Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1] 2 Next   Go Down
  Print  
Author Topic: Hustler 6BTV Vertical with Bouncing SWR - Part 2  (Read 2250 times)
KB3MDT
Member

Posts: 193




Ignore
« on: March 15, 2013, 01:50:02 PM »

Hi,
     After doing a complete overhaul of my Hustler 6BTV Vertical  (See post "Hustler 6BTV Vertical with Bouncing SWR") , I though I solved the problem with the erratic SWR and Power.   I used the antenna a couple of times and the problem came back!.   SWR jumps from around 1.5 up to 8.   I've seen the problem on both 10 and 15 meters.  I haven't tried 20 meters yet.

 I hooked up a new Dummy Load to my coax at the base of the antenna and had no issues.  Thus it looks like my antenna is still the culprit.     I lowered the antenna and used a volt ohm meter to check the continuity of the inner conductor of the pigtail to the antenna, through the traps and all the way to top of the antenna.   I wiggled the antenna while hooked up to the meter.   Resistance was almost 100% constant and was around 3 ohms (consistent with the very long jumper leads I used to measure from one end of the antenna to the other).  It varied by 0.1 ohm, which I think is well within the limit of the "free" meter from Harbour Freight.   I also did the same with the ground side of the pigtail to the ground wires.   Also a 0.1 ohm variation max. regardless of how much I flexed the antenna.

     A couple of questions:

1)   One of the trap coils had a "1/16 inch nick" on the enamel insulation on the outer surface of two adjacent windings.  I could see the bare copper wire.  However, the location of the scratch did not look like it caused the windings to short and didn't show any signs of arching.    I run Barefoot with the antenna, digital modes, no high power.   QUESTION - Time to buy a new trap?

2) The Base of the antenna is starting to show its age.   The screw at the bottom of the aluminum tube for the center conductor of the pigtail is rusted firmly in place.   Luckily the wire connector is still in one piece and I could solder the center conductor of the pigtail to it.   However, I read an article (http://www.mods.dk/view.php?ArticleId=4418) that says the screw goes into a steel insert that is press fit into the aluminum tube.   One person found water in the bottom of the tube and it was very rusty.  QUESTION - Time to buy a replacement base?   The author of the above article cut off the bottom of the tube and used an expansion bolt to make a new contact.  Or could I just drill a small hole about 1" from the base of the tube (i.e. directly in the side of the tube) and use a stainless steel screw for my pigtail connection?    I realize I may have to tweak the tuning as the antenna would be slightly shorter.   

3)  Any other ideas?   Thanks.

73
KB3MDT
Ken

Logged
KK5J
Member

Posts: 76




Ignore
« Reply #1 on: March 15, 2013, 02:08:23 PM »

I have had a similar experience with the 20 meter resonator. Insulation between two adjacent windings wore away. Typical VOM resistance measurements won't really see that kind of problem, which I attributed to flexing in the wind. SWR will vary or ramp up suddenly for no apparent reason. I replaced the resonator and moved on. I also guy the 6BTV now.

I managed to get the center screw on the base of the 6BTV loose after first time seeing corrosion. Now I check it regularly and remove whatever corrosion is there. I'd try to get it out before buying a new base. Thats up to you, but the screw may be cleaned and reused if its not totally gone. The screw is what actually corroded, the base was in good condition as well as the associated threads.

Water is always a problem, but regular maintenence of that screw makes it a non-issue. Mine begain rusting within a year of installation.
Logged
W8JX
Member

Posts: 5467




Ignore
« Reply #2 on: March 15, 2013, 04:43:28 PM »

My screw seized up a several years ago. I drilled a hole in side of mast at bottom of base and feed it there now with no problems.
Logged

--------------------------------------
Entered using a  WiFi Win 8.1 RT tablet or a Android tablet using 4G/LTE or WiFi.
KB3MDT
Member

Posts: 193




Ignore
« Reply #3 on: March 15, 2013, 08:04:31 PM »

Hi,
    I did some more testing of my antenna this evening.  I removed my 12 and 17M mods to simplify everything.   I have erratic SWR  (I.e. goes from 1.5 to 8 at times and back again without changing frequency or power levels) on 10 Meters and 15 Meters.   Before refurbishing the antenna I had the same problem on 20 Meters.  Now 20 Meters seems to behave OK (well almost) with SWR moving between 1.25 and 1.5 at times even though frequency is constant.

