On The Art of NDB DXing
by Sheldon Remington
©
1987-2000 All Rights Reserved
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CHAPTER ONE: INTRODUCTION
This series is an exposition of strategies and techniques for DXing non-directional radiobeacons (NDB's), which operate in the longwave spectrum from 190 to about 535 kHz. This pursuit has recently begun to come of age and is at an exciting point in its evolution. It is hoped that this series will be a catalyst for NDB DXers, both newcomers and oldtimers, to maximize their individual and collective progress. Most of the techniques have evolved slowly and painfully as each DXer tackled the challenges uncovered by earlier successes. Some were brought to NDB DX from other bands where weak-signal techniques were specially developed for the problems of those bands. In fact, the maturation of the NDB DX quest is due in large measure to the influx of refugees from overcrowded bands, particularly the medium-wave broadcast band which has deteriorated substantially since the 1960's in its ability to produce weak-signal observations. There are, in fact, many similarities between BCB DX and NDB DX: each has a similar number of worldwide transmitters on a similar number of assigned channels, and some of the propagation patterns are similar. The main differences are that the BCB has wideband music and voice, while NDB's use slow Morse code fixed-frequency tones; and NDB's identify continuously, just a pipe-dream for broadcast DXers. Other refugees came from the HF amateur bands where very little remains to be done that hasn't been done before. Another impetus to the growth of NDB DX is the simultaneous growth of activity on the 1750 Meter band (160-190 kHz), where experiments in extremely low-power communications, mostly oriented around homebuilt beacons similar to NDB's, are conducted. The techniques for that band share much in common with those of NDB DXing, so a symbiotic growth is now occurring. Also, NDB's are probably the best indicator for 1750 meter DX work, as propagation is essentially identical on the two bands. The official purpose of NDB's is to provide navigation to aviators and mariners. It is the oldest and most primitive type of radio navigational aid, in contrast to the high-tech Omega, Loran, VOR, DME, and ILS systems. NDB's are likely to be rarely used at major international airports, which have those other systems in profusion. But, it is simple, reliable, and inexpensive, so it's very important in remote areas such as northern Canada, A simple receiver, called an Automatic Direction Finder (ADF), has a compass indicator which tells which direction an NDB lies from the craft. The tuning is manual, and so is the NDB identification. Nautical and aeronautical charts show which "dots-and-dashes" identifier lies at what location. The maritime NDB's are situated at prominent points along coastlines, often near other marine navigational devices such as lighthouses, jetty lights, and foghorns. In the U.S., they are installed and maintained by the Coast Guard. The aeronautical NDB's are situated in the vicinity of airports, under inbound flight paths, and may also be known as outer, middle, or inner markers. In the U.S., they are operated by the Federal Aviation Administration (FAA), except for a few operated by the military of by private firms, usually engaged in exploration for natural resources. The same pattern holds true worldwide, with civilian government agencies operating most of the NDB's. The aeronautical beacons greatly outnumber the marine beacons: a few are intended for both types of user. DXers, of course, need not concern themselves with the official purpose of NDB's. For our purposes they simply constitute propagation beacons much like those in the 14, 28, and 50 MHz amateur bands. All we need to know is that they generally operate continuously, around the clock, with equal radiation in all directions, and rarely change their identifier, power, frequency, or location, as broadcasters are wont to do. Their precise coordinate locations are easily obtainable, which assists in propagation studies. And, best of all, they do not emit sideband splash/buckshot/splatter as do broadcast transmitters. This is a great aid to weak-signal work. This series will avoid the use to technical jargon, mathematics, and schematic diagrams, insofar as possible. It is not necessary to know the inner workings of your equipment or the physics of the ionosphere in order the chase NDB DX successfully. However, some constructional abilities will be helpful, as in any branch of the radio hobby. Actual construction projects will not be part of this series: instead, references will be included to point the reader toward sources of information on particular devices. Topics to be covered include:
Although this series will be as comprehensive as possible, much further
development is possible in many areas. Discussion and debate is welcomed,
as are any questions left unanswered in the series. Many more DXers of
serious intent are needed: we have established effective monitoring in
only a few areas of North America and Oceania. This is the Golden Age of
NDB DXing: much fun can be had, and perhaps a bit of scientific progress
as well.
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