Copyright © 2002-2011 by Harold Melton, KV5R. All Rights Reserved. Feel Free to Link to This Page.
NVIS: Why Do It?
First and foremost, to completely eliminate the skip zone. This enhances all forms of local and regional HF communications, for all practical and experimental purposes.
Emergency groups such as ARES and RACES are studying NVIS propagation, techniques, and equipment deployment for emergency preparedness. NVIS is the tactical communication system of choice in mountainous areas, any areas without complete repeater coverage, and all situations where repeater-based systems have failed or might fail. With the recent release of manufactured mobile and even portable HF radios, HF, and antennas employing NVIS propagation, should become much more popular and useful for disaster tactical communications.
Researchers and users have observed that NVIS antennas work considerably better in the valley than on the mountain top. This is due to much better ground conductivity in the valley than on the dry, rocky mountain top. This happy fact eliminates a lot of unnecessary climbing, and allows the antenna to utilize trees for both support and cover.
NVIS-equipped Amateur fixed stations enjoy regional nets and rag-chews without the annoying skip zone. It is particularly useful to net controllers and emergency practice groups. All fixed stations should take steps to immediately supplement their antenna farms with at least a dual-band NVIS antenna (described herein).
Antenna and propagation experimentation is FUN! Building and deploying antennas is as close as many hams get to home brewing. NVIS is as easy as antenna experimentation can get. The antennas are simple, and are installed very low. Light-gauge wire and nylon string may be nailed to trees at extension-ladder heights. Dropping a dipole and making a change to it takes only minutes and may easily be done by one person without the need to obtain helpers or plan a big event.
NVIS antennas are stealthy. Communism-by-contract property owner’s associations have restricted the placement of visible antennas and severely stifled Amateurs’ pleasure, emergency preparedness, experimentation, and innovation. With NVIS, a fine wire may be brought through the trees, or routed along the top of a privacy fence. The Ham thusly equipped may never win any low-band DX awards, but will still have ample opportunities for QSOs and nets within the regional circle provided by an NVIS antenna in the daytime, in addition to some low-band DX at night, particularly in the winter when the storms are gone.
If you could only have one antenna, it should be an NVIS with ladder-line feed and a tuner, as this may be operated on all bands. The “best” multiband antenna is probably the 260-foot dipole, or 520-foot loop, with 76 feet of windowed ladder-line and a tuner.
Continued…