[upl-image-preview url=https://storage.hamcq.cn/2023-05-14/1684028783-28015-img-20230514-010229.jpg] 前几天把857的5兆频率扩出来以后，这几天测试了一下效果，夜间200公里以内（太原-石家庄），信号最好的时候在-2（我的发射地底噪在s9+），ssb抄收到字母解释法，证明5兆业余频段的可用性还是不错的，现在唯一的问题就是5兆没有人活动，这几天ft8时，频率上空空荡荡的，倡议大家来5兆玩一玩，增加频率使用度

@"SuoYuC"#p2249 应急通信手段之一，多玩一玩熟悉一下传播什么的，有备无患

@"BH3XZT"#p2250 还有一点是这个段最大等效全向15瓦，限制功率的，还得结合增益算输入到天线的功率。

5M CQ DX 可能就不太对了（逃

5MHz我使用20米端馈天线配合天调调整，河北唐山通联天津市南开大学。5MHz还是比较适合使用高仰角天线完成近距离的NVIS通信，而且楼上BY1HT讲到的，要求等效辐射功率不大于15瓦。因为5MHz是个对于专业通信业业务比较重要的频段，业余业务只能在相当有限的范围内活动。

@"venzo"#p2257 请问这是为什么呢

@"BI3PIE"#p2279 我不太了解这个段的其它业务的用途，烦请您指教一下。顺便，请问南开大学的集体台还在活动吗。

@"BY1HT"#p2281 我感觉是因为五兆通讯距离不是很远 cqdx不合适

60米中国刚开放给业余业务的时候，我做了一些国内国外的QSO，冬季的半夜和欧洲国家通信非常顺利，有了FT8更方便联络DX电台。

@"BY1HT"#p2282 首先，根据2018版的《中华人民共和国无线电频率划分规定》，60米波段，大部分划分为“固定”业务，少部分划分给陆地移动和航空移动业务。详见图片。 [upl-image-preview url=https://storage.hamcq.cn/2023-05-16/1684203380-162377-1.jpg] [upl-image-preview url=https://storage.hamcq.cn/2023-05-16/1684203380-327939-2.jpg] [upl-image-preview url=https://storage.hamcq.cn/2023-05-16/1684203380-424115-3.jpg] 其次，一些单位拥有的大型专业短波天线，利用这个频段可完成近地（约百公里内）的固定台与移动台（车船人机等）之间的通信，加大功率的话，可以完成临近城市之间的通信联络。数传、语音、电报各种业务，很拥挤，业余只有窄窄的一小段，而且限制功率。

The first QSO at 5 MHz

BH3XZT

After expanding the 5 MHz band for the 857 a few days ago, I tested its performance recently. The results were promising: at night, within 200 km (Taiyuan-Shijiazhuang), the best signal strength was -2 dBm (my transmitting site has a noise floor of S9+). I also confirmed that the 5 MHz amateur band is still usable, as evidenced by the ability to receive SSB messages using alphabetic decoding. The only issue now is that there's no activity on 5 MHz; during FT8 sessions, the frequency appears completely empty.
Encourage everyone to use the 5 MHz frequency for a short period to increase its usage.

SuoYuC

5M (without scoring) mainly refers to:

BH3XZT

SuoYuC One of the emergency communication methods; it's a good idea to familiarize yourself with how to transmit and receive messages, just in case.

BY1HT

BH3XZT Another point to consider is that the maximum equivalent isotropic radiated power of this segment is 15 watts, and this must be combined with the gain calculation to determine the actual power input to the antenna.

venzo

5M CQ DX might not be a good idea (escape)

BY1HT

venzo Could you please explain why this is happening?

BI3PIE

Using a 20-meter band antenna with an appropriate feed, I achieved good results at 5 MHz while adjusting the transceiver. This setup is particularly well-suited for near-distance NVIS communication using high-angle antennas, as mentioned by BY1HT on the upper floor, where the equivalent radiated power should not exceed 15 watts. Because 5 MHz is a very important frequency band for professional communications, amateur radio operations are limited to a relatively small range.

BY1HT

BI3PIE I'm not familiar with the other business applications of this segment. Could you please provide some guidance? Also, are the collective tables at Nankai University still in use?

BG2LHM

BI3PIE Regarding why 60 meters is suitable for NVIS, even though it's a shortwave band: It's simply that setting up low-angle antennas on 60 meters can be difficult. Furthermore, it doesn't rely on ionospheric propagation. Its propagation characteristics are similar to those of 80 meters, so the distance over which communication is possible depends on how the antenna feed is installed and whether the sun is in a quiet phase. With a ground-mounted end-fed antenna, you need at least 15 meters; with a single GP dipole, you need almost 15 meters. However, most people use it for short-range communication. Personal opinion.

YofoaStudio

BY1HT
I think it's because the communication distance of 50 MHz isn't very far.
CQDX is unsuitable.

venzo

BY1HT NVIS functionality, used to ensure short-range communication beyond visual range.

BI3PIE

BY1HT
First, according to the "Regulations on the Allocation of Radio Frequencies in the People's Republic of China" (2018 version), the 60-meter band is largely divided into "fixed" services, with a small portion allocated to land mobile and aviation mobile services. Please see the image for details.

Secondly, some organizations possess large professional shortwave antennas. Utilizing this frequency band allows for communication between fixed and mobile stations (e.g., vehicles, ships, people) within a range of approximately 100 kilometers, and with increased power, it can also facilitate communication between nearby cities. The use of data transmission, voice, and telegraph services is very crowded, leaving only a small segment available for amateur use, and with limited power.

BI3PIE

BY1HT I am communicating with university students who have set up shortwave radios in their dorms. We are roughly the same age. This is not a collective station; I don't know much about how other schools operate. Because my dorm room, located on a higher floor of the building near the window, allows me to use a portable radio with 15 watts to contact an amateur repeater station in Tangshan, Hebei province, I learned through that station that there are several students at my school who have call signs.

BH6KWC

When 60 meters was recently opened to amateur operators in China, I made QSOs with stations both domestically and internationally. My nighttime communications with European countries were very smooth, and FT8 made it much easier to contact DX stations.

BH3XZT

No problem with 15W power within 200km, clear SSB voice between Taiyuan and Shijiazhuang at night.

BH6KWC

BG2LHM Well, that's my opinion.

BI3PIE

BG2LHM You are right, it is difficult to install low-band antennas with a low angle of elevation. Furthermore, some units using dual or triple-wire antennas and 7.2-meter support poles definitely have a takeoff angle that is not low. It's not really about whether it's suitable or not; the suitability is relative. Adjusting the shortwave antenna's angle of elevation can achieve NVIS or DX, but based on propagation, I think that the 3MHz to 10MHz band is more suitable than the low-band, as you mentioned. In conventional antenna installation methods for the low-band, this is a prerequisite…

BG2LHM

BH6KWC How should I say it?

BG2LHM

BI3PIE Well, there aren't many people playing at 60 meters, so fewer people are coming. If someone takes the initiative to create a good atmosphere and promote positive development, it will gradually become more lively.

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