Therefore the Great Circle Map generated below should be Read More, Multiband End-Fed Half-Wave EFHW Antenna The End Fed Half Wave antenna or the popularly known EFHW antenna has been around almost ever since the inception of HF radio. So, I embarked on testing it for myself. I am testing it with the tuned tank circuit and a coax to the tuner with and without a common mode rejection choke. There is no substitute for playing with the analyzer, trimming the wire, adjusting the compensation coils, etc., and going through the process for a few iterations to get the multiband antenna to work well for you as you have it installed. Feeling brave, I decided to tape my coil up and solder connectors on and hope I would be one of the lucky ones who wouldnt need much coil adjustment (will I be right??). EFHW Antenna Frequency Compensation Lead 5,144 views Jan 20, 2019 188 Dislike Share Save Steve Ellington 9.92K subscribers 8 inches of wire attached to the antenna post can lower the frequency. Of course, if both ends are raised higher, it will produce a more efficiently radiating antenna, but the portable and temporary installation is always compromised by conditions given by a location and its restrictions. However, to minimize capacitance, you want to spread turns and keep windings apart, so what is the right approach? ON7EQ EFHW Antenna - qsl.net 2006. 73! Thank you for your comment and feedback on the article about the EFHW antenna. coil inductance calculator at 66pacific.com. The VSWR plots below show results from the same transformer tested on the bench with minimal output capacitance, with a primary compensation capacitor, either 100pF or 27pF included, with the transformer installed in its aluminum box including antenna connector feedthrough, and with the transformer with an 18 clip-lead on the antenna output. The transformer was attached to the 30 meter EFHW antenna and turns were removed for best match to 50 ohms. In his article, I will try to bust some of the myths associated with Inverted. VSWR<1.8 over all of HF. Nothing drastic but likely the SWR on the summit will vary as conditions and the setup change. The End-Fed Half Wave Antenna a bit Differently However, it has its idiosyncrasies. Two layers of 1mil Kapton tape are placed over the winding. The impedance per unit length of a lumped transmission line is where L and C are values per unit length. I fashioned an antenna connector with washers made from some acrylic rod I had on hand. I drilled a couple of holes at each end of the former, a small one for the wire to pass through and a larger one for a bolt and wingnut for wire attachment as I wanted the end result to be portable across different antenna projects. The combination of the transformer with the end-fed dipole results in a positive reactance. This gave me an effective coil diameter of 40.5mm. A radio station is as good or as bad as the antenna it has. It may be one or even five kilo-ohms. Be aware counterpoise or ground radials are required for all hf antennas for better performance. Tuning the antenna to its resonance will result in 50 seen at the output of the SWR circuit. There is much more that can be written about this antenna and its matching, but that was not my aim. 'Capacitor flattens SWR at higher frequencies' - WA7ARK. The effect of the capacitor is very apparent for 17 meters and above, flattening and lowering the SWR curve through 10 meters. However, a key restriction is its 25W power rating, due to the small matching transformer. The EFHW transformer box from outside. (The antenna wire could also be tuned for the lower end of 80 meters without the coil but the . But Ill find the error of my ways.and there are various on-line calculators to help me ensure I get the decimals and (H, mH, uH, pH, etc.) From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. Payment: If you are eligible, Crosswalk CAA will make the appropriate payment to your energy provider (s) on your behalf. Being end fed, it needs a transformer to transform the higher impedance of the wire to the 50ish ohms the radio is expecting. There is no BIG secret about the EFHW-8010 antenna, it is just a wideband low loss transformer and a piece of wire. This article will not address that antenna type. For the antenna wire itself, I used 119 feet of 22g stranded hookup wire. is the initial disequilibrium temperature, is the equilibration time constant, and is the heat capacity. Below about 7 MHz, transmission losses increase as the core temperature increases. I used a section of 40mm external diameter PVC waste pipe and 1mm diameter enameled magnet wire to make the