Wednesday, February 1, 2017

Ham Radio, an ununsual stealth antenna one foot above ground. Post #1030.

An unusual stealth antenna one foot above ground
(http://www.southgatearc.org/news/2017/february/an-unusual-stealth-aerial.htm#.WJJMLv8rLIU).
Accessed on 01 February 2017, 21:35 hrs, UTC.
Author:  John Allsopp (G4YDM).
Please click link or insert title URL into your web browser to read the full article.

Comment:

For those of us who live in deed-restricted homes or "space challenged" urban lots, the use of a full length dipole or vertical antenna is often out of the question. Your antennas of choice will be limited to what can't be seen or removed quickly as the situation demands.  Often, your antenna will be a highly compromised version of a dipole, vertical, or even a magnetic loop.  You can certainly make contacts with these antennas, but what you need is a full performance dipole on a deed-restricted lot.  Impossible? Not really, if you follow the instructions presented in this post from John Allsopp (G4YDM).

According to John, just build a standard length dipole for your favored HF band and raise it only 1-foot/0.304 meters above ground level.  Feed the low-level dipole with 75 or 50 ohm cable and use your antenna transmatch ("tuner") to control the SWR.  What you've created is a NVIS (near vertical incident skywave) antenna capable of reaching out 300 to 400 miles/486 to 648 km.  A NVIS antenna is perfect for local, regional, or state-wide nets and, will on occasion, get you a few dx contacts.  Isn't this better than having no antenna at all?  In this article, John builds a 40 meter dipole and uses it in a NVIS configuration. You can get a bit more gain by placing a reflector wire about 5% longer that the main dipole elements a few inches/cm off the ground.  NVIS antennas seem to work better for 160, 80, and 40 meters.  Military forces have been using these antennas for decades. Why not try a NVIS antenna and get back on the air?

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Aloha es 73 de Russ (KH6JRM)