The NVIS is like any other dipole. Its about 66 feet long on 40 meters . I use a 1:1 balun and 70 ohm RG6 but after that it gets weird. It must not be over 7 feet 3 inches off the ground!! Then it must have at least one reflector cut about 5% longer than the driven element just pinned to the ground. What you have is a 2 element parasitic pointing straight up! If you have to mow just take the end pins out and coil up the reflector and set it aside while you mow. In fact just put one under your fence support and don't coil it up when you mow.
I now have 6 ground reflectors. They are obviously reducing ground loss .You can use the number of reflectors that are practical for you.All you really need is 1.
I use my fence as the primary support (see photos below) and I used fiberglass spreaders to extend to the 7 foot three inch level. To avoid sag I use an extension supports about every 10 feet or so. I attach the fence post extenders wit electric tie. I space my reflectors about 4 feet apart but I don't think it matters. When I placed one 20 feet from the center reflector I saw more TVI on my tv monitor in the shack so I moved it in until it stopped. I do think that you drop the angle of radiations by moving the reflectors out because I do get out of my back yard and that may be the reason.several nice qsos over 1200 miles out but the biggie on November 16 2011 was Andy, HB9CVQ 5301 miles with 500 watts and OV1CDX 5042 miles with 800 w. Hilarious from 7 feet 11/16/2001 Ok I challenge anyone to break this record, LZ1JPk 900 watts nvis at 7 feet. Go gettem boys-
This antenna is vastly underrated. I use it with 200-250 watts out but it matches reports on almost any one with 100 watts on any antenna..My SWR is dead flat. . It is not a DX antenna-- I enjoy many stateside chats.
It dawned on me that for deed restricted areas or old guys like me who don't climb anymore-- or hams that like to" keep it simple" This antenna has great utility and absolutely has been over looked. Give it a try. Ask any questions you have at firstname.lastname@example.org and I'll try to help. Use your imagination on the supports at 7 feet. This antenna does not work above 7 mhz and is just too big on 80 to be practical. Good Luck!!
Here is the feed line going to the Balun at the center mast.This is a fiberglass support attached to the fence post with electrical ties. Keep it simple!!
Another shot down the fence line.
Try it with 5 ground reflectors !!!
I call it the w5zo 40 meter NVIS
GOOD LUCK AND 73!!! Mike