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Author Topic: Melting Antenna Problem  (Read 840 times)
K2WH
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« on: February 20, 2002, 02:39:23 PM »

Hi, I recently built and installed a 65' all aluminum vertical for 75 meters.  The antenna is constructed of aluminum tubing, 1.5" at the bottom and tapering to 3/4" at the top.  The antenna performs great at low power (100 watts).  When I run high power, in a very short time, the antenna starts to smoke and if I continue to transmit the aluminum will start to soften and I feel if I transmit longer than this, I will have aluminum slag on the ground.  More than once I had to go out an straighten the antenna due to the aluminum distorting.  I had to wear work gloves because it was so hot.  I even had to change the guy wires to stainless steel because the original nylon guys just melted away.  Any ideas why this may be happening.  Has anyone had this happen to their antennas? Thanks.
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K2WH
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« Reply #1 on: February 20, 2002, 02:56:15 PM »

Sorry, this was not meant to go out.
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K3AN
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« Reply #2 on: February 20, 2002, 03:31:47 PM »

I bet this wasn't supposed to be posted until April 1st.  ;-)
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K5DVW
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« Reply #3 on: February 20, 2002, 03:46:03 PM »

I like to use tungsten antennas for this very reason!
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RobertKoernerExAE7G
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« Reply #4 on: February 20, 2002, 04:06:01 PM »

I have the same problem with my tower.  Once or twice a year it falls down; sometimes while I am out there checking the bolts on the guy wires.

But, then I wake up.

It is a real pain to have to go through this, yearly.  Seems to happen just after I've decide it is time to do my yearly tower check.

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N2ERN
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« Reply #5 on: February 20, 2002, 05:14:15 PM »

Re:K5DVW:

Tungsten! Neat!

If you coated it with fibreglas and sucked out the air, it would sure look purty when you ran a kW through it!
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AD7DB
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« Reply #6 on: February 20, 2002, 06:14:04 PM »

To all radio amateurs.
From: FCC, CIA, Dept of Defense, Pentagon.

Please disregard the above information. The above mentioned amateur's antenna project is now in our capable hands. Our top people are investigating this device in the interests of national defense.

(Overheard in the Pentagon: General, you should see this thing! Our new particle beam weapon is already obsolete!)
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WB2WIK
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« Reply #7 on: February 20, 2002, 06:37:06 PM »

I recently installed a cylinder of nitrous oxide under my operating bench.

I notice with changes in barometric pressure, like when a storm is coming, the cylinder or its valve fitting leaks and it causes me to start laughing, even if I'm on the air!  It's very embarrassing.

Does anyone else have this problem, or knows of a cure?

WB2WIK/6
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AD7DB
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« Reply #8 on: February 20, 2002, 06:45:20 PM »

Sure! When the barometric pressure is high, it makes you say "Hi Hi!"  Listen on the bands, you'll hear many hams with the same situation!
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AC5E
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« Reply #9 on: February 20, 2002, 09:29:06 PM »

Chuckle: Actually, I can envision one scenario where this might actually happen. Even with legal limit power.

But, to quote an alien's line from one of "Kendall Foster Crossen"s classic science fiction stories, "A pulled leg never shortens."

73 Pete Allen  AC5E
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WD5KCA
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« Reply #10 on: February 20, 2002, 09:58:03 PM »

Which brand of whiskey do you drink?
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KG6AMW
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Posts: 616




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« Reply #11 on: February 21, 2002, 12:15:50 AM »

Back in the 60's when my brother and I would get bored we would start experimenting with electricity.  One involved taking the carbon cores out of "C" batteries and making an arc lamp.  I sure the ham down the street wondered what the hell was going on with the band that afternoon.  Another involved taking a 12 volt door bell and wiring it up to 120 volts.  Man, I never heard a door bell ring so fast.  It continued to ring until it caught fire.  Oh how I miss those times.
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K1CJS
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« Reply #12 on: February 21, 2002, 12:26:04 AM »

   Hey!!  Just keep the thing going till summer and you
won't have to heat up your grill for your weekend cookout!
You can just do the cookout in conjunction with playing
radio.  I'll even bring the hot dogs and burgers.  HI HI
HI HI (Oops! Forgot the nitrous was on.....)
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WA7KPK
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Posts: 129




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« Reply #13 on: February 21, 2002, 09:39:57 AM »

Yeah, this happens to me when I crank the linear up to 100,000 watts too. Smiley

Actually the first thing I thought of when I saw this was the antenna array at HCJB in Quito, Ecuador back in the 30s. The combination of the altitude and the high power caused pieces of molten antenna to drip off the ends! Someone set about to solve the problem and thus was the quad born. No ends, no drip I guess.

Shows the way my mind works at 6:30 in the morning, I guess. hi

73, Creede
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KB1HJW
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« Reply #14 on: February 21, 2002, 11:10:45 AM »

I have found a solution to all of the problems listed here. I now build all of my equipment out of unobtainium.
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