A foot length of 12 gauge PVC covered stranded wire slopes up from the ground system to the 40 foot level of the 45 foot tall fiberglass flagpole about 60 feet of wire length and then proceeds about 70 feet toward the far back edge of my property.
The 90 foot start-to-finish dimension just fits my city lot. At the end, the antenna wire is terminated at about 15 feet above the level of the back yard. This antenna is used on meters only and is coaxial cable fed. In place of an active tuner, a 10 turn 4 inch diameter tapped coil wound of 0. Two vacuum relays are used to select the correct amount of the coil for a particular band segment. No coil turns are added to the top band segment, 7 turns are connected in series for the middle tuning range and the entire coil is used at the bottom end of the band.
All of the base load components plus the static discharge arrestor are located in a 7 inch square weatherproof box that is bolted to the ground structure. The coaxial cable entry point is sealed with silicone sealant to keep the spiders and moisture out. The wire that brings power to the relays is TV rotor cable which is rated to be used outside in the weather. The transient suppressor and coaxial cable braid bus-work is bonded to the ground system with a heavy braid.
The cross-section of the metal drainage ditch that is used as the ground system for this antenna is shown below. This metal drainage ditch is about feet long and runs along the top of a five foot high concrete block wall that defines the eastern boundary of my city lot. The drainage ditch measures 12 inches wide and 12 inches deep. All of the 10 foot long metal sections are electrically bonded together along the length. An improvement that I am considering for the ground system is to add a couple of wire radials in addition to the drainage ditch ground system.
These radials will be run underground by fishing them through the drainage pipes buried under my driveway and front lawn. Another improvement under consideration is to add a number of 10 foot long ground rods along the length of the metal drainage ditch, especially near to the antenna feed point. Very interesting?? The antenna wire coming from the weatherproof box mounted on the metal drainage channel lower center of the photo first goes up to the top of the brown painted PVC pole at the upper right of the photo.
From there it proceeds up to a point about five feet from the top of the 45 foot tall fiberglass flag pole. This places the meter antenna five feet below and at about 30 degrees crosswise to the OCF Windom antenna wire to minimize interaction between the two antennas. The far end of the antenna is attached to t he fence with a pulley and one gallon paint pail counter weight that takes the sag out of the antenna wire and allows the antenna pole to sway freely with the wind without stretching or breaking the antenna wire.
The maximum SWR at the edges of each of the three segments is less than 2. Since the static discharge protection is located at the base of the antenna, the coaxial feed line goes directly to the shack through a foot length of coaxial cable. The antenna loads nicely and shows virtually no change in SWR when operating in either dry conditions or on a rainy day. The antenna handbooks show that the inverted L has a more or less omni directional pattern that is uniform within about 1.
The signal reports from any direction using this antenna are always as good as or better than the signal reports for other hams using top loaded verticals, full wave loops and dipoles at similar heights.
This antenna is not a multi-element full size vertical array using massive towers, but it does work and works quite well. This is the one band where I often run the full power in order to overcome the very noisy band conditions that are typical at the receiving end. This loop often delivers the best quality receiving signal, especially if there are plasm TVs operating in the vicinity see the PIXEL loop page for more details about the performance of this loop on the meter band.
Notify me of follow-up comments by email. Notify me of new posts by email. Please input symbols from picture. Amateur Radio news from Italy. Leave a comment Cancel reply Your email address will not be published.For several years, I have been struggling with atmospheric noise on the meter band.
On one of the reflectors I saw a comment by N7TK, John, that he uses a coaxial loop on for receive. I asked him about his success and his response was favorable enough to try one myself. But they are at the bottom of the ladder compared to Beverage and AY Loops in performance. Nonetheless, I thought that I would try one. I hopped into the car and went to the local Comcast center to see if I could get a donation of hardline coax scraps.
It was my lucky day, they were taking down a ft tower that was loaded with coax. I got about feet in 20 and 40 ft pieces. The following pictures and text show how I built it. I am extremely pleased in it's performance. No longer are my ears burning with high levels of noise when trying to pick out a signal. I decided that a 6 ft diameter loop would work out in terms of available space. I measured the halfway point and cut out 1 inch of the aluminum shield using a copper pipe cutter.
Then with the help of my wife, and using the patio table as a form, we bent it into a circle. Here you can see the cut in the shield and the T fitting ready to slide into place.
As I said, I used a pipe cutter to break the shield then I used a Dremel tool with a saw blade bit to slice the shield lengthwise so that I could separate it and remove it. Here is the T fitting slid over the coax shield break. Keep the coax from the MFJ to the clip leads as short as possible. I attached an aluminum box purchased from DigiKey Corp.
