This was presented at Ham Com 2013 in Plano, Texas by WB5CXC and W5WF. This project is to construct an End Fed Long Wire Antenna. The antenna is an inexpensive, multi-band, end fed HF antenna. It has a matching network consisting of a toroid core and an antenna lead of 30’, I have also used it with a 17 1/2’ wire. The matching network is a 1:9 UnUn trifilar wound transformer using a T106-2 iron toroid core. UnUn is a transformer for Unbalance to Unbalance devices. This provides matching the 50 ohm coax to the high impedance of the end fed antenna. It will handle a 100 watt transmitter and will require an antenna tuner to achieve satisfactory SWR on all bands. The normal internal antenna tuner should be able to tune the antenna from 40M to the 6M band.
End Fed Matching Network 1 1/2” Cap & 1 1/2” Plug
Matching Network in an 1” LR Electrical Fitting
Wound Torrid - T106-2
We will wind a T106-2 toroid core with 9 turns of trifilar winding. Trifilar means that there are three wires. We will use three different colors of wire so we can tell which wire to use later. Notice that there are letters, these are important because they have to be connected properly to work. This is a 1:9 UnUn. This means that the device is going from unbalance circuit to another unbalanced circuit and has a ratio of 1:9. Coax is 50 ohms, input so the output will be 450 ohms. (If you were going from coax to a dipole you would use a Balun – Balance to Unbalance (Balun)– the dipole is balanced and the coax is unbalanced.)The toroid is a T106-2. This is a powered iron toroid. The T106 means that it is 1.06” in diameter. The -2 means it is a #2 mix. This defines the frequency etc. for the toroid, they come in other mixes also T106-6, etc. The toroid can be purchased from various vendors for $1.05 - $ 1.80 + shipping. (Other toroids have been successfully used – T130-2, FT140-43, FT140-61.)
Notice the Letters of the winding. If you get them backwards, then the impedance would really be crazy. We will start with ~ 2’ of each color of wire. Start winding the toroid. Leave 2” of spare wire at the start. This will be required to connect it in the circuit. This is a 1:9 UnUn. You will notice that there is 1:3 step up windings. For impedance transformation, it is the square of the turns ratio, so the impedance is 32 = 9. Connect the Black wire on the left side (b) to the Orange wire on the right side (A). Strip the insulation off each wire and solder. Now twist the Green wire on the left side (c) with the Black wire on the right side (B). Remove the insulation on the end of the Green and Black wire about ¼”. We will solder it to the center of the SO-239 during the assembly process. On the Green wire (C) on the right side, solder a lug on the end. This will be secured under the screw holding the SO-239. On the Orange wire (a) on the left side, solder a lug on it. This will be secured under the screw for the antenna wire. Place the wires for the SO-239 through the hole for the SO-239 connector. Solder the wires to the (Green & Black) center of the SO-239. Mount the SO-239 on the drilled 1 ½” PVC plug. There is one threaded 6x32 hole on the plug, this is used to make mounting the SO-239 easier. Install three of the bolts to secure the connector. Place bolt in the last hole of the connector and place the lug (Green wire) on the bolt and secure with a nut.
Matching Network Diagram
Place a 10X24 screw through the lug on the Orange wire and place it into the hole on the side of the PVC Cap. Install a 10X24 nut on the outside of the PVC Cap and tighten the bolt. Ensure that the network is correctly wired, and then glue the top cap on the PVC plug. (Installation in a 1” LR Electrical fitting is similar.)Install a lug on the end of the 30’ piece of wire. Place a washer on the bolt on the side of the network, then place the lug of the antenna wire, then another washer and then secure it with a wing nut. This Network can be used with different lengths of wire. For all band operation, the wire can’t be a ½ wavelength or multiple ½ wavelength on any frequency you intend on using. This limits the lengths of wires you could use. Some of the lengths that should be acceptable are: 17, 36, 44, 49, 53, 59, 72, 88, 98, and 102. The longer the antenna wire, the better.
This antenna requires the use of at least 30’ of coax for the antenna to operate properly. We mounted the antenna using an MFJ 1910 (33’ fiberglass pole than lets down to ~ 4’). We were looking for a temporary easy set-up and take down. You can put one of these up in approximately 5 minutes. This will be a very good installation for portable operations or HOA problems etc. The performance of this antenna is very good.