Discovery of persistent ionospheric frequency shifts of a few Herz and impact on time and frequency transfer

M. Underhill
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引用次数: 6

Abstract

Unexpected frequency shifts and occasional splitting of short-wave Standard Frequency Signals into components with persistent frequency shifts of up to a Herz or so have been `discovered' using SDR receivers with milliHerz resolution. Such spurious signals have also been observed on AM carrier frequencies and DRM signals between ~1MHz and 25MHz. The frequency shifts are in general downwards like `Hubble' shifts but at times can be upwards, depending on the time of day and direction of the path around the earth. Shifted components in general correlate with the existence of an ionospheric propagation path. At some times an unwanted frequency shifted component can be stronger than the original carrier signal and then the Standard Frequency Signal cannot be used as an accurate reference frequency. There are also problems with inaccurate pirate standard frequency signal transmissions on some frequencies. Small short term, diurnal and seasonal frequency variations are being investigated as a possible method of detecting gravity waves.
电离层持续几赫兹频移的发现及其对时间和频率转移的影响
使用具有毫赫分辨率的SDR接收器,已经“发现”了意想不到的频率移动和偶尔将短波标准频率信号分裂成具有高达赫兹左右的持续频率移动的组件。在AM载波频率和~1MHz ~ 25MHz之间的DRM信号上也观察到这种杂散信号。频率的移动通常是向下的,就像“哈勃”移动一样,但有时也会向上,这取决于一天中的时间和绕地球轨道的方向。移位分量一般与电离层传播路径的存在有关。有时,不需要的频移分量可能比原始载波信号强,然后标准频率信号不能用作准确的参考频率。在某些频率上,盗版标准频率信号传输也存在不准确的问题。正在研究短期、日和季节频率的小变化,作为探测重力波的一种可能方法。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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