This assembly prevents chafing of the coax jacket and makes a nice snug fit for the coax.Tribal bids
The terminal strip istands on standoffs to align the coax and provides a convenient mount for the trimmer capacitor. The box is grounded to the coax shields through the standoffs and the wires shown which will connect to the coax shield.So hacker of note and dedicated amateur radio operator [Jeri Ellsworth AI6TK ] has started a video series devoted to building a magnetic loop antenna for the and meter bands.
The first video, included after the break, is an overview of the rationale behind a magnetic loop. We were sorry to hear that castAR, the augmented reality company that [Jeri] co-founded, shut its doors back in June.
The main killer is the capacitors. Even butterfly caps of sufficient power can cost a quite a bit. Vacuum varicaps are not actualy the lowest loss capacitors in this frequency range, Q is usualy in the range of a few hundered.
Modern high performance ceramic chip capacitors from companies like American Technical Ceramics have far greater Q. This has the disadvantage of not been variable however. If you want to make your own variable capacitors it is also quite easy! Some tunable PA designs use a set of binary valued ceramic caps and connect them using relays to make a variable cap.
I have links on my youtube channel you can check out. You can make variable capacitors from a can inside a can, tubes inside of tubes, sheets overlapping and even tune-able plate style. I was thinking adding a threaded rod to one can, where the rod is free to rotate and stationary on one end and a nut on the other end for the can or tube style and the other tube or can is fixed in position to really be able to tune finer and more accurately. I was just thinking now similar to my idea of placing the Medocino Motor in a vacuum tube and making a magnetic clutch… I wonder what the magnetic field of an easier to glass tube seal and blow really melt the ends closed make vacuum capacitor using a magnetic chuck to rotate the shaft of a plate variable capacitor.
I am not sure if the magnetic chuck design is feasible. Just like batteries, resistors, capacitors, inductor coils, electromagnets, relays, variable inductors and other electronics components, we can all make our own variable capacitors. However… yes… we can make our own variable capacitors rather easily using commercial off the shelf items.
Small Transmitting Loop Antenna Calculator
Man, do I need to play editor before posting on some days. So if your not operating at high power the vaccum is just and additonal complication. Excellent, thank you sir. Softer for better seal, sublimation or am I totally missing the point? There is no clutch inside a vacuum cap. They have a continuous path of smooth copper in the form of a wide area bellows. You are absolutely wrong and giving out completely false information.
This is just a stone cold fact. The very high Q is one of the major reasons why vacuum caps are used in Q-critical circuits, and circuits with very high RF currents. I have typos and you might of misunderstood what I was stating. Then have a finger on the one side of the contact that would rotate with the magnetic clutch dial.
I am still wondering what the effect the magnetic field would have. That is all. Did you read that and comprehend that, you might be misunderstanding what I was inventing… not misleading… I was questioning. As you go to longer wavelengths and employ modern DSP digital modes, very low frequency long wavelength frequencies do become interesting, but difficult to implement.
I should have been more clear that I was referring to the HaD article, not the video linked to. Multiple loops can make an array.Airfoil generator software
Now we can get even more directional than bi.Post a Comment. Loop antennas have always fascinated me.Steam iron keeps tripping
They can be highly effective as well as portable. My initial thoughts were to build a loop for 40 meters but, after researching K8NDS's design for a helically loaded magnetic loopI have decided to build my first antenna patterned after his design.
Added specifications, preliminary discussions, and references. While I could put up a tower, it would dominate the neighborhood and is not something I want to do from both a cost and good neighbor point of view. The Loop Skywire antenna I use for daily work works well for my purposes but it suffers from not being up as high as it should be to be most effective.
This is where the magnetic loop really shines. While the Loop Skywire or dipole is more efficeint that a magnetic loop, that holds true only if they are up at the proper height.
Capacity or capacitance hats
If they are not, the magnetic loop is likely to be more efficient. The magnetic loop advantages readily become apparent in the first two pages of this paper.
If they are, in some situations, so much more efficient, then why don't more hams use them? It is because, being small, they have a much higher Q factor than standard antennas and, therefore, must be tuned, even for short moves across the band. This can be difficult to achieve since the tuning must take place at the antenna if losses are to be kept low.
There are hundreds and hundreds of articles about magnetic loops. Rich, K8NDS, has pioneered the design of a helically loaded fractional wavelength magnetic loop.
