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Author Topic: Attic Dipole Versus 6BTV Vertical???? HOA Condo  (Read 1240 times)

N3HKN

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Attic Dipole Versus 6BTV Vertical???? HOA Condo
« on: June 21, 2019, 10:08:09 AM »

I have a 40/20M dipole in the attic. A Dentron Super Tuner and an Icom 7300 in the "shack". Also, on a deck at main level is an amplified loop for receive. The building is 3-floors, common walls, with the exposed basement (on a slab). My dilemma is - Would the same antenna at 27ft, but outside, perform noticeably better? The underlying question is - what factors in an attic can cause a reduction in antenna performance?

In this case no electrical equipment in the attic. Only one electric circuit parallel to the dipole for lights which is always off. There are ceiling wires under the attic floor but they are  not powered and serve ceiling lights that were never installed. There is one return air duct under the attic floor parallel to the dipole.  The roof is new and clad with fiberglass shingles. The vent in the peak is plastic. There is no aluminum clad insulation. So, as attics go, it is not bad with +6ft height at the peak. The coax is 9913 (fore-runner to LMR) I had from the real satellite days. Common mode choke. Tests with FT8 map shows possibly decent coverage (tough to judge).

The amplified loop has 1 S-unit of noise on 40M while the attic dipole has an S-7. Obviously that make it useless for reception. But what harms it in terms of radiation? Would a 6BTV vertical really be worth the cost, and HOA hassle, versus the dipole for transmission?
Dick  N3HKN
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K7JQ

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RE: Attic Dipole Versus 6BTV Vertical???? HOA Condo
« Reply #1 on: June 21, 2019, 11:19:26 AM »

Dick,

There are so many factors when you put antennas in an attic, it's really difficult to answer your question. In general though, anything outside is better than inside. However, an outside vertical close to your condo structure will have strange radiation patterns, plus the ability to have and arrange radials. RFI will also create problems, especially at higher power levels. From your description, the lack of much metal construction material and objects in the attic is in your favor.

Now, my experience similar to yours. I am in an antenna restricted HOA community, and have remotely-switched mono band dipoles for 10, 12, 15, 17, 20, and 40 meters in the attic (single story house), also with very little metal stuff to affect the radiation. I also have a screwdriver antenna mounted on a 6'x70' steel fence (counterpoise) about 20 feet in back of the house. As far as radiation comparisons, it depends on propagation as to how well each one works when talking to the same station and switching back and forth. Each one works better than the other at different times. The main difference is on receive. From all the electronic gadgets and appliances in the house, the attic antennas are more noisy, as much as 3 S-units more than the screwdriver. Obviously, if you can't hear them, you can't work them, so I find myself using the screwdriver more.

And then with the vertical, you have the HOA to contend with. I feel your pain :-\. Experiment if you can, and see what works better for you. Good luck.

73, Bob K7JQ
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AI4JD

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RE: Attic Dipole Versus 6BTV Vertical???? HOA Condo
« Reply #2 on: June 27, 2019, 02:42:24 PM »

Any antenna system outside is far better then an attic installation. Weather you have power running though that power line in your attic or not does not matter. Anything metallic can interfere with the pattern of your antenna. As already stated build a dipole and install it outside and see what if anything changes id would imagine you will be surprised.

As far as your noise level on receive keep in mind your magnetic loop antenna is not really a 40 meter antenna so to speak. It is a compromise antenna. With your attic installed antenna you could very well be receiving more man made noise due to the proximity of it to something in the upper floors of your home like an led light bulb or it could quite possibly be working that much better then your indoor magnetic loop your using for receive.

Look for a hustler 5 or 6 btv on the used market and see. One can generally find one at a reasonable cost used. I utilize a 6btv here at my qth which is also an HOA neighborhood. I have mine installed 40 feet behind my shack with approximately 1500 feet worth of 14ga ground radials under it. I can tell you that i am very happy with the performance of mine at my location. On receive sometimes on 40 meters it may be an s2 or it could be an s7. Noise levels change like propagation does. Keep in mind a vertical antenna is also more prone to pick up man made noise over a horizontally polarized antenna. I have also used my screwdriver antenna here at the qth over the same radial system and had great luck with that as well. As stated you can use a chain link fence post but your radial system is not very good with that. The links in the chain are not welded together and can move and make poor contact. Ive tried all kinds of things and found even 15 to 20 good length radials to be superior to chain link in my installation and to what i seen on my s meter.

Good luck with your project and testing. What you decide is best for your situation may not be for the next. Every lot and antenna location is unique just as its installation. 73
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W1BR

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RE: Attic Dipole Versus 6BTV Vertical???? HOA Condo
« Reply #3 on: June 27, 2019, 03:00:12 PM »

Is the yard a common area for all condo residents?  That would be a big problem
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