Fox hunting bidirectional loop

this type of antenna is a Receive Only antenna.  when hunting RF signals you are triangulating RF signal strength. you do not need to transmit.   This antenna is a simple one to build and it can be fashioned out of any type of wire from a coat hanger to brazing rod or even aluminum rod or copper tubing.   I fashioned this one from aluminum rod left over from the LPDA project.

Using a tubing bender, or by hand bend the antenna conductor material in a complete 7 - 8" circle. Now  cut the circle into two equal halves.  Now take a piece of non conductive material, like CPVC TEE which I used and cut it in half and drill two holes. One hole in each side of the tee. flatten your antenna rod half and drill a similiar size hole in that. and fasten with #6 nut and screws. At the top of the loop slip a piece of shink tubing over both ends, but be sure to maintain a air gap of 1/2" between the ends of the loop.
 now you can connect a bnc or sma connector, whichever is needed to connect to your handheld.  Connect the short coax just like a dipole.  center to one side and shield to the other.
 It is that simple to build a bidirectional fox hunting antenna.

The 4 element LDPA

This is a new take on an old design. This author read a article couple of years ago in January 2010 QST magazine about this antenna and the success that author had. I had to build one to see for my self. what I discovered in building this antenna is there are many varying factors that will lead to a success or a failure. Those factors are the type of coax used to feed the antenna, the element spacing and the double boom spacing.

The idea behind the Log periodic Dipole array(LPDA) is very simple. The antenna is driven from the end elements, and the mast. the mast or boom is separated and insulated from each other. Thus. the coax is connected with the center lead to one side and the shield to the other side of the antenna.
This 4 element LPDA being built entirely out of aluminum, is very portable and light weight. it is also very directional and has a high gain.
 The Feed line variable;
You will want to  feed with RG-58 U coax in an odd multiple of 1/4 wave lengths of 2meters. feeding the antenna in this manner it has a broad band coverage of 1.3:1 at 140 MHZ to 1.2:1 at 150 MHZ with a dip of 1:1 at 144 to 146 MHZ. This author discovered that using RG-8U or the mini 8 coax  caused undesirable readings and performance.
Construction ;
the antenna boom is constructed of two (2) pieces of 3/4" aluminum angle cut at a length of 23 1/2".  starting at one end you can mark holes for drilling a 1/4" hole in both angles.  You can clamp both angles back to back to drill.

Hole spacings ;
1)  1" from end
 2)  4"
3)  8"
4)  12"
These are for your antenna radials to mount to.  Now, unclamp your mast and switch it so you can drill through the other half of the angles.  put the undrilled sides back to back.  This will allow you to drill boom spacing mounts and antenna mounting points.
boom Spacing measured from same end as Radial #1 hole.
1)   6"
2)  18"
Okay now your boom is almost complete. You can begin to assemble it.  you will need (8) 1/4"x1/2" bolts, couplers.  These are for your antenna radials to mount two.
For your boom spacing, you will need (2) 1/4" x2" nylon screws and (6) 1/4" nylon nuts.  start with a boom spacing of  1/2". 
For the  eight antenna radials,  you'll need to cut 1/4" aluminum rod into the following lengths.
4) 19 3/4"
3) 17 3/4"
2)  16 1/4"
1) 16"
Now that you have (8) radials cut you need a way to mount them.  on one end of each radial you will need to install 1/4"x20 threads about one inch long.  This will allow enough threads to install locking nuts on each radial.
Feed Line installation.
As discussed earlier in this blog, cut an odd length  multiple of 2m.  Using RG-58U coax.  strip and separate about 4" of the coax.  I recommend soldering on lug rings that will attach under the #4 couplers. Remember, center lead to one side of boom and shield to the other.  I also installed a ferrite core along the coax 6" from the feed point.

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.