Antenna strengthening

[KD6VXI]

I have a problem.....  ICE.

I realize this might not be the appropriate forum, if not, please put it where it belongs, moderators...

I'm attaching a pix of my 10 meter vertical (with the leader for the HF vert trailing off, and another leader that lost it's wires in the iceload last night, but I'll fix that next time Mr.  Sun decides to come out...  It's COLD out there!

This is a HIGHLY reinforced vert, double walled with a small 6 inch piece of slip-tubing at each vertical joint to step down to the next size. 

As you can see, the ice load makes it a bit hard to 'stand erect'

Any ideas?  Anyone tried reinforcing internally with wood?  Anything else?  I can live with the matching hairpins being encrusted in ice, those can be heated....  BUT, the tuning does suffer when your vertical element becomes a horizontal element!

Thanks, in advance...  Enjoy the ice pictures from sunny, snowy Southern California!

[KD6VXI]

Nevermind, I guess.  It's now laying on the ground.

HOWEVER, if anyone has any ideas, I'm still interested in them   Just for the next iteration....

[K5UJ]

I've always figured with ice, that beyond a certain amount, it's game over (but this depends on your structures, wire gauge etc.).  Ice wins.

Ice is what brings down TV towers--massive Magnum solid steel towers with 6 foot faces.  If a guy can't afford a VOA grade dipole, he's better off setting up some weak link...something cheap and easy to fix that will snap under a real heavy load and save his tower, masts, more expensive stuff.   It's better to have a dipole or something fold than have it buzzardly hanging in there only to have its support masts fold over.

Ice and wind...short of a tornado or hurricane or direct lightning hit, ice and wind together are antenna killers.

[KD6VXI]

Pretty much my thoughts, too.

Bummer, it was a REALLY good performing antenna, presented a perfect match (the mfg includes tuning instructions for 30+ mhz down to the bottom end of 12 meters).

I've posted a copy of the pictures in the forum the manufacturer lurks in (it's a sideline job, NOT his 'real life job', so to speak), and we shall see how they handle it.  I'm confident that the broken piece will be replaced....  I'm really interested to see if he can come up with a stronger method..  Thicker walls, I guess.

Interestingly enough, the antenna was tested to 100 mph.  They convinced a couple radio enthusiast lokel yokel cops to let them hit 100 with a prototype antenna mounted in the back of a pickup truck.  Guess my 100 mile an hour winds and 2 inches of ice was too much

--Shane
KD6VXI

[K1JJ]

Interesting that the vertical portion is leaning over like that.

The only thing you can do is guy it, use a larger diameter tubing or add some more internal sleeving to effectively increase the wall thickness.

After all, as an extreme example,  a 10" diameter pipe would handle most any ice load as well as a well guyed tower.

In your case I would opt to slide in some sleeving to stiffen it up. Probably just one additional alum sleeve would do the trick. It may still bend but only a small amount and spring back afterwards.  Texas Towers has tubing that would probably be a perfect diameter fit for you since most antenna manufacturers pretty much use the same aluminum schedules.

T

[KD6VXI]

Tom,

Thanks for the input...  I was hoping someone with lots o antenna experience would chime in...

I just looked over the instructions:  They are pretty detailed.  Looks like it starts out at 1.25 OD aluminum tubing, and is 1/8 wall all the way top to bottom.  There is a 4 inch sleeve twice that extends 3 inches into the next larger section and extends 1 inch above to strengthen the joint when he had to go down from say 1 1/8 to 7/8 inch.

The bottom failed (I'm assuming) at the point where the teflon insulator ends....  If not, right above that area.  As far as I know, I'm the FIRST one that has failed, out of 575+ in the field....  Interestingly, the antenna is locally built and designed for exactly this area   Maybe I just had a weak piece of aluminum and it showed...

I believe Jay told me in the past that he purchased the aluminum from DX Eng.  We have a supplier semi-locally in Bakersfield, but I'm not sure the quality of their products......  IE, dunno if they carry decent stock for what we need....  Could be brittle, etc.

Incidentally, someone on another forum had a thought of using that yellow spray foam and filling the entire antenna with it.  Might work in strengthening it, but another brought up the swaying 'element' into the equation and thought that it might break the spray foam up over time...  Any thoughts on that?  It'd be pretty hard to ensure their where no air bubbles, but it might work....

I think your method would be the best...  BUT, I'm afraid that the failure is going to be at the 'center insulator'...  If that's the case, a sleeve on the outside maybe?  Would PVC (assuming I could find the proper ID) slid over that section provide any REAL WORLD strength, or you think that would be antenna voodoo?

