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Author Topic: Be Careful w/ Vent Pipe Antennas  (Read 344 times)
WA1RNE
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Posts: 825




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« on: July 08, 2004, 10:28:26 PM »

The post made by W0FM brought 23 replies, 24 including this one.

There are 4 really good reasons to keep antennas off of vent pipes:

1) There is no good way to get a feedline into the house without messing with the integrity of the vent pipe itself.

2) Depending upon the length of the antenna, mast, etc. and it's weight, you will eventually LOOSEN and crack the water tight seal between the roof and attic. It may take a while on a new house or not long at all for a pipe that has been exposed to heat, cold, UV, wind, etc. over many years. The result is obvious and not worth the aggravation.

3) There are LOTS of better ways to erect antennas on a house.

4) There isn't one person that that can be considered an expert on the subject including me. RELY ON COMMON SENSE!!

Now who would have thought this would be such a complex subject??
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K0RFD
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Posts: 1368




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« Reply #1 on: July 08, 2004, 10:56:11 PM »

Yep, 24 replies to the question about the vent pipe, and nobody else but me told the guy in "Keying up wipes out computer equipment" NOT to transmit without a license.

I guess we each like to solve certain kinds of puzzles.
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KZ1X
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Posts: 3229




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« Reply #2 on: July 09, 2004, 12:32:11 AM »

Actually, I'd encourage people transmitting without licenses to buy $2400 radios and then transmit only into wires adjacent to their computers, frying them.

My wife says I'm a jerk, sometimes.  But I only chuckle and think about the Galapagos Islands, a ship called "The Beagle" and a certain occasionally-unpopular scientist.
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KA5N
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Posts: 4380




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« Reply #3 on: July 09, 2004, 10:29:29 AM »

Everyone carries baggage and approaches a problem differently.  No matter how goofy an idea is somebody will tell you how to accomplish it and describe just how they "did" it.  One story I like is the ham who was running RG-8 coax into his shack and found that fire blocks (2X4's in the walls parallel to the floor) blocked the way.  He had drilled into the cap 2X4 in the attic and thought that since coax is about half an inch and a 45 automatic slug is about half an inch.  So ... back into the attic with his 1911A pistol with the muzzle on the half inch hole and bam!!  The recoil unbalanced him and he fell through the ceiling.  The sudden extra 400 cubic feet of gas produced by the 45 blew the dry wall off inside the shack.  There was no longer any problem getting to the fire block to drill a hole for the coax.
His solution was not a good one but it worked!!
Allen
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WB2WIK
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Posts: 20574




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« Reply #4 on: July 09, 2004, 01:51:41 PM »

The whole vent pipe antenna thing was a lot more controversial than I thought it deserved to be.

For better or worse, in sickness and in health, people have used vent pipes to support all sorts of stuff for several decades.  Sometimes, that stuff falls over, or falls down.  Same can be said for using a brick chimney, a gable mount, and lots of other overstressed supports.

The "gas hazard" issue, though, took on a life of its own.  As someone who's spent more time on roofs than any fifty normal people should, and having owned fifteen homes with lots of vent pipes on each, I've never smelled anything coming from any of them.  Having bought fifteen and sold fourteen homes, I've also never seen this even as a point of note or inspection during costly (and often required by escrow) home inspections.  I'm certain that if I had sawed every one of my vent pipes in half just below the roofline over all those years, every single home would have passed inspection, anyway.

Interesting reading, though.

WB2WIK/6
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W0FM
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Posts: 2054




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« Reply #5 on: July 09, 2004, 01:57:59 PM »

Never thought this would stir up such a response.  But we are all thinking and we learn something and that's healthy.

Terry, WØFM
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AA4PB
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Posts: 12788




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« Reply #6 on: July 09, 2004, 04:01:17 PM »

Well, with a septic system I've certainly smelled sewer gas when the water evaporated from the trap in the laundry room floor drain. That indicates that it is present in the system even if the quantity is not enought to smell in the open air on the roof. I also imagine that there would be no need for traps if there were no sewer gasses. I guess if you must use the vent pipe for an antenna mount and cable conduit then you take your chances on several counts. Personally, I'd recommend a good tripod unless the goal is to desquise the antenna.
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K1CJS
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Posts: 6007




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« Reply #7 on: July 09, 2004, 08:51:15 PM »

"The "gas hazard" issue, though, took on a life of its own......I've never smelled anything coming from any of them [vent pipes]......

Its doubtful you would--unless you stuck your nose into the pipe, even they you may only catch a whiff.

......I'm certain that if I had sawed every one of my vent pipes in half just below the roofline over all those years......

Why don't you try that, leave it for a few days, then go into your attic near the pipe and light a match.  Nothing may happen--but are you prepared for the boom if you're wrong???  Some of those gasses are odorless.  That is the one overriding reason why you shouldn't leave open holes in vent pipes.
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K1CJS
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« Reply #8 on: July 09, 2004, 08:55:08 PM »

Oh, BTW, the reason why the inspection doesn't cover that issue is that nobody in their right mind would fool with the stack vent.  And, the inspection doesn't cover every switch, outlet and fixture in the house, either.  But they are also dangerous--and people don't usually fool with them either.
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K0RFD
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Posts: 1368




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« Reply #9 on: July 09, 2004, 10:51:34 PM »

Well, I think there were 2 issues in that thread.  Supporting an antenna with a vent stack is one.  That's not so big a deal.  If it breaks, big deal.  Drilling holes in the vent pipe, indoors, is another issue entirely.

I was worried only about methane and flammability hazard.  I had forgotten about H2S--glad one poster brought it up.  We used to work with it when I was in grad school.  It's toxic at parts per million levels; fortunately the human nose can detect it at parts per trillion levels.  It's also explosive.  Nasty stuff.  I still chuckle about the time a lecture bottle of H2S got out of control because a fume hood motor burned out in one of our labs and the gas went down the elevator shafts.  The university had to close the elevators for a week while they pumped the stuff out of the basement.

I don't get hysterical about things.  But I'll be darned if I was gonna tell the guy that it was OK to run wires down his vent stack and drill holes in it.  I might do that MYSELF, but telling somebody else it's OK is a whole different matter.  I guess in a weird sort of way, there's some serious ethics involved in posting advice.  Doing stupid stuff ourselves is lots different than telling somebody ELSE it's OK to do something that could get them hurt or worse.
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KD7EVS
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« Reply #10 on: July 13, 2004, 03:34:06 PM »

I'll second RFD's point on advice.    if we do something stupid, it's our own fault.   If we tell someone else to do something stupid (without telling them it's stupid), then we really are stupid.

I do stupid stuff all the time, but I don't go posting a how-to of sorts about it...    though sometimes it ends up in the 'how not to' forum.




zeb
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