Not everyone has measurement equipment for testing 2.4GHz antennas laying around. There are however some simple tests you can perform to establish if an antenna behaves as an antenna, or an elaborate air-cooled dummy-load. Here we make use of standard Radio LAN equipment to assess your homebrew antenna.
You will need an Access Point as an RF Signal generator and a Wifi client to determine signal levels. The Antenna Under Test (AUT) can be connector to the Access Point (or wireless router, as a transmit-antenna) or to the client (as receiving-antenna). Antenna parameters have reciprocity – This means that an antennas parameters are the same in both directions; transmitting and receiving. You can either connect the Antenna Under Test to either an Access Point or Wifi Client to test it.
Connect the antenna with a minimal length of coaxial cable. The cable must be suitable for the frequency and should have the lowest loss possible. This minimises the effect of the coaxial cable on the measurement results. Make sure that the connection is secure. Nothing is more frustrating than an intermittent contact during measurement.
For a reliable measurement you must get a descent distance between the antennas of the Access Point and Client. 10 to 20 meter will do just fine. Best results are obtained with measurements in free space. En open field is ideal, but may not be practical. You may use an Access Point that is part of somebody else’s network, just as long as you have an idea about the physical location of that AP.
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