محدوده دریافت آنتن های دیجیتال تحت تأثیر عوامل زیادی قرار می گیرد. معمولا می تواند برسد 50 به 100 کیلومتر در شرایط ایده آل, اما در کاربردهای واقعی ممکن است به دلیل تفاوت در محیط به طور قابل توجهی متفاوت باشد, پارامترهای تجهیزات, و غیره. در زیر یک تحلیل خاص است:
عوامل اصلی تأثیرگذار
شرایط فرستنده
- انتقال قدرت: هر چه قدرت انتقال ایستگاه اصلی بیشتر باشد, دامنه پوشش سیگنال بیشتر است. مثلا, قدرت انتقال باید حداقل 5 کیلو وات باشد (قدرت دیجیتال) پوشش دادن در مورد 90 کیلومتر در شرایط ایده آل.
- ارتفاع برج فرستنده: ارتفاع برج فرستنده مستقیماً بر فاصله انتشار در خط دید تأثیر می گذارد. If the transmitter tower is 400 meters high and the receiving antenna is 2 متر ارتفاع, the theoretical line-of-sight coverage can reach 90 کیلومتر.
عملکرد آنتن
- Gain and type: High-gain antennas (such as Yagi antennas) can significantly increase the receiving distance, but the beam width is narrow and needs to be accurately aligned with the signal direction. Directional antennas and reflector antennas are suitable for long-distance reception.
- Polarization mode and frequency: Terrestrial digital television (DTMB) uses the UHF band (470-806مگاهرتز), and an antenna that supports this band must be matched. Vertical polarization has less attenuation on rainy days, and horizontal polarization has low ground reflection loss.
عوامل محیطی
- Terrain and obstacles: Flat terrain is conducive to signal propagation, while obstacles such as mountains and tall buildings will block the signal, causing multipath effects or attenuation.
- Atmospheric conditions: Humidity and temperature gradients may cause signal refraction or beyond-line-of-sight propagation, but extreme weather (such as heavy rain) will increase signal attenuation.
محدوده فاصله دریافت معمولی
پوشش متعارف (50-90 کیلومتر)
- ISDB-T signals usually cover a radius of about 50 کیلومتر, suitable for cities and surrounding areas. If the transmission tower is high, the power is sufficient and there are no obstacles, the coverage can be extended to 90 کیلومتر.
- مثلا, using a Yagi antenna in an open area with high transmission power can achieve stable reception.
توسعه راه دور (بیشتر از 100 کیلومتر)
- If coverage of more than 100 km is required, a higher gain antenna (such as a multi-unit Yagi antenna) or an additional relay station is required to supplement the transmission.
- The nominal “120-160 km reception range” of commercial antennas is mostly based on ideal conditions, and actual optimization needs to be combined with terrain and installation height.
پیشنهادات بهینه سازی
انتخاب و نصب آنتن
- Outdoor priority: Yagi antennas are suitable for medium and long-distance reception due to their high gain and directivity; avoid obstacles when installing and try to place them at a high place.
- Indoor antenna restrictions: only suitable for strong signal areas (such as within 10 kilometers from the transmission tower), and avoid electrical interference and concrete obstructions.
اشکال زدایی سیستم
- Calibration direction: Use a compass or signal strength detection tool to adjust the antenna direction to ensure that it is aligned with the transmission tower.
- Signal enhancement: Adding a low noise amplifier (LNA) can improve the reception capability of weak signals.
سازگاری با محیط
- Complex terrain: In mountainous areas or areas with severe obstruction, try different installation locations or use relay equipment.
- Anti-interference measures: Stay away from interference sources such as microwave ovens and WiFi routers, and use coaxial cables with good shielding performance.
استانداردهای صنعت و نمونه های کاربردی
- Automobile and aviation: Antennas with vibration resistance and wide temperature range (-40℃~125℃) are required, which meet USCAR-21 or SAE AS7928 standards.
- Rural and remote areas: ISDB-T is used as a supplement to cable TV and needs to be matched with high-gain antennas to achieve stable coverage.
خلاصه: The receiving range of digital antennas is not a fixed value and needs to be comprehensively evaluated in combination with transmitter parameters, antenna performance and environmental conditions. In practical applications, by optimizing antenna selection, installation location and system debugging, محدوده پوشش نظری را می توان به حداکثر رساند.
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