You know your antenna gain by checking the manufacturer's specifications (in dBi or dBd) for a theoretical value, using antenna modeling software for prediction, or measuring it in an anechoic chamber with a calibrated reference antenna for accuracy, often using a Vector Network Analyzer (VNA). Gain tells you how well it concentrates radio energy in a specific direction, with higher numbers meaning a narrower, more focused beam.
The formula for calculating antenna gain is G = 10 log (P2/P1). Antenna gain is pivotal in different types of antennas like dipole, Yagi-Uda, parabolic, and patch antennas. Understanding it is crucial for designing efficient wireless communication systems.
A medium gain antenna (6.6, 5.1 dBi) has a more rounded, wider pattern than a high gain antenna. This means the signal is less likely to be obstructed by obstacles such as buildings, trees or mountains.
A good all round 2m/70cm base antenna is the Diamond (or equivalent) X-200 (6/8dB gain), in hilly or built up urban areas an X-50 (4.5/7.2dB gain) will be better or if you are in absolutely flat areas you can go all the way up to an X-700 (9.3/13dB gain).
Antenna gain is the measure of an antenna's ability to radiate a signal in any direction compared to the theoretical isotropic radiator. Antenna gain is typically given in decibels relative to isotropic (dBi). While it is closely related to directivity, it also considers the efficiency of the antenna.
The higher the gain, the more directional the antenna becomes. For instance, a 3 dB increase in gain doubles the signal power, while a 6 dB increase doubles the range. However, it's important to remember that increasing gain doesn't amplify the signal itself; it focuses the existing energy into a narrower beam.
Adjust The Position
If you're using an indoor antenna that's installed near your TV, like those popular flat ones, the best tip for improving your reception is to reposition it. This sounds obvious, but with a little easy research, it can vastly improve your experience.
High gain is a powerful boost for many aerials, and certainly make a difference to your maximum reception range, but at the cost of a more directional and potentially higher-energy set up.
10 dB gain/loss corresponds to a ten-fold increase/decrease in signal level. A 20 dB gain/loss corresponds to a hundred-fold increase/decrease in signal level. In other words, a device (like a cable) that has 20 dB loss through it will lose 99% of its signal by the time it gets to the other side.
With this very high gain, the signal can receive from a very long distance but at a very narrow path. It will miss hotspots within a few miles and is designed to connect remote miners and other IoT devices to the Helium network from an exceptionally long distance of 10 miles over open terrain, or more.
A DBI of 80% to 99% was considered normal, and a DBI of <80% (low) or DBI of ≥100% (high) were considered abnormal. DBI values ipsilateral to the AVF were used for analysis. The primary and secondary access patency rates were calculated using reported standards and compared using standard statistical techniques.
Then we measure your antenna's gain (in dB isotropic or dBi) via the substitution method. The substitution method involves setting up our calibrated laboratory reference antenna over a radiated path accross the chamber, then normalizing (or “zeroing”) that path loss to 0 dB.
Antenna gain refers to the ability of the antenna to focus signal energy in specific directions. It directly affects signal reception quality. Higher gain improves sensitivity and signal-to-noise ratio, especially in challenging environments.
High-gain antennas are directional, meaning they focus on a specific direction when transmitting or receiving. One example is GNSS receiving antennas pointing up to the sky to maximize reception of satellite signals.
At its simplest, testing involves sending messages from different locations and seeing which ones are received, and then comparing the results against other antennas. At the complex end, this can be using expensive test chambers and equipment to measure the signal strength, gain, and radiation patterns.
dB and Voltage gain (20dB = 10x)
When talking about voltage, 6dB represents a ratio of two to one or a doubling of voltage. 20dB would represent a ratio of ten to one for voltage - so 20 dB would be 10 times the voltage. A 40dB voltage gain would be 100 times the voltage.
Loudness is measured on a logarithmic scale. This means that an increase of 10 decibels (dB) represents a 10-fold increase in sound intensity and a doubling of the perceived loudness.
However, the absolute best way to turn a weak -110 dBm signal into a strong –80 dBm, is with a cell phone signal booster.
While high values of gain - in the 7 to 12-decibel range - are usually better than low gain values, you would be better off not focusing on the gain, but instead purchasing an antenna that provides good overall performance, as long as it meets your reception and installation requirements.
By attaching tin foil to your antenna, you were, in theory, increasing the reception by extending the antenna. If you were lucky, and the foil happened to mirror incoming radio frequencies, this might have worked in a past case. On the other hand, it was just as likely to mess up your reception for other channels.
When measuring antenna gain, the network analyzer sends a signal into the antenna and then calculates the received signal strength. The received signal strength is then compared to the signal strength if the antenna were omnidirectional, and the difference is the antenna gain.