高頻無線電波藉由電離層進行遠距通訊時，電波的能量會受介質影響並隨路徑增加而逐漸衰減，此衰減的多寡將直接影響高頻通訊的品質與通達率。故了解傳播前後電波的強度變化與其所需之最低發射功率，對高頻通訊是極為重要的。因此本論文運用無線電波強度預估方程式結合自由空間傳播損耗、設備增益校正與IONCAP模式中電離層損耗的計算來預估電波強度的變化，並將預估結果與中壢動態式電離層探測儀(Dynasonde)的實際量測值進行比對。 經由比較預估值與量測值的差異，發現此預估方程式在日間會低估，而低估的程度會隨著時間逐漸變小直至15:30後變為高估。另外，藉由數據統計得知中壢Dynasonde垂直探測的傳播損耗約為90-120 dB，則考量回波可以與背景噪音辨別的門檻值以及中壢的背景噪音，故推論本系統需提供50 dBW以上的垂直傳播有效電波強度將可確保電波的傳遞。 High-frequency (HF) radio propagation through the ionosphere offers long-distance communication. Theoretically, radio intensity is decreased with increasing path and is affected also in different media. Therefore, it is important to estimate wave-propagation loss for HF communication. We have applied wave intensity equation which combines basic free-space path loss, equipment gain and the ionosphere loss quoted from IONCAP model. Then we compared the estimations with the measurements from the ChungLi dynasonde. From the comparisons, the results show that the estimations are less than the measurements in daytime but larger after 15:30 local time. Meanwhile, the results show a propagation loss around 90 to 120 dB in vertical sounding above ChungLi. Considering local background noises and distinguishing threshold from system, the ChungLi dynasonde system has to provide more than 50 dBW efficient radio power that radio waves can be successfully measured.
