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Magnetic loop antennas seem to be really popular but I'm concerned about RF exposure issues. It seems the voltage of these is quite strong however in doing an RF assessment based on the ARRL web page calculators, I I do not know what the gain of a magnetic loop antenna is so I do not know what a safe distance would be. My power output would be no more than watts pep, which comes out to a maximum average power of 40 watts, per the assessment guidelines.
I figure I would be feet away from the antenna Also, looking at the MFJ and Buddistick as a quick way to get on the air. How effective are these if mounted outside on the balcony?
Rf Exposure with a mag loop, and MFJ 1622, Buddistick effectiveness
I also have attic access so that might be a possibility. The attic is all wood and composition shingles so very little metal that I can see. Again, when calculating RF exposure levels is it safe to assume these have the same gain as a dipole? Unless you have a mag loop with remote tuning, attic mounting is a non-starter. They are typically very high Q and simply do not have the bandwidth to cover any of the bands completely.
Even then, since the "rough tuning" is mainly accomplished by listening to the noise level from the receiver as you turn the capacitor for a peak, doing so without the receiver near you as you tune would be difficult.
Fine tuning for lowest SWR would be even more difficult After waiting six weeks for my backordered MFJ to be built and delivered, when it finally arrived the control box proved to be DOA; it would not power up. Having traced the problem to a defective 2. The technician said they have no control boxes available and it would take at least another five weeks for them to get another one for me, he was completely unsurprised when I requested a return label for a full refund.
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Learn more about TLS. Our selection of limited space small loop antennas offers great options for small lots, apartments, condos, hotels, and even homeowners associations with tight restrictions. Find your limited-space solution at DX Engineering today! What good is a portable transceiver without an antenna?
This co Moonraker Ltd Whizz Loops are compact QRP portable loops that are perfect for attaching directly to your ft or other Magnetic- loop antennas have existed almost since radio began.
Lots of amateurs in these situations are doing so successfully, especially on HF. Other locals are using screwdriver-style mobile HF antennas that can work with a proper ground plane installed as a base below them; aluminum plates or chicken wire can be used to create the required ground reflection.
Another local uses an HF loop antenna tacked up around the circumference of the ceiling of a second-floor bedroom. In the uppermost space I had already installed a 6M horizontal loop and two perpendicular noise canceller sense dipoles, along with a weather satellite Fig.
After a quick tape measure check, I found there was sufficient floor space to install a rotator and my homebrew 3-element 6M Yagi. There was enough space above them to stack the other three smaller antennas on a short mast.
The rotator I used is an old Yaesu model that sat atop our last HF tower for over a decade. It had been in storage for almost as long but still functioned properly. I attached the rotator body to a small piece of plywood using the original tower mounting plate bolts. The holes for the bolts were drilled through the wooden plate and countersunk on the bottom side so the plate would lay flush against the attic floor Fig 4.
A new control cable was also run between the rotator and the control box in the shack. An Ameritron 5-port remote RF antenna switch I had on hand was put into service; it did need a separate small-gauge multi-wire control cable to be run to the attic.
With that in mind, I added preamps for and MHz to make up for line loss. The preamps are connected directly to the antennas and are powered over the coax Fig. The Ameritron switch can be configured so that ports default open when switched instead of to ground; this allows power to be fed to the preamps without the possibility of the switch shorting the power source Fig.
Once all the Yagis were bolted in place on the mast, I used my antenna analyzer to adjust their driven elements to provide the best match in the weak-signal portions of each band. In addition, the close proximity of the antenna booms to one another probably adds to the RF fog of confusion that must surround the array.
The Dipole vs Indoor Magnetic Loop Antenna
With attic antennas, it simply is what it is. But my results so far have been good, at least on 6M. There are numerous online RF exposure calculators that can help you accomplish this important task.
So if you are unable to erect any outdoor antennas, you should consider whether an attic antenna will work for you instead. Overall, antennas are at best a compromise and sometimes are as difficult to install as outdoor antennas. But they can be worth the effort to continue enjoying our great hobby. As we old-timers will tell you, a compromise antenna is always better than no antenna at all!
It only takes a minute to sign up. I would like to mount this in the attic horizontally. Will I loose much performance between mounting it horizontally verses vertical? A small horizontal loop will have two sharp nulls: one pointing straight up and one pointing straight down.
