打算DIY一个20米端馈天线，打算拿漆包线来做振子。大概也就 10-20w 发射。计划是用无人机绑着鱼线飞过去对面楼顶一个废弃的晾衣杆绕一圈再飞回来，然后绑着漆包线慢慢拉出去。为了防止有碍观瞻，所以线越细越好，目前手头上有一捆 0.5mm 直径的漆包线，不知道会不会太细。

交流电欧姆定律和直流电差不太多，就是[imath:0]U=IZ[/imath:0]，阻抗在天分的史密斯图上就能看到，加上功率，这俩反推可得电流。集肤深度[imath:0]\delta=\sqrt{\frac{\rho}{\pi f\mu}}[/imath:0]，[imath:0]\rho[/imath:0]为电阻率、[imath:0]f[/imath:0]是频率、[imath:0]\mu[/imath:0]是磁导率，可以问商家得到。有了集肤深度就可以得到截面积，现在有了截面积、电流、然后商家肯定也能提供线缆在不同横截面积下的最大电流，适当大一些就行，毕竟大部分能量都会辐射出去，剩下的才会发热。 @"BA7KSH"#p43057 万一是喜欢放风筝的大爷呢。

天线上的功率是以电磁波的形式辐射出去高频信号有集肤效应所以粗细对功率的消耗并没那么明显线的粗细主要影响带宽 , 有看到说用0.12mm的镀银线 600w测试都没问题. 唯一麻烦的在于线细了容易拉长变形和断裂实际上消耗功率的大头在巴伦上所以都是考虑巴伦的耐受值天线振子可以忽略不计

@"BI7KGD"#p42896 感谢友台，拉长和断裂的问题有考虑过。线材只能裁剪到 20M 的样子，然后剩下的交给天调，断裂的问题因为用了鱼线，增加了韧性，应该也还好。先架设解决有无的问题，后续升级可能会考虑用特氟龙镀银线。

我先不说别的。。你这带宽基本就没了

要注意下占空比，玩SSB和玩数据的耐功率是不同的。

我用过0.5mm包塑钢丝，10多米，阳台拉到楼下树上，天调调谐，使用和带宽没问题，通联也还OK，不过我一般不用大功率，怕影响邻居;漆包线肯定也OK，只是相比钢丝容易断，尤其是刮风拉回晃动的时候，连接处有断的风险，安全措施要做好。

@"BG2EFX"#p42929 有天调还管他个锤子带宽🤭

@"BG2EFX"#p42929 大概差不多就行了，剩下的就交给天调。谁不想搞个750正V，无奈在市中心中间楼层，实在是无奈。

@"BI1JNP"#p42953 好的好的，估计拉好天线也就玩玩FT8，白天上班忙，晚上传播又不行。只能挂挂FT8了

@"BI1AVH"#p43001 钢丝貌似也不错，我最近看了下特氟龙镀银线和漆包线。漆包线是最细的，就一根线拉直了几乎不可见，缺点上面的友台也说了，就是时间长了会拉长导致谐振点变化。还有一个问题就是你说的，刮风来回晃动担心存在金属疲劳断掉的风险。砸楼下倒是不太担心，因为巴伦一头计划使用伞绳绑着的，就算漆包线断掉也没啥大问题

漆包线估计不抗拉，还是得注意

How to calculate antenna power tolerance?

BI7LVX

I plan to build a 20-meter end-fed antenna and use coated wire for the matching section. I'm aiming for around 10-20 watts of transmission power. My plan is to fly over to the opposite building, attach a fishing line to a discarded clothesline pole on the roof, loop the antenna around it, and then slowly pull it out using the coated wire. To avoid obstructing the view, I want to use as thin a wire as possible. Currently, I have a bundle of 0.5mm diameter coated wire, but I'm not sure if it will be too thin.

BI7KGD

The power transmitted from the antenna is in the form of electromagnetic waves.
High-frequency signals exhibit skin effect, so the difference in power consumption due to wire diameter is not as significant.
The thickness of the wire primarily affects bandwidth. I saw that using a 0.12mm silver-plated wire for 600W testing did not cause any problems.
The only real problem was that the wires were very thin and prone to stretching, bending, and breaking.

In reality, the majority of power consumption occurs on the Baren platform.
Therefore, we should consider Barron's tolerance values; the antenna vibrator can be ignored.

BI7LVX

BI7KGD Thank you, friend. We have considered the issues of stretching and breakage. The cable can only be cut to approximately 20M, and the remaining part will be handled by the antenna tuner. The breakage issue should also be fine because we used fishing line, which increases its flexibility. First, we will install it to check for any problems, and in future upgrades, we may consider using Teflon-coated silver wire.

