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Author Topic: Is 40 feet a waste of time and money?  (Read 5392 times)
WB3DLO
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Posts: 18




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« on: November 11, 2012, 02:53:15 PM »

I've heard the optimum antenna height for 20 meters is around 1.5 wavelengths, or somewhere around 100 feet. That being said, is erecting a 20 meter Yagi at 40 feet a waste of time and money?
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WB6BYU
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Posts: 13576




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« Reply #1 on: November 11, 2012, 03:31:59 PM »

Certainly not.

Well, it depends on what your personal preferences are.  If you absolutely have to
be the top dog in the pack, then you won't be happy with anything less than stacked
5-element yagis on a 200' tower.  But if you just want reasonable results, it will make
a lot of difference over a dipole on the roof or a mobile whip.
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LA1BRA
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Posts: 53




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« Reply #2 on: November 11, 2012, 03:32:38 PM »

Depends, if you want to be the big gun on the air, by all means...100 foot hihi
ARRL did a article on your very subject, might be worth a read.
It covered take off angles and received angles and plotted it against height above ground...if I remember correctly.
I seem to recall 50 foot was about the lowest where one could expect a decent performance on a yagi...
I worked a guy one time who had his 4 element yagi setting on saw horses in his back yard, so conditions play a lot into what you can expect.
My 3 ele StepIR is at 45 feet in Texas, it works, it plays, I like it. I had a chance to live in Norway for 6 years, we had a 4 element StepIR at 60 some feet at the radio club house, it was awesome.....
73
tom
XE3 / KB5VWZ....on assignment...
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N3OX
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« Reply #3 on: November 11, 2012, 04:34:46 PM »

No, 40 feet is a pretty good height, will be a good improvement over something like 20 or 30 feet (see here for a good discussion that combines antenna pattern and propagation statistics: http://www.karinya.net/g3txq/hexbeam/height_2/), and a yagi at 40 feet will often run circles around a lower, simpler antenna like a vertical.

Hard to say whether it's a waste of money without knowing what your alternative is, but I wouldn't hesitate to put up a 40 foot tower if that was what I could have. 
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
ZL1BBW
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Posts: 413




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« Reply #4 on: November 11, 2012, 04:36:31 PM »

My dd had a 3 ele 20M up at about 40feet facing down a slight hill and then the sea, tremendous signal.
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ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
KM3F
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Posts: 525




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« Reply #5 on: November 11, 2012, 05:19:16 PM »

I am at 40 feet with a Tri Band 20/15/10m.
It works well for me not to say it could not be improved but not very soon, if ever.
A dipole for 75 and 40.
The difference between them when the dipole is matched on 20, 15 or 10m is no contest for the dipole. Beam wins everytime.
Good luck.
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WA8UEG
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Posts: 399




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« Reply #6 on: November 12, 2012, 08:14:27 AM »

No, not a waist of time or money. Of course the higher the better but you will be happy with 3 elements at 40'.
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KA5N
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« Reply #7 on: November 12, 2012, 09:21:12 AM »

No, not a waist of time or money. Of course the higher the better but you will be happy with 3 elements at 40'.

Is a "waist of money"  a money belt at maximum capacity?

Allen  KA5N
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N6AJR
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« Reply #8 on: November 12, 2012, 01:10:46 PM »

I have a 3 element steppir at 40 feet.  It works well.  the magic number on 20 meters is higher than 1/2 wave which is around 32 feet, so even though 40 feet is not an amazing height it does allow the antenna to function as designed. so yes, 40 feet is a good place to start, and it also works well with a rohn 25 tower  bracketed against the house with a 3x3x3 foot concrete base and perhaps a set of guys at the top.  all and all a doable setup.  you will find it is more than adequate.
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NK7Z
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« Reply #9 on: November 12, 2012, 02:01:54 PM »

I am putting up an antenna as well...  At 40 feet...  I have a choice of putting it out in the open, (open being defined as nothing for probably 75 from it, or up closer to the house, or against the house...  Any thoughts here?  Would I see a big difference from open, vs. with a house under it at about 25 feet.
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
WB8UHZ
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Posts: 125




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« Reply #10 on: November 12, 2012, 08:45:35 PM »

  No 40 feet or actually 50 feet could be considered optimum for many conditions.At 50 feet you are at 3/4 of a wavelength but even at 45 feet you will have a take off angle of about 15 degrees pretty good for DX. At the lower height you will also work North America very well. I have in my ham life used a 3 element mono band yagi at 45 feet the Hygain 203ba and worked the world. Have fun.
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W4RS
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Posts: 66




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« Reply #11 on: November 14, 2012, 04:39:54 PM »

there are many hams on the dxcc honor rolls with a tri bander at 30 to 40 feet. if thats the height you have, use it and wkem!
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W5DQ
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« Reply #12 on: November 16, 2012, 03:24:30 PM »

I've heard the optimum antenna height for 20 meters is around 1.5 wavelengths, or somewhere around 100 feet. That being said, is erecting a 20 meter Yagi at 40 feet a waste of time and money?

I have a Force 12 C3S at 40' and it does a very nice job. Sure it isn't a 6 element monobander at 100' feet but I didn't have to sell my soul to the devil to put it up either. In fact the only cost was the antenna and feedline. Tower was a 'come get it out of here' deal from a guy renovating a house locally and I had a rotor from previous install to use..

From my experience and observation, the majority of ham yagi supports (towers, masts, etc.) are in the 40-50' range.

Good Luck but make sure it is a solid well engineered installation cause anything falling 40' will hurt it it hits you and probably kill you too.

73

Gene W5DQ
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Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
WA7PRC
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« Reply #13 on: November 23, 2012, 12:01:51 AM »

Rule of thumb: antennas start to resemble their models from around one half wavelength above ground, and higher.  Below that height, they tend to keep the worms in the ground warm.  40 feet AGL on 20m is good but higher is better.  My olde Cushcraft A3S worked OK at 30' but, my Force12 C-4XL at 72' works AWESOME!  Cool
« Last Edit: November 23, 2012, 12:06:46 AM by WA7PRC » Logged
G3TXQ
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Posts: 1533




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« Reply #14 on: November 23, 2012, 03:55:50 AM »

Dan (N3OX) already referred to my web page which discusses - objectively - the relative performance of an HF beam at different heights, based on Angle-of-Arrival statistics for various paths; it formed the basis of a QST article some time ago [What's the best height for my HF beam?, May 2009, page 43, http://p1k.arrl.org/pubs_archive/135769 for ARRL members].

The chart in Section 2 may be of interest:
http://www.karinya.net/g3txq/hexbeam/height_2/

Let me quote from the Conclusions:

Quote
For those of us constrained to use a single multiband antenna mounted at a fixed and modest height, the results offer some encouragement: if we can get the antenna up around the 40ft-50ft mark we will be within 1dB of the optimum height for short-haul and medium-haul paths on all bands 20m thru 10m. And we will probably accept the "half S point" penalty that our modest height suffers on the long-haul paths.

If our antenna is presently at the 20ft mark, the effort and expense required to lift it to around 40ft looks well worthwhile; we will see improvements ranging from 1dB to 5dB, depending on the path and the band.

For the "serious" operator who is able to justify the expense and engineering challenges of lifting the antenna to 80ft or more, the results show that significant benefits will accrue on the long-haul paths; but the ability to switch to a lower antenna under certain propagation conditions becomes increasingly important, particularly at the highest frequencies.

73,
Steve G3TXQ
 
« Last Edit: November 23, 2012, 04:03:01 AM by G3TXQ » Logged
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