如题，目前我的设备在1.9Mhz - 21Mhz 驻波均可达到1.5以下，但28Mhz的驻波却始终在接近2左右，理论上地网应该与天线的工作波长相匹配，较高频率可以使用较小的地网，尝试缩短地网后28Mhz驻波有所下降，但1.9Mhz-21Mhz驻波立马就开始飙升。我现在不明白应该如何调整天馈系统使其在工作的所有波段都达到驻波1.5以下，毕竟如果每次玩10m还得去扯下地网还挺麻烦的，求指教。我的现状：电台：Icom IC-718 长线天调：Icom AT-120 天线：铜包钢707被复线（天线从7楼斜拉至地面，目测40-50米）地网：排线撕开自由下垂

QRZ,的动漫做的不错。为啥你户号5位。。。。你这天线是40米端馈？可以这么理解吗？

@"BD3PZF"#p28611 因为我就是五位呼号啊，长线和端馈的振子相似吧，但是端馈是依靠巴伦自然谐振来支持多波段的，我是靠长线天调来实现，还是不一样🥲

[upl-image-preview url=https://storage.hamcq.cn/2024-08-13/1723527011-478665-mmexport1723179371799.jpg] 附上接线示意图，目前的讨论结果来说，下面接线应该叫做平衡线，而不是地网，一会按照群友的建议设置多个波段的平衡线再测试一下

这玩意不是越长越好随意的。。每个频率都有一个几个数值是死区拉不下来的所以要找那种综合几个频率都没问题的长度

@"Shiro"#p28616 这种天线效率怎么样？。。。。通过天调出来长线20-100米是怎么架设？

@"BD3PZF"#p28666 参考长线天线~ 找个锚点拉直就行~

长线缩短成多少米啊，20多米吗？那不就成20米端馈天线了吗😅 我的天调也没架好，不知道从窗户里申出来，长线能不能拐弯。我想往上折一点，架高一点。

@"BG2EFX"#p28664 我手上没有工具能够测量天线长短所以踩坑了，购买前翻看过VK6YSF的长线天线文章，确实给出了整理好的频率表格顺便附上供其它友台参考 https://vk6ysf.com/longwire_antenna.htm [upl-image-preview url=https://storage.hamcq.cn/2024-08-13/1723543280-222783-image.png]

@"BD3PZF"#p28666 效率这个问题我无法回答具体数值，但是目前通联情况相比鱼竿架设的GP效果要好不少，通联欧洲效果不错，架设的话就是扯根线就行，然后避免天线在1/2波长和与1/2波长谐波相关的长度。

@"BG6QFO"#p28669 长线天线是一种长度超过操作波长的天线。自然谐振的话至少得是一倍，不过有ATU就好说了。线材可以拐弯，我为了绷紧天线还打了结，下面附示意图。我选择他主要搭配天调后线的长度没端馈那么讲究，并且很适合小区学校隐蔽架设，我使用的是707铜包钢被复线架设，站在5m外得盯着看才能注意到，20m外不可见。 [upl-image-preview url=https://storage.hamcq.cn/2024-08-13/1723544106-824322-image.png]

Could you please explain why a ground plane can be so long and still not exhibit a significant reduction in standing wave?

Shiro

As the title indicates, my equipment currently achieves a VSWR of less than 1.5 across the 1.9MHz - 21MHz range, but the VSWR at 28MHz consistently remains close to 2. Theoretically, the ground plane should match the working wavelength of the antenna. While shortening the ground plane slightly reduced the 28MHz VSWR, the VSWR in the 1.9MHz-21MHz range immediately increased.

I'm currently unsure how to adjust the antenna system so that it achieves a VSWR of less than 1.5 across all operating bands. It would be quite inconvenient to have to disconnect and reconnect the ground plane every time I used the 10m band, especially since it's not always practical. Could you please offer some guidance?

My current situation:
Radio: Icom IC-718
Long-range weather beacon: Icom AT-120
Antenna: Copper-clad steel 707, re-routed (The antenna runs diagonally from the 7th floor to the ground, approximately 40-50 meters in length)
Ground wire: The cable has been cut open and hangs freely.

BD3PZF

The anime on QRZ is pretty good. Why do you have a 5-digit user ID? Is your antenna a 40-meter end-fed antenna? Can I understand it that way?

Shiro

BD3PZF Because I am a five-way splitter, and the long-haul and short-haul splitters are similar in principle, but the short-haul splitter relies on the natural resonance of the cable to support multiple frequency bands, while I rely on the long-haul antenna tuning to achieve this.🥲

BD3PZF

Shiro What is the efficiency of this antenna? How are long wires (20-100 meters) achieved using a directional antenna?

Shiro

Please see the wiring diagram for reference. Based on our current discussion, the wiring below should be labeled as a "balance line," not a ground wire. I will follow the suggestions from other group members and set up multiple balance lines for different frequency bands to test again.

Shiro

解决了，不是地线的问题。
单纯天线太长，天调拉不下来，缩短天线长度后全波段工作正常。

BI3BUV

Shiro What will be the length of the antenna array after trimming?

BG2EFX

This isn't about making it as long as possible; it's about finding a length that works across multiple frequencies. Each frequency has specific values, and if the length is too short, it will result in a dead zone where the signal won't transmit properly. Therefore, you need to find a length that works well across all the frequencies.

Shiro

BG2EFX I didn't have any tools to measure the length of the antenna, so I made a mistake and bought it without checking. Before purchasing, I read VK6YSF's article on long-wire antennas, which did provide a well-organized frequency table.

Also, I'm including this for reference by other stations.
https://vk6ysf.com/longwire_antenna.htm

BG2EFX

BD3PZF Refer to long-range antennas. Find a reference point and draw a straight line.

Shiro

BD3PZF Regarding the efficiency issue, I cannot provide specific numerical values. However, compared to the GP effect achieved with a fishing rod setup, the current "Tonglian" (presumably a product or system) performs significantly better. The "Tonglian" European version also shows good results. If using a fixed antenna, simply connect a wire and avoid lengths related to half-wavelengths and their harmonics.

BG6QFO

How much shorter does the antenna need to be, approximately? Is it around 20 meters? Would that then make it a 20-meter end-fed antenna?😅 The antenna I installed isn't working properly, and I don't know if it can be extended from the window to reach a longer distance. I was thinking of bending it up slightly to raise it higher.

Shiro

BG6QFO A long-wire antenna is an antenna with a length greater than one wavelength of the operating frequency. Ideally, it should be at least twice the wavelength, but using an ATU (Automatic Transmit/Receive Unit) can compensate for this.
The cable can be bent; I also tied it in a knot to tighten the antenna, as shown in the diagram below.

I chose this particular type because it's easy to install and doesn't require precise alignment after the initial setup, making it ideal for discreet installation in residential areas or schools. I used a 707 copper-clad steel cable, which was re-laid and installed on a support structure. From a distance of 5 meters, I could easily see it, but from 20 meters away, it's completely invisible.

BG2EFX

BG6QFO Whether you need to use a 1:49 or 1:64 barrel depends on whether you are using end-fed antenna.

BG5JKZ

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