This type of antenna is very easy to install because there is no need . This was 9m vertically metres up a fishing pole and then about 5.8m out. Here they are in order: x {avla[g#+yt]Mk"B` xp[AO8;c=\b}|8p4cSmzgU7be,+i5ci6uq.x T/s@9uk-oZX;u`=U >8rsIXW B:uUVr6a] Shortwave Listening , Most matching problems occur when the antenna system %PDF-1.5 % Save program output in file named 'f', and use 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. UJM-49-1 $56.99 Save up to 6% when you buy more. Step 1: Drill holes for and install the SO-239 or BNC connector, the stainless steel machine screw antenna connector and the ss machine screw ground connector. License Study The bandwidth where SWR was below 2:1 was about one MHz. 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. Ham Radio Videos! When on the trail, at Field Day, or whenever a good antenna is >> Theme designed by Papathemes. I did not want to put the transformer in the housing until I tested it. What these lengths are depend on your tuner and also the wire's surroundings and also the ground system. 33 ft #18 insulated copper wire (20m half wave), Counterpoise: 1 meter coax (0.05 x wavelength) connected between 64131 and Balun Designs 1115d Isolation /Choking balun, 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. Lengths for Long-wire Antennas Jack - VE3EED Recommended lengths: 29 - 35.5 - 41 - 58 - 71 - 84 - 107 - 119 - 148 - 203 - 347 - 407 - 423 Not recommended lengths: 16 - 19 - 22 - 26 - 32 - 33 - 38 - 44 - 46 - 48 - 52 - 64 - 65 - 66 - 76 Change the program to use 423 if desired.) This project assembles a 49:1 ferrite-core ("FT") type #43 transformer that matches 50 ohm input to 2500 ohm end fed antenna. (Originally published February 22, 2021). >> these are the worst lengths and you want to be as far from colored /Pages 3 0 R a more capable tuner - see AA5TB's 3. /ProcSet 7 0 R >> 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 Let's have a look at a few details on how to build a 49:1 impedance . This is a followup video to #344 where I assembled the 49:1 UNUN kit from HF-Kits / ARRL. >> See the picture below. 9:1 Unun 1.5-54MHz 2kW 9132S. After winding #2 is made and extends down the backside of the toroid, untwist the wires. Longer wire is always more The most important length is one that is non-resonant on any band. I connected it to a 33 wire running from my balcony, through the trees, and ran WSPR overnight to check things out. it is easy to pack and easy to install. There probably should be some holes for ventilation. endobj I only used two screws instead of four. So those are the numbers above thatwe have to stay as far away from as possible when building a long-wire antenna. Palomar Engineers employs a dual core matching system that offers wide bandwidth (1-61 MHz), 500 watt PEP rating, and a connection for a counterpoise or ground if desired. stream Work all bands from 80 through 10 on it. I used the RigExpert Zoom AA-55 to test VSWR of the 49:1 unun impedance transformer. endobj I have not done this yet. 35. /Filter [ /FlateDecode ] https://elginradio.wordpress.com/2017/10/17/end-fed-half-wave-antennas/. used by hams for dipole lengths. endobj [ /PDF /Text /ImageI ] and leave the unun on the ground. , Reprinted with permission of Hamuniverse, this is an excellent explanation of SWR and how to best me Because I'm more visually oriented I then plotted the many overlapping "red zones" and ended up with the page at: SWR was good after cutting the wire to appropriate length. <>/Metadata 239 0 R/ViewerPreferences 240 0 R>> frequencies for your country or favorite modes. << Just an FYI that I thought you might be interested in. 1 0 obj Turns 1 through 14 are secondary windings (the long wire). "Here's the word on random-wire antennae.". Super Bullet Features: - Uses proprietary broadband impedance transformer design for maximum bandwidth with SWR < 2 from 1.8-61 MHz for 1500 Watt model and 1.8-30 MHz for 3000 watt model thank you. Mike ab3ap, Editors note: Many thanks to Jack, VE3EDD (SK)and Mike, AB3APfor sharing their math and computerskills with us. Wire lengths for the 4:1 ratio in models 4932 and 4935. I plotted the results for the U.S. CW band edges for use with my4 band Elecraft K1 qrp rig. Powered by BigCommerce. $1YacO5Q}YC\>qZ } 1 bolt for antenna hook up (with nuts, washers, lock washers, and possibly thumb screw; I used #8 diameter, about an inch or so in length.). 