The Arrow Log Periodic Antennas
- 06 Dec, 2021
Pointy and Effective at Getting Better Cell Phone Signal, it's The Arrow, by Bolton
Pointing the arrow in the right direction might seem challenging, but what if we told you it could drastically improve your cell phone signal?
That’s probably the last thing you expected us to say.
Let’s talk about The Arrow, the latest log periodic antenna by Bolton Technical. It can give you cell signal other directional antennas couldn’t dream of.
What is a Log Periodic Antenna?
A log-periodic antenna is known by many names: LPDA (short for log-periodic dipole array), log-periodic dipole antenna, log-periodic aerial, or just a log-periodic array. They have a simple job: to operate over a wide band of radio frequencies. What these frequencies bandwidths are vary based on the type of log periodic antenna you buy.
They’re more common than you might think. You’ve probably noticed log periodic antennas in passing all your life, sitting atop rooftops, poking out on apartment balconies. Traditionally, log periodic antennas have been used for analog television, which was the dominant style until digital replaced it. Even still, they remain used in many areas, and, as a quick search for a TV antenna will show you, they continue to dominate that market.
The reason for this is simple: they have excellent range and can cover a wide range of broadband frequencies. Their directivity allows them to have a narrower focus than the yagi antenna, which gives them increased power. Properly installed, they will work in fringe areas yagi's just can’t. But their value as a TV antenna is only the tip of the iceberg.
Now that cell phones are an essential part of most people’s lives, these cellular radio waves are constantly around us. This has led to a massive flood of other cellular-compatible devices, and that will only continue as time goes on.
The Arrow Log Periodic Antenna, a Cellular LPDA for Any Building
The Arrow will receive all kinds of cellular signal (including 4G, LTE, 3G, 2G signals across all major networks, including MTN, Vodacom, Cell C and Telkom). Its directional nature means it can target a single cell tower at a time, allowing for very specific tuning of any system you use.
The Arrow is an extremely effective antenna to pair with any cell phone signal booster, providing consistent cellular or data indoors. It won’t work without being attached to some sort of system, as it requires the system as a power source.
If you’ve never heard of a cell phone signal booster, they’re also called amplifiers or repeaters. They work rather like a WiFi router: they need a source of signal, and, once obtained, they rebroadcast it within a confined space. The Arrow is tailor made to be the outside antenna used in one of these systems, able to provide +12 dBi gain to the signal propagated by the booster.
The Arrow can be used in both urban and remote areas. It has over 8km of range and can reach faraway towers, and can bring even the most stubborn cellular signal indoors. It also is great in urban areas, which have a very different problem: over saturation of noise. The Arrow cuts right through the urban radio noise directly to a designated cell tower, and provide amazingly clear signal indoors.
How Do Log Periodic Antennas Work?
Log periodic antennas (hereafter referred to as ‘LPDA’ or ‘LPDAs’) normally consist of half-wave dipole elements each consisting of a pair of metal rods positioned along a support boom lying along the antenna axis. The spacing of these elements are what allow for the tuning of the frequency range of the LPDA - meaning, The Arrow is finely tuned in such a way as to pick up cellular frequencies between the 698-2700 MHz frequencies. Other LPDA antennas focus on VHF, UHF, WiFi, and other wavelengths in the high frequency GHz spectrum.
LPDAs are contrasted with EMC antennas, which operate electromagnetically, and array antennas, which are big, complicated arrays of numerous antennas that can both transmit and receive. LPDAs are significantly more diverse in their usage - they can operate off of standard power, and can be installed just about anywhere at not too great of a cost.
A key element of LPDAs is a focus on antenna gain (measured in dBi). This is accomplished with a relatively focused radiation pattern, at a roughly 30 degree beamwidth. The Arrow provides up to +12dBi, a significantly higher number than the max gain of a cellular yagi.
A radiation pattern with such high gain and wide bandwidth is achieved by creating, more or less, a three-element yagi antenna. The directors and reflectors are in reversed positions on The Arrow, with the shorter pieces acting as the directors and the longer ones toward the back as reflectors. The design of the Arrow provide polarization along the back ratio. The directors and reflectors are far less obvious and ostentatious than on a traditional LPDA rig.
Every element of an LPDA is a driven element, connected electrically to the feedline. This feedline - usually coaxial cable, but sometimes twin-lead or ladder line - zig zags between the dipole elements. Certain LPDAs are known as log-periodic zig zag antennas because they replace the dipoles with the feedline itself, but this is not true of The Arrow.
What Kind of Log Periodic Antenna is The Arrow?
The Arrow is an upright planar LPDA, which is a size-reduced LPDA. This is what gives it its signature “arrow” shaped design, and allows us to make silly quiver, bow, and arrow related puns.
So you know, it’s actually easier to aim The Arrow than a typical LPDA, as most LPDAs are placed horizontally. It is even possible to sight directly down the transmission line of The Arrow to aim it, which is very difficult on traditional LPDAs.
Power is transferred through the coax cable, with an efficient, high power VSWR. Energy transfer is affected by the length of the cable run, which provides a certain amount of loss, both in terms of power and signal strength. The Arrow, like most LPDAs, runs on 50 ohm impedance. Its default connectors are N-Female, necessitating a coax with N-Male connectors to use with it.
Now, as has been pointed out, the main purpose of The Arrow is to improve cellular signal. There are very few cellular log periodic antennas on the market, and The Arrow is undeniably the most powerful of these.