coil. PDF MANUAL: ENDFEDZ 40-10-KW EFHW 1KW ICAS ANTENNA - Vibroplex So I built myself an improved replacement matching transformer. One of the many confusing terms used in Workers' Compensation, "IME" stands for Independent Medical Evaluation or Independent Medical Examination. The previous table already contains these measurements. You cant really see the antenna wire, but the red line shows the antenna path. Another completed tuner, which is more compact then the pervious one shown, also it is lighter, more suitable for portable operations. Above is a thermograph of the transformer at 20W input at 3.6MHz. The last few years have seen a resurgence of interest in the end fed half-wave wire EFHW antenna. Highest frequency = 14.350 MHz. Impressive article and so well done that I may give it a try. Could it be something to do with the new vertical aerial I had recently installed? In an ideal setting, the center of the antenna will have the lowest voltage, consequently impedance, which is why it is possible to feed it by 50 or 75 coaxial cable. It is common to use compensation coils of a few turns of the antenna wire to improve the alignment of the bands. Jos van den Helm's (PA1ZP) article published in Radcom: Fig.1 - Withdraw the radiating element carefully to avoid damaging the matching components A few years ago I bought a secondhand Diamond X50 dual band (144/430) antenna at a radio car boot sale. (The antenna wire could also be tuned for the lower end of 40 meters without the coil but the . The vector sum total of all currents flowing on various physical antenna wires plus other currents like CMC on the transmission line or parasitic induced currents on masts or nearby objects must always be equal to zero. One cable is the coax feedline, the second is the supply to the cooling fan and control of relays. A lot of radio amateurs have made similar antennas to this with larger transformers for higher power handling. A method for estimating the impedance of a ferrite cored toroidal inductor at RF. (30 votes, Rating: 5.00) - Please vote the article with your valuable star rating. Essentially, the matching is done with a tank circuit, which represents the highest impedance when it is tuned to resonance. I have seen and read quite a few reports of making this antenna, and some got away no problem with the 110uH when they came to set up and adjust the antenna, others needed to tweak their coil turns. EFHW 80m extension - MI0KXX The toroid with its many taps may be soldered directly on a multi-position switch. Select components with good insolating materials and properly chosen, relatively high voltage rated parts. To this end, I weighed the main components of the box and looked up the specific heat capacities to get an approximate overall heat capacity for the entire box. A graphical presentation of the mathematical analysis of EFHW antenna SWR variations on account of variations in counterpoise length as well as the Unun impedance transformer at the feed-point. Basically, the loading coil is operating as a trap. In an urban area we are much more restricted, especially if we need to be stealth about it. The transformer was attached to the 30 meter EFHW antenna and turns were removed for best match to 50 ohms. I cut 2.5m of 16AWG wire, added a connector, and hooked this up to one end of the inductor. Tackling both of these issues at once led to a much smaller, lighter, and less costly transformer with better loss characteristics than previous designs. Inverted V Antenna A popular Dipole variant, EMI-RFI and Noise related HF Radio Station performance loss. See the table above. Lets call this element the LoadAttenuator. My question is what is 'higher frequency' specifically? The SWR for the 20 meter EFHW antenna was < 1.2:1 It uses a coil as a compensation unit, and no counterpoise. 3) Total losses are approximately independent of core volume. : I see you were able to post your comment now, so I just copied my email answer here for others to see. It depends on the selection of the inductance and the capacitor values. Consequently, this is how the capacitance values are determined. Krem, rja le, mi a krdse. However, from the measurements we made on the self resonance frequency, we know that most of this capacitance is right at the output of the transformer and not internal to the windings. As I reexamined my formula, you pointed it out correctly, there is an error in it. What seemed to work best was to concentrate the turns on the tap-side of the secondary winding, using several (#28) wires in parallel for the primary turns such that they covered about half