9 0 obj One is for the top of the box so that it can be hung up. /ColorSpace 11 0 R Please note that I will not be describing the construction of the antenna wire radiator here. The 49:1 impedance transformer will help you bring down the high impedance of your resonant EFHW antenna to almost 50 Ohm. You also want the antenna to be at least 1/4 wavelength long for each band you plan to use. Contact If the choices are. So after much frustration..down it comes and you go on to a totally different type of antenna.all that time just wasted inyour opinion..until now! is helpful if you're in a hurry to get on the air, read up on the topic Drill another hole in the same side as the antenna radiator wire mount hole. answers on D - one setting. /Width 748 While these lengths have been shown to work well on many bands, which 22.00 + 5.00 Postage. Jack, VE3EED - SK. << for your country and favorite modes of operation. Tools %PDF-1.5 http://udel.edu/~mm/ham/randomWire/. I took a literally random length of 14 gauge house wire and attached a banana plug to be shoved into the antenna port of the tuner. Figure 2 Schematic of the 9:1 voltage unun . Thanks for your answer,I will probably go with the 9:1 then. random wire should use 423/f. 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. =======================, More on Random Wire Lengths from Mike, AB3AP (06-29-2012), I was surfing around Hamuniverse.com and found thIs page on random wire antennas: Its really an impedance transformer (9:1) to feed a high impedance, end fed (unbalanced) random wire which is likely to be a few hundred ohms, and transform it into something closer to a 50 (unbalanced) coaxial input, hence UnUn. Our newdesign isperfect for matching both long and short length wire antennas for multiband use. N4UJW. This design is excellent for matching both long and short length wire antennas for multiband use. In the first year using this unun with a random length endfed wire (Aluminum Elec fence wire at that) I managed to confirm WAS via LoTW on 10m, 15, 17, 20, 30, 40, 80. . endobj This design is excellent for matching both long and short length wire antennas for multiband use. RFI Tips and Tricks It may not display this or other websites correctly. var sc_invisible=1; It is optimized for 3.5/7/10/14 MHz but will work reasonably well on all amateur bands from 80 meters thru 10 meters with a 135 foot length of wire and a short connection to ground. Turns 1 & 2 are primary windings (the short wire). 32.00. Lengths to avoid are not always the same as endobj It uses an FT140-43 or FT240-43 toroid in a 49:1 impedance matching unit at the base and a 110 micro Henry (H) coil to act as a loading coil for 80m and a choke to stop higher frequencies using the last 2m of wire. WwS`8o}=n,pjhzRa]Ju/Ru ni4=UvZ:u9*@ Xz+zZcXm}i[Z;Z>.u!*eQVjucXeqYZnSJu)U[n>>KXzZ.Lz sqxcGj]%q}i6=-?YTlnZXV6}=U >5`ZNxChzRa]JU.6TVr6a] Enclosure Height: 5.000 in. SWR will vary based on topography, wire orientation and use of ground or counterpoise. understand its properties. Gil Gruson 1 Campaign | Comines, France $0 USD 0 backers 0% of $3,450 Flexible Goal Follow Story FAQ Updates 0 Comments 0 Prototype The project team has a working demo, not the final product. but instead of the Jaycar core, we used an Amidon FT-240-43; anyhow, we also followed the UnUn with a 1:1 guanella choke and boxed everything, at that point, we . so that it is not a halfwave multiple of any frequency you want to use. Product Reviews Moving the pot up and down gives a feel for the SWR