各位大佬好，请教一下关于天线的问题。有一根 1m 长的车载天线，测试**不通联**时接收到的同一频率信号强度，不同的接法发现接收到的信号强度不同。 - **直接拧在手台上**：S0 ~ S1 - **拧在磁吸底座上连接手台**：S1 - **通过 6m 50-5 馈线连接手台**：S2 - **加磁吸底座吸在窗外栏杆上，接上述馈线**：S8 这是否意味着最后一个接法有问题？有没有什么办法可能改善这一现象？

有没有看看驻波？可能背噪本来就很大但是天线的接收效果不好

@"BD7PRI"#p40671 还没有测过，我也倾向于可能是天线接收效果的问题🤔

没看出来有什么问题，手台听底噪干嘛，手台一般都设置静噪的啊。距离室外越近接收效果越好，相对应的收到的底噪也更多。正确的测试方法应该是找一个中继守听一下，按照不同接法观测接收对方话音的清晰度，或者直接CQ找友台做信号测试。

uv感觉应该差距不大吧，不过短波GP天线确实底噪更大一些

@"someham"#p40670 没太看懂，这是从上到下信号依次增强吗，要是这样的话那没问题啊

@"BG2EWI"#p47969 是背噪声增强了，没有通联时能接收到的信号强度

查一下是不是车上什么干扰电台了，，我车一挂倒挡，倒车摄像头一有画面，就干扰电台

@"someham"#p47974 不知道你具体遇到的是什么情况，最好录一段视频看看，因为对讲机在没有接收到有效信号时输出的噪声是由环境底噪和机内噪声经鉴频形成的，这个噪声大小与天线接收到的底噪幅度无关。换言之就是不管你把天线插上还是拔下来，喇叭里发出的都是同样的雪花声。不过还有一种可能就是你的周围存在干扰源，发出的干扰信号被你的设备收到了，具体表现就是底噪里有“嗡嗡”的电流声，而不是纯净的雪花声。这种干扰会随着你所接天线接收性能的增强而进一步增强。

Help for beginners: Back noise issues with antennas

someham

Hello everyone, I would like to ask for your advice on antenna-related issues.
A 1m long car antenna was used for testing.Unable to connectWhen receiving the same frequency signal at the same time, different connection methods result in different received signal strengths.

Simply screw it directly onto the work platform.: S0 ~ S1
Attach the microphone to the magnetic base.: S1
Connect via a 6m 50-5 coaxial cable.: S2
Attach the magnetic base to the window frame and connect it to the feed line mentioned above.: S8

Does this mean that the last connection is faulty? Are there any ways to improve this situation?

BG2EWI

someham I didn't quite understand. Is this a situation where the signal strength increases progressively from top to bottom? If so, that sounds fine.

BD7PRI

Have you checked for standing waves? It's possible that the noise level is already high, but the antenna isn't receiving well.

someham

BD7PRI I haven't tested it yet, but I suspect the issue might be related to the antenna receiving performance.🤔

BI7LVX

I couldn't see any problems. If the handheld radio is picking up noise, it should be set to a low-noise mode. The closer you are to the outside, the better the reception will be, and correspondingly, more noise will be picked up. The correct testing method is to find a repeater that is listening, and then observe the clarity of the other party's voice using different antenna configurations, or directly contact another station for signal testing.

someham

BG2EWI The background noise has been enhanced, and the signal strength that can be received when there is no communication link has also increased.

BG2EWI

someham I don't know the specific situation you are experiencing, but it would be best to record a video so I can see. The noise produced by the radio when it doesn't receive a valid signal is formed by environmental background noise and internal noise amplified by the frequency. The size of this noise is independent of the amplitude of the background noise received by the antenna. In other words, whether you have the antenna plugged in or unplugged, the same "snowy" sound will be emitted from the speaker. However, another possibility is that there are interference sources around you, and your device receives these signals, which manifests as a "buzzing" electrical sound within the background noise, rather than pure "snowy" sounds. This interference will further increase as the receiving performance of the antenna increases.

BH9FPK

I checked, and it seems like there's a radio interference issue in the car. When I put the car in reverse gear, the backup camera starts showing an image, which is likely caused by the radio interference.

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