Whenever, once hear,have in the query " best " I have two words mug-up is unripe cowardly. The reason is a certain east east to the likelihood is best specific person or environment, and such to be not however someone else or environment.
So we change an angle to discuss, what kind of standard should we hold to choose aerial?
Above all, the antenna that searchs those your disinclination frequency is no point, is you should consider preparation be receive HF or to receive VHF/UHF?
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To a kind of any antenna, it is decision polarization direction next. The some that is horizontal polarization and perpendicular polarization normally is planted. Horizontal polarization means parallel of aerial radiate unit to be installed at the ground, and the antenna of perpendicular polarization brace up child perpendicular at the ground.
From function take an examination of fine to set out, polarization mode is special cultured reception news report to apparent distance. When the polarization mode when two stages is abhorrent may loss 20dB or more power. In fact this is opposite merely apparent distance communication is applicable. If depend on F2 or similar ionosphere transmission, do not have too big difference.
In HF paragraph, the biggest distinction is " radiation horn " . The antenna that you can discover part of an inferior radiate compares antenna of horn of a taller radiate to having farther radiate to be apart from.
So, to aerial buy what do this mean the home? A word, the antenna of perpendicular polarization is having inferior radiation angle of elevation. Unless the installation of horizontal antenna exceeds the 1/2 of its lowermost frequency wavelengh highly, the radiation angle of elevation of horizontal antenna wants prep above perpendicular antenna. Likewise loving and perpendicular antenna also is based on the consideration that installs a space. A perpendicular antenna often takes up the domain of very few area, and horizontal antenna (the area that takes up like DIPOLE) should be gotten more much.
Why is horizontal antenna so popular? Here has a lot of reason. Low-cost, and get not easily the pollution of noise. The cost that antenna of a Dipole increases installation has 25 beautiful circles only or lower. And most perpendicular antenna needs 100 beautiful circles at least.
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OK! So what is " directional antenna " ? The antenna of tropism of an in the right way is ideal antenna. It is you not just can to certain signal radiation direction emits power with gathering, and plant through this " directional antenna " or " 8 wood antenna " tectonic, allow you to excise or weaken you to want the interference at the back of the signal direction that listen. This says for " around is compared " . An antenna has 6 DB not only or taller forward gain. The signal field that also can weaken backside likewise amounts to 20dB or more by force.
Why is such antenna hand one? Because this kind of antenna is a bit costly, often be by erect together in the sky of height of at least half wavelengh in order to obtain inferior radiation angle of elevation, still should equip at the same time rotate device makes this kind of antenna truly useful.
In VHF paragraph, the thing becomes have little complex, it is little merely just. If you operate FM on VHF frequency, successful key is to use perpendicular polarization. If you use SSB or CW to do QRP, you are OK from the benefit in horizontal polarization.
Good, let us discuss gain again. What does 6dB gain mean after all? Suppose you and someone else contact, you two people use 0 gain antenna, you increase emissive power double, if arrive from 50 tile 100 tile, you can express those who be pleasant to the eye to have 3dB to signal intensity by force to increase from the field of receiver, if you will launch power to increase 200 tile from 100 tile again, you can see signal field has the addition of 3dB by force again in the watch head from receiver. If want to increase 3dB again, you must increase your emissive power from 200 tile to 400 tile.
Gain can come from aerial as much. The effect of the antenna of 6dB gain is equal to break up two times at projecting yours power, add from 50 tile to 200 tile. Additional, the broadcasting station of other one party of communication and liaison also but from which benefit, when the other side blasts off, his signal arrives at your receiver to be able to increase 6dB. This dispute the power of constant petty gain. If bilateral broadcasting station has the antenna of 6dB gain. . . . . . . . . . . . . .Wow!
If you think abate the signal of a certain broadcasting station, you can carry directional antenna on the back face signal direction, this can weaken signal to amount to 20-25dB. Assume the power of this broadcasting station is 100 tile, signal field is strong will be weakened to be amounted to 7 times by halve. Stay without how many signal so, the n that perhaps disturbs you is equivalent to the broadcasting station of 1 made of baked clay power.
8 wood antenna is truly exciting antenna, have not little advantage. However, application has descendent tendency. Because of erect the charge of a directional antenna compares erect level occasionally extremely child the charge of electrical wiring wants tall, be like the charge of iron tower considering installation orgnaization even. If you can not aim directional antenna a certain broadcasting station, this antenna cannot develop effectiveness, so you still must consider to rotate the charge of device and join cable.
So what is " best " aerial? This is a first-rate problem, have a lot of results, the law that aerial chooses is: Wear aerial high than low wear aerial to be close friends, big antenna is close friends than small antenna. Remember this two principles you forever won't wrong!
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