versus antenna impedance sensitivity. Again, the bands are USA, so change them the program as I did, above, for my K1. STORE Liquidtight NM 90-Degree Connector(Home Depot). Power handling is 100 watts CW / SSB & 25W Data modes. Hertz Antenna" shows in line 2 of the table that a similarly installed The transformer usually used with an end fed wire is a 9:1 transformer. Here I show finalizing the antenna, getting it in the air, and run. 8 0 obj ?7{*. You are using an out of date browser. The idea Picture Information. endstream /Count 1 REVISED: 16 19 22 26 32 33 38 44 46 48 52 64 65 66 76 78 80 88 92 95 96 99 104 110 112 114 123 128 130 132 133 138 144 152 154 156 160 165 171 176 182 184 190 192 195 198 208 209 220 224 228 230 231 234 240 242 246 247 256 260 264 266 272 276 285 286 288 297 304 308 312 320 322 323 325 330 336 338 342 352 361 363 364 366 368 369 374 380 384 390 396 399 400 414 416 418 429 432 437 440 442 448 455 456 460 462 464 468 475 480 484 494 495 496. /Resources << 9:1 Unun EF Random Long wire matching Transformer with BNC or SO-239. End Fed Antennas. Designed for those who want the maximum isolation and choking across the full HF spectrum. results. We are working every day to make sure our community is the best Radio Hobbyist's site. Cut a 4 foot length of AWG #18 enameled wire. 3 0 obj config file by typing gnuplot rw.gnu. bands you're intested in in a vector like the example below, by typing. . There are numerous configurations available online that will accomplish this on multiple bands (Google search "end fed half wave antennas"). I say run what you got and don't worry about it. rig, often with no feedline, and the other end in the air attached to The 9:1 may work best with that length wire and a tuner, but some say that length is undesirable for the hf HAM bands. /&KWA7{L=D]g0Z!F9;V{zL[h-D,u(.9rg(RHI{f t*C/?? google_ad_height = 600; 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. Typically unbalanced = 50/75 ohms too unbalanced = 450/675 ohms. Some important and helpful references I used for this work: https://elginradio.wordpress.com/2017/10/17/end-fed-half-wave-antennas/. End fed 9:1 58ft wire and 17ft counterpose wire touching ground. An Unun is used to match an unbalanced line to another unbalanced line. 2 0 obj These dimensions were derived from modelling the antenna in EZNEC. , This is a partial reprint (with permission) of an excellent series of articles published by KV5R Usually any wire length that is non resonant on the band or bands desired will work with the 4:1 ratio. For those that enjoy the LNR and Hy Endfed antennas, but want to run more power, We have also installed an additionalstud which can be used for a separate counterpoise wire rather than forcing the use of the feedline's coax shield, ttaching a counterpoise wire to the common point of the auto-transformer, provides the antenna radiator something to push against rather than the coax shield. My homemade 49:1 EFWH with a 60 wire (cut for 40M) would do just fine! gnuplot 2 0 obj So for example 80m could range in length from 120 to 133 feet. x@ Odds are that most lengths are fine though, so the easiest solution is to pick a length based on something else (like, the room you have available) and if you get unlucky, roll the dice again. Post Reviews Alternate connectors and Mounting Options are available in the. 1. is that for a given ham band there are min and max frequencies which We hoisted the free end of the antenna wire approximately 30 feet into a tree. Repeater Builders Using a 49:1 transformer shoot for the best 50 match @ appx 2450 load over your working frequency bands. Prescott Hamfest 2023 Saturday - May 13, 2023 - 0800 to 1200 MST Granville Elementary School 5250 Stover Drive, Prescott Valley, AZ 86314 The 2023 Prescott Hamfest is co-sponsored by the Yavapai Amateur Radio Club (YARC) and the Amateur Radio Council of Arizona (ARCA). 