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

Shiro

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

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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