BG2EFX

I won't say anything else for now.
Your bandwidth has essentially been cut off.

BG5BQB

BG2EFX One day, he didn't care about his bandwidth at all.🤭

BI7LVX

BG2EFX It's good enough, and the rest can be handled by the system. Nobody wants to deal with a 750-level VIP, but it's really inconvenient to have one in the middle of the city center.

BI1JNP

Also, pay attention to the occupancy ratio. The power consumption of SSB and data transmission are different.

BI7LVX

BI1JNP Okay, it seems like I won't be able to properly set up and use a full antenna for FT8. During the day, I'm busy with work, and at night, I can't transmit effectively. So, I guess I'll just stick to using FT8 casually.

BI1AVH

I have used 0.5mm plastic-coated steel wire, about 10 meters long, and strung it from the balcony down to the trees on the ground floor. The tuning was fine, and I didn't experience any issues with bandwidth or connectivity. However, I generally avoid using high-power setups because I don't want to disturb my neighbors. Shielded wire is also a good option, but it's more prone to breaking, especially when exposed to wind and movement. There's a risk of connection failure in these situations, so it's important to take safety precautions.

BI7LVX

BI1AVH The steel wire also seems okay. I recently looked at Teflon-coated silver wire and insulated wire. Insulated wire is the thinnest, and when stretched out, it's almost invisible. As my friend mentioned, over time, it can stretch, leading to changes in the resonant point. Another concern you raised is the risk of metal fatigue and breakage due to wind swaying back and forth. I'm not too worried about knocking down the building below, because the Balen rope will be tied with a rope, so even if the insulated wire breaks, it won't cause any major problems.

BG2EFX

BI7LVX I'm giving you an option to search for the Litz line.

BD4RHV

The insulated wire seems to have a low tensile strength, so it needs to be handled with care.

BI4MIG

I've seen many posts suggesting the use of thin wire to make antennas, claiming that it makes them less noticeable to neighbors. However, I'm still concerned about another issue: if they are less noticeable, will that also mean they are less likely to be "detected"? This seems a bit roundabout. What I want to know is: without warning lights, would there be any safety concerns? And if warning lights are added, would it actually make them more easily detected?

BG2EFX

BI4MIG Warning lights? Are you planning to install warning lights as well? To interfere with yourself?

BA7KSH

BI4MIG Without lights, it would be impossible for anyone to run between two high-rise buildings, wouldn't you agree?

BI7LVX

BI4MIG The main reason for not using a prominent antenna is to avoid arguments and to have time to explain amateur radio to neighbors and Mr. Hat, rather than shouting "CQ" repeatedly. Also, the flashing light is intended to warn about something? I plan to use a wire from the 8th floor to reach the opposite 9th floor; this height would be inaccessible to airplanes, cyclists, or pedestrians.

BI7LVX

BG2EFX It seems like the Leeds line isn't working. The antenna feed cable can only be a single conductor. If there are multiple thin wires twisted together inside one cable, and each wire is also insulated, this will significantly affect the transmission efficiency.

BloodBlade

交流电欧姆定律和直流电差不太多，就是U=IZ，阻抗在天分的史密斯图上就能看到，加上功率，这俩反推可得电流。

集肤深度\delta=\sqrt{\frac{\rho}{\pi f\mu}}，\rho为电阻率、f是频率、\mu是磁导率，可以问商家得到。

有了集肤深度就可以得到截面积，现在有了截面积、电流、然后商家肯定也能提供线缆在不同横截面积下的最大电流，适当大一些就行，毕竟大部分能量都会辐射出去，剩下的才会发热。

BA7KSH 万一是喜欢放风筝的大爷呢。

BI4MIG

BI7LVX 现在那么多个人飞无人机的，不知道那个自动避障能不能发现。

BG2EFX

BI7LVX 我用了好几年。。。。。。。
而且最好的特氟龙镀银阵子不也是这样的结构么。。
你想多了，试试再说别只考虑理论

bg2kud

I used a thick string to hang it down from the windowsill. When my neighbor asked, I told him it was an antenna for a radio. I didn't need to explain anything about amateur radios or similar topics; the more I said, the more he seemed to understand.

BI7LVX

bg2kud Haha, that's not high enough for me. I live on the 8th floor, and even with a 3-meter ceiling height, I'm only 24 meters above ground.

bg2kud

BI7LVX 我是6楼斜拉 20米端馈或者16米1:9都行

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