Here's a cute aerial for portable operation. It's a modified Slim Jim end fed aerial made out of 300-ohm ribbon feeder cable. I have not tried this aerial so I can't guarantee it's performance. I think you would have to install this aerial, on site,either onto a piece of plastic tubing or drape it down the window glass, assuming the window is church size! (A band II version will be arount 7ft long) It could also be fastened to a piece of wood, but keep the aerial clear of any metal work. It wont work laid on your car roof unless the roof is non metallic. Remember, this is a vertical aerial anyway, so it has to be installed UPRIGHT! The picture shows it horizontal, but don't use it that way! One more point is that I would not recommend the aerial be used with more than 40 watts due to the fact that a trimming capacitor is used, unless that component is rated for very high voltage and current application.
这里有一个可爱的便携式操作天线。这是一种改进的超薄吉姆
端馈天线制成的300欧姆带状馈线电缆。我没有试过这种天线，所以不能保证它的性能。我想你应该把这个天线安装在现场，或者放在一根塑料管上，或者把它盖在窗户玻璃上，假设窗户是教堂大小的！（一个带II版本将绕7英尺长）也可以固定在一块木头，但保持任何金属工作的空中清晰。除非屋顶是非金属的，否则它不会在你的车顶上工作。记住，这是一个垂直天线反正，所以它必须安装垂直！这幅画是横向的，但不要用那种方式！还有一点是，我不
建议使用超过40瓦的天线，因为使用微调电容器，除非该元件额定非常高的电压和电流的应用。
144 MHz Example
The picture above was kindly supplied to me by an amateur radio enthusiast, and as you see it shows dimensions for 2 metre ham radio use (144 MHz), which is no good to us, so I have included a revised picture below showing the dimensions for the same aerial scaled for 100 MHz. Unfortunately, it gets a bit longer in overall length!
上面的图片是好心的业余无线电爱好者提供给我的，正如你看到的，它显示了2米的无线电使用（144兆赫）的尺寸，这对我们不好，所以我已经包括了一个修改后的图片显示的尺寸相同的天线规模为100兆赫。不幸的是，总长度变长了一点！
100 MHz Example
Now, this Slim Jim is different from the usual aluminium Slim Jim in that the feed is at the very bottom, not tapped in a short way up. Also the bottom of this aerial is not looped (short circuited) and the braid of the 50 ohm feeder coax feeds the aerial via a series trimmer capacitor. This trimmer capacitor is adjusted for lowest SWR. It should also be pointed out that the 2 cm gap is actually a capacitance and this gap can often be made smaller (or longer) to further improve the SWR.
现在，这个苗条的吉姆是不同于通常的铝瘦吉姆在饲料是在底部，而不是在一个短的方式上升。此外，天线底部没有环（短路）和50欧姆馈线同轴编织通过一系列微调电容器天线。这是最低的SWR调整微调电容器。还应该指出，2厘米的差距实际上是一个电容，这种差距往往可以做得更小（或更长）进一步完善
驻波比。
Although the input arrangement is different, the type of operation remains true to the classic Slim Jim principle. It is an end fed half wave folded dipole matched to 50 ohms using the bottom quarter wave j-type matching stub. The currents in the top half wave legs are in phase and reinforce each other, but the currents in the lower quarter wave matching section are in opposite phase and cancel. So all the radiation takes place from the upper half wave (above the 2 cm gap) and no radiation emerges from the bottom quarter wave section. Which is just as well because if the bottom quarter did radiate, the radiation pattern would be ruined with all the power going up into the sky!
虽然输入的安排不同，但操作的形式仍然符合经典的苗条吉姆原理。这是一个端馈半波折合振子匹配到50欧姆，底部采用季度波型匹配短截线。上半波腿上的电流处于相位并相互加强，但下半波波形匹配部分的电流处于相反的相位并取消。所以所有的辐射都来自上半波（超过2厘米的距离），并且没有从底部四分之一波截面产生辐射。这也一样，因为如果底部辐射出去，辐射模式将被摧毁，所有的权力上升到天空中！
Working out the length of a Slim Jim Aerial made out of 300 ohm ribbon cable
计算出由300欧姆带状电缆制成的细长吉姆天线的长度
You must get the total length something like correct for the whole aerial to be resonant and present a good SWR!
你必须得到总长度是正确的整个空中出现共振，呈现出良好的驻波比！
As I have already stated, I am a newcomer to making aerials out of 300 ohm ribbon cable. However, using a velocity factor of .935 (93.5%) seems to be the way to go along with the usual calculation. Below is the formula for the total length. Remember that the Slim Jim is in total, a three quarter wave long aerial, although only the upper half wave radiates.
正如我已经说过的，我是一个新手，用300欧姆的带状电缆制造天线。然而，使用935（93.5%）的速度因子似乎是通常计算的方式。下面是总长度的公式。请记住，苗条的吉姆是一个三分之一波长的空中，虽然只有上半波辐射。
Total Aerial length = 300/frequency x .935 x .75 Please note the answer will be in metres!
总天线长度= 300 /频率x。935×75。请注意答案将是米！
That's 300 divided by the frequency, then multiply by .935 and then multiply again by .75
这是300除以频率，然后乘以935，然后乘以75。
In the 100 MHz example above, the total length calculation is 300/100 x .935 x .75 = 2.103 metres which is near enough to 210 cm.
在上面的100兆赫例子中，总长度计算是300/100×935×75＝2.103米，接近210厘米。
To calculate just the upper half wave section length, do this: 300/100 x 935 x .5 = 1.4025 meters which is close to 140 cm
要计算上半波剖面长度，做到这一点：300/100×935×5 = 1.4025米，这是接近140厘米。
If the frequency of operation were to be 105 MHz, the calculation for the Slim Jim total length would be 300/105 x .935 x .75 = 2.003 metres which is 200 cm just about!
如果操作频率为105兆赫，那么苗条的吉姆总长度的计算将是300/105×935×75＝2.003米＝200厘米左右！
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