Attic Mounted HF Loop Antenna In HOA, Does It Work?
The best way to view the actual pattern is to model one. Here is a 4nec2 NEC file for a horizontal loop. You can compare that to this model of a vertical loop. Links on my old STL page. In fact, if you want a horizontally polarized antenna with equal gain in the horizontal plane, a horizontal small loop is a great way to do it.
A horizontally polarized dipole by comparison would have two nulls off the ends of the antenna. The nulls may or may not be useful for you. Nulls can be useful to exclude sources of interference.
But if you can't rotate the antenna they can also exclude stations you want to contact. Horizontal polarization is less effective for ground wave propagation. If your primary concern is DX contacts on 20 meters, this is irrelevant as these contacts happen through skywave paths where any polarization works equally well or poorly, depending on conditions. If you are more interested in local rag-chewing on 80 meters you may have more of an issue, both due to the reduced propagation range of your own signal, and the likely case that most other people are using vertically polarized antennas.
Best Magnetic Loop Antenna
Because it loses its directionality, you also lose some of the gain, although this may not be all that significant. Another possible side effect is that a horizontal transmit loop antenna in the attic might couple more strongly into the house's AC wiring below it than a vertical loop or monopole.
The house wiring might or might not distort the antenna's pattern much; but you may have to be more careful with regards to RFI getting into household appliances and electronics.
The performance difference between horizontal and vertical is about the radiation pattern and what objects are near the antenna.This is why having the best magnetic loop antenna will solve all the problems. Again, if you want to replace your radio, then you will not have to go through the trouble of getting a new one because the antennas might be the problem. Magnetic loop antenna enables the radio to pick up waves and convert them into sounds.
When buying a magnetic loop antenna, several factors should be kept in mind. It is crucial to carry out some research on the product and make a comparison to ensure you get a high quality antenna. The things that you must check include; its design, polarizations, and signal strength. You should decide on the type of antenna that will satisfy your needs considering your location.
For it to give you the best results, you should ensure your site can access direct signals with less amount of the reflected signal. If you are in a densely populated area, you will have to go for an antenna designed with sharp directivity and not a high gain antenna.
You need to look for the highest quality antenna with superb aesthetics and great design before you settle on one. The best brands are awesomely crafted and well designed. They feature eye-pleasing qualities. You will get the best design from ethical manufacturers. It is essential to understand your location to ensure you get the best possible reception.
If your location is in an urban area, you will have to find the best antenna that can keep off multipath interference. Most of the manufacturers with quality products will provide a guarantee to back up their items. In most cases, such products are even used for a lifetime requiring minimal maintenance.
If you want a unit with both unwired and wired connection, then this Kaito AN AM radio loop antenna is the best choice for you. For wireless usage, the antenna works by induction. It is ideal for the radios with poor AM reception. If the receiver has an external AM antenna jack, it can be connected to the antenna directly using the output jack. At the same time, the other option is to keep the antenna close to your radio.
The high antenna features a tuning knob for adjusting the reception for each of the stations. Besides, it is designed for all brands like Grundig, Panasonic, Sony, Kaito, and many more.
Again, the antenna is passive, so there are no batteries required. The enhanced AM reception is impressive, and it is up there with Terk indoor for the reception coverage. Kaito AN tunable antenna has a compact and lightweight design that appears very stable. This is a very high-quality FM loop antenna that is well designed for the installation in your home, office, or on an RV, whether outdoor or attic mounting.
The antenna is constructed with heavy-duty material that features integrated balun, stand-offs, high-quality tubing as well as attaching hardware.
Unlike its competitors, this fantastic Tesslor FM loop antenna can be assembled easily within three minutes and has a The omnidirectional antenna is well-engineered for outdoor use due to all-direction pattern recognition. This great feature enables it to obtain all types of FM stations. It provides an excellent enhancement in the FM reception of digital and analog signals versus the whip antennas or indoor dipole.
The Ohm FM antenna is ideal for high-quality reception. Furthermore, the degree device is enabled to receive signals as far as 20miles away. This type of antenna is also the best when it comes to permanent installations.What does this mean? It means the primary coupling loop inductively couples to the secondary. The secondary loop has a variable capacitor to electrically adjust its resonance.