2 0 obj Legal Stuff x[q;`&z`uAlo#V@;hvOYt, @*Ys~_W_~W_aw_ p[N+}[t-^oLy}xz>7/~c|ZZt75;kN^=>Y+_~|b~"m*tw>xG=x6Qwz|xvz- | <> . doing the initial 468/f on C and D scales. google_ad_slot = "1982258389"; We have also installed an additionalstud which can be used for a separate counterpoise wire rather than forcing the use of the feedline's coax shield. These are sometimes known as a Magnetic Longwire Balun. 9:1 or 49:1 unun for end-fed long/random wire? As typically Continue twisting the entire length of the short wire. When do you use a 1:1, 9:1 or a 49:1 balun? Having the option to switch rapidly between 49:1 and 64:1 should prove to be a really nice feature.. Vacation Closure - See Homepage for Next Availability. Each vertical blue line represents an amateur radio band. 80m up, W3EDP's 84' antenna, 17' counterpoise is probably the way to go. It will be good for 15m, and 10m. Bullet 50:450 (9:1) HF Unun, 1.8-61 MHz, 1500 Watts, End Fed Antennas. 1 X FT240-43 Ferrite Toroid Core 43 Material(Mouser Electronics), 1 X SO-239 UHF PANEL JACK S/CUP SO-239(Mouser Electronics), No. Kj8~q7c? The graph below shows lengths to avoid for different collections of bands. The second smallest number I measured was 2.7pF, derived from the self resonance at 2.72 MHz with the magnetizing inductance (measured at 25.8 H) with the secondary open and the output wire folded to a small 1/2 length. For a better experience, please enable JavaScript in your browser before proceeding. I will also find some sort of heat resistant packing material to help hold the transformer in place. Both were on 20 meters at 97 watts, Icom 7300. The unun was floating at about 15 feet above ground. multiples, and of course different band combinations yield different <> Experimenting by slightly changing the wire length (+ or-) is encouraged to provide best overall performance. something as high as you can find. Therefore, we came up with the following numbers to avoid (IN FEET): These lengths in the table beloware the culprits that cause all of the trouble when using random lengths. Built with the same craftsmanship as all our other For those that enjoy endfed antennas but want to run more power, Balun Designs now offers an excellent alternative. 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. good show chuck, you said ya picked up a 430, did i tell i fried the 0ne i got from you, can anyone point me in the direction of a 2 pill schem for the HG 2879? Coverutilizes integralneoprene gasket for weatherproof integrity. It is important to use a counterpoise. Caution: When used atfull power rating of 1kW, the antenna must have a low SWRon the band selected and be used on a 50% duty cycle. (A t0 B) Fold over 6 to 8 inches and twist it together. HF & Shortwave 10C) for the 10-80 m bands, or even 6-160 m: 17 ft (5.2 m) of twin-lead and 68 ft (20.7 m) of antenna wire (i.e., standard dimensions). If you plan on stringing up a dipole you use 2 equal lengths of wire with the Balun in the middle. 35-43, 49-63, 70-85. Multiples are on C and Use a slide rule! j#f5(fk0?P[polEo5b2-/oVZu1Qo-I6C/M@TbddPc#cdZZ|7+|o{}!F#?Go7ju|?wwgow/c2/W-m~~hn[S29OU}}r7lc]wsw[shS[#qbrrK[7*0,Xv{k+o {=*vo S__O~*=y/zk75O?yjCnXS{`~Ii'c_GxN. If you want all the bands from Wire-Lengths-for-9-1-ununs.pdf Created Date: 12/12/2022 11:20:42 AM . I swept the VSWR of the unun and resistors as described from <1 to 55MHz. /Type /Catalog So, having nothing better to do one day, I re-did the calculations going out to 500 feet. Computer Help Make sure the beginning few inches of twisted wire is not involved in the winding (i.e., just hanging down from the toroid). recommended on VE3EED's page because I use all halfwave For example, 9:1 UnUn End Fed Long Wire Lengths - Pretty Simple. I usually go with a 3.2k transformation wire winding ratio of 8:1 which is a final impedance conversion of 64:1 (50ohm * 64 = 3.2k ohm). 