Heavy duty 5kW, unun designed for use with wire verticals, long wires and monopole verticals. Utilizes stacked cores to deliver efficient broadband performance and high power rating across all HF frequencies.
Works well with both internal transceiver and external antenna tuners. If a lower power version is desired, please see our model Installation Notes. Rating Required Select Rating 1 star worst 2 stars 3 stars average 4 stars 5 stars best. Email Required. Review Subject Required. Comments Required. Current Stock:.
Downward impedance transformation by factor of 4. Alternate connectors and Mounting Options are available in the Accessories section. Quick view. Model - QRP Unun 1. Model - Unun 1. Model - Balun, 1. Model - Current Balun 1.
Subscribe to our newsletter. Core Material. Custom mix low permeability ferrite by Fair Rite Products for maximum bandwidth. Winding Type. Winding Material.Multiband antennas comprising a non-resonant length of wire that is fed via coax and an impedance transforming UnUn have become very popular of late - they are convenient and a low cost alternative to siting a remote tuner at the base of the vertical.
The inclusion of the UnUn is designed to limit the high SWRs that would occur on some bands, and thereby avoid some of the very high coax losses which might otherwise occur.
This page describes a series of experiments I carried out to try to understand better how typical UnUns perform in this application. The antenna comprised 40ft of insulated wire taped to a fibreglass fishing pole mounted vertically at ground level on the corner of my garage. It was fed via a length of RG58 coax from the nearby shack. The following chart shows the measured SWR on the 80m thru 10m bands under four different sets of conditions:.
The green bars show the performance with the feed coax connected directly to the vertical; no UnUn was used, there was no connection to any ground system, and no RF choke was used. The SWR varied from a low of 5. Given that no ground system was used we might wonder what forms "the other half of the antenna":. The answer is clear when we add a common-mode choke at the feedpoint to prevent current flowing on the outside surface of the coax braid - we get the performance shown by the turquoise bars.
With the exception of the 30m and 15m bands all of the SWRs are worse - often by a very large margin. This demonstrates that, as expected, if you have no ground system the coax braid becomes an integral part of the antenna system. Next I added a modest radial system comprising six 25ft wires laying on the ground and arranged as evenly as I could within the constraints of my back yard; the results are shown by the grey bars. On all bands except 30m there is an improvement in the SWR - on most bands a very significant improvement.
Finally I added at the feedpoint a UnUn comprising 12 bifilar turns on a T iron dust core; the results are shown by the red bars. I next decided to investigate how UnUns of different designs compared. I wound a UnUn comprising 9 trifilar turns on a T core, a UnUn comprising 12 bifilar turns on a FT core, and a UnUn comprising 12 bifilar turns on a FT core; here are the results:.
Clearly, introducing any of the UnUns makes a dramatic improvement to the SWR on most of the bands; the exceptions are those bands where the SWR is already low. Choosing between the various UnUn designs is not easy - one does better than the others on a few bands, but is worse on others. Taken overall, with this particular antenna the UnUn wound on Type 2 material probably has the edge.
What is not obvious from these results is just what impedance transformations are being introduced by the UnUns. Particularly at the lower frequencies, a combination of the low permeability of iron dust material and the reactive antenna impedance means that the impedance transformation ratio is far from the or that might naively be assumed.
This arises because the UnUn is far from being an ideal transformer, and its low inductive reactance combines with the capacitive reactance of the load to form a tuned circuit which, if close to resonance, will produce impedance transformations far removed from the ideal.
Fortunately, this does not matter in this application - the actual impedance is largely irrelevant because a tuner is used at the shack to provide a match to 50 Ohms. But it does mean that any theoretical evaluation of these types of antenna system is suspect if it assumes that the UnUns behave as ideal impedance transformers.
A further consideration with the UnUn is what loss it introduces to the antenna system. Knowing the UnUn secondary impedance and the antenna impedance, we can estimate the losses introduced by each design:.
How to Make a Balun or Unun
Notice that losses with the Type 31 material are significantly higher than with any of the other designs. This is to be expected because the complex permeability of the Type 31 ferrite mix has a large resistive component; this is an advantage in common-mode choke applications, but not so useful when acting as the core of a transformer potentially handling high voltages.
Of the remaining designs, the UnUn wound on Type 2 material probably has the highest loss. To put the numbers in context, a loss of 0. With all the UnUn designs, loss becomes much higher at low frequencies if the antenna is shortened; so be very wary of the power-handling claims for UnUns wound on T toroids and used with short antennas. It's also worth noting that at low frequencies, where the antenna is electrically short and its reactance is high compared to its radiation resistance, high voltages can be generated across the UnUn at modest power levels.
