Lengths to avoid are not always the same as If you plan on stringing up a dipole you use 2 equal lengths of wire with the Balun in the middle. These dimensions were derived from modelling the antenna in EZNEC. 3. This transformer is designed to be used with an end fed half wavelength of wire only. so that it is not a halfwave multiple of any frequency you want to use. I included the tools I used to analyze the transformer as well; this is only necessary if you are interested in analyzing your project. Here Is a 250 Watt Home-Brew That I Made In about an Hour. Figure 3 Wiring of the 9:1 voltage unun. You will also need a half-wavelength length of wire (14 or 12 gauge typically) in order to construct an antenna radiator for whichever ham band you choose. Ask Elmer Recommended wire lengths for Unun models 9130, 9132 & 9135 Table shows typical SWR relative to installed wire length. 748 0 0 752 0 0 cm K1S Valentines Are (Almost) Out The Door! This was 9m vertically metres up a fishing pole and then about 5.8m out. endobj As an example, a 28-31 foot wire will typically allow 40 thru 10 meter coverage and a 43-50 foot wire will provide access to 80 thru 10 meters. I say run what you got and don't worry about it. <>/Metadata 239 0 R/ViewerPreferences 240 0 R>> After winding #2 is made and extends down the backside of the toroid, untwist the wires. endobj This type of antenna is very easy to install because there is no need . You also Here are the final numbers (in my opinion) in green below that would be good for a long-wire antenna: (You may want to make a note of them), REVISED: 29 35.5 41 58 71 84 107 119 148 203 347 407 423, REVISION NOTE: We had a note from James, KB5YN, pointing out that one of my so-called GOOD numbers was 220 feet. My commercial EFHW is 130 feet long for 80 and up, and my 40 meter homebrew antenna is about . Reading Room (Also check out AB3AP'Swebsite and say thanks for sharing his skills. /Type /Page A level of 500-600 watts is the maximum with a further reduction onany band measuringabove 3:1. /Resources << &nb If the transformer is used with an externaltuner in conjunction with a single wireantenna typically 130-135 feet in length, power should be reduced on those bands that show an SWR above 1.6 to2:5 withoutthe tuner. If you want all the bands from transmit frequency the impedance is so high that tuners in most rigs I attached the toroids to a PVC DWV test cap with 3 cable ties. Theme: Newsup by Themeansar. <>/ExtGState<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> The counterpoise wire, This transformer is designed to be used with an end fed, Approx. 35. >> At this point, Ive only used the 49:1 tap, but plan to take the 64131 whenever I operate portable. Just an FYI that I thought you might be interested in. endobj For example a 32 foot length is actually a half wave on 20m with an impedance of about 3500 ohms and requires a 50:1 balun. Make sure the beginning few inches of twisted wire is not involved in the winding (i.e., just hanging down from the toroid). (Originally published February 22, 2021). random wire should use 423/f. Just add or subtract as needed a little at a time to get the best compromise. When on the trail, at Field Day, or whenever a good antenna is "Here's the word on random-wire antennae.". If the choices are. I use this 8010 EFHW at home, too. An end fed half wave antenna is one of a specific length depending on the frequency that it is to be used on, for example, an end fed half wave antenna for 80 meters is about 130 long. I'm not saying aliens are in the radio, but aliens definitely are in the radio. /MediaBox [0 0 748 752] << Ultimately, this housing works fine, but it is heavy and clunky.). For best results, use the Wire Length Feet 1.8 MHz 3.7 MHz 5.3 MHz 7.1 MHz 10.1 MHz 14.2 MHz 18.1 MHz 21.2 MHz 24.9 MHz 28.5 MHz 50.1 MHz The popular End-Fed Half-Wave (EFHW) Antenna is an easily portable, high-impedance (2,000-4,000 ohm) wire antenna that resonates on its fundamental frequency and all harmonics above. Superior Essex Heavy build polyamideimide. So for 80 meters (say 3.525 MHz) this gives you about 133' of wire. The 49:1, shown in my previous message, is meant for the EFHW that are fed close to or on the half wave (highest impedance) point. google_ad_slot = "1982258389"; 3 0 obj You will also need a half-wavelength length of wire (14 or 12 gauge typically) in order to construct an antenna radiator for whichever ham band you choose. End Fed Antennas. Use with other lengths can potentially damage the transformer depending on power level in use. bands