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. So for example 80m could range in length from 120 to 133 feet. 2 eyehooks with washers and nuts (I used #8 diameter, but size is up to you.) Ham Hints I actually did this first and before the connector was bolted to the box. are blocked out because an antenna should be at least that long. Part List: ones The 49:1 End Fed Half Wave Antenna is very popular choice for home & field use, Ideal for limited space and stealth applications. Recommended wire lengths for Unun models 9130, 9132 & 9135 Table shows typical SWR relative to installed wire length. shown in the column e. var sc_project=8077274; 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 . 20/40/17m. /BitsPerComponent 8 /MediaBox [0 0 748 752] endobj Generally an EFHW will be in the range of 2,000 to 5,000 ohms at the very end of the dipole when resonant. Dimensional Drawing of Standard Enclosure, 1:1 Common Mode Choke / Noise Suppression, Core Material Selecton for Baluns and Ununs, Antenna Matching Problems When Using Ladder Line or Open Wire Feedlines, Model 4932 - 4 & 9:1 Unun 1.5 - 54MHz - 2kW, Model 49130 - 49:1 - 80-10m EFHW - 200 watts, Model 64131e - 64:1 & 49:1 - 80-10m EFHW - Up to 1kW, Model 4116 - 4:1 Hybrid Balun 1.5 - 54MHz 3kW, Model 9130sw - QRP 9:1 Unun 1.5 - 54 MHz - 300 watts, Model 1115d - Max Choking 1:1 Balun, 1.5-54 MHz, 5kW. endobj x 2 in. The QRP End-Fed Half-Wave Antenna 49:1 Transformer Building a great impedance transformer for Ham Radio end-fed wire antennas. The free end of the untwisted portion of the long wire (past the 14th winding) will be secured to this bolt as well on the inside of the box, while the radiator will be secured to it on the outside. installed, it is a compromise antenna but great for portable use because <> ), Note that Jack, VE3EED,went SK several years agohe will be missed. He was so impressed that he purchased a 9:1 unit from you, his will be delivered Saturday. I imported my spools from the US, but I have seen them on Ebay in the UK. A standard recommendation (see QST, March 1936, p. 32, "An Unorthodox UNUN 9:1 or 4:1- 3kW ICAS This is is dual 9:1 and 4:1 UNUN used for popular "non-resonant" length END FED wire antennas or verticals like 27 or 43 feet. %PDF-1.7 Connect this ring terminal to one of the SO239 chassis bolts. 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. Quantity: Sold individually. Cut the center conductor wire (free untwisted end of short wire) of the unun to the correct size, scrape the enamel insulation off of the free end with a box cutter, and solder it to the SO239 connector. Any SWR measurement taken with the transformer at the feedpoint should not exceed 1.5:1withNOtuner in use. all US ham bands. which got me thinking. I purchased a MFJ-16010 Random Wire Tuner and an LDG RU 1:1 unun. . A few more comments about this 49:1 autotransformer EFHW design. 27.00 (27.00/Unit) Free Postage. The random wire antenna is probably one of the least expensive, easiest and cheapest HF antennas to use if you have a tuner and you want to get the "most" out of a length of "random" wire without having to pull out that calculator, doing the math, getting the center insulator built orbought, running the feedline, and all the rest that goes with putting up a more elaborate antenna. stream The WorldwideDX Radio Forum was originally established in 2001. Note: My (A to B) length was 6 inches. The graph below shows lengths to avoid for different collections of bands. Thank you so much for such a great product! On our next windy free day, AA1F and . 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. uR5I5z G^u2`j[}+sy9 /Kids [ 4 0 R ] hbbd```b``^ "Cs;D2 I*`0D;+EVUHy`qml0{YVw`b0i DvkAh |"w I2% ?W%@Fg`` 6 You can add your own wire or get the complete product from this link EFLW-3K antennas. /Producer (XnView, http://www.xnview.com) This transformer is designed to be used with an end fed half wavelength of wire only. 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! 