For example, if this 40ft antenna were radiating W there would be a voltage of over 1kV pk across the UnUn; well-designed UnUns will have winding insulation which takes account of this. Just because one design of UnUn has slightly more loss than another doesn't necessarily mean that its transmitted signal will be weaker; if that design results in a lower SWR on the feedline - and therefore lower feedline loss - it could still produce the net greater signal.
To take account of these factors I measured the signal picked up from the antenna by a local receiver, and swapped between the UnUn designs.Install July Requiring a balun to feed a balanced feed line with an un-balanced T-Match network a Ruthroff voltage balun design using a T Toroid core was selected.
While the ratio is often referred to for the interface between T-Match network and a balanced antenna system it will often not be the ideal choice when very low impedances are encountered. It is for this reason that I chose to not include the balun as an integral feature of the T-Match network, opting for the flexibility of an outboard balun and the ability to trial various baluns subject to the antenna system and impedances presented.
The T powdered iron Toroid core was tightly rapped in a lay of overlapping PVC electrical tape to prevent the enamelled copper wire's insulation being damaged during winding and to offer some additional electrical insulation with core. The double bifilar winding of 17 turns are wound evenly spaced around the toroid core with the two individual windings wound close together. The exact number of turns is not critical but the numbers listed in the preceding table should yield good results.
It is possible to exceed the power ratings listed above but the performance of the balun may be degraded during high SWR causing heating of the core. Note this drawing shows winding connections and not the number of turns required.
Table 1 lists alternative toroid core with winding suggestions. See Fig 3 for details. Figure 3 Sealed Polycarbonate Enclosures 82 x 80 x 55mm details. The evaluation of the efficiency of the balun over the desired bandwidth 1. The efficiency is shown to cut of sharply below 1. The below antenna analyser plot viewing a ohm resistive load attached to the balanced side of the balun and measured at a nominal impedance of 50ohms presented as anticipated an approximate 25ohm load to the analyser and produced about a SWR.
Despite not having carried out this test previously the results are more or less what was expected and demonstrates that the balun's voltage transformation occurs efficiently from 1. The results are not as satisfying as those carried out on the voltage balun showing significant reactance across the band. Despite the less than ideal analyser plot the balun appear s to work well as an interface between the T-Match tuner and the balanced multi-band antenna system.
Note the ohm resistor appears as 25ohms due to the balun ratio resulting in an ideal SWR of AIM C antenna analyser explanation. Standing Wave Ratio. Total Impedance. Resistive component of the total impedance. Inductive being a positive value and capacitive being a negative number.
Phase angle between voltage and current. Return Loss. Total reflected system loss. An additional evaluation of the efficiency of the balun was preformed by simply measuring the RF power at selected frequencies fed into the balun and measuring the out put power from the balun using the set up shown in Figure 7.
In this set up it was necessary to have two identical baluns, the second to step the impedance back down to the 50 ohms for measuring. It is critically important that the two baluns be made in a identical fashion as the results need to assume that half the losses are as a result of each of the baluns as that the below formula simply halves the resultant overall loss. For example, RF was applied to the input of the Balun at a frequency of 1.
The below formula was applied revealing a Balun loss of 2. Figure 5 shows the results of measurements taken at various frequencies including the calculated loss.I first did some experimenting with the "un-un" when I built a new vertical antenna to use with my pop-up camper.
I was so impressed with the performance of that antenna that I built a second un-un for general-purpose portable operations. I merely built one based on information from others and adapted it for my own purposes. Check the references below for a couple of sites that inspired my version. So, what is it? As you probably know, a balun is a transformer that is designed to go between a balance load like a dipole fed with balance line and an unbalanced source like the coax from your rig.
Hence the name balun. Well, the un-un is very similar except that it is designed to work with unabalance load, something like a random wire up in a tree with a counterpose wire laying on the ground or a vertical with ground radials. Hence, the name "un-un. When used with an auto-tuner, the un-un turns a simple piece of wire and a counterpoise wire or radials into a multi-band antenna.
The popular foot vertical antenna configuration typically uses a un-un at the feedpoint. Several vendors offer these commercially. Stock BX About 6 inches of ohm coax Some ring terminals to facilitate coil and coax connections crimped and soldered 2 strips of double-sided foam tape to hold the coil in the box It's very easy to build. This one took about 2 hours to put together.
IW7EHC's web page shows how to wind the toroid and make all of the internal connections, so I won't try to duplicate that here. You can build it with a smaller toroid and lighter guage wire, but I went with the larger toroid and heavier wire to minimize losses.
