[视频描述点这里](https://b23.tv/xQ0o5YK)两台对讲机，一个 k5，一个森海克斯8600Pro，409和435，这两个不一样的频率，却能够互相通信。已经排查过，没有连上中继频率，没有设置频差。打开电脑，在SDR里也看了一下，UVK5和8600Pro在409和435频率发射的时候，都只在附近小范围有散射，而且也不强，但在对方的频率上都没有散射。为了验证是不是通性，我又试了几个其他的频率，比如把409变成410，435变成434，结果这种情况就没有了。这是咋回事儿，大伙有没有知道的？

碰巧最近在研究超外差，正好回答一下楼主的问题首先uvk5/k6用的射频ic是BK4819，这是一颗高度集成、超外差结构的射频ic，据查询技术手册可知第一中频的混频器本振频率ωl0是26Mhz [upl-image-preview url=https://storage.hamcq.cn/2024-09-28/1727554155-807087-img-20240929-035923.jpg] 混频后的频率ωIF＝输入的高频信号(也就是你的发射频率) ωRF ± 本振频率ωl0 其实混频后还有两个频率分量也就是原来的未经混频的ωRF和ωl0，所以混频后其实一共有四个频率分量 : ωRF、ωl0、ωRF+ωl0、ωRF–ωl0，只不过混频后要把用不到的频率分量用BPF衰减滤掉回归主题楼主在其中一台对讲机设置接收频率435Mhz，另一台设置发射频率409Mhz，所以发射后在接收机内混频产生的四个频率分量为:409Mhz±26Mhz＝383Mhz和435Mhz，26Mhz和409Mhz 混频后的435正好就是接收机调谐的435，所以能解调听到声音，这里有用的IF其实是383，只不过场强太强中频的BPF衰减不动了，另一台同理，435±26＝461/409，这叫超外差的中频干扰，B类题库中也有提到过，感兴趣可以看我发的另一篇帖子[upl-image-preview url=https://storage.hamcq.cn/2024-09-28/1727557634-143521-img-20240929-045636.jpg] https://forum.hamcq.cn/d/1348/2

@"Syryia"#p34864 毒德大师，学习了

@"Syryia"#p34864 感谢友台的专业解答，学习了👍

@"Syryia"#p34864 诺，这就叫专业

刚才又验证了一下，确实如此，我在U段设置了好几个频率，接收和发射相差26兆，结果都是一样的，互相能够通信。条件受限，没有办法远距离测试，不确定是不是场强太强，抑制起不到作用。

@"[未知用户]"#p34864 膜大佬解答

Why can two walkie-talkies with different frequencies still communicate?

HLY01922

Click here to view the video description.Two handheld radios, a K5 and a Senhaix 8600 Pro, operating on frequencies of 409 and 435, were able to communicate with each other. I have already checked that they are not connected to any repeater frequency or using any frequency offset. I also looked at the SDR in my computer while both radios were transmitting on the 409 and 435 frequencies, but there was only very weak and localized scattering, and no scattering on the other radio's frequency.
To verify if it was a general issue, I tried several other frequencies, such as changing 409 to 410 and 435 to 434. However, this problem disappeared. Does anyone know what's going on?

BA4QNS

Syryia Toxic De Master, learned

BG2ELG

Syryia Professional

YAOQI

Syryia Professional

BG5VYL

Learned

BG5ATV

Membrane

HLY01922

Syryia Thank you for your professional answers and guidance. I have learned a lot.👍

reqack

Syryia Yes, that's what I mean by "professional."

HLY01922

I just verified this again, and it's correct. I set several frequencies in the U-band, and the difference between transmission and reception is 26 MHz, but the results are the same, and they can communicate with each other. The conditions are limited, so I can't perform long-distance testing. I'm not sure if the field strength is too strong, preventing it from working properly.

BG4ILW

HLY01922 I have a question: Can SDRs really be seen on?

BH3PTS

[未知用户] Solution from the "膜大佬" (the respected expert)

BG4JIE

Syryia Understood.

YAOQI

Syryia After reading this article by the master, I tried it at home using two QS UV-K6 units and one Yaesu FT5D unit. Indeed, both the QS UV-K6 transmission and the Yaesu FT5D transmission could be received by the other two receivers: 436MHz transmission, and the other two receivers receiving signals at 410MHz and 462MHz. However, due to the close proximity of the test distance and the strong signal strength, I am currently unsure how far apart the two resonant frequencies need to be before the signals can no longer be received on the other two frequencies.

yyy8

Syryia Learning from seniors

BH9FPK

BG4JGL

The LK8041-LK8044 questions in the B-level question bank fall into this category.

Ethan

[未知用户]

YangZifan-BA7KVH

Membrane

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