The following is a list of materials required to make a 49:1 unun impedance transformer for an end-fed half wave antenna. A 50 foot run of RG-8X coax connected the antenna into the LDG Z100-plus tuner and then a Yaesu FT-891A transceiver. (Also note that here may be instances where the suggested lengths may not work exactly due tothe many variablesin the surroundings of the antenna, wire length variances,your tuner, it's height above ground, it's construction,etc. What these lengths are depend on your tuner and also the wire's surroundings and also the ground system. Tweak the antenna length if necessary and then maybe adjust the turns ratio again. stream
Wire lengths for the 4:1 ratio in models 4932 and 4935. Placing 3000 to 4000 ohms of resistance between the free end of the twisted portion of wires (the gound) and the free end of the long wire (the wire that connects with the antenna radiator after the 14th winding), can simulate adding an antenna radiator wire to the unun impedance transformer. 1 0 obj I actually did this first and before the connector was bolted to the box. That is the 10th multiple of a half wave on 15 meters. The 30 day return period lapsed before I could get the antenna deployed to test it. Cut a 4 foot length of AWG #18 enameled wire. "Here's the word on random-wire antennae.". The Nelson antenna 9 to 1 unun did the trick. I will also find some sort of heat resistant packing material to help hold the transformer in place. endobj
The other is to provide strain relief for the antenna wire). (Center fed is so appealing because you avoid this.). Solder a the 100pF capacitor between the center conductor wire and ground wires. This is a 4:1 Current Balun.That means it can match a 200ohm antenna to a 50 feed line. Use with other lengths can potentially damage the transformer depending on power level in use. A 49:1 would match 50 ohms to about 2,450 ohms and a 64:1 matches to 3,200 ohms, typical of a 1/2 wave end fed. Here I show finalizing the antenna, getting it in the air, and run. Connect this ring terminal to one of the SO239 chassis bolts. Save program output in file named 'f', and use The fewer bands, the fewer high impedance regions to avoid. <>
BUILD INSTRUCTIONS FOR 49:1 UNUN IMPEDEDENCE TRANSFORMER: WX1MAR and I brought the DIY 49:1 unun with a borrowed antenna radiator wire cut for 20M half-wavelength to Ashland State Park K-2417 in Massachusetts for a Parks-on-the-Air (POTA) activation. Power Handling (CW/SSB): 100 W/200 W Enclosure Width: 2.500 in. EFHW unun Resonant Long Wire 49:1 Transformer With BNC or SO-239 | Mobile Phones & Communication, Radio Communication Equipment, Antennas | eBay! Technical specification : Type : 49:1 Unun Frequency : 1.8 MHz - 7.3 MHz Turns ratio: 1:7 Impedance ratio: 1:49 Input Impedance: 50 Output Impedance: 2450 Power Handling (CW/SSB/ Digital Modes) : 2Kw of peak power / DM Modes 500 watts Core Type : 3 x FT240-43 by Fair-rite Co. Wire type: Enamel copper wire 2.0 mm (AWG 12) Assembled and tested. So for 80 meters (say 3.525 MHz) this gives you about 133' of wire. Support The Site In fact, the 9:1 unun that I built is actually an autotransformer. stream Note: My (A to B) length was 6 inches. So, having nothing better to do one day, I re-did the calculations going out to 500 feet. Attaching a counterpoise wire to the common point of the auto-transformer provides the antenna radiator something to push against rather than the coax shield. At this point, Ive only used the 49:1 tap, but plan to take the 64131 whenever I operate portable. Start winding the toroid with the twisted wires at loop #1 (see schematic below). it is easy to pack and easy to install. In stock . The length should be calculated based on the lowest frequency to be worked. However, the list has been revised and is good for wires as long as 500 feet. Technical specification : Type : 49:1 Unun Frequency : 1.81 MHz - 30MHz Impedance ratio: 1:49 Input Impedance: 50 Output Impedance: 2500 Power Handling (CW/SSB) : 250W Core Type : 1x FT240-43 by Fair-rite Co. Capacitor 100pF 3KV Assembled and tested. In addition to multiples, A couple hours later when I sat down to do some more DXing, I made contact with a gentleman in Slovenia-my second European contact. Ham Hints 35-43, 49-63, 70-85. The 49:1 impedance transformer will help you bring down the high impedance of your resonant EFHW antenna to almost 50 Ohm. /Height 752 RFI Tips and Tricks Drill a hole in the top for an eyehook (to be used to secure the unun to whatever it is you want to hang it from.). It is used fornon-resonant verticals like 43 foot or 33 foot Or Wire antennas like an End-Fed1/2 Wave Multiple Length Wire Antenna. /Count 1 A 9:1 matches 50 ohms to 450 ohms and that turns out to be an ok compromise for feeding 50-100ft of wire for general purpose SW receive. I connected the free twisted end of the short and long wires (the ground) the chassis wire (ground) of my homemade testing jig with alligator clip. You also Cannon". I included the tools I used to analyze the transformer as well; this is only necessary if you are interested in analyzing your project. The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. you're using different ham bands than in these examples, modify and rerun He knew that in order for the tuner to "see" a fairly low swr to work within it's range,that the antenna had to be NOT A HALF WAVE ON ANY FREQUENCY that we wanted to us, because a half wave will give us a very high impedance and the resultingswr into a 50 ohm transmitter! /ColorSpace 11 0 R Vhf and Up So you have the freq range of interest and the total length of the wire, figuring out wich balun will be a better match for 50ohm coax should be easy. A way of connecting the analyzer to the transformer. For instance, to work 40m be sure the antenna is at least 10m or 33' long. this Both were on 20 meters at 97 watts, Icom 7300. Meet 'Balun One Nine', a small, cost-effective balun. Because I had some spare Cu-Wire I wound another 1:49 Unun on a smaller FT-140-43 toroid and tried different capacitors between feedline and ground (to compensate for the 10m band). Do what works best! Hertz Antenna" shows in line 2 of the table that a similarly installed The major point of this message is to tell you that approximately 20 minutes after I connected the balun unit to the antenna, I made contact with a gentleman in Italy-my first European contact!! The length of a half wave antenna is calculated using the following formula: L (ft) = 468 / f (freq in mhz). June 8, 2022 at 9:17 am.