Antenna worked AWESOME before this...  I'd like to get it back up, 10 was opening up when I heard the thud   The 80 meter vertical is about 3 s units below this antenna, on 10 and 12.

Thanks, again.

--Shane
KD6VXI

[KD6VXI]

Was just informed it's 6063 aluminum....  I thought it was 6061-T6.

Is their THAT much difference between them? 

--Shane
KD6VXI

[K1JJ]

Boy, 1.25" dia at 1/8" wall is pretty strong stuff. Maybe it WAS the insulator that failed.

For the tubing, I would stick with additional alum tubing sleeving to increase wall thickness.. Don't bother with the foam.

Whatever alum you can get to slide inside properly with a good fit will be fine.

As you know most of the bending moment/load is at the base and gradually gets less as we go higher up the whip. So you may only need to reinforce the first 1/3 bottom area, etc.

The Teflon insulator is another issue and you'll have to check around to find a bigger and stronger part to replace it if needed.   Even a larger tube of PVC pipe that fits well could be slid over the original and fastened with clamps for more strength.


T

[KB2WIG]

Maybee address the ice buildup??. Here in the grate white north, ya can buy various pipe,  flashing and sidewalk electric heaters to keep the ice away.


klc

[K6IC]

Shane,

Sorry for your loss.

DXEng 6063-T832 0.058" wall drawn tubing:
http://www.dxengineering.com/Products.asp?ID=279&SecID=136&DeptID=43

DXE 0.120" wall drawn tubing is 6061-T8:
http://www.dxengineering.com/Products.asp?ID=304&SecID=136&DeptID=43

Radial Ice plus wind are not a great combination.  I'd listen to JJ Tom and others who build REAL antennas.

72  GL  Vic  K6IC

[flintstone mop]

I had a crappy GAP 45 foot antenna for 160M do the same thing in strong winds and icing.
Top half bent over and it killed itself. Cut it up and threw away, and discovered about 100 feet of coax stuffed inside.
Bought a short Unihat antenna 30 feet tall (1995) AND now (2008) a Cushcraft 27 foot top loaded vertical and never looked back.

Great performer now with the elevated radials
Fred

[KD6VXI]

Heres some pix I took with the digi camera out in the sun today.

The aluminum either bent above, or at the center insulator.

From what I UNDERSTAND, it's ALREADY double walled from the insulator up for a section....  Maybe to where it failed, again I'm going to have to wait probably 1 more day before the crank-up tower can actually be cranked down:  The area where the two sections come together is still iced up ...  However, I heard that second hand, I haven't heard from the person who builds them. 

He asked me for some pix, so I went out and snapped up some more today and checked in here, too.

DX Engineering is where the antenna material came from already  

In speaking with the person who built the antenna and markets them, this is the first failure in > 7 years that can be attributed to the antenna.  One other one came down, but so did the 100 foot tower it was on....  All due to ice loading.

BUT, I had a 31 foot vertical monopole up before this, and it survived two winters, so I KNOW it can be done...  I'm really starting to believe there was a weak spot in the aluminum.....  BUT, it WAS flexing pretty good in the storm.

--Shane
KD6VXI

[W1ATR]

Ahh the interceptor 10K. Wasn't cheap, but it's a nice antenna. I think he'll make good on it.

[KD6VXI]

lol..  Someone else knows of Jay's antennas.

When he was starting out modifying old CB antennas they found in the Mojave desert, I helped him out a lot with the theory and such.  Jay and I have had a semi-symbiotic, if not semi-rocky relationship for a decade ++....  He's already been in touch with me, I sent him copies of the pictures, and he's looking up what can be done to strengthen my antenna.

From his reply, this is actually a point designed to fail.  The antenna is rated for 100 MPH, or a large ice load, not both.  He acknowledged I get > 100 mph wind up here, and the gusts are > 125 (as high as my old wind indicator would read), so I need robust.  I've already decided that aluminum antennas aren't going to be the most reliable   Wire it be.  The inverted L ground plane worked throughout the entire storm:  BUT, the tuning was changed a LOT.  I got RFI in the shack on bands not before, and some bands that I could tune flatly before would only get 1.8 or so.

SO, the mfg is looking into strengthening and what it will take.  The Delrin or Teflon center insulator made it, the initial double walled aluminum from the center insulator appears to have made it, and the antenna folded at the "100 mph" point, as designed.

Guess I need a stronger antenna.  Or just load up the tower

--Shane
KD6VXI