Tuesday, January 18, 2011

NVIS Antennas for the Base Station Operation

For those who live in in Mobile or Manufactured homes, maybe are restricted because of various conditions, or regulations. Here are some workable ideas that have been constructed in the Skagit Valley area by member of the Radio Amateurs of Skagit County.
This author has constructed a NVIS antenna system stretching around a portion of the back yard fence. I have a 6' tall cedar privacy fence around my back yard. Basically, what I have is a off center fed dipole stretched on top of my fence. One leg is 90' and the other is 38' . I run this through a MFJ 941 tuner. this is working just great for my operations on 80 - 40 meters. I have a three element, tri-bander for 10 - 20 meters.

Another NVIS Design is using Concrete pier blocks with PVC pipe glued in the hole of the block. This creates a sturdy support to hold the antenna wire above the roof of a older mobile home. Remember the old flat roof models? the NVIS antenna is 3' above the the roof and runs the entire perimeter of the home. the wire is cut to the 80 meter band and tunes up nicely on 80 meters and through a tuner 40 meters is good also.
Remember, the ideas behind the NVIS antenna is the RF signal is reflected off the ground into the ionosphere and bounces back to earth in a 300 mile radius. imagine a water hose shooting straight up in the air and coming down. same idea only using radio waves.