    Do these symptoms point to the 10 Meter trap being defective?   (I.e. intermittent coil connection to aluminum tube or intermittent short between coils.)   Do you think its the 10 Meter trap?  Replacement traps are about $41 plus shipping from DXEngineering.   I'd like to identify and replace the bad part the first time around.   I can almost buy a whole new 6BTV antenna for the price of four replacement traps  (10-15-20-30 Meters).  Throw in a new base (because the center screw that connects to the coax is rusted tight) and its cheaper to buy a new antenna.    :-)

    Thanks.

Ken
KB3MDT
Logged
KK5J
Member

Posts: 76




Ignore
« Reply #4 on: March 15, 2013, 08:56:00 PM »

Which resonator had the defect? Does 20 mtrs still have an SWR problem or not? At one constant frequency the SWR should be solid.
Logged
N4CR
Member

Posts: 1650




Ignore
« Reply #5 on: March 16, 2013, 04:28:29 AM »

I've seen the problem on both 10 and 15 meters.

This alone should tell you all you need to know.

If the problem is on 10, it's extremely unlikely that the trap is shorting out and an open would really not be a problem creating 8:1 magnitude on 10.

I suspect your problem is at the feed point or feed system.
Logged

73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
SM5MDN
Member

Posts: 27




Ignore
« Reply #6 on: March 16, 2013, 03:45:07 PM »

I just fixed the same problem on my 6btv, cant get at the old coax as the ground is still frozen solid with a foot of snow over it, so I laid a new coax and re done the pig tail and all is well again, just buried the coax under the snow for now until the ground thaws out, started out with high swr on 40 meters that would not tune out no mater what I done, then my new amp turned up and that killed the swr on all bands, but the new coax fixed it all back to normal now
« Last Edit: March 16, 2013, 03:49:21 PM by SM5MDN » Logged
WB0CJB
Member

Posts: 38




Ignore
« Reply #7 on: March 16, 2013, 06:54:35 PM »

Whenever you have an issue with a trap on a 4/5/6BTV you can take the trap apart and re-do the connection. I had a trap get damaged by a neighbor catching one of my guy ropes with his riding mower and pulled the antenna over, bending the 10 meter trap 90 degrees just below the clamp on the bottom of the trap. As I have had a couple of traps go "bad" on me during my last interstate move I took the extra 10 meter trap I had and took it apart. I found the bad trap had corrosion where the coil was riveted to the aluminum tubing.Such corrosion is caused by water getting into the trap through a cracked trap cap.Eventually the corrosion made the trap go bad (lost continuity).

I drilled out the two rivets that ran through the tubing being careful not to make the holes bigger and drove out the two rivets. Taking some fine emery cloth I cleaned up the brass terminals that are soldered to the ends of the coil (be sure to get under these terminals as well), as well as removed the corrosion that was on the aluminum tubing. Once everything was nice and clean I went to the local hardware store and purchased a couple of 1 inch screw posts. Reattaching the coil wires to the aluminum tubing using the screw posts gave me a good electrical connection. Once I checked the continuity of the trap with an ohmmeter I sprayed the coil connections with clear Krylon.I re-assembled the trap and put a new trap cap on and shined up the trap joints using a Scotch Brite yellow/green scrubbing pad. If you use steel wool it can leave microscopic bits of steel wool and can eventually mess up the connection.

I used the vertical at last year's Field Day and the trap performed flawlessly. Even though it was an old trap it worked like a new trap and saved me over 40 bucks.Again the vertical will be used at FD and once its over I plan to re-raise it at my home QTH, making sure that there isn't any possibility that someone can pull it over again with a riding mower.I can't wait to have it back in the air again and making all kinds of contacts!!!

In case you wonder why I don't have it up already I have a backup vertical that I'm using right now that I put up when the 6BTV got damaged.Its a Cushcraft AV-4 and is not as good as quality as the 6BTV.

Logged
K5LXP
Member

Posts: 4448


WWW

Ignore
« Reply #8 on: March 18, 2013, 05:59:38 AM »

Is the problem power sensitive?  An intermittent connection would present this problem no matter what the power level (or even receive), but something "arcing" would require a certain power level.  Basically, test it at say a watt or two and then 100W (or more) and see if the problem's the same.  Might help to isolate it.

