在hamcq关站的这段时间里，大家都跑到国际站去了，在那段时间，我发布了有关西安市431.635中继的第一个帖子【位于国际站点，大家可以回忆一下：（https://forum.hamcq.net/d/72）】现在已经一个月了，让我接着上一期的后续讲讲后面是怎样处理的

好了各位同志们，我已经把视频搞好了，参见 https://b23.tv/D5CoaQL 当然也拍的很模糊…… @"BI2QHS-Jerrystyle"#p73868

首先，经过那一天高强度的测向，我的身体已经筋疲力尽，缓了几天，我又与 @"BI9BUT"#5382 组成一队继续对这个中继进行干扰查找，BI9BUT有一台刷了场强固件的UVK6（当然场强数值可能仅供参考），使用一根U5V2 的莫克森八木天线进行测向，这个天线的增益我们没有测，但是应当与上期的八木增益相近

当然我也伤的很惨，可能没有休息好，在那天上天台美美的绊了一跤，脚好像摔骨裂了？反正到我发帖子这一天，我的脚还是隐隐作痛。 **由于我们接下来测向的地点逐步逼近中继，以下地点将保密**

我们首先来到了某个楼的33楼天台，测试此时中继的信号场强来到了-53dBm，由于这栋楼朝向中继的方向有遮挡，所以我们换了马路对面一个没有遮挡的楼

在这栋楼顶上测向，发现信号惊奇的来到了-43dBm，我们能明显感觉到中继确实离我们越来越近了。通过单次方位角定位，我们确认了中继所位于的大楼，是一栋普通高层建筑

我们走到了这栋楼的底下，这时测试信号场强不升反降，来到了-56dBm，我们又开始对于这栋楼持怀疑态度，由于上一回在楼顶测向所指向的方向上有2栋以上鹤立鸡群的高层建筑，我们才会选择楼下测向（这时我还没有意识到“灯下黑”的原理，其实不应该在楼下测的）

最后，我们走到了另一栋距离仅300m高层建筑的楼顶，通过交叉测向法，确认中继确实位于这栋楼的楼顶。这时的信号场强来到了-30dBm。由于我们没有带上SDR或者tinySA的频谱分析仪，难以通过频谱确认干扰源是什么，遂作罢，短暂休整2天后，我们又来到这栋楼上。

这会我们携带了SDR与电脑，在分析频谱的时候果然发现了问题。这时的433.5-434.2MHz上原来有大量的LoRa设备！这些设备用NFM模式听起来就和中继的干扰声听起来一模一样！！我都没注意到！面对这些设备我们完全失去了测向能力，因为你一看频谱图你就知道了……[upl-image-preview uuid=9131a48d-43be-4b53-8eb3-64aa5b06769b url=https://storage.hamcq.cn/2025-08-12/1754983085-400038-img-7380.jpg alt={TEXT?}]

~这hamcq为什么上传不了视频和文件，我拍了视频了，一上传就报错……

这些信号基本上都能来到S6左右，再加上大量的便宜且质量超级超级差的设备，想阻塞频率轻轻松松。可能他们发射功率只有1/3在发射，其余都是杂散

这些信号都是隔一段时间内发射，且发射时长都不超过5s，都不够我举起八木绕一圈的，根本没办法，而且这些信号大量的重叠，你听都听不到什么信号是什么信号…… 于是我将这件事和相应的视频发给了学会赵老师，并且给出了建议：换频率，除此之外别无他法。赵老师那边行动很迅速，先是关了中继，随后切换频率到439.900MHz，在最近重新开放并正常使用，北郊的台友又恢复了正常的通联

Follow-up on interference from the 431.635 kHz repeater in Xi'an.

BI9BUM

During my time at the hamcq station, everyone had moved to the international station. During that period, I posted the first message about the 431.635 repeater in Xi'an, which is located at the international site. (Please recall:https://forum.hamcq.net/d/72) Now that it's been a month, let me continue with the follow-up from the previous episode and explain how we handled things afterward.

