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Monday, February 6, 2012

The 75/80 extended efficiency mod to the 4-btv/5-btv Antenna!(Revisited)

First build a 40 meter trap with a 3/8 24 bolt to connect to the top of the BTV. The following link is the easiest I have found!

After you have completed your trap screw it to the top of the BTV and add about 26 feet of wire in a flat top or Sloper configuration running from the top of the trap. Trim the wire until it is resonant on your favorite part of the band. My wire liked about 22 Feet of wire for around 3.850.

Here is a SWR curve of a bone stock 5-BTV with a very decent radial field(BLUE) and my new SWR curve of my modification! (RED) I measured all of the curve with 100 Watts on a IC-746 that is very accurate! Also there are no Coils,matching devices, Balun/unun's on the antenna during the test. Just strait Radio and 50 Feet of RG-213. I also have about 30 30 foot radials down.
3.5 Mhz has a 4:1 or so SWR and 3.6 has a 3.5:1 that's makes the entire 75/80 meter completely useable with a tuner.3.2Mhz to 3.9Mhz SWR is useable without a tuner at all!  My tuner sucks ass and works fine for the whole band!

Good luck and have fun with a more efficient 80 meter BTV.

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