The antenna system consists of a 40-10 EFHW (~60' Wire matched to a QRPGuys EFHW transformer mounted on a DIY wire winder cut from a yard sign), 5 aluminum tent pegs, 2 pieces of shock or bungee cord for tying off the antenna ends, a 25' BNC terminated RG-174 coax, and a 14-1/2 ft fiberglass fishing pole with DIY collar and guy lines. The schematic of the homebrew matching unit is shown below. In those days it was even simpler to match as all transmitting equipment was tube driven and this already had a very high output impedance. I included a switch to be able to use either. Will cover 160 - 10m with a tuner. There are two main benefits in using an end fed half wave antenna over a coax fed half wave dipole. This confirmed that I had a resonant half wave and that I was feeding it at or very close to the peak voltage point and the feed impedance was around 3200Ω. http://m0ukd.com/calculators/ohms-law-calculator/, Your email address will not be published. This is an End-Fed Half-Wave (EFHW*) antenna for 40/20/15 and 10m bands. Apr 18, 2017 - End Fed Half Wave Antennas. Once again, these are not polarized, so it doesn’t matter which binding post is connected to which terminal. I have been wondering of ground systems in HF-manpacks with whip antenna. G0KYA's HF End Fed Half Wave (EFHW) antenna – construction details Introduction The EFHW monoband matching unit (inspired by AA5TB) allows for a half wavelength of wire to be connected, giving a 50 Ohm impedance match to the transmitter (without a ground plane or … The coax is soldered to the primary, the terminal block is just to hold it in place. But performance is down about 8-12db on a dipole on 80m. I then wound the primary coil, which had to be a slightly larger diameter so that it could fit over the secondary coil and provide inductive coupling. A centre feed gives around 70Ω. You can opt out by clicking the configure button below. We also know, that both ends of the half wave antenna will have the highest voltage, thus impedance, which may reach up to several kilo-ohms. The EFHW-8010-1K provides an easy-to-deploy antenna that can be operated on all HF bands, except 60 meters, with a low enough SWR to be used without an antenna tuner on most bands. End fed half wave antenna length. These dimensions were derived from modelling the antenna in EZNEC. Impedance transformation is calculated by squaring the secondary turns ratio (note ratio, not actual turns) 8² is 64. 128 – 5-Element Log-Periodic Vertical Antenna for 80m, 40m, 20m Figure 1. var freq = parseFloat(form.MHz.value); I. It is a resonant Half wave on 80m (3.5MHz) therefore also resonant on second, third, and fourth harmonics, etc. (e.g. The coupler will also not be working as it was designed and will be inefficient, generating heat. I haven’t seen any, although there’s no reason why not. counterpoise = (14.1 / freq).toFixed(3); What followed was 3 months of confusion, learning and experimentation. For calculating the length of a half wave in metres, I use 141÷ƒ(MHz) for wire elements. Do you foresee any problems using this on a sailboat for a vertical or sloper wire antenna? four + three =. Using the technique of your choice, support the other end from a tree or other tall support. 6.65 metres of wire on a 9 metre fibreglass pole. John. 4:1 impedance ratio is 2:1 turns ratio. It sounds like quite obvious solution for manpack whip on HF. They are easy to make and easy to set up. if possible, so I suppose they are usual coil loaded quarter wave vertical whips. The coupler is a tuned impedance transformer, not an antenna ‘tuning’ unit. But performance is down about 8-12db on a dipole on 80m. A half-wave conductor when excited at its resonant frequency will display a voltage and current distribution as shown in Figure 1. Its’ feed-point affects its impedance. High current, low voltage at center; low current high voltage at ends. Your transformer is a 2:16 winding ratio, and a 1:64 transformer, not an unun…perhaps take the 14. winding to the antenna, and achieve a 1:49 transformation to improve swr…..then add a 100pf 15KV capacitor across the feed….yours seems a little lower voltage, and may not last? Brian says the homebrew antenna works very well. The antenna has a full 300kHz bandwidth on 80m between 3:1 SWR points. Get a PAR quad band resonant EFHW, it will make the Comet look like a dummy load. Next time I use it I will take some measurements and add them to the page. Tried w/wo CM choke, Ground at window Tried various coax lengths to find resonances Tried all bands where no tuner needed Highest CM sometimes outside (Standing W) This is an End-Fed Half-Wave (EFHW*) antenna for 80/40/30/20/17/15/12 and 10m bands. Portable EFHW Antenna. Notably since then I have acquired a Mini 600 Analyser. 14.2 is a frequency approximately in the middle of the band, which gives a length of 468/14.2 = 33 feet. The problem with end feeding a half wave is also its advantage. Save over 40% off the annual cover price. They have their differences, but I will make them a happy ‘couple’! Its an excellent performing end fed half wave antenna. The antenna has a full 300kHz bandwidth on 80m between 3:1 SWR points. However, it needs a tuner to get the SWR low enough on some bands. Be careful of power lines and other hazards! Materials (pictured) It's a good idea to have your antenna at least one half ( 1/2 ) wavelength of the antenna. The 67cm counterpoise just hangs down in free air. Attach one end of your antenna wire to one of the binding posts, either directly or using a jumper wire. For a quick band switching I used banana male and female connector cables. After acquiring a MTR3b for SOTA activations I decided I needed a different antenna than the End Fed Random Wire (EFRW) or the speak As the name indicates the EFHW antenna is half a wavelength long on the lowest band of operation. one quarter (1/4) wave is the minimum height above ground for effective performance. There are always suggestions to use them with ground stakes, counterpoise wires etc. Next, create the counterpoise. EFHW-4010-1K Multi-Band End Fed Half Wave Antenna. It is a resonant Half wave on 80m (3.5MHz) therefore also resonant on second, third and fourth harmonics etc. Nice description of building. A half-wave antenna is a resonant radiating element with an electrical length of one half-wave. This way, I can build it with a 16 turn secondary, and at the inductance I wanted by altering the diameter and/or length of the coil. Cut your half-wavelength antenna wire(s). This is an End-Fed Half-Wave (EFHW*) antenna for 40/20/15 and 10m bands. You would have to experiment though, it would be another thing to get right! Diana was a contestant on Project Runway season 2, graduated from RISD, and currently lives in New York City. Sometimes however, the centre feed is not ideal, for example when you want to use it as a vertical. End Fed Half Wave Antenna for 6 / 40 Meter 6m to 40m EndFed Half Wave Antenna project produces an inexpensive, multiband, end fed HF antenna matchbox that is quick and easy to setup and use. The antenna is very easy to install because there is no need of a high feed point like a dipole antenna. Written on 23 June 2019 This is based on an article published in Sprat 177 (Winter 2018/19). There is also an update at the end. Hi Barry. The MFJ-1714 has “Super Long Range” baby! On top of the first wire, wrap a second one around the toroid three times (I used a red wire for this). G. 4 jumper wires with alligator clips (you may need more) We continue our antenna offerings with this single band, 80m-10m end fed half wave wire antenna. The last few years have seen a resurgence of interest in the end fed half-wave wire EFHW antenna.A half-wave at the lowest band of interest will also work well on all harmonically-related bands which has become particularly attractive to those wanting a quick portable wire antenna. 50×64=3200Ω (our input impedance x 8²). Solid Core Wire (two colors, 24-gauge recommended) Start by wrapping the wire around the toroid. I use EFHWs that are driven by a low pass as impedance match, much like the original Par Endfedz and had the same experience. , therefore very little ground is required large for 30MHz 49:1 auto transformer will bring it your. 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