40-30-20 . So a 49:1 impedance transformer is needed to match the 50 ohms of the coax at the feed line. The goal of the impedance transformer is match the 50 ohm impedance of the feedline (coaxial cable) with the potential 3000 to 4000 ohm impedance expected from an end-fed half wave antenna wire radiator. 59 0 obj <>/Filter/FlateDecode/ID[<81C501BAF3AD19DF6B2122F37F15AF84>]/Index[25 50]/Info 24 0 R/Length 149/Prev 898971/Root 26 0 R/Size 75/Type/XRef/W[1 3 1]>>stream . . You also A good place to start is the formula 468 / f (MHz) for a 1/2 wavelength wire antenna. SBULLET-9U-1500. W3EDP's results in the above referenced 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. 4 x 4 x 2 electrical junction box (available at big box hardware stores), One PVC DWV Test Cap (available at big box hardware stores in plumbing). I'm not saying aliens are in the radio, but aliens definitely are in the radio. A 9:1 unun is a transformer that reduces the impedance at the input by a factor of 9. SO-239 (UHF female) chassis mount with screws, nuts, lock washers. Vhf and Up endobj I have found this calculation to work well, however it depends on many factors such as wire used, location etc. A level of 500-600 watts is the maximum with a further reduction onany band measuringabove 3:1. Use with other lengths can potentially damage the transformer depending on power level in use. endobj https://elginradio.wordpress.com/2017/10/17/end-fed-half-wave-antennas/. It is not a good choice for working lower bands from a too short wire, that is, if you have cut your wire to a 20m halfwave, it ain't much punkin' for 40m, 80m, or 160m. 4 0 obj often can't match it. Wire lengths for the 4:1 ratio in models 4130, 4132, 4134, 4932 and 4935. The beauty of the halfwave antenna is it's a complete antenna in the sense it needs no counterpoise. FCC Information I got three FT240-43 toroids (two would be lighter, but three increases the curie point so it can handle longer duty cycles), a spool of the 14 gauge enameled wire . A success! Superglue 2 toroids together. Privacy Policy Each winding is counted when the wire enters through the center hole of the toroid. It is used for non-resonant verticals like 43 foot or 33 foot Or Wire antennas like an End-Fed 1/2 Wave Multiple Length Wire Antenna. 73, Weight: 0.380 lbs. Cannon". Reading Room Continue on winding the long wire through the toroid to complete loops 3 through 14 as shown in the schematic below. You have to give up a band or two, like 60m and 6m, as endobj /Creator (XnView) (Note: I am not satisfied with this part of the project, so I will describe it here briefly. A 50 foot run of RG-8X coax connected the antenna into the LDG Z100-plus tuner and then a Yaesu FT-891A transceiver. excellent page for EFHW info - or, addressed below, to cut the wire He had heard good things about 'Balun Designs' so he recommended you. google_ad_width = 160; This will be for an eyehook in order to provide strain relief for the radiator wire. V#X~[Z?\ZcX:-Y?&Y?IqTnayZ{jTZOub}=UTWu1G>o.,RaT c=W>:sECXTkc=X % Notice from column f that there is no length giving low impendance for 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. So, if you connect a length of wire that presents an impedance of about 450 to the input, you'll get an impedance of about 50 on the output. SSTV Repeater Basics This is the latest and greatest transformer design for End Fed Half Wave (EFHW) antennas. 35-45, 54-64, 67-77. The following is a list of materials required to make a 49:1 unun impedance transformer for an end-fed half wave antenna. (The numbers aboveare a great start, thanks to Jack and Mike! First, it is important to understand the difference between the end fed half wave and a random wire (or "long wire") antenna: the random wire is just a piece of wire that is matched to 50 Ohm impedance using an antenna coupler, sometimes adding a 9:1 unun. At multiples of half wavelengths of the In fact, the 9:1 unun that I built is actually an autotransformer. The following wire connections do not need to be made in the order I described.
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