of the underlying secondary winding. Basu (VU2NSB), Antenna Bearings Geodesic Map We present automatically rendered Antenna Bearings with Geodesic Paths projected on a Rectangular Map. It is much easier to wait ~2, know that you are going to see about 86% of the temperature change you would see if you waited until time infinity, and just make a simple correction. It is basically an end fed half wave dipole on 20m/40m and an end fed full wave dipole on 10m. It is important that resonance may be achieved at each tap of the inductance. Typical EFHW Antenna Characteristics & Performance, Influence on Performance due to Deployment Environment, Construction Variables and Transmission Line Interface, Optimum Counterpoise length and Coupling Transformer, Influence of EFHW wire orientation on performance, Good Antenna for any Radio Station is vital The importance of antennas for radio communications can never be over-emphasized. How does this SWR meter works? I decided to play with this to see what I could accomplish. I designed and built a few EFHW tuners already (calculating them from scratch, I only optimized the formula for the article). Basu Bhattacharya (VU2NSB). However, let me write about it from a slightly different perspective that was not very obvious from the articles I read. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. After cleaning it up and testing it, I installed it on the side of my house on top of a straight pole. Im very pleased with that indeed. End Fed Half Wave Antennas: Is a Primary Capacitor Really Needed? Although it is simple to build and is a multiband antenna, it has several attributes that . With a very short counterpoise it is difficult to resonate the fundamental with any drive impedance. Next, I started winding the transformer. This gave the RF some place else to go, trapped by the coil and capacitively shunted to ground, rather than on to the transceiver. . End Fed Half Wave (EFHW) Antenna Upgrade Part 2 - The Loading Coil Evaluating it at a we get: which gives the power dissipation simply in terms of the heat capacity, cooling time constant and the temperature difference from ambient. The other end, attached to the transformer and antenna analyzer, is about 1 meter above the ground. This will yield the maximum capacity of the variable capacitor. That is an end-fed, but very different then the half wave construction. As the length of the antenna is around 2/3 of the span of a half-wave dipole on 80m, there are two compromises. http://www.hamuniverse.com/randomwireantennalengths.html, https://km1ndy.com/diy-491-unun-impedence-transformer-for-end-fed-half-wave-efhw-antenna/. <> The cooling curve I measured is shown below. These dimensions were derived from modelling the antenna in EZNEC. I may try to bring down the 20, 15 and 10m bands at some point, either with a small coil 2m from the feed point or with a short section of wire as a compensation lead added at the feed point as shown in the video below from Steve Ellington. This could be achieved by: Using thicker wire; increasing the diameter/length ratio; using a low loss former. The overall lenght is only 15m. Therefore, installation is quite easy, and its tuner circuit is rather simple as well. Since I wont be connecting a counterpoise, the antenna will use the coax shield as the counterpoise, so the RF choke will keep any unwanted RF from feeding back through the coax. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. Being a more efficient design that some, it might result is a wider VSWR excursion that those others as transformer loss can serve to mask the variations in the radiator itself. This will allow good matching of the half-wave radiating antenna wire to the 50 coaxial cable at virtually any location. It is worth experimenting with its length also. I wish you lots of productive experimentations and successful portable operations. 101: The Independent Medical Evaluation - "IME" By: Cynthia M. Hennessey Attorney. Research salary, company info, career paths, and top skills for Software Engineer - EDI As it turns out K1RF had similar questions about the capacitor and published data showing that the capacitor does improve SWR performance at frequencies higher than 20 meters. I then added two 220pf capacitors in series between the center conductor and ground. In the problematic upper bands, the resonant wire significantly improved the in-band SWR compared to the resistively terminate box (purple). I checked the inductance again to make sure this hadnt been overly affected, and it remained unchanged at 109.8H, good enough! The 1:64 transformer is wound on 3 