quite portable and compact.

Even with its unique design, the Diversity Fin offers plug-and-play simplicity with most systems. The antenna has a mounting block with 1/4"-20, 3/8"-16, and 5/8"-27 threads, so it can be mounted on most stands (an unmarked white- or black-coated wall mount version is available for installed applications). After you have it mounted, connect it to your receiver or distributor with its BNC outs, point it at the stage, and you are good to go.

So, what does it do differently?

Looking different is fine, but to understand how the Diversity Fin is functionally different from most antenna systems, we need to talk quickly about how most wireless systems with standard diversity reception work. When a wireless transmitter transmits, the radio waves it sends will bounce off whatever is in their way, such as walls (if indoors), as well as any other object in their path. This results in what is termed "multi-path interference," which can be likened to echoes when talking about sound waves.

These multi-paths create patterns of nulls which, simply put, are bad news for good reception. These patterns are constantly moving, and as more transmission occurs, more patterns are created. If your antenna is in the path of one of these constantly moving nulls, you experience signal loss, resulting in your mics or instruments momentarily cutting out. So how can this be avoided?

Enter diversity reception. As diversity reception systems consist of two spaced antennas, the system will automatically detect which of the two antennas has a stronger signal at any given time, to minimize these dropouts. Other systems use a technique called "maximum ratio combining" (or MRC) that has both antennas active simultaneously, but with a varying ratio.

Unlike those techniques, the Diversity Fin’s approach to reception takes advantage of the fact that radio waves are polarized, which means they are either horizontally or vertically orientated in space. The Diversity Fin’s shark-fin configuration picks up vertical waves, while the dipole takes care of the horizontal.

So why does receiving waves based on their polarization provide improved reception? As a microphone transmits, the pattern of nulls that is created for vertically polarized waves is almost always different than the one created for horizontally polarized waves. This means these moving “dropout zones” will almost never be in the same place at the same time for both horizontal and vertical waves. Based on this, the single antenna Diversity Fin can decrease the instances of dropouts while taking up less room than a spaced pair of antennas.

What to take away

The Diversity Fin’s design and approach to reception are fairly unique, since it requires only one antenna to provide a diversity signal based on wave polarization. Its ability to provide reduced signal dropouts makes it well suited for a variety of live sound and conferencing applications, especially those located in large cities where there is a large amount of wireless signal traffic.

Electrical Characteristics
Operating Frequency 468-740 MHz
Bandwidth 272 MHz
Average Return Loss -9.4 dBm
Impedance 50 Ω
Pattern Type Dual Omni-Unidirectional
LPDA
Beam Width 140º Azimuth
F/B Ratio 8 dB
F/S Ratio  5 dB
Gain 5 dBd
Polarization Vertical
Dipole
Beam Width 100º Azimuth
F/B Ratio 5 dB
F/S Ratio  13 dB
Gain 1.8 dBd
Polarization Horizontal
Physical Characteristics
Mounting Block 1/4-20, 3/18-16, 5/8-27
Operating Temperature -10 to 130F (-23 to 54C)
Connectors 2x BNC
Length 12" (300mm)
Height 15" (370mm)
Weight 1 lb (454 g)

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