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reflector design for a monopole antenna


Advanced Member level 2
Jul 4, 2005
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im currently designing/optimizing a reflector for a monopole antenna. When I was optimizing the distance of the reflector, at a particular distance, I could see the far-field radiation got chopped off in the middle (place where the reflector is located) but I could see the radiation at both sides of the reflector. what does it indicate?
An electronics genius told me about AM 'power' stations that broadcast their signal to a different direction at night, to reach a different (or larger) geographical area.

The transmitting array consists of two or more vertical antennas, separated by a particular distance (hundreds of feet), calculated as a certain fraction of the broadcast wavelength. By varying the strength of transmission at one or the other antenna, it changes the shape and intensity of the lobes reached by the signal.

Perhaps you observed a similar operating principle?
I'm trying to find the minimum distance a reflector can work. So far, when I put the reflector at a distance very close, it has no effect. At 5mm from the antenna, it's killing the signal at the location of the reflector.

the 1/4 of the wavelength is 90mm. Any idea if this indication at 5mm can give me any clue for reflector placement?
If you have a reflector to chang the antenna radition pattern ,then the performance of the reflector is affected by two aspects,one is the length of the reflector itself,and the other is the distance between the reflector and the antenna.Refering to the Yagi antenna principle,the reflector length is 1/2 of the wavelengeh,and the antenna spacing is 1/4 of the wavelength,and the reflector's reflection ability is maximum.However,in actual use,usually due to space reasons,the spcacing between the reflector and the antenna is not enough,usually we adjust the antenna spcing to 1/8 or 1/16 of the wavelength,but in this case,the reflection performance of the reflector is sacrifficed,but he can still play a reflection role.
Will 1/16 of wavelength spacing work? Do you have any example of a 1/16 wavelength spacing reflector antenna? By the way, I brought the reflector away up to 1/22 of wavelength spacing, and it didn't work.
I made 2.4GHz antenna before,dipole from plus a reflector,reflector and antenna spcacing is 1/16 wavelength.antenna gain is 5dBi
May I ask which type of reflector you use? I'm trying to understand if reflector type has anything to do with 1/16 distance. I have attached popular reflector types here.

Similar to the director diagram in the above picture.above the antenna is a dipole,below the reflector is a reflector.I guess your reflector is not good because of the reflector length,the reflector can reflect the frequcecy is not what you need.

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