为什么国外ham比较常用的（至少arrl天线手册里很多）梯形平衡馈线国内没什么卖的呢？（还是我关键词用错了？）

同轴电缆对架设环境要求较低，只要是馈线外皮不参与发射的情况下，长度和摆放对谐振点和天线效率几乎没什么影响。国内ham普遍住公寓楼，没有大house也没有后花园。

这个天线优点好像是效率非常高, 只是对于架设场地匹配调整略微麻烦, 有次和朋友试过, 可能架设高度, 振子长度, 等情况影响,半天调不好,带的小天调也拉不好谐振, 放弃了相比之下, 端馈更简单些, 或者水平DP,倒V就更简单了

@"Ethan"#p103084 不太可能吧，梯形馈线就是用梯形外皮连起来的两条明线，技术含量能比同轴馈线高吗？

@"BA7NNC-JOE"#p103082 是馈线不是天线啊（

@"antimonysin"#p103103 技术含量没有，感觉（假如）贵的主要原因是材料多，以及市场小，自制还容易，没人愿意批量做。

@"antimonysin"#p103105 知道,就是梯形馈线, 300-600欧的,不是普通50欧同轴馈线, 梯形线是高阻抗平衡输入，所以必须使用带有平衡-不平衡转换功能的天调（或独立的天调+1:1巴伦）来拉匹配!

@"antimonysin"#p103103 记得Ebay上只有几家卖，英国那边，还很贵🤣

@"Ethan"#p103132 草，那就属于是核心技术了😂

小时候在房顶弄室外天线很常见的平行馈线现在罕见了大概是成本和效果不如同轴线吧

Why are trapezoidal balanced feeder cables, which are commonly used abroad, less common in China?

bg5iyz

Typically, the center of a large loop antenna is paired with a 1:4 Balun for tuning to a specific frequency. This often involves using non-resonant lengths to achieve multi-band resonance. Using a 1:9 or 1:4 ratio can reduce impedance, thereby reducing the voltage and tuning stress on the antenna. The input impedances of parallel transmission lines are determined by their length, which corresponds to the wavelength. This effectively creates a 50-ohm impedance for the antenna. There are four variables in total: the two input impedances of the parallel transmission line and the impedance of the antenna itself. Furthermore, parallel transmission lines utilize their high impedance characteristics to reduce transmission losses.

bg5iyz

This typically applies to frequencies lower than HF.

bg5iyz

Parallel Transmission Lines: The characteristic impedance is only related to the conductor diameter and spacing. Typically, 300-600 ohms are chosen. The input impedance on both sides is only related to the electrical length. Typically, 50 ohms on the radio side. On the antenna side, it varies depending on the length of the parallel transmission line, such as half a wavelength, which is also 50 ohms. All these values are variables, so you need to match them with the antenna tuner. This is why coaxial cables are convenient.

BA7NNC-JOE

Well, using a balanced feed line antenna system seems simple at first, but actually setting it up requires careful consideration of the environment and wiring methods. If not done properly, it can easily affect performance. However, if done correctly, it will work well. But if the debugging process is difficult, it can be quite frustrating.

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