stacked FT240-52 toroids, this provides same. The aluminum box is the logical heatsink, so I cut a few scraps of aluminum to make a thermal connection to the bottom of the box and to the lid, adjusting with aluminum shims so that when the box lid is screw down, the entire thermal assembly, with the cores in the middle, is under a little compression. At equilibrium, the heat leaving the box due to cooling will exactly equal the heating power input. I settled on a compact secondary using #28 wire. . This condition is rarely met in typical amateur radio EFHW antenna deployments leading to compromised overall antenna system performance. Zin=46.52+j6.72. Im not interested in trialing coil-loaded dipoles at the minute (from my limited reading bandwidth can be a real issue) so the options I like include: The G0KYA/PD7MAA/IK0IXI EFHW extension to cover 80m calls for a 110uH coil placed at the end of the EFHW, with a further 2-2.5m of wire beyond this. It does not need any special components; in fact, most of us may have them in our shack drawers already. Software Engineer - EDI - salary.com A week or two later I started to notice an occasional knocking sound inside the house. HA5CBM Mikls, Finally the tank circuits specification is complete, which is sown below. point to the loading coil is 20.2m and this sets the 40m resonance at 7.1MHz, which in turn dictates the responses of the harmonically related bands 14MHz, 21MHz and 28MHz. = 258 * 10^-12. The technical storage or access that is used exclusively for anonymous statistical purposes. What are its disadvantages? Real end fed antennas operated harmonically do not present a constant impedance, not even in harmonically related bands. clear. I have been using a 40m End-Fed Half Wave (EFHW) antenna very successfully for the last few months and I wanted to extend the design to multi-band whilst avoiding the need to take a . Finally the tank circuits specification is complete, which is sown below. The final turns ratio turned out to be 3:29. Interpretation of S-Meter Noise Floor in HF Radio Receivers. Once completed and tape-wrapped, I applied a layer of liquid electrical tape over the surface and the interior wire connections, ready to go outdoors. My End-Fed Half-Wave (EFHW) AmateurRadio.com The SWR for the 20 meter EFHW antenna was < 1.2:1, The SWR for the 40 meter EFHW was ~1.4:1 for 40 meters and 1.2:1 for 20 meters (full wavelength), For my 20, 30 and 40 meter EFHW antennas I will not use a capacitor in the primary. A transformer was wound on a FT50-43 toroid with 3 bifilar turns followed by another 31 turns of #26 enameled magnetic wire. It was difficult to work out where it was coming from but I found that it was more noticeable when it was windy outside. 100W on a Wire antenna! I would mention first its ease of installation. It turns out that we can easily measure the effective parallel secondary capacitance by looking at the primary self resonance when the secondary is open. When I'm measuring the half way point on my EFHW, looking for 67', how do I factor in the compensation coil on the MyAntennas wire? Does your station desperately need a good RF ground to behave properly? My favorite SOTA antenna is the End-Fed Half Wave Antenna. I tossed the line as far up as I could in a tree. Energy Assistance (LIHEAP) | Crosswalk Community Action Agency If not a lightning strike, I will write an article about the experience as well. The 40-10m EFHW camping antenna is late but done. More info in - reddit Well, in ham radio, everything works. With very little counterpoise, the antenna is being fed at a high impedance point so a rather large impedance step-up is employed. In theory, the examination is supposed to be used to help clarify your medical condition and . Thanks for your comments. From experience, I found that with this tuner my SWR was better by simply disconnecting the counterpoise at lower bands. The orientation of these lobes varies with the frequency band of operation thus resulting in directional inconsistencies between bands. Having recently built a MTR2 3-band CW transceiver, I was keen to make band switching on a mountain top as simple as possible. There are many resources online that explain the details better than I can, so Id suggest doing your own research if youd like to build one for yourself. . Disclaimer | Privacy Policy | Cookie Policy | Terms of Use. The technical storage or access that is used exclusively for statistical purposes. 100W on a Wire Antenna - Is it good enough for DX? It is not necessary to calculate the above; the results are sown in the following table. Commercial Coils, