80m folded dipole

80m folded dipole

B-Square Engineering is the first to offer a Terminated Folded Dipole antenna, truly optimized for amateur radio use. B-Square Engineering doesn't make cheap productsjust products that offer users a great value. Excellent performance at low mounting heights. There are no coils, switches, taps or traps to require attention or cause problems. Terminating resistor uses the latest in non-inductive thick film technology, a waterproof monolithic package, complete with an integrated heat sink.

A B-Square Engineering exclusive! Use as a flat top, inverted V or sloper. Comes completely assembled, center support, end yokes, and swivels included.

All cable connections are crimped and soldered. Following assembly they are coated with high voltage motor varnish to offer the very best in corrosion protection. Designed for zero maintenance, yet totally field serviceable. Attach your coax via a standard UHF connector and you are ready to start communicating. Like all B-Square Engineering products, the Terminated Folded Dipole is built to give a lifetime of satisfying performance, all for a remarkably low price. It's the perfect choice for anyone wanting the greatest capability for the least expenditure.

And you buy with confidence! We offer day refund privileges on all purchases. Why use a Terminated Folded Dipole antenna? Although performance can be enhanced at high mounting heights, it performs well at heights as low as fifteen feet. If you have the means to install an eighty meter dipole, thirty feet high, this antenna will replace it neatly.

80 Meter NVIS Antenna

String it up with a 50 ohm feed-line and start talking. Its great for field day activities or for those of us that live in town and are unable to hang an antenna sixty feet up. Foolproof tuning: Have you ever jumped bands to chase rare DX, only to find your antenna is tuned to the wrong band.

With the terminated folded dipole you can switch bands as fast as you can change the frequency on you transceiver. The antenna system requires no attention. Value: With a B-Square Engineering Terminated Folded Dipole, it is possible to work all the HF bands with one antenna, one feed-line and one installation without the expense of a tuner.

Forgiving of Real World Issues: Not only will the Terminated Folded Dipole continue at low installation heights, it is less effected by nearby obstacles than most any other choice.

Although this does not mean that it will offer excellent performance in all installations, it can be counted on to deliver when dipoles and doublets have problems. Enhanced RX Signal to Noise Ratio: Seeing is believing, when everyone else is failing to pull a signal out of the mud the Terminated Folded Dipole delivers the signal with S-units to spare.

In Mr.Dipoles are widely used on bands like 80 metres, 40 metres, 20 metres, 15 metres and 10 metres where they can provide excellent levels of performance. A dipole antenna can be a very effective antenna, providing a good level of performance especially if it is erected as high as reasonably possible and away from obstructions, etc.

Building am HF ham band dipole does not have to be expensive. Often the items needed can be salvaged from previous antennas, or bought for relatively small cost. Wire, feeder, insulators and fixings are all that is required. Building the antenna and erecting it can provide a great insight into the aerials or antennas and how they work, and in this way the performance of the station can be enhanced even further.

Wideband 80m Dipole

The most straightforward way to install a dipole is as a horizontal antenna, although this is by no means the only way. Also a dipole is most commonly found as a half wavelength dipole, although this is not the only length that can be used. Feeding the dipole at a high current point, as in the case of centre feeding a half wave dipole means that it is fed at a current maximum pint on the antenna.

It is also possible to have longer lengths - antennas with lengths that are odd multiple of half wavelengths long also provide a low impedance. This means that a 40 metre dipole can also be used as a three half wavelength dipole on 15 metres. The basic half wave dipole itself is quite straightforward, consisting of a radiating element half a wavelength long and fed in the centre.

The diagram above gives the basic format for the antenna, but in reality the antenna will need to be erected between two supports. The diagram above shows a typical installation for a ham band dipole antenna. Often the supports may be a suitable point on a house and another support in the garden.

On the house it can be possible to attach the dipole to the chimney, or other high point. Then another support may be a pole or even a tree. There even may be another suitable building. It is possible to erect the antenna in many places, using the supports that are available or that can be erected.

A little thought and ingenuity will provide a number of different options. If using a tree as a support, it must be remembered that the tree will move in the wind. If the antenna wire becomes too tight as the wind moves the tree back and forth, it could break the wire. This must be taken into account, and there are several methods of overcoming this. Typically coax fed dipoles are a half wavelength long as described above to give the required feed impedance.

In order that the dipole is an electrical half wavelength long, it needs to be a certain length. This is not exactly the same as that of an electrical half wavelength in free space as factors like the end effect - an effect caused by the fact the wire does not go on for ever, the wire thickness and a host of other factors affect the length of the antenna. In view of the fact that there are many variations in the calculation of the length of the antenna, and these even include the proximity to other objects and the local conditions, etc, it is always best to cut the antenna slightly longer than expected, and then trim it to provide the optimum performance.

Build an HF Ham Radio Dipole Antenna

Also it may be that the dipole needs to be optimised for operation on a particular section of the band. The length will be slightly different for the best performance at the top of a band compared to the bottom of the band. Often it depends upon whether Morse of SSB operation is envisaged.

Fortunately with the addition on an antenna tuner in the radio shack, it is possible to reduce the SWR seen by the transmitter to anywhere in the band. If no antenna tuner was used, then the level of SWR might rise to a level where the transceiver output protection could start to reduce the power level at one extreme of the band or the other.

A few items are needed to make an HF dipole for the amateur bands. These are normally quite easy to obtain, normally for a relatively low cost.My website uses JavaScript for menus etc.

It is currently disabled in your browser! Please re- enable it for full functionality. This technique is typically used in antennas that have radiating elements that are too short for the desired resonance frequency.

There are several standard ways to load a radiator ref. Obviously these loading methods can be combined. Linear-loading and end-hat loading, by themselves, will not sufficiently reduce the resonant frequency of a radiator that is really short. It will have to be combined with inductive loading.

Let's take a dipole that is short with respect to the desire operating frequency. To make it resonant at that frequency, some form of loading is required.

By the way: resonant operation is not a requirement - it just makes coupling to a feedline easier.

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One standard solution is "inductive loading": placing a loading coil somewhere between the feedpoint of the dipole and the tip of each dipole leg. The current-distribution along the radiator is such that the current is highest at the feedpoint. Placing a loading coil here, requires the smallest inductance. The current-distribution tapers off, from maximum at the feedpoint to zero at the tip of the radiator element.

So, as the loading coil is placed farther away from the feedpoint, a larger inductance is required. At the tip of the radiator, the current is zero. This would require an infinitely large inductance. See the diagram below. The placement of the coils does affect the shape of the current distribution, but does not change the fact that it is maximum at the feedpoint and zero at the tip. Center-loading i. So why not always use center-loading? This is primarily driven by coil losses, hence, efficiency of the antenna.

The coil losses basically depend on the current, coil dimensions, material, construction, and core.

80m folded dipole

Note that the efficiency-vs-placement curves are fairly flat over a relatively large range around the mid-point. Note that this tends to shift towards the tip of the radiator when "capacitive hat" loading is added. My 80 m short vertical dipole with center -loading is described on this page. The minimum installation height of a horizontal dipole is often stated as about 0. Clearly not possible at my QTH.

Furthermore, the floor of my terrace is reinforced concrete - "bad" soil. As a consequence, my dipoles will have much? The experiments described below are a nice exercise in building and tuning a dipole, but were doomed from the start from a DX-performance point of view.

I am not interested in local QSOs. Caveat emptor!My website uses JavaScript for menus etc. It is currently disabled in your browser!

80m folded dipole

Please re- enable it for full functionality. What is a folded dipole? As the name suggests, it is simply a dipole with the tips folded towards each other. There are three basic variations, based on whether the tips of the folded dipole legs are interconnected, bridged with a terminating resistor, or left unconnected:.

The two halves of the folded dipole can be thought of as two transmission line stubs that are shorted at the end. The inductance of these stubs can compensates the capacitive reactance of a shortened dipole. The feedpoint impedance at resonance of a half-wave folded dipole is four times that of a regular half-wave dipole. See ref. Folded dipoles do have a slightly larger bandwidth then the equivalent un-folded dipole. Standard recommendations for the dimensions of a folded dipole are based on the lowest operating frequency MHz mini.

Build your own Wire Antenna!

The span of the antenna can be further reduced, by folding the dipole legs into a zigzag though this may complicate feeding the antenna :. TFDs have a terminating resistor across the ends of the folded dipole legs. The resistor has to be inductance-free. The recommended resistor value appears to be 1.

Note that it is not easy to make a balun with a flat transformation ratio over multiple bands, and balun losses increase on frequencies for which the antenna is shorter than 0. Installation is typically oriented horizontally "flat top" or "tilted" up to 30 deg. Have not seen such HF antennas installed vertically. Another option is an Inverted-V configuration spacers horizontally.

Skimming the available advertizing and some unserious sales literatureonce comes across the following spectacular claims:. As always, the Universal Law of Conservation of Misery applies: you don't get something for nothing! These antennas are convenient as they can indeed be made broadband - but at the cost of performance I really do not see much advantage, if any, over a standard "unfolded" dipole with the same span, and fed via twin-lead or ladder line and an automatic ATU.

But, in all fairness, antenna tuners are often an overlooked source of sometimes significant losses. This type of antennas is commercially available from a number of sources ref. For experimental and "household" use, such antennas can be made for a fraction of their prices. Which is what I did. My reason for doing some experiments with folded dipoles, is that I had a dipole laying around that is too long 2x So why not fold it and see what happens?

Note : I have not completed all necessary experiments and measurements yet. One of these days I may dig up the antenna from my "antenna cemetery" and finish it, for a final verdict.When you subscribe, you receive only messages for the product you have subscribed to.

