Data

摘要

The recent allocation of NoVs for experimental transmissions on the 501 to 504kHz band has inspired a range of interesting tests using RTTY and other data modes on LF. But first, a bit of background. On the 73kHz and 137kHz bands electrically short and hence extremely inefficient antennas mean that high power transmitters are needed to achieve any reasonable level of transmitted EIRR This fact, taken with the narrow bandwidth of the allocations (only a couple of kHz in width) meant that the vast majority of amateurs adopted highly efficient switch mode transmitters operating in class D or E, rather that the more traditional linear amplifier approach used at HF and above.