Hustler 6BTV Vertical with Bouncing SWR

[KB3MDT]

Hi,
    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?

    Thanks.

73
Ken
KB3MDT   

 

[N4NYY]

Make sure there is no water in the traps. Check the piping connections at the clamps making sure is has not oxidized. Check the feed to make sure that has not oxidized.

[KB3HG]

Fine scotch brite, then jewels rouge followed up by No ox at the joint. possibly check out DX engineering web site followed by W8JI.com . Theres much back ground work on the site. Then he is another couple of pages to read.
http://www.mosley-electronics.com/pdf/cleaninginstructions.pdf

[K7MH]

What is the Recommended spray to use on the aluminum tubes where they overlap to ensure good electrical contact?

There is a conductive copper paste you can get for that. KLM used to include some with the KT34A.

[KU4GW]

GB Brand OX-400 Anti-Oxident Paste Compound

[W5DQ]

1) What should I use to clean the Aluminum tubes where they fit into each other?   Is fine sandpaper okay?

NO SANDPAPER - Creates rougher surface - even high grit numbers. Use 00 or 000 stell wool and polish them smooth.

2) What is the Recommended spray to use on the aluminum tubes where they overlap to ensure good electrical contact?

No spray. Use No-OX (available in small tubes from most ham supply) or Butternutt 'copper grease'. Do not use an regular oil or lube on the joints. Will not allow good metal to metal 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).

Make sure all solder joints are solid and then cover them back up. You should not need to mess with the rivets unless corroded.

4) What do you recommend I do as the next step?

Does the SWR jumping occur during a wind or sitting still? Is the tube clamps between section VERY tight. When I assembled my new 6BTV a while back, I found I had to REALLY crank down to get the tubes to not slip after I put on a very fine layer of No-OX. Ensure your radials are secured too. Are you using any feedpoint impedance loading coil (like the one from DX Eng)?

Good Luck. Let us all know how you progress.

Gene W5DQ

[WA3SKN]

You have a bad connection somewhere.  Get a dummy load and install at the antenna base... do you still have the problem?  If yes, check the coax and connectors.  IF no, then start checking all the antenna connections for corrosion, etc.  A simple ohmmeter can be used here.
Good luck with the project!
73s.

-Mike.

[KB3MDT]

Hi,
     I took apart my 8 year old ground mounted Hustler 6BTV after labeling all components and recording all measurements.  This included the traps.  I used a brown Scotchbrite pad designed for metal from the hardware store and Kitchen 409 Cleaner to clean the outer surface of all the aluminum tubes.  I also cleaned up the last 9 or so inches of the inner surface of any of the connecting tubes that slide over the trap tubes.  (I.e. all places that should have electrical contact).  I wrapped the Scotch Bright around a stick to clean inside the ends of the connecting tubes.   I cleaned the smaller inside end of each of the trap covers also.   I inspected the traps carefully and found only minor surface oxidation on the rivets and solder joints.    A quick brushing with a brass wire brush cleaned them up.  Don't brush or Scotchbrite the trap coils - you could mess up the enamel wire insulation.   

     Once everything was clean, I started putting the antenna back together.  I reassembled the antenna using the dimensions on the tubes and Traps that I recorded before disassembly.
 I used new trap covers from DX Engineering as the originals were split and had been repaired with Electrical tape.  I used Penetrox to "grease up" all places where the tubes fit inside one another.  I stripped about half of the original Stainless Steel clamps when I tried tightening them up nice and snug.    I bought new Stainless Steel Hose Clamps from a local auto store to replace the stripped clamps.    I also replaced the Pig Tail Coax Cable on the bottom of the antenna. 

     With everything back together  (including my homebrew 12 and 17 meter modifications) I started tuning up the Antenna using the SWR meter on my ICOM 718.   It took about 25 Trips up and down from the basement to make measurements and then go outside to adjust the antenna.    I'm glad I have the DX Engineering Tilt over base.  Its a life saver.   I now have 7 of the 8 bands tuned to lowest SWR at the PSK digital frequencies.  I settled for a SWR of around 2 on the 17 meter modification as it interacted with the 10 Meter band.  I decided lowest SWR for the 10 Meter band was more important.  My tuner can tweak the 17M band without any issues.   Note, I have around 50+ ground radials of various lengths (i.e. as long as would fit in my yard) buried in the grass.   This improves antenna performance, but also makes tuning by adjusting the tube lengths (by sliding them up and down - NOT CUTTING) and traps a little more challenging.   

    Problem solved.  No more "jumping" / "sporadic" SWR changes while transmitting.   I hope this "tuneup" is good for many years.   Maybe even more as I used Penetrox instead of WD-40 as the lubricant and protection from Oxidation.  Hint - Never use WD-40 as its the wrong stuff and may have been the cause of my problems. 

   One last word of advice if you are refurbishing a Hustler Vertical Antenna.  Make sure you download a copy of the DX Engineering instructions for the Hustler BVT-6 antenna, especially if you plan to dissemble the traps.  The instructions are much better and include information on adjusting the traps.   The Hustler instructions don't include this information.   

   Pictures of the antenna are on http://qrz.com/db/KB3MDT

73
Ken
KB3MDT

   

[N4NYY]

I used a brown Scotchbrite pad designed for metal from the hardware store and Kitchen 409 Cleaner to clean the outer surface of all the aluminum tubes

This is really overkill. The method is fine, but I would only clean the tubing joints that come in contact with each other. The aluminum oxide that forms on the outside of the tube would actually protect the aluminum.

I am glad it worked. The one thing about this antenna is that you really need a short pigtail and analyzer to adjust it outside. I too, had to make the 25 trips up and down and it got tiring. My problem was I had all the bands in check, except 20M. I emailed the company and they had me adjust the trap ever so slightly, and 20M then fell into place.

FWIW, I never used any anti-oxide or conducting grease on any joints and never had any issues. However, that is a pretty good idea. and would do it if I ever own another one of these.

And yes, DX engineering is just a superb company.

[AC5UP]

I used a brown Scotchbrite pad designed for metal from the hardware store and Kitchen 409 Cleaner to clean the outer surface of all the aluminum tubes.

This might be irrelevant thanks to product development, but back in the 70's when I spent a fair amount of time with 600+ pounds of Honda between my legs it was common knowledge that '409 would pit aluminum. Fantastic spray cleaner was the preferred product back then and if I had plans to rebuild an aluminum antenna I'd probably swing by the local scooter shop to see what's the hot tip for cleaning a vee twin............