Today I will talk about 'life-saving straw' for everyone! So the question is, what are the biggest restrictions on our information age? Signals! WiFi signals, mobile phone signals, TV digital signals, and other signals are our life-saving straw. In other words, it has been flooded, so we are no longer limited by hardware conditions when exchanging information. Of course, TVs, computers, mobile phones, and tablet computers are now popular. While this isn't exactly a carefully calibrated, quantitative measurement of antenna gain, it is an objective way to validate that you have indeed constructed an effective antenna, that your Yagi is better than a $1 dipole, or that some modification or adjustment you've made to the Yagi has made a measurable improvement.What is the most important in the information age? Of course, it is a communication tool. If you receive twice the power with your Yagi versus the reference dipole, then you know the Yagi has 3 dB more gain than the dipole. You can also replace the Yagi with a reference antenna like a dipole for comparison. If you are testing modifications to the Yagi you can compare the received power before and after the modification and quantity the change. However, what you can do is perform the same test again and compare the results. Without the tightly controlled conditions of an anechoic chamber you probably can't know the receiving antenna's gain. This doesn't tell you gain unless your spectrum analyzer is calibrated and you know the gain of your receiving antenna. Due to reciprocity, the results you obtain will be identical. If it's more convenient, you can also run this test in the other direction, transmitting with some other antenna, and receiving with the Yagi. Read the received power at the receive antenna with your spectrum analyzer. Make sure the receive antenna has the same polarization. Make it at least 10 wavelengths, but even farther is better. Set up a receiving antenna some distance away. Measuring received power is pretty straightforward.

Gain of an antenna