Here are a couple of examples of how I have used it so far: foot vertical. Using a foot Jackite pole for a support, I had a ft vertical wire connected to the hot side red binding post on the un-un and 6 ft radials connected to the ground side. The un-un was about 3 feet above ground, so the radials gently sloped downwards and laid on the ground.
This works well from meters. I supported the antenna with my trusty foot Jackite pole. I used 6 foot radials an a couple of foot radials. The un-un, of course, was located at the feed point and fed with ft of RG-8x coax.
This was my antenna for Field Day and it worked great on meters. A "No Counterpoise" antenna. This is basically a foot length of speaker wire with feet removed from one of the conductors.
Connect the foot side to the red binding post and the foot side to the black binding post. It loads up fine from meters but I haven't really used it on the air yet. I've been told by another ham that my "Dollar Store Special" wire antenna works well with an un-un.
Just remember to keep the coax run between your tuner and the un-un as short as possible to minimize losses and have fun!We often get the question — Do I need a balun or an unun?
The proper question is — do I need a feed line choke or an impedance transformer whose output is configured as balanced balun or as unbalanced unun? Feed line chokes and impedance transformers can be configured as unbalanced or balanced output each having identical ferrite transformers. Impedance transformers and feedline chokes can be configured with either balanced output balun or unbalanced output unun.
Note: If the sleeve feed line choke had an output of two wires instead of a coax connector it would be called a sleeve balun balanced output and could be used with dipoles, beams, etc with two balanced outputs. An impedance transformer all ratios can be configured as a voltage transformer equal voltages on balanced outputs or as a current transformer equal currents on balanced outputs.
The ferrite transformers use slip on beads, snap on beads, ring toroids or binocular cores depending on power requirements, frequency range and impedance ratio required.
Super Choker for high power antennas. Feed line chokes configured as ununs with coax input and output.Tune Around! Topics For Technicians! Loaded with info for new ham radio operators! Ham Exams! Ham Radio Videos! This article presents a project to construct a four to one current balun also known as a "Guanella" balun. The balun I made was constructed in the Summer of and has been neatly hidden in my engineering notebook since.
Antennas are a fascinating aspect of radio and baluns are an integral part to most radio amateurs stations. The term balun " It's primary function is to prevent common-mode currents, while making the transition from an unbalanced transmission line to a balanced load such as an antenna" 1 One of my favorite wire antennas is the Off Center Fed Dipole OCFD really a doublet, good topic for another article for it's solid performance and useful operating characteristics.
My balun will be part of an OCFD I plan on having some K2GXT members help construct during the winter along our underground tunnel system as a neat, quick, and fun one meeting side-project. This project can be used for a variety of applications not pertaining to just OCFD's, another popular use is in converting coaxial cable into balanced feed line ohm.
If you have never built a balun before then this might be your invitation to do so. I first built one of these during a local club meeting back in Massachusetts with the Billerica Amateur Radio Society about five years ago. All the transformer parts come in a kit, however you are given the freedom to make whatever style balun that may be of interest. One thing I would like to stress is that all metal hardware such as nuts, washers, and bolts are stainless steel in this project.
Any metal hardware used on antennas should be stainless steel when possible because it will not corrode which helps keep a good electrical and mechanical connection for years. However, you cannot solder to stainless steel which demands other methods of joining the metal such as nuts and bolts. Designing and Building the Balun. This kit includes the proper toroidal core, Everything you need to build the balun is included including instructions on winding the wire.
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Balun is an acronym for BAL anced to UN balanced, which describes certain circuit behavior in a transmission line, source or load. Most communications applications deal with two-terminal sources, transmission lines, and loads. This includes coaxial cables, open wire lines and systems working against earth or a ground plane as the "second conductor". The balun has to do a good job and be reliable. DX Engineering has the expertise to design and build a better balun that will deliver more power to the antenna, be more reliable, and in many cases cost less than products made by others.
We also realized that advertising hype over the years had confused the issue of just what type of balun was appropriate to each antenna. This article is an attempt to define in simple terms how to get the most performance from your system, both on receiving and transmitting.
The first thing to realize is that there are two types of baluns: Current Baluns and Voltage Baluns. The balun's ratio is normally stated from balanced to unbalanced just as the words appear in the acronym. A balun has four times the balanced impedance as unbalanced impedance. Balanced lines and loads, by definition, have equal voltages from each terminal to ground.
Each balanced terminal or conductor must also carry precisely equal and exactly out-of-phase currents. If the feedline does not have equal voltages, equal currents, and exactly out-of-phase currents at every point, the feedline will partially act like an antenna.