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Author Topic: 10-15-20 Yagi for the roof?  (Read 6355 times)
NI0Z
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« on: May 04, 2012, 08:49:48 AM »

What are some reasonable options for this that people are using.  I am concerned that that it may just be too big for the roof but I really would like an antenna with some gain as what I run now is lossy.

I guess I should say that I want to do it right the first time so I don't have regrets.  A tower is not a. Option for me where I live and the antenna on the roof will probably be pushing my luck a bit.  I have some tall trees that rise above my roof line that will limit the turning radius a bit.

Thoughts/suggestions?
« Last Edit: May 04, 2012, 08:55:02 AM by EVERSTAR » Logged

WB2WIK
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« Reply #1 on: May 04, 2012, 10:23:23 AM »

I've installed HF beams every year for 43 years now and might have some suggestions but it would be really helpful to know:

-How tall is the roof, and how high can the antenna be above it?

-How close are the trees, and what is the turning radius limited to?

-Do you have access to an attic below the roof?

-Can you install near the center of the roof and guy to the corners?
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N7SMI
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« Reply #2 on: May 04, 2012, 12:06:27 PM »

Thank you for asking this. I am wondering the same question. My roof is about 20' up. I already have a reinforced vertical mast on the roof at at 20' that should easily carry a fairly heavy beam, etc. Turn radius of maybe 20 feet before infringing on neighbors properly.

Don't intend to hijack the thread, but I'd be interested in any responses to the OP.
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K3VAT
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« Reply #3 on: May 04, 2012, 12:09:24 PM »

What are some reasonable options for this that people are using.  I am concerned that that it may just be too big for the roof but I really would like an antenna with some gain as what I run now is lossy.

Mark,  

Along with the Qs that WB2WIK asks here's another set:

What are your goals with this triband yagi?  DXCC, continental, do you have icing at your QTH, etc.

Tribanders, even those considered for roof mounting vary greatly by size, weight, wind load and price.  You can use a 2 element version (full size or reduced size) ... you can also consider the wire beams (Optibeam for example) or homebrew your own.

As Steve intimated, this is a system with several key components.  The antenna must conform to the specs of the roof tower; the roof tower must adhere to the building parameters of the roof (substratum, roof trusses, etc.); and you need a way to mount it to the roof (attic?).

GL, 73, Rich, K3VAT
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K3VAT
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« Reply #4 on: May 04, 2012, 12:28:11 PM »

Thank you for asking this. I am wondering the same question. My roof is about 20' up. I already have a reinforced vertical mast on the roof at at 20' that should easily carry a fairly heavy beam, etc. Turn radius of maybe 20 feet before infringing on neighbors properly. ...

Jared,
Thanks for your post.  The same Qs asked would appear to apply to your situation too.
I surmise that you already have roof access as you have a roof-mounted vertical, correct?

If you have a 20' turning radius, then you 'could' go with a full size 10-15-20M tribander (or a combination using the WARC bands of 12 & 17M).  These antenna often perform well even at heights below 30', especially on 10M where you have a nice low-angled main lobe.

Glen Martin has been building roof mounted towers and accessories for a long time.  They have a number of different towers you might consider depending on your station operating goals, construction of your roof, and of course your budget.  See especially, http://www.glenmartin.com/catalog/page14.html

Important Note: the installation of a roof-mounted triband yagi & tower takes considerable planning.  Obtaining an Engineer's Feasibility Report is worth the extra price.  Often the use of a crane is needed, depending on your setup (such as roof pitch).  Plan accordingly.

GL, 73, Rich, K3VAT
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KF7CG
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« Reply #5 on: May 04, 2012, 01:11:11 PM »

As a datum point. The turning radius of a Mosley TA33 is just at 15 feet and it is a full size trap tri-bander. I have used one at about 25 agl with good results.

Most antenna descriptions in the catalogs give the turning radius.

KF7CG
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K3VAT
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« Reply #6 on: May 04, 2012, 01:18:08 PM »

As a datum point. The turning radius of a Mosley TA33 is just at 15 feet and it is a full size trap tri-bander. I have used one at about 25 agl with good results. Most antenna descriptions in the catalogs give the turning radius. KF7CG

Thanks David.  I was referring to a full size tribander, where the 20M reflector is ~34'.  The TA33 (because the traps effectively reduce the overall size of each element) is 28'.  73, Rich
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WB2WIK
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« Reply #7 on: May 04, 2012, 03:27:26 PM »

Thank you for asking this. I am wondering the same question. My roof is about 20' up. I already have a reinforced vertical mast on the roof at at 20' that should easily carry a fairly heavy beam, etc. Turn radius of maybe 20 feet before infringing on neighbors properly.

Don't intend to hijack the thread, but I'd be interested in any responses to the OP.

