Friday, July 13, 2012

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

KH6JRM's Amateur Radio Blog

Post 167

INTRIGUING ANTENNAS

Hawaii Island dodged a potentially wet weekend with the passing of tropical depression "Daniel" Thursday evening.  The island is receiving some high surf and a few heavy showers, but that's about all the storm could do.  "Emilia" is still churnging about about 1000 miles to our east, but, it too, is predicted to track south of Hawaii Island.  The hightened alert gave amateur radio operators here a chance to check out their emergency "go" kits and review their own procedures for such continguencies.

While I waited for the bad weather to pass, I found three articles in the 13 July 2012 edition of "e-ham.net" that could provide antenna ideas.

For those amateurs involved in emergency communications, a good NVIS (near vertical incident skywave) antenna is a must for regional HF  operations out to about 300 miles.  Pat Lambert, W0IPI, has published an excellent tutorial on NVIS antennas which are easily built, portable, and easy to maintain.  Pat notes that many amateur radio operators already have a NVIS antenna and don't know it.  All one has to do is lower a 40-meter dipole to 10 or 15 feet to get strong, no fading signals out to about 250-300 miles.  He provides the necessary graphs and test instrument readings to support his designs.  This is a good, informative read.

Next, Cecil, W5DXP, has published approximately 20 antenna ideas that could provide some excitement on your "antenna farm."  What caught my eye was what Cecil called a "no-tuner all-hf band antenna" using ladder line and a 1.1 balun.  The antenna can be either a flat-top dipole measuring 130 feet long at an elevation of 37 feet, fed by 90 to 110 feet of 450-ohm ladder line attached to a 1:1 balun.  He has a smaller design incorporating a flat-top dipole measuring 66 feet at 37 feet, fed by 60 to 90 feet of 450-ohm ladder line.  The ladder line is attached to a 1:1 balun.  Cecil provides extensive photographs, smith charts, and illustrations on how to erect this antenna. 

Finally, for your mobile operators (including me), James Bennett, KA5DVS, has reprinted his popular "Build the PAC-12 Antenna" for portable operations.  The article was published originally in issue #8 of "QRP Homebrew Magazine".  Like the other two articles, James provides an ample amount of pictures, parts lists, and construction techniques for the experimenter.  The antenna is now being marketed as a commercial product by Pacific Antenna (www.pacificantenna.com).  You can also contact the designer by visiting ka5dvs@arrl.net.

That's about all for this week.  Have a good, safe, and productive weekend.  Until next time,
Aloha es 73 de KH6JRM--BK29jx15.