The answers to this question explain why it's difficult to transfer power from a transmitter to an antenna that is λ/2 in length (or a multiple for long wires, or as half a dipole's length).

Are there reasons why this length would not work or be less efficient when used for a receive-only antenna?

  • $\begingroup$ You mean besides needing twice the wire of a quarter wave? $\endgroup$ – Zeiss Ikon Feb 11 at 19:58
  • $\begingroup$ What's the desired frequency range, Ronald? $\endgroup$ – Mike Waters Feb 12 at 18:45

The difference between transmitting and receiving is that a good receiver has a dynamic range in the neighborhood of 75-100 dB, i.e. very weak signals can be amplified to an acceptable level. An efficiency of 1% is terrible for a transmitting antenna system but may be hardly noticeable for a receiving antenna system. For instance, a Beverage antenna has a negative gain (-3dBi) but is a good receiving antenna because of the dynamic range of communications receivers.

In defense of 1/2WL end-fed transmitting antennas, the famous Zepp antenna is a 1/2WL end-fed antenna that is reasonably efficient because of the 1/4WL parallel matching section.


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