如题，准备在楼顶架设端馈天线，或从7楼往地面斜拉，请教哪种效果更好？环境：7楼朝北，市区边缘，楼高11层，楼顶有一层高保护墙。另：馈线选用20米50-5，够用吗？[upl-image-preview url=https://storage.hamcq.cn/2024-07-23/1721711416-915942-img20240518183302.jpg]

[upl-image-preview url=https://storage.hamcq.cn/2024-08-02/1722605834-166010-img20240731181029.jpg] [upl-image-preview url=https://storage.hamcq.cn/2024-08-02/1722605834-581909-img20240802192106.jpg] [upl-image-preview url=https://storage.hamcq.cn/2024-08-02/1722605834-853411-img20240802192110.jpg] [upl-image-preview url=https://storage.hamcq.cn/2024-08-02/1722605834-998417-img20240802192119.jpg] [upl-image-preview url=https://storage.hamcq.cn/2024-08-02/1722605835-157384-img20240802193935.jpg] 傍晚终于把端馈装好，不知道为啥，驻波一直在2.5左右，通过25米50-7馈线到楼下，机器收到的全是底噪，只有FT8能隐约听到声音，7M左右有CW信号，这个是因为城区原因吗？

楼顶水平架设吧，别的不说看起来也隐蔽不少，而且没有遮挡；架设时注意安全！短波传输20米50-5损耗能接受的，如果担心不够长可以买长点的

@"BG6HFD"#p24317 架楼顶有点恐高

@"BI7ALG"#p24351 哈哈，一次架好，后面一般就不用管了

@"BG6HFD"#p24369 一定要突出楼体最高处吗，没有超过两边炮楼的高度，有没有影响，我看楼顶有扶手梯可以爬到最顶上，就是恐高不敢爬

@"BI7ALG"#p24370 主要是距离地面越高越好吧，用绳子拴住天线两头然后拴在俩个炮楼之间，可以拴在扶手梯上，离地面至少两米五到三米这样

[upl-image-preview url=https://storage.hamcq.cn/2024-07-26/1721960784-851233-img20240725185247.jpg] [upl-image-preview url=https://storage.hamcq.cn/2024-07-26/1721960792-222319-img20240725185252.jpg] [upl-image-preview url=https://storage.hamcq.cn/2024-07-26/1721960861-582513-img20240725191609.jpg] 两个单元的顶楼距离，刚好20米，层高6米，按K4EDF卖家的说法，等有至少24米的净空空间，现在两端没有足够的净空空间，这种情况下，能安装吗？

@"BI7ALG"#p24815 这种时候看一看有没有固定点，可以让你水平斜拉的了，两边太靠近墙体的话对驻波和效率都有影响

楼顶水平拉比斜拉好，最最起码底噪应该会小一些空旷的楼顶利于电波辐射如果可以的话在梯子上绑两根支撑杆效果应该不错没办法空出两米就这么着也不错我以前直接从窗户框固定也用了好久 OK的

@"BI1AVH"#p25149 大概估算，斜拉长度21.5米，距离也不太够，能确保处在基本可用状态吗？

Is it better to mount the antenna vertically or horizontally?

BI7ALG

As per the question, I am planning to install an antenna on the rooftop or run a cable from the 7th floor down to the ground. Which of these options would provide better results?
Environment: Located on the 7th floor, facing north, at the city's edge; the building is 11 stories high, with a protective wall extending from the roof.
Also: Regarding the feeder cable, should I choose a 20m 50-5 cable? Is that sufficient?

BG6HFD

Ideally, install it horizontally on the roof; this would also make it look more discreet and provide better coverage.
Please pay attention to safety when installing!
With a 20-meter band, a 50-5 antenna should be sufficient. If you're concerned about it not being long enough, you can purchase a longer one.

BI7ALG

BG6HFD I'm a little afraid of heights.

Gintoki

BG6HFD 大佬大佬，请问一下，短波状态下馈线的规格与损耗的情况应该怎么计算？

BG2EFX

Top-level horizontal

BG6HFD

BI7ALG Haha, once it's set up, you usually don't need to worry about it anymore.

BI7ALG

BG6HFD Does it absolutely have to be the highest point of the building? If it's not taller than the two flanking towers, will that affect anything? I see a staircase on the roof that could reach the very top, but I'm afraid of heights.

BG6HFD

BI7ALG Ideally, the antenna should be as high as possible. It can be secured to both ends of the antenna with rope and then tied between the two gun emplacements. Alternatively, it could be attached to a handrail, ensuring that at least 2.5 to 3 meters of the antenna is above ground.

BI7ALG

The distance between the two units on the top floor is exactly 20 meters, with a ceiling height of 6 meters. According to the seller's statement (K4EDF), there needs to be at least 24 meters of clear space. Currently, there isn't enough clear space on either end. Is it possible to install something in this situation?

BG6HFD

BI7ALG At this point, it's important to check for any fixed points that might allow you to create a sloped angle. If the speakers are too close to the wall, it can negatively affect both standing waves and efficiency.

BI8DHZ

BI7ALG Simply level it horizontally. The antenna doesn't necessarily need to be completely straight; it will have some sag due to its own weight. The two sides should have enough space reserved for it.

BI1AVH

The horizontal dipole antenna mounted on the roof seems to work well, and the noise should be minimal. An open rooftop is ideal for radio wave transmission. If possible, attach two support poles to the ladder; the results should be good. Since I can't spare two meters, this setup also works fine. I used to fix it directly from the window frame, and it worked well too.

BI7ALG

BI1AVH Roughly estimating, the slack length is 21.5 meters, and the distance may not be sufficient to ensure it remains in a basic usable state.

BI1AVH

BI7ALG Okay.

BI7ALG

BI8DHZ I heard that if you don't keep it straight, the resonant frequency will shift?

BI8DHZ

BI7ALG My previous ground-wave antenna had a slight sag, or was naturally drooping to some extent. The frequency range worked fine. However, if the antenna was pulled very taut, and the ends were too close to the building, it could potentially have an impact.

BI7ALG

BI8DHZ Currently, I'm using a clove hitch to make sure both ends are perfectly horizontal, so that they are less than half a meter away from the wall.

BH9FQT

The effect is good; it's seven stories high between the two floors.

BI7ALG

BH9FQT Is this a K4EDF antenna? I am currently using an end-fed antenna, installed on the 13th floor, with a 25m 50-7 cable to feed it to the 7th floor.

BI8DHZ

BI7ALG What kind of antenna is being used? Is it a JYR antenna? What are the VSWR (Voltage Standing Wave Ratio) readings for the antenna?

BOBAFETT

BI8DHZ jyr40米端馈非常好，八波段都在1.5以下

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