you're intested in in a vector like the example below, by typing. /CreationDate (D:20221212112042) CQ-Calling All Hams! 1863 1.49 swr 3915 2.50 7200 1.80 14.332 1.29 18.130 1.07 21.300 1.40 24.950 1.30 28.400 1.37 This is a great antenna that is . You need to use these lengths and the longer ones . an auto-tuner at the base vs. the same antenna fed a 4:1 balun wound with 75 ohm coax on two separate type 43 ferrite cores and a remotely sited tuner fed via 200ft of low loss LDF2-50 coax vs. a broadband antenna of the same element length. Liquidtight NM 90-Degree Connector(Home Depot). While these lengths have been shown to work well on many bands, which The beauty of the halfwave antenna is it's a complete antenna in the sense it needs no counterpoise. This design is excellent for matching both long and short length wire antennas for multiband use. answers on D - one setting. 4 0 obj https://www.kb6nu.com/playing-end-fed-wire-antennas-91-ununs/, http://www.hamuniverse.com/randomwireantennalengths.html, https://www.youtube.com/watch?v=sty7RlXQoJI, https://www.youtube.com/watch?v=WwJnXTVUrgI, Quote from: refmo on October 15, 2019, 2036 UTC, Quote from: joczo on October 16, 2019, 0815 UTC, http://www.w3pga.org/Antenna%20Books/Reflections%20III.pdf, http://www.arrl.org/files/file/Technology/tis/info/pdf/7007024.pdf, http://www.tasrt.ca/AntennaTips/AntennaTips.htm, http://www.wb2rcb.com/documents/balunlin.pdf. (Also note that here may be instances where the suggested lengths may not work exactly due to the many variables in the surroundings of the antenna, wire length variances, your tuner, it's height above ground, it's construction, etc. The graph below shows lengths to avoid for different collections of bands. Theme designed by Papathemes. (Note: I am not satisfied with this part of the project, so I will describe it here briefly. On our next windy free day, AA1F and . However, the list has been revised and is good for wires as long as 500 feet. The key to end fed antenna success is the matching network interface between the long wire antenna and the coax feed line and feed line choke at the transceiver. 2 eyehooks with washers and nuts (I used #8 diameter, but size is up to you.) Allows the internal tuner of most rigs to tune remotely mounted single wire antennas. , Reprinted with permission of Hamuniverse, this is an excellent explanation of SWR and how to best me 2 0 obj Work all bands from 80 through 10 on it. I wrote a small C program that does just what Jack did, butI used the band edges. %%EOF <>>> Some important and helpful references I used for this work: https://elginradio.wordpress.com/2017/10/17/end-fed-half-wave-antennas/. Each vertical blue line represents an amateur radio band. /Parent 3 0 R used by hams for dipole lengths. They just saved you and I loads of time and frustration. Change the program to use 423 if desired.) all US ham bands. I'm looking forward to getting off work and hitting 40 & 20 meters again!! All you need for a random wire antenna is some wire, your tuner, one or more supports up as high as you can get them to string the wire from the supports to the tuner, at least one or two insulatorsand a little time. Proudly powered by WordPress Use a slide rule! Following the directions exactly as specified (0.47wl / 0.05wl matching counterpoise) and drilling two weep holes in the appropriate position, I had a 10 meter EFHW antenna up in less than ten minutes. 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! Electronics The 49:1 unun with 3000 ohms of resistance shows a VSWR under 10:1 from 160M to 15M, and less than 3:1 from 80M to 20M. which got me thinking. I'll get a 9:1 unun,and use a suggested random wire length to avoid half-wave and it's multiples then,that sounds like the best things I can get out of this setup. Ham Radio Videos! If you would like to use high power up to legal limit with a single end fed wire antenna (not necessarily a half wave) consider using our Model 9135 along with one of the wire lengths shown in the Installation Notes. A good place to start is the formula 468 / f (MHz) for a 1/2 wavelength wire antenna. Thus a 1/4 wave for 20m@16ft, 40m@33ft as examples are not going to work. Use with other lengths can potentially damage the transformer depending on power level in use. He was so impressed that he purchased a 9:1 unit from you, his will be delivered Saturday. The "9:1 UNUN" are for random length wire antennas fed at the end. Again, the bands are USA, so change them shown in the column e. var sc_project=8077274; Care to buy us a beer? << Do what works best!