Antenna and Tower Assembly Help

[unit_399]

I just bought a 60' tower, and am having it professionally installed on our farm. I built a 4-element quad to put atop the tower. My question is ... should the bottom of the antenna be above the top of the tower ?? (See the crude drawing below).

I always mounted my antennas 36' (11 meters) to the antenna's base, with great DX results. I can just use 3 sections of the tower to get close to 11, but have been told that "height is might" and I should go with the full 60. Opinions ??



- 399

 

[undertaker]

Go all the way!!

 

[pienari]

I sold my old 4el quad (6.5m boom) to my friend and he installed it to 45m hi tower.
I used it to 35m tower.
45m is much better for long qso.

 

[groundwire]

See the arrl antenna handbook for angle of radiation vs height. All your questions are answered in there. Once you pass 1 1/2 wavelength in height the antennas designed radiation pattern starts splitting into all kinds of weird and unnecessary lobes, and takeoff angles will start to change as well. Heights over 60ft for 11m is unnecessary and a waste of money (diminishing returns). Just more cb radio false information.

 

[The20poundhammer]

I would have the bottom of the quad above the top of the tower. 60 feet of tower with 10 foot of mast should be perfect.

 

[DoctorAudio]

10-11 meter beam antenna skip range generalities.

36 feet= Good for E layer and shorter F2 (1000-2250 miles)
46-52 feet= Slightly diminished short hop, great for 1500-3500 miles. High enough for double hop. Best all around height.
72-100 feet= Almost no short skip. best for international, double hop F2 or extra-long single hop F2. (3000-15,000miles)
60 feet= Too high for reliable E layer skip and short F2. Great medium-long range F2, single and double hop. (2500+ miles)

 

[unit_399]

I would have the bottom of the quad above the top of the tower. 60 feet of tower with 10 foot of mast should be perfect.

Once you pass 1 1/2 wavelength in height the antennas designed radiation pattern starts splitting into all kinds of weird and unnecessary lobes, and takeoff angles will start to change as well.

Viente Libra Martillo -

I agree 100%. My mast will be 2.4 meters, which will put the bottom of the reflector about 1 foot above the top of the tower using 5 of the 3-meter tower sections.

GW -
per your suggestion, I read the section of the ARRL ANTENNA HANDBOOK regarding takeoff angle vs antenna height. In one case it said higher is better. But in another case it said too high is bad. Don't know what to believe. And it didn't state examples at specific frequency ranges. Duuhhh !!

So I think I will try a 15 meter (5 section) tower,and a 2.4 meter mast. I can always add the other tower section later.

Hasta luego.

- 399


-

 

[unit_399]

Dr Audio -
Thanks for posting. You reinforced my decision to go with the 15 meter tower and 17.5 Meter total height. Looks like it's the best all -around choice.

After a huge rain and windstorm years ago took down all of my antennas, I have been off the air for over 10 years. Finally TOOK the time to get it back together. Can't wait to key up for the first time !!!+

- 399

 

[groundwire]

Viente Libra Martillo -

I agree 100%. My mast will be 2.4 meters, which will put the bottom of the reflector about 1 foot above the top of the tower using 5 of the 3-meter tower sections.

GW -
per your suggestion, I read the section of the ARRL ANTENNA HANDBOOK regarding takeoff angle vs antenna height. In one case it said higher is better. But in another case it said too high is bad. Don't know what to believe. And it didn't state examples at specific frequency ranges. Duuhhh !!

So I think I will try a 15 meter (5 section) tower,and a 2.4 meter mast. I can always add the other tower section later.

Hasta luego.

- 399


-

Because the operating frequency does not matter in this case. We are looking at optimum antenna height vs take off angle. The books wording can be confusing, they are known to be guilty of that. Higher is better but too high gives unfavorable results, thats what it means. Bottom line is 60ft is the sweet spot for 11m. 60ft tower, 5ft or 10ft mast and call it a day.

 

[unit_399]

Thanks again GW -

I'm good on radios, but aren't the best when it comes to antennas. One thing I've learned over the years, is that antenna stuff isn't an exact science. Close counts. I've run antennas that talked skip with the best of them, when most people said my setup was a waste of time. So ... I know antenna science isn't perfect. Still, I want to do the best I can with what I've got, and I look for advice and direction. I have a good tall tower, but I'm willing to give up a bit of height if shorter equals out to be the best all-around result. I've been wanting a setup like this for as long as I can remember, and I want it to be the best that it can be. So, forgive me when I ask for advice that will hopefully turn my rig into a bigstrapper. Once my workers get my antenna set up, there's no turning back. I'm too old to climb up the tower and make changes. So . . . I'm asking you guys to help me get it right from the get-go.


- 399

 

[wavrider]

Height versus take off angle

Dipole Antenna Radiation Patterns by WB4YJT

Some good reading in the above links
especially the dipole radiation pattern, since a yagi or quad is just a dipole with reflector and director.
Friend of mine has a 4 element at 110 feet
he also has a 2 element quad at 20 feet.
consistently dx from europe tells him he is stronger on the quad at 20 feet that the yagi at 110 feet.
Of course local he is stronger on the taller antenna.

Mount your quad at 17 meters, install some standoff and pulleys to hang dipoles at 11 meters and 6 meters, then compare the dipole to quad and see how height does not necessarily mean better dx,

 

[wavrider]

????

 

[pienari]

My opinion about install height is 11m band vertical quad it have to be about 30m hi on the ground.
Then beam cant see near trees or buildings etc.
If you havent tested you cant know.
I have build and tested quads over 25 years.

 

[Captain Kilowatt]

See the arrl antenna handbook for angle of radiation vs height. All your questions are answered in there. Once you pass 1 1/2 wavelength in height the antennas designed radiation pattern starts splitting into all kinds of weird and unnecessary lobes, and takeoff angles will start to change as well. Heights over 60ft for 11m is unnecessary and a waste of money (diminishing returns). Just more cb radio false information.

Well actually when the lobe splits it allows the antenna to respond better to a variety of take off angles and tends to work better over a variety of distances.

 

[wavrider]

As you increase height AGL as indicated in the above links i referenced the lobes do indeed split into multiple lobes.
But the negative side to it is the nulls where the lobes are not at. You wont hear some stations if the angle of arrival is in a null.
As a general rule the higher the antenna install is best. But it does cost more to get an antenna higher in the air,
on 10 meters I have compared dipoles at 1/2 wl agl 18 feet, to my mosleypro67b at 60 feet agl.
basically the same signal reports, maybe 1/2 S unit more on the yagi as to be expected.