Manual 1:9 UnUn 600 Watts for long-wireantennas

Manual 1:9 UnUn for long-wire antennas

The 1:9 UnUn is wrongly called a 1:9 BalUn in many sources. In my opinion, this is incorrectbecause there is no transformation to a balanced antenna system. The feed point of a long-wireantenna is nothing more than a broadband impedance transformer. In the case of a 1:9 UnUn, thepower line (coax) impedance of 50 ohm will be transformed up to an impedance of 450 Ohm. Afterall 50 x 9 = 450. This means that the length of the long-wire antenna must be chosen in such a waythat the impedance in the feeding point on as many frequency bands as possible is about 450 ohm.Over the wire length more later. The transformer consists of 8 primary windings and 24 secondarywindings. This gives a ratio of 1 to 3. The voltage is therefore three times higher and the current isthree times lower than the power source. This gives an impedance adjustment of 3 x 3 = 9. Theimpedance of 50 Ohm is thus increased a factor of 9, this makes 450 Ohm. The entire 1:9 UnUnassembly will be wrapped around a FT240-43 ferrite toroidal core with broadband properties. In thisManual 1:9 UnUn, you will be helped step by step in the construction.

The enclosure

We start by marking and drilling the hole for the coax connector. The diameter of this hole should be16 mm. This is a large hole and therefore it is easiest to create it with a ‘sheet step drill’. (Google isyour friend, if you’ve never heard of such a thing.) Drill the hole 1.5 cm from the top, this makesconnecting later easier. After the 16 mm hole has been drilled, the chassis part can be put upsidedown in the hole for drawing the 4 attachment holes.

Now drill the four fastening holes with a 3.5 mm drill. In addition to the coax connector, drill a 5 mmhole for the countercapacity connection. Once this is done, we’ll turn the box over. Now we continuewith the marking and drilling of the holes for the long wire antenna connection and the strain relief.It is especially recommended to use a strain relief for antennas that will be placed for the long termof even permantently. The hole for the stainless steel eye should be drilled with a 6 mm drill and thehole for the antenna connection should be drilled with a 5 mm drill. Personally, I think it’s nice toattach the strain relief in the middle. The place where the holes are drilled is to your own liking.

After drilling all the holes, we can find out if everything fits the way it should. Here you can see theresult of drilling the holes and tightening the screws. When attaching the 5 mm bolts on the inside ofthe box, use two tooth-spring rings. One above and one below the cable lug, this will prevent it fromrotating later when connecting the antenna wire or counter poise capacitance. Use a tan to pull theblue plastic part of the cable lug.

The Impedance transformer

The Manual 1:9 UnUn continues with the following section. The time has come to begin the 1:9impedance transformer. Cut off 55 cm of wrapping wire. Let about 5 cm of wire protrude before youstart wrapping. Wrap this wire 8 times evenly around the core as in the first image. If it’s all right,you’ll have about 120 cm of wrapping wire left. Twist this loosely around the piece of wire of the firstwinding as on the second picture. Now wrap this thread 8 times around the core parallel to the firstwire. If you have been around 8 times you can immediately make 8 windings parallel to the first twowires, this starts at the point where the red wire goes over in the color purple on the schematic. Thisis purely to clarify the schematic image, but the thread does not have to be soldered or anything likethat. Now the wrapping of the 1:9 UnUn is ready. We now see three connections at the bottom of thecore. From left to right: Ground -> 50 ohm coax core -> long wire antenna. At a later stage we turnthe core around, so don’t get confused by this.

Below you will find the same story again in photo view. It’s noticeable that I’ve wrapped the wiresparallel together here. This makes wrapping easier. At a later stage, it is easy to distribute thewindings evenly over the core.

See below the result. After the windings are evenly distributed, we turn the core around! Theleft-to-right connections are now: Longwire – > Coax core – > ground/countercapacity. Because wehave flipped the core, this sequence of connections corresponds to the connection points on theenclosure. Now secure the core to the four-cable binder attachment plate.

Finishing up

Now carefully adjust the core in the housing and cut all connection wires to size. After all wires arethe correct length, the insulation should be removed from the wrapping wire. This is an importantjob, if this does not happen well soldering is almost impossible and an unintentional resistancearises. Dilating the enamel insulation layer is possible with a sharp knife, coarse sandpaper or asmall file.

After the connecting wires have been properly removed from the insulation, the connections can besoldered. Use a soldering iron with sufficient power. Now it is time to attach the lid withaccompanying weir (resembling a white string). So far the manual 1:9 UnUn.

Applications

There are a lot of antenna variants to think of in combination with the 1:9 UnUn. In principle, it ispossible to mount any length of wire, but in practice it appears that there are favorable and lessfavorable wire lengths. The wire can be mounted horizontally, vertically, as a sloper, Inverted L andas Inverted V. The long-wire antenna has the advantage that when using the right length wire, it canbe used on many HF bands. This means that the antenna on many HF bands shows a reasonableSWR and often the internal tuner of the transceiver is sufficient.

Wire length

A lot has been written about the antenna length of the long-wire antenna. The basic rules are asfollows: Stay away from quarter and half wavelengths on the frequency bands where you want towork. At the lowest frequency at which you want to be active, approach at least a quarterwavelength. So not exactly a quarter wavelength! In my opinion, the ideal wire length will be slightly

different for everyone in practice. Nevertheless, the Internet is a beautiful source of inspiration.Lengths mentioned a lot: 7 Mtr, 9 Mtr, 16.1 Mtr, 18.7 Mtr, 27.5 Mtr, 38 Mtr.

This is at least a nice starting point to start the experiments. Here’s some inspiration:

http://www.hamuniverse.com/randomwireantennalengths.html (lengths in feet)

https://vk6ysf.com/longwire_antenna.htm

http://webclass.org/k5ijb/antennas/End-fed-multiband-antenna-BalunDesigns.htm (lengths in feet)

Need counter poise capacity?

A long-wire antenna requires a countercapacity. This can be resolved in several ways:

coax cable of the power line as countercapacity (high risk of interference problems)earth pen or earth net as countercapacityone or more pieces of random wire length as countercapacitya sinking gutter, steel fencing or anything else made of metal

Common mode choke

TIP: With a 1:9 UnUn and long wire antennas always use a common mode choke. The main reason touse a common mode current filter is to ensure that the coax cable does not become part of theantenna system and therefore starts to radiate unwanted. This has all sorts of nasty effects, think of:interference, EMI, RFI disrupted radiation pattern of the antenna, restless noise level. This last pointis because not only does the coax cable’s shield radiate when you transmit, but the shield also worksas a receiving antenna. You can link the common mode choke directly to the 1:9 UnUn with a PL-male-male connector or leave some distance. This piece of coax cable between the 1:9 UnUn and thecommon mode filter then serves as a countercapacity.

Interested? Click here for the 1:9 UnUn DIY kit