The 4BTV is a vertical antenna with 40M, 20M, 15M and 10M bands and can also operate on 80M with an additional 80M mobile antenna (making an 5BTV). This is a trap vertical, there is a trap for most bands. There is no operation on the new bands (you can now buy additional traps for some of the new bands). I saw several articles on the Internet about adding 1/4 wavelength wires on the side of the antenna. I added a 17M wire off the side and it worked great. I then decided to add 30M similar to the 17M modification. I searched the Internet and didn’t find any modifications for 30M. The manufacturer has an 30M modification by changing out the top 1 1/4” tubing and adding a 30M tap and different length of tubing.
I cut 2 - 18” 1/2” PVC sch. 40 pipe. I drilled a 5/8” hole through one side (only) and a smaller hole through the other side. Drill a 1/8” hole a each end of the pipe. I used a #12 self tapping sheet metal screw to hold the bars on the antenna. I placed one bar just above the capacitance hat and the other on top of the mount bottom. The bar are about 1 foot longer than the required 12.9 feet, so you will need an isolator from the end. I used #14 enamel wire for the element. The wire will be approximately 9” from the antenna and shouldn’t effect the operations on the bands.
Modified 4BTV antenna with 17M & 30M Modification
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 feet 4 inches. I used a 1/2” sch. 40 PVC pipe to make an extension. It is approximately 3 feet in length. I used a ‘U’ bolt tto attach the extension to the 4BTV. The aluminum tubing is 1 1/4” in diameter so you should use a 1 1/2” ‘U’ bolt and it should be at least 2” long. You can get these at Lowe’s or Home depot fo about $ 2.00. You will also need to purchase some 1/2” PVC sch. 40 and 2 - 1/2” PVC elbows. You will also need some PVC cement for 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 antennas so I usually have some on hand to use.