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Showing posts with the label Emergency Antennas

Simple Ham Radio Antennas: How to make a NVIS HF Radio Antenna. Post #329

. Here's a very simple, basic NVIS (near vertical incident skywave) antenna for portable or emergency use. Most of the parts can be found in your shack or at the nearest hardware or home improvement outlet. Although there are losses in the system (primarily from the coax), the antenna does well, giving good local coverage out to 200- 300 miles/320 - 480 kilometers, depending on the band for which the antenna was designed. If you want to build a more permanent NVIS antenna for various local or regional nets, I would recommend feeding the antenna with 450-ohm ladder line into a balanced tuner or through a 4:1 balun and then into a "regular" tuner. With this arrangement, you can get multiband coverage with reduced losses and manageable SWR readings. Plans for this antenna can be found here: http://home.centurytel.net/w9wis/NVIS. For the latest in Amateur Radio news and events, please check out the blog sidebars. These news feeds are updated daily. You can follow

Simple Antennas for Amateur Radio Operators--a continuing series

KH6JRM's Amateur Radio Blog Post 166 EMERGENCY ANTENNAS Hurricane season has arrived in the Hawaiian Islands and local civil defense officials are encouraging local residents to prepare for some rough seasonal storms.  In the Central Pacific, hurricane season runs from June to November.  Presently, there are two storms which will impact Hawaii Island--Daniel, now a very wet tropical depression, and Hurricane Emelia, located about 2,000 miles east of Hawaii Island.  Although the storms are predicted to weaken as they pass below Hawaii Island, they will bring heavier than normal rain, gusty winds, and storm surf ranging up to 10 feet in some lowland areas.  This is a challenging time for surfers, who have been warned to stay clear of rough spots, and for local residents, who could lose power and suffer building damage. With the exception of Hurricane Iniki in 1992 and Hurricane Ewa in 1982, Hawaii has been spared the full force of seasonal hurricanes thanks to the storms ente

Simple Antennas for the Amateur Radio Operator--a continuing series

ANOTHER EMERGENCY ANTENNA There are quite a few birds in my area that often use my antennas as perches or launching platforms for their flights.  Normally, the smaller birds (finches, cardinals, and an occasional native bird like a honey creeper) don't create problems.  However, a sizeable bird such as a pu'eo (Hawaiian Owl) can damage a dipole or even the bird itself.  Such was the case yesterday when some kind of bird bumped into the 450-ohm twin lead feeding my 40-meter inverted vee.  I cut out the damaged section of the feedline and decided to replace it temporarily with about 50 feet of RG-6 I had stored in the "junque" box.  I didn't have the Drake MN-4 ATU handy at the time, since the MN-4 was being cleaned on the workbench (the kitchen table). So, I borrowed an idea from Dean, KH6B, and rigged up what he called a "James Bond" antenna--named after the famous fictional spy created by Ian Flemming.  All I did was connect the coax to one end of