After several weekends I was still having problems with my Hustler 6BTV Vertical and erratic SWR. I just finished rebuilding the four traps this afternoon. Two of the traps had rust underneath the steel rivets that fastened the trap coils to the aluminum poles. I ground off the heads of the rivets, cleaned everything up, and used brass screws as replacements for the rivets. I used Penetrox on the electrical connections as I did the reassembly. I used my bench grinder to remove the ends of the screws extending beyond the nuts so that they were flush. Otherwise, the bottom of the screws would have been too close to the aluminum trap covers for comfort. For good measure, I ground off a little of the screw heads also to play it safe. Note, I only run 100 watt max, not legal limit. I used a center punch to make a small depression at the "thread boundary" of the screw and nut to help lock them in place. (at least that's the theory).
I put everything back together and ran some tests. Still the occasional erratic SWR, plus I couldn't get the SWR below 2.5 on 15M. Grumble, Grumble, Growl. Its only 30 degrees outside with occasional snow flurries. I removed the antenna base and took it completely apart. I removed all the scale on the plastic insulators, and checked for any arc traces in the plastic. Everything looked good. I put everything back together and did more testing. Still the occasional erratic SWR.
I decided to "reinspect" (i.e. remove tape) the barrel connector between the main coax line and the "new" antenna pigtail I installed 2 weeks ago. It seems raising and lowering the antenna about 100 times on the tilt mount caused the connection to come loose. Plus, the "new" $1.99 PL-259 barrel connection already had some oxide on the center pin. I went to my parts box and found that some of the "Brand New" barrel connectors also had traces of oxide. I found a good barrel connector, tightened up the connection, and taped it all back up.
More testing, and still problems. I temporarily replaced the entire RG-213/U coax run (about 100 feet) with some used RG 8/U coax. 15M SWR dropped from 3+ to under 1.75. Okay, something must be up with my feedline, even though its less than 1 year old and worked perfectly with a Dummy Load instead of the antenna, one of my first tests.
I decided to take the RG-213/U coax directly into my shack, bypassing the New Alpha Delta "Spark Arrestor" (I replaced the old one last week). This also eliminated a 10 foot section of RG 8/U that ran through the wall from the Spark Arrestor to my Tuner. Last week I replaced every cable in my shack except this piece of RG 8/U because its a pain to replace. I thought it was a piece of Belden RG 8/U, but it turns out it was Radio Shack RG 8/U. Ahhh!
Anyway, I connect everything back up minus the extra piece of Radio Shack RG 8/U and the Alpha Delta "Spark Arrestor". **** SUCCESS *****. SWR on all bands is good, showing a lower SWR in the middle of each band than at the edges (how I tuned up the antenna). I also have lots of ground radials. I reran my tests and the SWR holds steady. No more SWR randomly jumping from under 2 up to 8 and beyond. I'll add the Spark Arrestor back in later this weekend after I make up a new cable using a piece of RG-213/U coax.
Some Lessons learned:
1) A tilt base on a vertical antenna is invaluable!
2) The Coax Feedline can be bad even if a test with a dummy load instead of the antenna looks good. I wish I had a Domain Reflection Meter (or whatever they are called) to test coax.
3) Cheap coax connectors aren't worth it. Go for the good stuff!
4) Suspect every cable in the path between your rig and your antenna. Don't assume its good just because the connectors look clean or the cable is new. Don't use Radio Shack Coax (I've heard this before).
5) Document every change as you repeat your tests. (I used a spreadsheet).
6) Corrosion is your enemy. Seal every outside connection carefully.
7) Test your antenna with a short coax cable and Antenna analyzer if possible. I did all my testing with my 100 foot run of coax and the SWR meter on my rig. The long coax run distorts any antenna SWR readings. It also meant many trips from the basement to the back yard and back every time I made a change. **** Most important, I would have quickly realized the problem was not the antenna if I used a short piece of coax from the beginning for all antenna testing ****.
You might have more than one problem, making trouble shooting more difficult.
On the bright side:
1) I got lots of exercise with all the trips up and down the basement steps.
2) All this fun only cost me $50 for a tube of Penetrox and replacement hardware (mostly new Hose Clamps).
I hope you enjoyed my trials and tribulations. The *^&$#$ antenna better work tomorrow morning!