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Author Topic: Using Vent Pipe as Mast  (Read 1566 times)
WV4L
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Posts: 136


WWW

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« Reply #15 on: May 06, 2008, 06:55:58 PM »

"If you can find a decent sized ( smallish) antenna that will fit the vent pipe, I would probably go ahead and try it. Something like a dual band comet or diamond mobile style, that is maybe 2 or 3 feet tall and fairly slender."

I have exactly what you are talking about. I have an Arrow 146/440 Ground Plane mounted on a short 4 foot mast that is hose clamped to my copper sewer vent pipe. It is a small well built antenna but that is what I wanted. I only needed something that I could use to hit the local repeaters so I stayed with a low profile installation. I'm still waiting on the wife to chew at me for putting up yet another antenna. Its been up since Dec. of 07 and she hasn't said anything to date. Wink It works great.

73

Wayne C.
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KB4QAA
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Posts: 2235




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« Reply #16 on: May 06, 2008, 10:34:51 PM »

I agree with the aformentioned risks,

but, YES, I've mounted a Ringo 1/2wave 2meter antenna on about a foot long piece of tubing using a generic mast mount from radio shack on an a black iron vent pipe.  

Everything was kept as short as possible to minimize the moment-arm.  It was located very low on my roof so it was fairly protected from winds.  Worked fine for me for several years.

Bill



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K1CJS
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Posts: 5807




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« Reply #17 on: May 07, 2008, 05:01:07 AM »

"The original post mentioned a 2m antenna. Seems like that could be pretty light (made with light thin aluminum or even an old TV antenna), and might be OK to mount on a vent pipe."

I think that is what I said!

And what is this about a crappy signal?  I would rather think it would be 'down the tube'?  ;-)
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K1CJS
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Posts: 5807




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« Reply #18 on: May 07, 2008, 05:05:32 AM »

"I wish you guys would not beat around the bush and just answer my question Wink"

But you asked for this:

"I am looking for a 2m or 2m/70cm setup right now. Any words of wisdom would be appreciated."

You did say 'any words'?  Well, you got what you asked for!!  :-)
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WA3SKN
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Posts: 5419




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« Reply #19 on: May 07, 2008, 05:22:38 AM »

This can be expensive!
Leave the vent alone.  There are better options (even for 2 meters)!
73s.

-Mike.
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K3ASF
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Posts: 121




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« Reply #20 on: May 07, 2008, 05:56:52 AM »

You mention that the vent pipe is 2". Unless it is an older home I doubt that cast iron was used. Most likely PVC or galvanized iron pipe. If the latter I see no problem.
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W3LK
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Posts: 5644




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« Reply #21 on: May 07, 2008, 06:54:08 AM »

Vent pipes and chimneys are NOT designed to be load-bearing devices. In most cases they can support their own weight and little else. They are designed to vent gasses into the air, nothing else. They are NOT designed to withstand lateral or torsional forces, both of which will ultimately be applied when an antenna is mounted on them.

I wouldn't mount ANYTHING longer than a couple of feet or weight of more than a pound on a 4' chimney, much less on a 12 to 14" vent pipe.

Incidentally, the gasses that chimneys and vent pipes emit are almost always corrosive and will destroy aluminum antennas, sometimes within a matter of months, if the chimney is an active one.

73,

Lon - W3LK
Naugatuck, Connecticut
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W3LK
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« Reply #22 on: May 07, 2008, 06:57:00 AM »

<< I have exactly what you are talking about. I have an Arrow 146/440 Ground Plane mounted on a short 4 foot mast that is hose clamped to my copper sewer vent pipe.>>

Copper vent pipe? If it's really copper, it is way too soft to be used as an antenna mast.

73,

Lon - W3LK
Naugatuck, Connecticut
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K5END
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Posts: 1309




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« Reply #23 on: May 07, 2008, 07:57:36 AM »

I'd put in a fake "vent pipe" that you can mount and secure properly to the roof, through which you can run your coax. If you're gonna do stealth, think like a spy. It doesn't have to be a real vent, now does it?

Advantages:
>You can choose the spot on the roof
>You can mount it securely to the sheathing and/or even one of the roof's structural members...what are those called...rafters? Joists? How about 2X8's.
>No risk on your plumbing
>Pulling one over on the HOA, priceless!!

Just make sure you seal the roof properly, but that should go without saying.
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NS5M
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Posts: 196




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« Reply #24 on: May 07, 2008, 10:07:13 AM »

<< I have exactly what you are talking about. I have an Arrow 146/440 Ground Plane mounted on a short 4 foot mast that is hose clamped to my copper sewer vent pipe.>>

I have this antenna mounted in the attic & hit all local repeaters with no problem, 5W out of a Yaesu 2600M. It is mounted on a short piece of pipe bolted to attic floor joist, about 14-15 feet above ground in that part of the attic over the garage.  

The only thing I'd attach to a vent pipe or chimney is a wire ground-plane & I'd expect to replace it every year or two.

Good luck, whatever you choose!
Jim N5VT
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W4VR
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Posts: 1189


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« Reply #25 on: May 11, 2008, 02:38:00 PM »

If I were you I would not attach anything to a vent pipe..you're asking for trouble...that is a very weak structural point.  If you have a chimney get yourself some chimney brackets and mount it there instead.
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W3LK
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Posts: 5644




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« Reply #26 on: May 11, 2008, 07:13:46 PM »

<<  If you have a chimney get yourself some chimney brackets and mount it there instead.>>

Equally bad advice, for all the same reasons as the vent pipe - PLUS hot chimney flue gasses will eat aluminum antennas in short order.

73,

Lon - W3LK
Naugatuck, Connecticut
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AC2RC
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Posts: 112




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« Reply #27 on: May 13, 2008, 02:05:13 PM »

There are designs for fake vent pipes with antenna inside the fake vent. One other point , antennas mounted on the house may result in RFI due to all the electronic hash that a typical house has !!
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KJ4DBD
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Posts: 21




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« Reply #28 on: May 27, 2008, 02:08:20 PM »

Jim, thanks for the response. I do have a couple of questions.

<<I have this antenna mounted in the attic & hit all local repeaters with no problem, 5W out of a Yaesu 2600M.>>

What do you consider local repeaters? I have line of sight to two of the busiest repeaters in my part of the state. There are several other repeaters I would like to hit that are 30-45 miles away.

<<It is mounted on a short piece of pipe bolted to attic floor joist, about 14-15 feet above ground in that part of the attic over the garage.>>

I might could do this. I do not have a lot of height in the attic (less than 5 ft.). Would the arrow fit? I had thought about the dual band j-pole as well.

Thanks again,

Steve/KJ4DBD
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