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Author Topic: Mazzoni Loop good near buildings?  (Read 482 times)

KM6ZX

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Mazzoni Loop good near buildings?
« on: July 21, 2021, 11:36:36 AM »

The bad news: I'm moving into a home with a very strict HOA. I'm basically inheriting it, and the location is perfect for my career. My dreams of owning a tower are once again on hold.

The good news: the home has a nice small atrium that is surrounded by high walls. It would be a perfect place for an antenna. I have been looking at the Mazzoni Loop as a possible solution to my problems. My two main questions are: How does the loop do when surrounded by nearby walls? The atrium is about 15 x 15 feet and the walls are 20 feet high. My second question is, is the loop an effective antenna compared to a dipole? I'm a low-power station, max 100W and do mostly CW. I'm mainly concerned about the walls and house attenuating the signal. I am looking at the full-size 80m to 20m loop and would mount it at the recommended height, about six feet above the ground.

I plan on hiding a dipole and a couple of delta loops in the attic for the higher bands above 20m. Even with these compromises, my antenna situation will be infinitely better than the small rental I'm now living in.

73 de Brian KM6ZX
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KG4RUL

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Re: Mazzoni Loop good near buildings?
« Reply #1 on: July 21, 2021, 12:46:52 PM »

If this is typical condo construction, the walls are stucco with metal mesh embedded.  Kind of like putting and antenna into a Faraday cage.
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W6MK

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Re: Mazzoni Loop good near buildings?
« Reply #2 on: July 21, 2021, 01:36:49 PM »

Go to the DXEngineering website and look up the Mazzoni loop antennas. The documentation tab there will allow you to download the manuals for the loops. In the manuals they specify proper locations for the antennas.

If can put a loop in the center of the atrium and just above the walls, that may an effective location. The minimum suggested height for the larger loop is a little over 8 ft. above ground. To get some useful low angle radiation I don't think you want the loop to be within the height boundry of a wall which is likely to be constructed as a Faraday cage.

The loops can be within an S unit of a dipole on the lowest tunable bands. On higher bands they can be pretty close to a dipole. We are talking about dipoles that are at least half a wavelength above ground level. The loops can work well at much lower heights.
« Last Edit: July 21, 2021, 01:42:11 PM by W6MK »
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W9IQ

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Re: Mazzoni Loop good near buildings?
« Reply #3 on: July 21, 2021, 03:05:38 PM »

The gain of a 1/2 λ dipole that is 1/2 λ above medium ground (S/m= -.0303, εr=20) is ~8 dBi or 5.85 dBd.

The maximum directivity of a single turn, small loop (Cλ<0.1) is 1.5 or equivalently, 1.76 dBi. The small loop suffers from efficiency issues due to its low radiation resistance so the gain will generally be substantially lower than this. If the loop is fortunate to achieve 50% efficiency then its gain would be -1.2 dBi.

The data sheet for the larger "MIDI" version states that at 3.5 MHz (Cλ<0.08) it is 4 dB below a (free space) dipole (with a 2.15 dBi gain). This sets it gain at -1.85 dBi indicating an efficiency of greater than 100%. Something is wrong with their specifications.

- Glenn W9IQ
« Last Edit: July 21, 2021, 03:16:39 PM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

KM6ZX

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Re: Mazzoni Loop good near buildings?
« Reply #4 on: July 21, 2021, 11:36:14 PM »

Thanks for the answers. I looked at the specs and it looks like it's a very effective antenna if set up properly. I really like the fact that it works on 80m with only 4 dB loss. There's no way I could string up an 80m dipole on this property. Being able to work effective on 80m is the main reason I want this antenna.

I guess my options are (1) put it in the backyard where it would have more distance from buildings and hope the neighbors don't notice or complain as its height would be well above the top of the fence line so would be visible to the neighbors from their back yards, or (2) put it in the atrium where it may be in a faraday cage, which was my main concern when asking this question. I met some of my future neighbors and they all seemed very cool, but obviously it only takes one person to complain. I guess the third option would be to put it in the attic if there's enough head room. I'll make some measurements next time I'm in the home.

I want to be a good neighbor and am sure I'll eventually find an effective solution.
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W9IQ

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Re: Mazzoni Loop good near buildings?
« Reply #5 on: July 22, 2021, 05:04:31 AM »

Thanks for the answers. I looked at the specs and it looks like it's a very effective antenna if set up properly. I really like the fact that it works on 80m with only 4 dB loss. There's no way I could string up an 80m dipole on this property. Being able to work effective on 80m is the main reason I want this antenna.

Just to be clear, the difference on 80 meters will be 10 dB (more than 1.5 S-units), not 4 dB. But don't sweat this issue. If you could get an 80 meter dipole installed at say 30 feet high, its gain lobe would point straight up whereas the loop will direct more of its energy at a lower angle.

The loop antenna sounds like a good compromise for your situation. There was a review of this antenna in a recent QST. Hopefully your surrounding walls and building won't pose a problem. Don't forget that under the new FCC regulations, you are required to do an RF exposure assessment.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

N6YWU

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Re: Mazzoni Loop good near buildings?
« Reply #6 on: July 29, 2021, 10:03:54 AM »

I guess my options are (1) put it in the backyard where it would have more distance from buildings and hope the neighbors don't notice or complain as its height would be well above the top of the fence line so would be visible to the neighbors from their back yards,

I want to be a good neighbor and am sure I'll eventually find an effective solution.

Do any of your neighbors have large garden ornaments or mini gazebos, etc.?  A loop doesn’t look like an antenna to a non-engineer.  So you might be able to put in plain view, and simply disguise it with some fake leaves, disconnected glass bulbs, or wood bird houses and such, and tell any nosey neighbors you’re experimenting with a lighting up an artistic yard decoration.
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