On January 20th, at 16:20 BJT, I successfully completed a two-way QSO with BD8AIS in Chengdu using the reflection from Mount Siguniang, operating on the frequency of 432.065 MHz, mode Q65-60B, and without any via.
Source of inspiration
I happened to see my friend, M, at the end of last year.Video, using the BI8FYG station in Kangyuan County to reflect the signal up to a repeater located in front of Chengdu, this gave me some ideas and thoughts. However, due to various reasons, I didn't implement it last year. Now that I'm back in Yibin during the winter holiday, I can try it out.
Existing knowledge base and prior research
1. Some research has shown that snow can reflect radio waves in the microwave and visible light frequency bands. Specifically, snow exhibits high reflectivity in both the visible and near-infrared ranges (which is obvious, as snow is white), while its reflectivity in the microwave band depends on factors such as the state of the snow and other variables. This forms the theoretical basis for remote monitoring of snow layers using microwaves. Unfortunately, there seems to be limited information available in the amateur radio field regarding snow reflection, particularly at the 70 cm frequency band. I can only estimate that the loss due to reflection would be approximately 20 dB.
2. The reflection of snow-covered mountains should be similar to that of the lunar surface.（EME）Therefore, Q65-60B was selected as the communication mode, as it provides relatively stable links (unlike meteor remnants and auroral scattering), while also having a weaker signal strength.
3. Before the formal experiment, some preliminary tests were conducted: first, SSB, CW, and FT8 modes were established with BD8AIS using reflections from Bingqia in Ya'an, Sichuan; second, a U7 Yagi antenna was used to connect to the Jiao Ding Shan repeater (which is also accessible from Chengdu), demonstrating that links via mountain reflection are feasible, while theoretically lower signal loss due to snow.
Link calculation analysis
Chengdu and Yibin are approximately 220 km apart. Due to the curvature of the Earth and the presence of mountains, including Longquan Mountain, direct communication is virtually impossible (excluding atmospheric waveguides and tropospheric scattering). (The link calculation uses the Link Visibility Analysis tool in the ZhiPu app, which is very useful and can be used frequently.)
**最初的构想中是通过贡嘎雪山进行反射**
**然而在实操时以上链路并未接收到信号，所以决定使用四姑娘山进行反射，如下图：**
**最终成功完成双向QSO，以反射损耗20db计，路径损耗大概160db**
Installation status
Using the radio: FT-991
Using feedline: DK7ZB 17EL Yagi antenna (constructed in the afternoon) + BU435
Summary and miscellaneous remarks
During the experiment, there were also various unexpected minor issues, such as the failure of the initial attempt to contact Gongga Peak, which was temporarily switched to Qiaoling Mountain (although I was initially pointing towards Gongga Peak during the QSO, and AIS may have directed us to Qiaoling Mountain, resulting in a SNR of -32 after two attempts). When trying to reproduce the success again, I encountered problems with the other party's equipment, including frequency drift, which made it impossible for me to decode. However, ultimately, we were successful.
Snow or ice reflections in amateur radio seem to be a relatively unexplored area. I believe it's a worthwhile method of communication, especially given the favorable VHF DX and atmospheric duct conditions along coastlines, which are difficult to achieve inland. Experimenting with snow and mountain reflections could provide a valuable path for DX communication in mountainous regions, allowing signals to be transmitted over long distances through mountains that would otherwise be blocked by obstacles.
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