I have a Ground Mounted Hustler 6BTV Vertical with about 50 radials buried just under the grass. The antenna is about 8 years old. Everything was tuned up with SWR under 2.0 on all bands and worked okay until recently. The SWR on the antenna "randomly jumps around" from under 2.0 to above 8.0 on 10, 15 and 20 meters. At first I could use the antenna for an hour or so before the jumping SWR occurred. Now I can usually reproduce the problem on at least one of the bands in about 2 minutes. I've spent the weekend troubleshooting my rig, my Antenna Tuners (Usually on Bypass for this antenna), Coax, all connectors, Lightning Protection etc. I don't think they are the problem. The only thing I didn't remove or replace during testing was the coax. It's only 6 months old. Just to play it safe, I attached a dummy load to the Coax at the base of the antenna (instead of the antenna) and repeated my tests. I didn't see any jumping SWR problems with the dummy load and Coax.
I have an ICOM 718 Transceiver. I also have a homebrew Fan Dipole for 80-40-20-10 Meters. I don't have any problem with the Fan Dipole. I don't have an amp. I have never used more than 100 watts on either antenna.
I then started examining the antenna. I had homebrew mods for 12 and 17ms on the antenna. (Basically wires running in parallel to the antenna). I took them off. I replaced the "pigtail" at the base of the antenna. I slid the covers off of the traps. The Coils are fine, the solder joints on either end of the connections look grey, and the rivets holding the ends of the coils to the aluminum tube showed a little rust on the "head". However, the connections were not loose and looked physically sound. The Trap Covers act as capacitors - no separate capacitors are in the traps The tubes themselves show discoloration where they "slide into each other" above and below the traps. I "goofed" when I originally installed the antenna by spraying WD-40 on the aluminum tubes to help them slide in place. However, I didn't see any white oxidation on the tubes. As it was getting dark, I didn't try polishing up the tubes before reassembly. I can try this after I get the right kind of spray to use on the aluminum. I still have the jumping SWR after I put the antenna back together. I'm glad I bought the DX Engineering Tilt Base for the antenna a couple of years ago.! I have raised and lowered the antenna and been up and down the steps to my basement shack many times this weekend. Note, I don't have an antenna analyzer, I use my ICOM 718 for testing.
Pictures of the Hustler 6BTV antenna are on http://qrz.com/db/KB3MDT
. (I removed the 12 and 17 Meter Mods to simplify any problem solving).
Thus, some questions.
1) What should I use to clean the Aluminum tubes where they fit into each other? Is fine sandpaper okay?
2) What is the Recommended spray to use on the aluminum tubes where they overlap to ensure good electrical contact?
3) Should I "monkey" with the Solder connections on the coils on the traps? Drill out the rivets and replace with Stainless Steel Screws? (I think I'm asking for trouble here).
4) What do you recommend I do as the next step?