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Author Topic: Through roof push up antenna.  (Read 815 times)

KD0HBJ

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Through roof push up antenna.
« on: June 02, 2020, 06:50:25 AM »

I can reach V/U repeaters with an attic Yagi in winter, but when the leaves on the trees come back its over.  Roof antennas up to 6' above roofline are permitted. 
A 20' - 25' mast on the roof would get me over the trees.  It just happens that I have 30ft from ground floor to attic roof at the back of entryway like a stairwell.  I would like to install a one piece push up mast indoors with the raising mechanism housed in the attic.  Outdoor Yagi and mast would normally comply with the 6" rule.  Excess mast tucked next to my stairway. But would violate the rule only when raised as required to make contact.  There would be a lateral support collar between roof rafters and another plumb between attic floor joists.  The lower mast would penetrate the attic floor/entryway ceiling and the upper mast would penetrate the roof right next to the ridge.  I would raise and lower with an electric hoist winch in the attic when necessary and rotate the mast by hand to point at specific signals.
Maybe it would be better to push up and down by hand and have some sort of catch or choker to prevent it crashing down.

What problems do you foresee with this?  I haven't worked out how to seal the roof or ceiling penetration, would like suggestions.  Also attaching winch line to bottom of mast while permitting mast rotation.  Whipping of the lower mast in high winds could be noisy inside.  Without guy wires, all wind loads will be cantilevered, requiring thick mast, which is heavy and potentially suspended above people by just a winch cable.  Building a box lined with rock wool around the lower mast might be necessary.  There could be some weird static electricity effects.  Might also need to insert reinforcing sleeves inside the mast in positions it normally contacts support collars when retracted/deployed.  Will install diagonal bracing from attic floor to ridge beam to resist racking forces when wind is blowing in line with the ridge.
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K5LXP

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Re: Through roof push up antenna.
« Reply #1 on: June 02, 2020, 07:42:55 AM »

That sounds like an awful lot of work for a V/U yagi.  My idea would be to put the antenna in the trees.  If there's a substantial enough branch you could affix it that way, or thread a mast up through to the crown.  Possibly being up that high a vertical may offer sufficient performance negating the need to turn a beam. 

Mark K5LXP
Albuquerque, NM
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K6PCW

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Re: Through roof push up antenna.
« Reply #2 on: June 02, 2020, 07:48:00 AM »

Hi Dustin!
Just build yourself one of these!
https://www.youtube.com/watch?v=qsh9HWm95_o

Let us know how it works!

Kidding aside, I agree with Mark.  Unless you want to spend the bucks, you'll likely encounter more headaches and irritating challenges than desired results.

Good luck,
73 Pete
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W0CKI

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Re: Through roof push up antenna.
« Reply #3 on: June 02, 2020, 07:59:22 AM »

If your allowed 6 feet above the roof, why not an antenna mounted on a small mast above the roof?
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KD0REQ

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Re: Through roof push up antenna.
« Reply #4 on: June 02, 2020, 08:12:27 AM »

you'll know when it rains, the ceiling would drop on you. if you're going to hack on the roof, a TV roof tower and 5 foot mast will get you that 6 feet height. run the coax up under the eaves and in. however, the way you worded the question raises a tickle in the back of my head... covenants? prohibitions? perhaps U-bolt the antenna to the side of a vent pipe, perhaps... then put a larger piece of matching plastic pipe over the whole shebang.
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KB7TT

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Re: Through roof push up antenna.
« Reply #5 on: June 02, 2020, 08:21:53 AM »

You can get some ideas watching Hogan's Hero's on FETV...
They had one built into the Nazi flag pole on top of the roof.
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KD0HBJ

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Re: Through roof push up antenna.
« Reply #6 on: June 02, 2020, 09:14:47 AM »

I don't see how climbing in a tree and running 280' of feedline and rotator is easier than just walking up the stairs inside my house and running 35'.  It involves punching 2 holes with a holesaw and carrying a pole through my front door.  There is doorway clearance to maneuver a 26' 2" pole in one piece.  Is there some complexity here I'm not seeing?  Or do you have some mad tree canopy climbing skill?  I do not.
If I used a vertical antenna, I might even be able to install it without getting on the roof, using a redundant plumbing vent as a stuffing box.
I doubt that just the 6' difference in height would be enough, and I do need to rotate to hit different repeaters.
It was probably a joke, but I actually do have all the materials on hand to make the friction wheel mechanism in that video.

Thinking of this gave me an idea for, I guess a site survey tool.  A log periodic antenna with foldable swept elements that can be fed through an existing roof opening like chimney or plumbing vent, or gable vent from the attic, then opened up and rotated.  It could be used to compare viability of roof mounted to attic mounted antennas and determine direction of signals relative to your structure.  Or for temporary deployments.