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Send To:. To build the largest and most complete Amateur Radio community site on the Internet. This project involves a management team of volunteers who each take a topic of interest and manage it with passion. The site will be something that everyone involved can be proud to say they were a part of.

Toggle navigation. Forgot Password. Reviews Home. Time Owned: 0 to 3 months. Bought Terry's T2FT after a lot of research. Due to space limitations, I bought the 66 ft version. Terry was kind enough to pick up my phone call and ship it expedite to the hotel where I was staying in Boston. Good and sturdy stuff. And I have installed the antenna in a less than optimal scenario, surrounded by a building and a metal fence. WTH, is the antenna deaf? By no means! The signals come stronger.

A QSO net coordinator signal strenght: S9.

80m folded dipole

The coordinator signal strenght: S8. You will not WANT to spend a hour trying to untangle the antenna and then giving up and resorting to the wire cutter. That broke my heart. Yes, that is true. So, what? Now you get off my lawn.The folded dipole is claimed to offer increased bandwidth, and to closely match ohm line. This is much like the double bazooka antenna, or coaxial dipole antenna. Inaccurate double bazooka and coaxial dipole claims have been debunked in numerous forums and texts, including in QST and Reflections by Walter Maxwell.

While double bazooka or folded dipole antennas can offer significantly more bandwidth than a thin wire dipole, it is important to understand why certain antennas have more bandwidth. Let's look at a folded dipole and see how it really behaves. False: On a single band, bandwidth is essentially no different than just tying the legs in parallel, splitting it in the center, and feeding it with coax.

We will see this in the models below. A folded dipole, like any dipole, is wider primarily from being made thicker. It does not get significantly wider not from the stub effect or folding, and not from the higher feed line impedance. False: The folded dipole is only useable with reasonable feed efficiency on the fundamental and on odd harmonics. The folded dipole is much worse than a regular ladder line fed dipole dipole for harmonic or out-of-band operation. On even harmonic bands, it appears as a nearly dead short.

It is not a good multiband antenna, and actually has excellent radiation suppression of even harmonics. Myth 3 -A twinlead folded dipole fed with twinlead will have an impedance around ohms on the designed band.

Variations in folded dipole SWR is less with changes in antenna length or frequency are less than in a regular coax fed dipole. False: SWR variations are essentially the same. On the fundamental and odd harmonics, the dipole impedance is about 50 to ohms. Don't be fooled by claims wide bandwidth means high loss, or that narrow bandwidth indicates high efficiency.

Bandwidth is related to system Q, but system Q is not determined solely by resistive or heat losses. System Q is really a function of stored energy to energy moved through the system. Energy can be moved through the system and exit as wasteful heat, or it can exit as useful work. Without knowing where energy is going, we should never assume bandwidth means anything other than bandwidth. Most antennas store a majority of energy in an electric field, although small "magnetic" loops have a lot of energy in a strong, very local, magnetic field.The 80m Amateur Radio band is wide… very wide.

Covering to kHz, this band extends well beyond the normal resonant range of a single dipole antenna. Sure enough, many approaches, both old and new, exist to help an 80 or 75m dipole present a decent SWR across the entire 80m band. Given time, many approaches in the Antenna Book would be well worth a try.

80m folded dipole

My total list of requirements included:. Doing nothing is no fun so Approach 1 is out. Using the internal radio tuner is certainly workable, but not elegant. Scratch approach 2. I thought real hard about the naturally wide band Cage Dipole.

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I even ran quite a few simulations see belowbut quickly figured it would take too much time and materials. Scratch 4. The requirement to use my existing dipole Req. These designs are inviting though.

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Antenna element resonators deserve a good hard look, but only when I have more than four days. Scratch 5 and 6. I looked at a fixed matching network at the antenna feed point with interest. Hmmm, well I would have liked to try this, but component availability was a big question in the short time frame. Scratch 7… for now.

Both TLR approaches use a a basic dipole cut to the midpoint of the band of interest. As I already have a dipole cut to 3. I have whittled the choices down to these two. Of these two approaches the one with stubs provides a feedline solution much shorter than the series resonator system.

One advantage of the Stub TLR approach is it uses 50 ohm coax for all transmission line components. Contrast this with the Series TLR which has a length of 75 ohm coax. I did not have 75 ohm coax on hand and needed to see how easy and quick I could obtain some. A quick check of their web site confirms RG11 is available at a reasonable price.

Once I received confirmation of my order, I put all the above to rest and settled on making the TLR Series feedline to broaden the bandwidth of my 80m dipole. I also simulated the Cage dipole in a few configurations.

A plot of all these SWR curves is usually the right thing to create, but I found the heat-map function in Excel to be more visually interesting. In the figure below, green shows an SWR ofyellow and red or more.

All this is above average ground.


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