4BTV Vertical - Modification 17M & 30M
The 4BTV is a vertical antenna with 40M, 20M, 15M, and 10M bands and can also operate on 80M with an additional 80M mobil antenna (5BTV). I saw several articles on the Internet on adding wire dipoles for 17M and 12M off the side of the 4BTV antenna. I added a 17M dipole off the side and it worked great. I then decided to add 30M similar to the 17M dipole. I searched the Internet and didn't find any modification for 30M. The manufacturer has and 30M modification by changing the top 1 1/4" tubing and adding a 30M trap.
I cut 2 - 18" long PVC sch. 40 pipe. I drilled a 5/8" hole through one side (only) and a smaller hole through the other side. I used a # 12 self tapping screw to hold the bars onto the antenna. I placed one just above the capactance hat and the other on the top part of the mount. The bar is about 1 foot higher than the required 12.9 feet long, so you will need about a foot long wire with an insolator for the end. I used # 14 enamel wire for the dipole. The wire will be approximatly 9" from the antenna and shouldn't effect the operations on the other bands.
17M Add-On Modification
30M Add-On Modification
The 4BTV antenna is only approximately 18 1/2 feet high + mount and the 30M modification needs 23.4 feet of wire. I used 1/2" sch. 40 PVC pipe to make an extension. It is approximately 3 feet in height. I use a U bolt to attach the extension to the 4TBV. The aluminum tubing is 1 1/4" in diameter so you should get a 1 1/2" "U" bolt and it should be at least 2" long. You can get these at Lowes or Home Depot for about $ 2.00. You will also need to purchase some 1/2" PVC Sch. 40 pipe and 2 - 1/2" elbows. You will also need some PVC cement fot putting it all together.
I used # 14 enamel wire for the element. You could use almost any wire but I usually use # 14 enamel wire for most of my antenna so I usually have some on hand to use.
Modified 4BTV Antenna with 17M & 30M