Or a wire antenna/feedline could be fed with fiberglass fish tape up a plumbing vent to make a quick temporary roof mount in a structure where you do not have roof access.

Isn't it great how everything works "in theory"?
W0CKI, I love that callsign.  If I could I'd make the Wookiee noise right now.
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W0CKI

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Re: Through roof push up antenna.
« Reply #7 on: June 02, 2020, 09:59:17 AM »

It just seems to me that your taking on a huge amount of work where there are other alternatives that should be tried first. I would think, based on experience that many alternative installations would solve your problem. But, to each his own.
WOOOKIE!
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KD0HBJ

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Re: Through roof push up antenna.
« Reply #8 on: June 02, 2020, 12:05:43 PM »

"there are other alternatives that should be tried first."
Ok, what are they? 

I'm not looking to make more work for myself.  I've just not done this before and that is what I came up with on my own.
I'm too fat and feeble to climb a tree and cannot picture how to secure anything but a wire in the canopy, let alone above the canopy.  If you have something to teach me, please show me pictures.  It seemed like getting closer to the trees generally made things worse, so putting antenna in the tree didn't sound wise.
.
The lot elevation decreases as you get closer to the metro repeater, west, in the direction of the trees.  There is a rural repeater to the southeast without obstruction but it is seldom used and not system fusion.  East, highest by the road, front yard, house, backyard, treeline, creek is the lowest, west.  Ground level at the house is about 20ft above ground level at the trees.
When the attic Yagi works in the winter, a half wave vertical next to it will not.
In the winter, Yagi on a temporary 20ft pole outside in the backyard does not work.
1/4wave mag mount in the car driveway north of the house does not work.  Back the car up 30ft to the road, elevation gain 2 ft, it works in winter and intermittent in summer.
The obvious thing missing is any tests above the house roof.  I have 2 roof tripod mounts but haven't used them because its a new roof I didn't want to damage and frankly, I'm scared of the height as I've fallen from 20+ft before.

There is a brick chimney to the west right outside the 2nd floor radio room.  That inspired the failed 20ft outdoor pole test.  But its height is quite a bit lower than the house ridge at 30ft.  Not sure how that passed building inspection.

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W0CKI

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Re: Through roof push up antenna.
« Reply #9 on: June 02, 2020, 12:30:09 PM »

Don't want to argue but sounds like you have thrown out anything other then the pole through the roof plan. Now you could find a handyman to mount an antenna on a roof tripod. Sealing it is no big deal and you can instruct how to mount it. Only a thought.
Roger, wilco and OUT.
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K6AER

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Re: Through roof push up antenna.
« Reply #10 on: June 02, 2020, 12:43:51 PM »

Use a Rohn 30” steel push up mast mount it on the side of the house with a side mount kit,

Rohn push up mast is: $90.00

Side mount kit is: $40.00

You mount the mast side mount  at the highest eve of the house. The base can be set in a one foot hole with the end on a flat brick. Fill in the hole with gravel.

The side mount will suport a HeX beam when the time comes for up comming HF antenna.
« Last Edit: June 02, 2020, 01:04:51 PM by K6AER »
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K5LXP

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Re: Through roof push up antenna.
« Reply #11 on: June 02, 2020, 04:43:04 PM »

I put wires over 100' ponderosa pines every time I go camping.  One of the antennas I usually deploy is a window line 2M J-pole.  That antenna, up that high, works tremendously.  No climbing, literally pushbutton with an air launcher.  Now, if your trees are located remotely from the house causing excessive feedline runs then that's a separate issue.  First test I would do is what pattern and gain will get me from here to there with an antenna on the house, and work the problem from that direction, rather than go through difficult measures which may not be entirely necessary.  You may learn that a different antenna at a more manageable height or different placement without mast gymnastics can get you there.

Mark K5LXP
Albuquerque, NM
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K3LI

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Re: Through roof push up antenna.
« Reply #12 on: June 02, 2020, 08:03:38 PM »

"Yagi works in winter".   I will guarantee you if you take your yagi out of the attic and put it on a 5 foot pole on the roof it will work 24/7, period.  No need for any other antenna.
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KB2WIG

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Re: Through roof push up antenna.
« Reply #13 on: June 03, 2020, 07:07:08 AM »



This Yagi. How is it " polarized"? Horizontal or Verticular?

KLC
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K0UA

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Re: Through roof push up antenna.
« Reply #14 on: June 03, 2020, 08:04:32 AM »

"Yagi works in winter".   I will guarantee you if you take your yagi out of the attic and put it on a 5 foot pole on the roof it will work 24/7, period.  No need for any other antenna.

That would make entirely too much sense!
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73  James K0UA
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