This design is excellent for matching both long and short length unbalanced long wire antennas for multiband use and will allow the internal tuner of most rigs to match a single long wire antenna. This unit utilizes stacked cores for increased power handling and added inductance for the better performance on the lower frequencies. Be sure to review the recommended antenna wire lengths in the link below to find a length that best matches your installation constraints.
Installation Notes and Recommended Wire Lengths
This unun should be used with the wire lengths listed in the table shown in the above link. Use of the 9135 for "random" wire lengths, other than shown, can potentially create an impedance that is too low for an ATU to match. If a wire length not shown in the table is installed, an antenna analyzer should used to determine the actual feedpoint impedance that will require matching for each band of operation.
"I would like to thank you for the prompt service and excellent condition in which the item was received. I have since erected a wire antenna at 40', using the installation-chart. I used the 53 ft lgth to start with and found the SWR-specs according to the chart to be almost dead-on. I worked the T32C expedition this past week-end on 9-bands with the single wire antenna and was very pleased with the ability of the #-9135 Unun, didn't need to use more than 100wts but if needed I knew the Unun could handle the added 'HorsePower". Thanks again for a great product, and I might soon be in the market for another one of your stout products, but will enjoy using the one I now have. 73..Alex"
"Living in an urban area and looking for an efficient low-band antenna, I need a compact vertically polarized antenna with most of its current as high as possible. The end-fed linearly loaded inverted L dipole was my first choice (duo-bander: 80-40m). After buying and testing a multi-bands end-fed antenna I quickly realised that its Unun unit could not be easily adapted to some of my antenna experiment (over-heating, coax radiation, odd impedances…). Thus, I looked for a more general purpose device that could also handle much more power; and I ended up buying a 9135 - 9:1 Unun from “Balundesigns”. What a difference! The SWR measurement matched quite closely my EZNEC simulation and the Unun never over-heated even after rather long CW sessions during pile-ups while operating from my Mauritius holiday QTH. I am now testing an “Up-side down vertical” with its counterpoise at the top in the shape of a spiral; perfect behavior of the Unun even when operating at high SWR during the recent WPX contest. I can highly recommend this 9135 - 9:1 Unun, in particular for the “low-band antenna experimenter"
”I've been using this antenna in a sloped configuration for 6 months. Over that time I experimented with direct grounding, counterpoise, etc.
I use a RigExpert AA-54. After many different configurations, I have discovered that three non resonant radials and a 53' longwire seem to do the trick. The AA-54 shows an average SWR of 1.6 - 2.0 without a tuner across 10 to 80 meters in the band segments normally associated with CW/digital. Tuning in the phone segment on 10m is a different issue as I have never been able to tune under 1.75:1 there.
The biggest issue I have is the tendency of the core to saturate during longer operating sessions. (editors note, referring to competitors unit)
A friend is running his end fed with a Balun Designs 5KW 9:1 (Model # 9135) using the same configuration, wire gauge, counterpoise, etc I use. There is no comparison. The Balun Designs 9:1 absolutely blows away the U****ax matching unit. Lower SWR across the bands, no saturation, and the core stays stable. I have ordered a 9135 but will keep the U****ax unit as a back up.
The U****ax is a good antenna for what it is. Comparing it to the Balun Designs unit is like comparing a BMW to a Ford. For those of us with restricted real estate, my advice would be to get your hands on a Balun Designs 9:1. It is more expensive but it just plain WORKS. Keep your U****ax for your back up, bug out bag, Field Day, etc"
Note that short antenna lengths will not be capable of performing as a highly efficient antenna, especially on lower bands. The intent of this unun is to allow HF coverage in restricted installations such as HOA managed communities. Longer wire lengths will always be more efficient and provide better performance.
Ununs are intended for use with unbalanced antennas such as verticals and long wires.
They are not designed for use with balanced antennas such as dipoles or loops and use with a balanced antenna may cause erratic operation and/or damage to the unit.
|Core Material|| Custom mix low permeability ferrite by Fair Rite Products for maximum bandwidth.
Cores are coated and sealed for long term durability.
|Winding Type|| Stacked cores with trifilar winding configured as 9:1 unun
Downward impedance transformation by factor of 9. i.e. 450 ohms to 50 ohms.
|Winding Material|| 14 gauge Superior Essex Heavy build polyamideimide Allex 240 Winding Wire.
Windings are inserted into Teflon tubes increasing total breakdown to 10,000 volts.
|Power Rating||1 to 35 MHz - 5kW, 35-54 MHz - 4kW|
|Useable Frequency||1 to 54 MHz|
|Insertion Loss|| Less than 0.1db
|Connectors|| SO-239 connectors are silver plated with Teflon insulation.
Studs and eyebolts are 1/4 inch.
Alternate connectors and Mounting Options are available in the Accessories section.
|Hardware||All Stainless Steel|
| Enclosure Type
|| NEMA rated 4x marine grade junction box for outdoor installations.
Cover utilizes integral neoprene gasket for weatherproof integrity.
|Dimensions|| 4x4x2 inches for main body of unit
Dimensional Drawing of Standard Enclosure
|Additional Info|| Very high efficiency.
Weight 1lb 6oz