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Summer 2003 Issue |
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VHF Propagation
The
Science of Predicting VHF-and-Above By Tomas Hood,* NW7US
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HF radio enthusiasts can hook up a light bulb and communicate with the world when propagation conditions are “just right.” Toss up some wire, tune up the rig, and talk around the world. Rumor has it that operators on VHF and higher frequencies work “real radio.” They cook their meals in front of their portable parabolic dish antenna. They bounce signals off the moon or meteor trails. Their DX is a raspy-sounding Morse Code signal propagated off aurora. You need to have more than a wet noodle, or the loss will make the coax nothing more than a dummy load. Propagation on VHF and above is not quite the same as it is on HF. Sure, F-layer refraction takes place at times on 6 meters and a bit higher. It is true that sporadic-E works on HF, but there is a whole different and exciting set of modes and techniques that are unique to VHF and above. This column focuses on propagation on very-high and ultra-high frequencies. What’s happening in the real world? What are the theory and science of radio-wave propagation at such high frequencies? What new aspects of propagation research are you, the reader, exploring in your daily amateur radio operations? What propagation discoveries are being made in the commercial VHF and UHF domain, and how can they be applied to our hobby?
When CQ VHF Editor Joe Lynch, N6CL, wrote and
asked me if I might be interested in writing this column, I hesitated. I
am a student of propagation, and there is so much to learn. Also, there is
so much to explore. The unique field of VHF/UHF propagation is one I have
not explored in depth as much as I have explored the HF side of our hobby.
However, I love to dive into new areas of knowledge, and while doing so, I
enjoy sharing my discoveries as well as my experiences with fellow
hobbyists. I cannot do this alone, though. Many of you have dedicated your
entire radio hobby to VHF and higher frequencies, modes, and techniques.
Please write to me and send me your observations, your corrections, your
insights, your questions, and your suggestions. I would like to make this
column one of community cooperation. I will list significant observations
and events that you send to me, as they relate to propagation. I’ll
research answers to your questions. I’ll editorialize, theorize, and
summarize. I hope you will enjoy this effort, and I hope the column will
prove useful to you. Write to me and let me know your thoughts. In the Northern Hemisphere the 2003 sporadic-E season took off with a bang early in the year. Watching the DX Spot Reflectors (i.e., the DX Summit by OH2AQ <http://oh2aq.kolumbus.com/ dxs/>) revealed activity starting as early as February. Propagation really got hot after April and in full swing by June. FM and TV DXers reported signals on the low TV frequencies between locations such as Manitoba (Canada), Idaho, Colorado, Arizona, New Mexico, and as far south as Mexico (XHFA-TV). (See the FM DX page at <http://www. amfmdx.net/fmdx/> for more on FM DX.) One amateur radio operator reported openings during June on 220 MHz between Idaho and Nevada, as well as 2-meter skip between Idaho and New Mexico, Mexico, Arizona, Texas, and Nevada. From Kansas came reports of FM and TV DX from Texas, Florida, and Ontario (Canada), as well as from Nevada, Utah, and New York. The cluster activity shows a good amount of two-way activity in North America as well as in Europe. I’d like to hear your reports, especially any surprising and unusual openings you experienced. Click here to return to Summer 03 highlights Click here to subscribe to VHF..
_________________ © Copyright 2003, CQ Communications, Inc. All rights reserved. This material may not be reproduced or republished, including posting to a website, in part or in whole, by any means, without the express written permission of the publisher, CQ Communications, Inc. Hyperlinks to this page are permitted.
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