Two key references for his loop designs are  and . Rich informed me that he has tried many different methods of driving the loop and that his favored matching method is the gamma match. Given his success, I will adopt the gamma match for the initial design. In short, there are no Hula Hoops that are 8.
The K8NDS design uses 3. A Google search turns up these sources: 4 in.My homemade amateur radio antenna for the meter band is the result of many considerations, inner debates and tests. This Page Covers 1. The Compromises 2. The Hard Choices 3. The Drawings 4. The Results.
June helped me understand what essential considerations I had to take into account. Nevertheless, the love of experimenting with antennas played a critical part in the successful outcome of this homemade antenna project. Granted, I could have considered a top "loaded" vertical, with a top coil inductance to make up for short physical height.
ButI do not like verticals, "loaded" or not! Furthermore, quarter wave verticals just "bleed" too much precious RF energy in the ground system for my taste. After playing with all kinds of weird configurations, I finally settled on a dipole for its inherently balanced and higher efficiency in capturing and radiating energy.
The result is a "hybrid" dipole or "ungrounded" vertical amateur radio antenna, depending on your point of view! I have never fed this antenna with more than watts. In fact, I usually work QRP. However, because the counterpoise lies on the ground, and is not buried, I would not be comfortable using this antenna with higher power.
There might be high RF voltage present at the tip of the counterpoise which might be harmful to humans or animals if they come in contact with the counterpoise part of the antenna system. If you have trouble getting your antenna tuner to deal with the reactance of this antenna, you can try As you can see, this amateur radio antenna system for meters is "unorthodox", to say the least. It is the best set of compromises I have been able to come up with, after many experiments.
It is definitely a keeper for me. Best wishes and 73 ". I am sharing this fitting video with you in these most challenging times. Let's keep the communication channels open while, by civic duty, we must maintain a vital physical distance from our fellow me….
Read More. To my chagrin. Puerto Rico's mag 6. FTC Required Disclosure : If you make a purchase via a link on this site, I may receive a small commission on the transaction - at no added cost to you. Thank you! Antenna e-Books.
The Classic Dipole. Wire Antennas. Space Saving Ant. Short Antennas. Carolina Windom. HF Vertical. HF Military. Design Software. Antenna Calculator. Homemade Ant.Small Transmitting Loop Antenna Calculator Small transmitting loop antennas, commonly called "magnetic loops" or "mag loops," can give surprisingly good performance when they are carefully designed and constructed.Embaixador de siao
Although this online calculator is intended to assist with designing and building homemade, ham radio loop antennas for use in the HF bands, magnetic antennas have been constructed that function in the VHF or even the UHF frequencies. The most common material for home building small ham radio loop antennas is common copper plumbing pipe. This calculator enables you to test the design of an octagonal loop antenna and to answer "what if" questions until you arrive at a design that meets your needs without a lot of experience in electronics.
Length of Conductor antenna "circumference" feet Please enter the length of the conductor. Side length:. Check out the recommended reading list. Small Transmitting Loop Antennas. Full-Wave Loop Antennas. Quarter-Wave Vertical Antennas. Coil-Shortened Vertical Antennas. Dipole Antenna Length. Coil-Shortened Dipole Antenna. Coil Inductance. Toroid Coil Winding.Ham Radio - 80 160 meter magnetic loop transmitting antenna
Capacitance Capacitor Design. Capacitive Reactance Xc.
Inductive Reactance XL. The pH Pages. The Simplest Possible pH Meter. Build a pH Meter and Controller. Buying a pH Meter. Recommended free Software. Create a Database Table from a Spreadsheet. Export a Database Table to a Spreadsheet. VBar Flybarless Controller. Accessing an Extra Channel on your mini VBar. Setting up the Governor on your mini VBar. Calculate Headspeed with your mini VBar Governor.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. If this is not possible on your variable capacitor then be sure to keep the connection leads as short as possible. I was afraid of losing the 20 meter 7Mhz band. At first I tried a 20 watt soldering iron with copper tip…. Yeah, OK.
I get it. This will however make it to field day and was a very fun project. For HF the size is very good compared to a dipole antenna or some others. It is however very directional, which can be good or bad, depending on use.
Also, The magloop does have an Electric field. It is just not found until you get a bit away from the antenna, my old field strength meter does show an electric field on its little vertical antenna when I get about a half wavelength or more away from the loop.
Inside that, it shows nothing. AA5TB gives us a great view of the antenna radiation pattern in the following diagram. I have heard there are reports of mag loops at watts blistering paint on wood a foot or two away.
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