Copyright © 2002-2011 by Harold Melton, KV5R. All Rights Reserved. Feel Free to Link to This Page.
What is NVIS?
Near-Vertical Incident Skywave is a combination of radio hardware, skywave radio propagation, operating procedures, cooperation, and knowledge used by a group of radio operators who need reliable regional communications. It fills the gap between line-of-sight groundwave and long-distance “skip” skywave communications.
German ground forces first documented NVIS techniques in WW-II. NVIS was more fully documented, studied, and used by US forces in Vietnam. Radiomen in military vehicles discovered that their HF whips would sometimes work much better when tied down horizontally. Amateur radio operators have been studying NVIS propagation and operating techniques for at least fifteen years. In tactical military use, NVIS allows communications around the region while providing very little groundwave signal for the enemy to home in on. Any radio operator that has used a horizontal antenna well under a half-wave high has used NVIS.
NVIS propagation is generally considered to be F-layer ionospheric reflection at angles of 70-90 degrees. It is skywave propagation without the usual skip zone. The purpose of NVIS is to communicate locally and regionally, out to a few hundred miles, with moderate power, simple antennas, and no skip zone. NVIS is typically used on 160, 80/75, 60, and 40-meter bands by Amateur radio operators using relatively low horizontal wire dipole antennas.
NVIS operations are optimized by understanding and controlling two major factors: (1) Proper antenna design and placement, and (2) proper training of the operators. The antenna is designed and placed to provide the maximum possible gain straight up, on two or three frequency bands. Operator training includes an understanding of antennas, ionospheric propagation, and operational procedures.
Hams have been using NVIS for at least the last seventy-five years. We just called it “short skip”
Yeah, I know, but packaging it as “NVIS” with a rapid-deployment em-comm flavor makes it more interesting. “Short skip” is simply high-angle propagation, but “NVIS” also encompasses a system of field deployment, prepping for emergency scenarios, etc., that sparks the imagination of eager new hams. It’s a good learning tool.
Few HAMS know about NVIS antennas and that is a shame. In case of national emergency, they will not have this capability.
Well thanks to an article by Gunter DJ8CY, I finally have documented proof of German WW2 NVIS. http://www.pa3ect.eu/start/nvis-en-radio-in-ww2-battle-arnhem-nederlands/
I purchased a reprint of D 1034/5 (Gebrauchsanleitung fur den Antennenanpassteil a fur Antennen zur Verbesserung von Kurzwellenverbindungen Vom 1.8.44) from Peter DF3KT. This publication leaves no doubt about their research into the subject of NVIS with practical recommendations for its use with the 15Wse etc. I have not found any reports of actual use of NVIS by Wehrmacht though.
73’s Aryeh 4Z5DF
Fascinating! We now have proof of the earliest military NVIS. I read the link you sent above, then followed it to your other forum postings and pictures of the Ant. 15a—essentially a big roller inductor in a box—that made possible the use of their radios with early NVIS wires. Now we take for granted that we can get a QRP T-tuner and put in a pocket, and a multi-band, multi-mode radio in another…
But it makes me wonder when the first Amateurs used it? It seems likely that early hams used low horizontal wires (being so easy to put up) even back to the spark age. Of course, they didn’t call it NVIS, just “skywave” or something like that, but the result was the same.
Thanks for reporting your research here!
The U.S. Military was conducting NVIS tests in Panama during WW II. See the article “Sky-Wave Aids Jungle Communications” in the Signal Corps Technical Information letter: http://www.radionerds.com/images/8/85/26_SCTIL_Jan_1944.pdf
Great find! THANKS!
Soooooo… The WWII Germans were using it, the Americans and Brits tested it (successfully), but didn’t implement it until it was accidentally re-discovered in Vietnam. Figures…
I would greatly appreciate receiving any info regarding “German ground forces first documented NVIS techniques in WW-II”. I have not found any DOCUMENTED evidence that they used NVIS. Their knowledge of HF propagation at that time was second to none but
where are the official reports ??
From my findings most of the Internet references of Wehrmacht NVIS are based on the articles by Lt.Col.Fiedler.
Sorry, I don’t remember where that reference came from. It was like 13 years ago I wrote that article, and I took my info from ARRL Antenna Handbook, Army FM-24-18, and several web articles as listed on page 8 of this article.
Thanks for reply Harold. I’ll have to keep searching for documented proof.
73’s and Happy New Year