Xiaohu3389

BI9BUM 我们这边业余段甚至有客车司机搭建的黑中继

BI9BUM

First, after that intense navigation exercise, my body was completely exhausted, and I rested for a few days before resuming. @BI9BUT Form a team to continue searching for interference on this repeater. BI9BUT has a UVK6 with a field strength module installed (of course, the field strength values may only be for reference), and uses a U5V2.
When measuring the Moksen Yagi antenna, we did not measure its gain; however, it should be approximately equal to the gain of the previous Yagi antenna.

BI9BUM

Of course, I was also very hurt. Perhaps I didn't rest properly, and one day I fell while standing on the balcony, possibly breaking my foot? Anyway, by the time I posted, my foot was still aching.
Since the location we will be using for triangulation is gradually approaching the repeater, the following locations will remain confidential.

BI9BUM

We first went to the rooftop of a building on the 33rd floor, where we tested the signal strength of the repeater and found it to be -53 dBm. This was due to obstructions in the direction the repeater was pointed, so we moved to another building across the street that had no obstructions.

BI9BUM

When measuring the direction from the top of this building, we found that the signal strength reached an astonishing -43dBm. We could clearly feel that the repeater was indeed getting closer to us. Through a single directional measurement, we confirmed that the repeater was located in a standard high-rise building.

BI9BUM

We reached the bottom of this building, at which point the signal strength readings started to decrease instead of increase. The reading dropped to -56 dBm, and we began to question the validity of our measurements from the ground floor. This was because, in the previous measurement on the roof, we had identified two or more prominent high-rise buildings pointing in the same direction. That's why we chose to measure from the ground floor (at this point, I hadn't yet understood the principle of "measuring under a light").

BI9BUM

Finally, we reached the top of another building, only 300m away, and confirmed that the repeater was indeed located on the roof of this building using triangulation. At this point, the signal strength was -30 dBm. Since we didn't have an SDR or tinySA spectrum analyzer to identify the source of interference, we decided to stop for a while. After a brief rest of 2 days, we returned to this building.

BI9BUM

We brought our SDR and computer, and when analyzing the spectrum, we definitely found the problem. At that time, there were a large number of LoRa devices on the 433.5-434.2MHz frequency! These devices sounded exactly like repeater interference when listened to in NFM mode!! I didn't even notice them! Faced with these devices, we completely lost our ability to determine direction, because you can tell just by looking at the spectrum…

BI9BUM

_{Why can't I upload videos and files through hamcq? I just recorded a video, but it immediately gives an error when I try to upload it...}

BI9BUM

These signals can essentially reach S6, and with a large number of cheap, extremely low-quality devices, it's easy to block the frequencies. It is possible that their transmit power is only 1/3 of its maximum, while the rest is scattered.

BI9BUM

These signals are transmitted intermittently, and each transmission lasts no more than 5 seconds. This is not enough time for me to raise my Yagi antenna and make a full rotation, which makes it impossible. Furthermore, the large amount of overlap between these signals makes it impossible to distinguish one signal from another.
Therefore, I sent the information and the corresponding video to Professor Zhao at the association, along with a suggestion: change the frequency; there is no other solution.
Mr. Zhao's team acted quickly, first shutting down the repeater, then switching to a frequency of 439.900 MHz, which has recently been reopened and is now functioning normally. The local ham operator in the northern suburbs has also regained normal communication.

BI9BUM

In summary, this describes a complete and thorough surveying process, but it also involves significant costs.~~After all, I was injured.~~Overall, there is currently no good way to identify and mitigate interference for LoRa devices. The only option is to change the frequency. I wrote this article as a cautionary tale, hoping that others can learn from my experience and find ways to address the interference affecting their repeaters._{（It hurts so much.）}

BI9BUM

Also, how do I send the file?🤔It's so difficult to post; can I only post images? Can someone please help me understand?

BI7BLA

BI9BUM

Bottom of the site Frequently Asked Questions ：

BI9BUM

BI7BLA Okay, thank you.

BG5BNW

Everyone can receive interference. Take a bearing and report your coordinates and the strength of the interference. If three people report, the approximate location can be determined.

BI9BUM

BG5BNW We had previously tested this (see details on the international station), and it was confirmed that the interference wasn't coming from external sources. Regardless of which amateur radio operator activated the repeater, similar interference was observed. Therefore, we narrowed down the source to the area around the repeater.