20' turning radius is okay for many HF multiband beams covering 20-10m (not 40m).  I'd worry about the reinforced vertical mast, though.  For one thing, unless you can lean a 20' ladder against it, the act of actually getting a rotator, short mast above the rotator, and beam up on top of it might be quite a trick.

For an HF beam on a roof, I'd always go for a 4-legged roof tower that can tilt over, which is not only a whole lot stronger than any sort of mast but also a lot safer to use for installation and maintenance.  As already pointed out above, Glen Martin Engineering makes a fine family of 4-legged roof tower products (like big tripods, but 4 legs instead of 3 -- and that has huge advantages) all of which allow you to install a rotator inside the tower and use a thrust bearing above it, which is the proper way to use a rotator on a load as large as an HF beam.

I've installed a number of those over the years and they all worked perfectly.  Lightweight, easy to assemble, very strong, climbable, non-rusting (all extruded aluminum, with stainless steel hardware) and really designed to do exactly what we're doing.
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N6EY
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« Reply #8 on: May 04, 2012, 07:59:08 PM »

I second Steve's Glen Martin roof mount tower option.  That, and a nice KT-34 make a decent roof mount antenna for 20/15/10.

73!

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73,
Jason N6EY
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NI0Z
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« Reply #9 on: May 05, 2012, 02:37:07 AM »


-How tall is the roof, and how high can the antenna be above it?

25-30 feet at peak

-How close are the trees, and what is the turning radius limited to?

Yes, I think I can handle 15 feet of turning radius

-Do you have access to an attic below the roof?

Yes, I would likely go with a 5 floor tripod, one that would be optimal for a rotar.

-Can you install near the center of the roof and guy to the corners?

Rather not guy, but yes to the center and I can bolt the tripod through the roof so it's clamped on.

Answers above and thanks for the help.  PS - I want to be able to run full legal limit as well in the future, I run about 300-500 watts right now on a vertical dipole.
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K9IUQ
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« Reply #10 on: May 05, 2012, 03:33:34 AM »

What are some reasonable options for this that people are using.  I am concerned that that it may just be too big for the roof but I really would like an antenna with some gain as what I run now is lossy.

Thoughts/suggestions?

I used a CushCraft MA5B beam for several years. It was pretty decent and not too big. I think it had a 8ft boom. This antenna could be easily roof mounted.

I replaced it with a Tenadyne T-6 Log Periodic. This antenna looks much like a TV antenna, just a bit bigger. Cheesy I have had the T-6 for about 6 years now. It is a really good antenna and has a 12 ft boom. The T-6 could be roof mounted I think. Anything bigger is just getting too big for a roof.

The MA5B can handle around a KW, the Tennadyne will take all you can give it.
FWIW I mounted the above antennas on a 40ft Tubular tower.

If I had to mount on a roof I would go with the MA5B or a Spider/Hex beam of some type.

Stan K9IUQ
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KC4MOP
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« Reply #11 on: May 05, 2012, 03:47:28 AM »

There are excellent suggestions here and excellent roof mounted towers.
This tower will have to be installed by a professional. It must be attached to the 2X4's or whatever is in your roof. It becomes "part of the house". It doesn't sit on the roof and support a tri-bander.
In a former QTH I had a 15 foot roof mount and it supported an A3S and the 12/17M Yagi Cushcraft sold with no problems. It took a tower crew 8 hours to install.
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K9IUQ
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« Reply #12 on: May 05, 2012, 03:58:20 AM »

There are excellent suggestions here and excellent roof mounted towers.
This tower will have to be installed by a professional.

My take on roof mounted towers is: Why do it? You devalue your home and probably put your home at risk in a storm. IMO roof mounted towers always look weird and make the house look CB. If I , as a ham op think they look weird just imagine what the neighbors or XYL will think.

Just install a small tower at either end of the house. It will look better and if/when you sell the house you do not have to worry about any damage to the house.

Stan K9IUQ
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M6GOM
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« Reply #13 on: May 05, 2012, 09:25:21 AM »

What about a Hexbeam? 5 bands, lightweight - can be turned on a TV rotator, 10.7ft turning radius and looks like an overgrown rotary clothes dryer.
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NI0Z
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« Reply #14 on: May 05, 2012, 04:00:39 PM »

Cushcraft And Hex sounds interesting.  I meant 5 foot minitower tower, just enough to mount it and install a decent rotar.

I am concerned about wind, we get some winds in the 70-80mph range 1-2 times every year or two.  I am concerned about appearance, but figured I would take it down in 8 years when I go to sell the house.  So the ability to take the tower down and leave the roof in good shape is a factor.

I am thinking about just having a pro antenna installer put up the antenna.

I have a gap Titan vertical right now, it's decent, but it had to be located in a noisy area in my back yard, just how it had to go.

I have a really nice rigg/setup and I just think its time to get a higher performance quality antenna setup now.  I run a G5RV for receive as well, helps as I have that in the trees and further away from the noise.

I really think having something directional will help!
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