Alternatively, Some people use a toroidal transformer, and still others use a gamma match. Some folks use a variable capacitor that is smaller and handles low wattage before arc-over. Keep in mind that an air gap of 1mm equates to a breakdown voltage of about 1KV, which can be encountered when as little as 20 watts is used. A Magnetic loop antenna for watts can be made fairly inexpensive. Here is a great calculator for sorting out lengths, values, etc.
You could use a very specific capacitor and not have it variable if you were only staying on a specific frequency, but what fun would that be? This thing is an amazing easy homebrew project. I can tune by simply listening to noise for highest volume when tuning but can also use an SWR meter and can cover multiple bands. In my testing with my antenna analyzer I found I get 1. This is ranging from 5. I will do this but am enjoying getting some of those ShortWave signals I have never received before.
A nice start to the project and a great excuse to start my magnetic loop build. The Variable capacitor was a gift from another ham in my radio club.
I bend the larger copper pipe to form a circle. Then I laid it out to get an idea of what it would look like and start to think about how I wanted to mount it. I laid out the ends onto a board and hammered the ends flat. Then drilled holes into the flat portion for a place to mount the pipe.
The variable capacitor has screws on either side so this is a good mounting spot for the secondary ends. I bent the freshly drilled holes up and mounted them directly to the variable capacitor.QRZ Forums. Mag loop antenna questions For a variety of reasons i have to mount a mag loop antenna in my attic. Pleased don't try to talk me into a fan dipole or outside antenna, they just aren't practical for my situation I am looking at the MFJ or MFJ because they can be Tuned with a remote control head loqc problems located near my radio.
Once this antenna is in the attic due to my physical limitations i will not be able to access it to retune when switching frequencies. Are there any other mag loops that can be remotely tuned when switching bands?
Or is there another tuning solution for a mag loop? Any advice will be appreciated.An inexpensive 3-Band Magnetic Loop Antenna
An auto-tuner like an SGC can be attic mounted and tune a loop of wire run around the attic. Can you get 25 feet or more in your loop? Not exactly what you were asking for, but it might work better and it is really easy to use. N3HGBNov 27, KA0HCP likes this. I too would be more enthused about a random loop around the perimeter of the attic with a remote tuner.
Efficiency, performance and bandwidth will be far higher. The horizontal polarization will have less local noise, and the pattern will be omnidirectional compared to a Small Transmitting magnetic Loop which has narrow but deep nulls. Last edited: Nov 27, My SGC tuner manual even has it illustrated in there somewhere. I could run a wire approx 25 feet east to west then 8 feet north to south and back 25 feet east to west total of 58 feet in a "U" shape.
I am not a "hands on" tech type and most of the Hams I j have met locally are against loops and long wires saying that they "don't work really well for anything" I am more than willing to compromise some performance in order to get on 40,20 and 10 meters but as i said, I cannot get to the antenna once it is installed and I hate to ask or pay others to fix things if I can't get to it myself.
That sounds like plenty of wire. It will not work as well as a beam on a towerbut most certainly will work and you will be able to talk to people and have fun. Unless the tuner breaks or the wire falls off, it doesn't need routine access to work. I use a random wire around the perimeter of my third floor ceiling, of a 12 - 15ft room. As a dipole it is resonant around 17m.
I experimented with a knife switch at the loop center point and found I had less electronic fog from my neighbors with the switch open, i. Caution: Using any antenna below it's resonant frequency creates increasing voltages as the frequency is lowered.
This can damage tuners, amps and radio finals. To compensate, output power must be lowered. However, CW and digital modes work well at low powers. I find that I can work 80m safely with power lowered to around watts. Generally, keeping my power below 50W avoids RFI into my home appliances.
Does the auto tuner have to be located at the antenna in the attic? I'd rather not have an electrical device up where i can't see it for safety reasons Can i run a long wire into a balun or a then run coax down to the tuner at the radio location? Auto tuners at the antenna run off a bias tee powered by your power supply. The amount of power is negligible because it needs only milliamps to drive, not anything to worry about, your rf is much higher.
They make auto tuners that are desktop if you wish for more clutter. W4IOANov 27, You must log in or sign up to reply here. Show Ignored Content.