Mark K5LXP
Albuquerque, NM
Logged
K8AXW
Member

Posts: 3666




Ignore
« Reply #9 on: March 18, 2013, 09:36:50 AM »

Ken:  Sounds to me like it's time to take the antenna down and completely refurbish it!  This means cleaning all aluminum contact areas.  (where tubes slide into tubes) with steel wool. 

Replace all screws, etc with stainless steel. If you have a sealed base, open it up with a drill bit so water will drain. 

Clean all wire to aluminum contact areas and refasten these contact points with the stainless steel screws.

You can do as your billfold and free time leads you but before I'd go and buy anything I'd tear the whole thing apart and clean it up finishing with stainless steel hardware.

Logged
N4CR
Member

Posts: 1650




Ignore
« Reply #10 on: March 18, 2013, 01:36:53 PM »

This means cleaning all aluminum contact areas.  (where tubes slide into tubes) with steel wool.

I must disagree with using steel wool on aluminum. The steel particles imbed into the aluminum and rust. A green scotch brite is a better way.

Also, put some penetrox on each joint so they don't corrode.
Logged

73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
N4NYY
Member

Posts: 4742




Ignore
« Reply #11 on: March 18, 2013, 01:51:58 PM »

This means cleaning all aluminum contact areas.  (where tubes slide into tubes) with steel wool.

I must disagree with using steel wool on aluminum. The steel particles imbed into the aluminum and rust. A green scotch brite is a better way.

Also, put some penetrox on each joint so they don't corrode.

If you use 0000 or 000 steel wool, the fibers are so thin that they rust away to nothing. I also use a compressor to blow anything away. I have used this method with my 5BTV and there was never a problem. The thicker steel wool could cause a problem.
« Last Edit: March 18, 2013, 02:38:58 PM by N4NYY » Logged
K5LXP
Member

Posts: 4448


WWW

Ignore
« Reply #12 on: March 18, 2013, 02:21:33 PM »

I must disagree with using steel wool on aluminum. The steel particles imbed into the aluminum and rust. A green scotch brite is a better way.

Green scotchbrite is OK if you like a "brushed" look.  0000 steel wool will leave a near-mirror finish and while this technique is not recommended for aircraft, it was specifically recommended to me by Mosley because that's what they use.  It works great for antennas.  I apply a coat of auto paste wax after to prolong the polish a while in the weather.


Mark K5LXP
Albuquerque, NM
Logged
W8JX
Member

Posts: 5467




Ignore
« Reply #13 on: March 18, 2013, 02:36:08 PM »

I must disagree with using steel wool on aluminum. The steel particles imbed into the aluminum and rust. A green scotch brite is a better way.

Green scotchbrite is OK if you like a "brushed" look.  0000 steel wool will leave a near-mirror finish and while this technique is not recommended for aircraft, it was specifically recommended to me by Mosley because that's what they use.  It works great for antennas.  I apply a coat of auto paste wax after to prolong the polish a while in the weather.


Mark K5LXP
Albuquerque, NM

While you want to clean connections, little is gained polishing the antenna overall as it actually increases its deterioration. As aluminum weathers it forms a oxide layer than slows further oxidation. Removing this oxide looses a few thousandths of aluminum and open door to further accelerated loose vs what you would see without polishing. Also while it might not be case here sometimes aluminum is coated with a very thin layer of pure aluminum (called Al Clad) that is very resistant to weathering, polishing will remove it. 
Logged

--------------------------------------
Entered using a  WiFi Win 8.1 RT tablet or a Android tablet using 4G/LTE or WiFi.
N4NYY
Member

Posts: 4742




Ignore
« Reply #14 on: March 18, 2013, 02:41:50 PM »

Quote
While you want to clean connections, little is gained polishing the antenna overall as it actually increases its deterioration. As aluminum weathers it forms a oxide layer than slows further oxidation. Removing this oxide looses a few thousandths of aluminum and open door to further accelerated loose vs what you would see without polishing. Also while it might not be case here sometimes aluminum is coated with a very thin layer of pure aluminum (called Al Clad) that is very resistant to weathering, polishing will remove it. 

I think we specifically mean to clean the pipe joints with steel wool. Not the whole antenna. I would never remove oxide as it actually protects the antenna. Only remove it at the connecting joints.
Logged
Pages: [1] 2 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!