Crewel J extremely child of aerial make and check

J pole child (J-Pole) aerial blasts off by wave of a 1/2 yuan (part of right graph A) match with drive of wave of a 1/4 implement (part of right graph B) form, it is equal in value at from extreme drive occasionally extremely aerial, because of its conductor shows J model, reason calls J pole child. Right graph is the J that with antenna of 300 ohmic TV line of flat make a present of makes extremely child aerial (apply to 30W the following, abbreviation crewel J extremely child aerial) .

Crewel J extremely child aerial has make easily, facilitate carry, facilitate conceal wait for a characteristic. Introduce its to make move in detail below:

Computational vacuum wavelengh: L=300/f rice, among them F is emissive frequency (megahertz)
Computational length A, B, C: A=0.5*0.94*L, b=0.25*0.87*L, c=0.053*0.87*L. Here 0.94 with the coefficient of 0.87 velocity of wave that are line of flat make a present of. For example, to F=93MHz, a=152cm, a=70cm, a=15cm.
The line of flat make a present of of antenna of 300 ohmic TV that cuts A+B+1cm of one end length. Will among them the 1cm that the bottom carries shucks insulation, be together solder of two core line.
From the bottom upright upgrade measures C, 5mm a paragraph of long insulation shucks, the core line of on left line solder 50 ohmic and coaxial cable, the screen line of line of coaxial make a present of on right string solder, see figure below C, D. (adjust length C adjustable the impedance of aerial. )
From the bottom upright upgrade measures B, 5mm of clipping of left line herein, see figure below B.
Diameter of forgive of will coaxial cable about the 4-5 of 10cm circle, fixed it is under C, formed the Balun that aerial place needs so, see figure below C.
With insulation line fasten in the top of aerial a crocodile is placed, use pensile antenna, see figure below A.

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Next graphs are crewel J extremely child the example photograph of aerial. A is pensile the aerial whole in high-rise corner, b, C, D is the detail enlarge photograph of concerned antenna.

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Crewel J extremely child aerial can furl like following graphs come, facilitate carry.

The important parameter that describes aerial efficiency is standing wave comparing (SWR) , standing wave comparing is more adjacent 1 better; Wave of 1 delegates reflex is 0, standing wave compares <1.6 (corresponding the power of 5% is reflexed to come back) had comparatived, standing wave is compared > 2.5 (corresponding the power of 20% is reflexed to come back) when the risk that has emissive power is too great and burned-out emitter.

Standing wave outputs power than can measuring a watch commonly at the same time (Forward Power) with reflection power (Reflected Power) , because this is general,call radio frequency dynamometer again (RF Power Meter) . Next graphs are the photograph of dynamometer of a kind of radio frequency; The TX termination catapult of backside is outputted, ANT termination antenna or false load (what next graphs receive is false load) .

We use behead demon a catapult makes signal source, its emissive power moves 93MHz, the crewel J that will abstain by above method extremely child aerial stands hang in basement (in order to reduce remote emissive power) , the length that changes C measures the standing wave of aerial to compare. After changing C we also adjust a distribution road of catapult to make its output power the greatest at the same time. Make below our experimental result: