Antenna Over House? (
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- čas přidán 26. 12. 2020
- A viewer writes asking about putting up a dipole that goes over his house. Here's the answer.
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My father had a 40 meter dipole in his attic that worked well, with one exception. Every times he keyed the transmitter, the doorbell rang. Mom loved that.
i could imagine the arguments!
I would have disconnected the doorbell. Solved two problems at once...no more interference and no more annoying visitors.
@@HNXMedia Easier way: Put a sign on the door that says, "Bell Out of Order. Please knock." No de-wiring necessary.
Maybe he used 1kw of power
It is highly probable that the problem was that the dipole is a balance load, but the coax is not. That means that if there is any impedance mismatch between the coax and dipole, there will be RF currents on the outside of the coax.
One way to correct this problem is to use a balun to transform the unbalance feed into a balanced input for the antenna. There are commercial units designed for that purpose, or a person can make their own out of coax. There are other methods to do the transforming.
Want to say thanks to my English teacher who teach me English languages in school, so now I can watch this video and learn something new!
Recently discovered these. What a great set of videos! Thanks David.
Glad to see you're feeling better.
I've got a homebrew QWGP antenna on my roof which I use for my HT and base radio. No problems since March until now.
Happy new year. 73.
Check power level in this antenna vs proximity to people using FCC guidance for exposure to RF. Usually at 40 meters and above RF levels may have to be lowered below legal limits. Check ARRL web site for details on RF exposure from near field antenna radiators.
Dave is absolutely right about the noise sources from the house. My first antenna was a 6 and 10 meter dipole which I had over the top of my house. The noise was horrible. It turned out to be a combination of RFI from electronics in my house and my wireless alarm system, as well as my neighbors solar power system and air conditioner. Anyway, I ended up building a 20, 40 and 80 meter fan dipole that I hung in a tree about 100 foot from the house and it solved most of my noise problems. The only time I have noise issues is when my neighbors air conditioner runs my noise floor goes up 2-3 S units on 80 meters. Thanks for the video Dave and Happy New Year! Ryan - KI5GZO
Thank you for such great service to the Ham community Dave! Your videos are some of the best. They have helped this Ham in many ways! 73 de W3DNQ
I've been using this exact setup on an 80 meter dipole and longwire, but a little higher up. Works perfect! Also, love the dietz air pilot lantern on your shelf in the background
Thank you Daven for this easy to understand antenna. I shall try this once I am back to my Delhi qth as there are quite many trees within our housing society.
Greetings from Kolkata ( formerly Calcutta), India.
Cheers & 73s
Hi Dave! Hope you had a great Christmas! My delta loop is literally ON my roof. Brown wire matches the shingles, u shaped staples secure it, and you can't even see it. Using a Balun Designs 9:1 along with a Palstar tuner, and have worked Europe, New Zealand, and a lot of the US. Optimal? No. But it works! 73 and Happy New Year!
Thanks Dave Happy New Year!🎆
Hi Dave, great video!! One Tip I'll give to the HAM operators who happen to also grow, like myself, I recommend using LED Grow Lights over the HPS lights that use Digital and Magnetic Ballasts. It's the ballasts that give off all of the stray RF. My Grow Room is directly below my antenna tower, and because I use LED lights, I don't get any leaky RF as a result. LED's use DC drivers, and also integrate well with solar panels if you have those installed on the property as well. Cheers and 73's.
I use an inverted V and an off center fed dipole both above a steel roof and they both work very well. The key to that is the fact that the feed point is 15 ft. above the roof. Talked to S. Africa the other night on the gray line with 100 watts on 40 meters.
Thank you, Dave. Another great video. Happy New Year. N0QFT
My dad ran a doublet over the roof, fed at the chimney and the elements running down at a slope. He ran that for years and talked all over the world on it, until he started making mag-loops.
Excellent video and content!
Another fab video Dave. I always worry about the two radios on your top shelf in the background and wonder how they are secured as they look a little precarious with their front feet hanging off the shelf! Best 73 from London, M0XXJ
I had a 40/20 meter attic fan dipole antenna at my home in JAX FL that worked great. I originally set it up with 40 and 17 meter legs but the SWR on 17 was too high. I never figured out the problem so I switched to 40/20 instead. The roof was composite. I secured the center to the ridge line and ran the legs to the opposite corners. I also separated the 40/20 meter ends to different corners.
I prefer inverted V dipoles since the feed point impedance is closer to 50 ohms and closer to Omni directional.
I would consider having the center of the dipole over the end of the house roof that is farthest away from all the appliances. My three biggest culprits are the bowflex tread climber, a sqeed queen washer and a blue ray DVD player.
David should he bin told about the safety issues with RF and human absorption? also what he could be doing to the TV Stereo computer etc.? Great stuff David Thanks for your time to show tell and teach us.
Jim
Love the whiteboard cad
Good explanation and great advice, Dave. Thank you for sharing it with us. 73 de K7RMJ
Tip: use weighted rope on pulleys to secure the dipole ends and have a means of twisting the split point of the dipole to optimize the length for the frequency. You get a universal dipole.
I have a fan dipole in the attic, shack on second floor. I have to shut turn off the breakers upstairs to operate as the transmit signal plays havoc with lights, and electrinics, especially 20 meters and above.
One bad thing you mentioned was right from the house. But it could be sending rfi into the home and causing phones and other electrical devices to react to the rfi. I have had this happen to me when I had a dipole next to the house roof. Especially if running any extra power. Thanks for the videos
Agree 100%
@@timg5tm941 Except the near field should be strongest on 80 and 40 meters and keep decreasing with higher frequencies. The multiplication factor is wavelength divided by 2 pi.
I think that you should analyze how much rf energy the people in the house might be exposed to. The house and the ground under the house are in the near field of the antenna. You certainly would not want to be running a 1500W amplifier. Some devices in the house may not work properly when you are transmitting. Similar concerns apply when operating with an antenna indoors such as a magnetic loop antenna.
Absolutely agree!
At 30 feet in the air and only 300 watts, the RF level will be fine. The should be tables generated by the FCC listing required distances by frequency band.
When I was first licensed, I lived in an apartment building. I had a dipole on the ceiling and when I used 40 meters, it would set-off the fire alarm in the building. 😬 Needless to say, I didn't use 40 meters.
I have also seen that cause the Garage Door Opener Lights to come on :)
My only problem was getting the wire antenna over the roof without getting stuck on the shingles. It's like petting a dragon backwards (with all those scales).
good to know
The antenna will work fine, however you will get some RFI in the house, no matter how resonant your antenna is. Trust me, I know. I had the same setup several years ago. I had a long run of Romex to an auxiliary tankless water heater that would pick up RFI and actually fry relays in it. After several relays, I decided to put ferrite chokes on the Romex as close to the heater as possible. that seemed to work well. RFI would also trip out computer monitors and made our dishwasher, Keurig coffee maker and fridge act weird as well. If you're willing to take those chances, go for it.
Only thing I would add is what if he experiences a strong lobe into his shack on a particular band such as 80? Could cause RF in the shack if the antenna is directly overhead
I Think OCF antennas have their main lobes off the ends of the wire, but do not remember for sure. Too many decades since I studied antenna theory.
I have my antenna that way, I have good luck with it
Is there a way to filter some of the home rfi generaters like wall warts, washers, dryers, microwave ovens, TV, and etc.? 73s de N5DHT
I have the same situation works better outside than inside the attic, 73 kd0qcs
I'd be curious what the EZNEC antenna model performance is with and without the presence of the house. The EZNEC ground conductivity would surely be affected.
Are constraints on antennae as stringent for swl as as for transmitting?
How noisy are the power lines? I’m a new general, and I have a transmission line about 30’ high that runs from a pole in the street to a transformer in my backyard, and then a supply line that runs from the transformer to the rear of my house. The only good spot that I could hang a dipole would be parallel to the transmission line, the dipole would be about 30’ away on the opposite side of the House at about 20’ tall. Would that get too much noise?
Grow lights, Dave ! I wonder what they would be growing? Lmao 😂😂😂😂
Have you looked at the price of tomatoes lately? 😉
It could be anything. In my case about $1000 worth of tropical carnivorous plalnts. They love fluorescent lights, which tend to be noise generators.
Thanks David . You are the answer man. KD9HWH
Hi Dave,
Happy Holidays to you and the family. Bill's question was an easy one to answer. Stay safe. 73 WJ3U
Hi, David. I just came across your channel last evening and I've already learned a wealth of information. I’m new to Ham so forgive me if I use the wrong terminology. I'll be putting up my Buckmaster 8-Band, 300 Watt, OCF Dipole Antenna that is 270 feet in length. I'll be suspending it on both ends by rope from two huge oaks on my land at a height of about 40 feet. My situation looks similar to the drawing you used for Bill Hill on this video, with composition roof shingles and no known foil or other metallic insulation beneath. The two trees line up just off of my 2-story house, and my dipole wire will be located about 12 feet away and roughly 20 feet above the roof. Fortunately the off-center feed will fall right outside my office window where I’ll set up my Ham system. My question to you is, would I do better to create a flattop V configuration with my longwire in order to skirt farther away from the house to avoid noise and then increase my coaxial cable to reach the feed? Also, how many feet of coaxial are acceptable/advised before it interferes with the antenna's performance? Thanks for you assistance. Brum
For best performance, you will need an antenna tuner. Does the Buckkmaster come with a 4:1 current balun? If not MFJ sells a suitable unit.
I wouldn't worry about the coax length, unless you were to run a really long length. For your 300 watts, you should be able to use RG-58 without excessive losses. That would keep the weight down on the OCF antenna.
Can you show us the radiation pattern of a 14 foot diameter mag loop antenna? I have been looking and have not found anything. Also, how would i figure input impedance?.. Thinking about installing a modofied trampoline frame on the roof, saddling the peak of the house. So it would be horizontal, not vertical as you normally see them.
Hi Jason,
Try this website for some loop antenna information. WJ3U
webclass.org/k5ijb/antennas/Small-magnetic-loops-K5IJB.htm
Mag loops all radiate the same when properly tuned. Size/frequency is irrelevant. Just Google, "mag loop pattern"...
Anyway i can tune My antenna to figurę out which neighbor's house Has THE cheap growlights in it? Like triangulate THE Location?
No. But if you have a portable radio that picks up the noise, you can wander around the neighborhood to at least locate the general area.
Usually power line noise is due to a loose or corroded connection to a power transformer or the fuse connected between the high voltage feeder and transformer primary.
Thanks for the great videos. I too am a beginner and am thinking of a dipole or some other type of wire antenna. The side of my house is about 45 feet long and it would have to go under the eaves near the rain gutters at a maximum height of about 10 feet. The roof is concrete tile and the attic has foil backed insulation. What’s my best antenna option in your opinion? I don’t have a radio or antenna yet, still at the point of studying for the test.
Vertical
What would you suggest. My yard is all concrete so I cannot bury radials.
To get a more meaningful reply you need to indicate the size of your land block and the location of the house. Add to that the bands you intend to use will also play strongly into any solution.
@@marks2254 you don't need to bury radials.
@@robbvk6es the room that’ll House the radio is on the south side of the house and my fence is 12 ft south of the house. The length of the south side of the house is about 45 feet with the room the radio will be in being about in the middle of the 45 foot length. It would be possible to run wire around the corner to each the front and back of the house for another approx 30 feet on each the front and back of the house. Would have to run it under the eaves, which are about 10 ft high. There is an 8 foot high wooden shed in that 12 ft by about 45 foot area.
The question reminded me of 3 Stooges "Goof on the roof".
How high would it have to be above the roof if his roof was a metal roof?
This may be a still stupid of a question, but could you run a dipole along the peak of a metal roof and would the roof act as a reflector?
No, it would be too close to act as a reflector and also would really mess up the feed point impedance.
What if I do find the sources of noise, like my deep freezers? How do I cure this w/o shutting them off?
You wouldn't be the first to have to decide between eating, and this hobby.
There are filters that can be installed to keep the noise out of the power cord. But I have no idea how effective they are.
What is an Auggie
A special tool used by amateur radio operators that requires certification to be able to use.
what is 73 mean???
It means roughly "Best Wishes".
What about grounding for lightning?
Kurt - KA7ZDD
If you are in an area prone to lightning, you should have an entrance panel with a proper lightning suppressor and good grounding.
😍👍
Never Never put any kind of antenna over your house! If it draws lightning, your gonna take a hit. I've seen 2 houses catch on fire from lightning hits.
First!
I have about the same situation but antenna up around 50 feet ,, but I have a metal roof. The metal roof is not grounded. Should grounding my roof make any difference??
Thanks for all your videos!! 73
Lance W7LDE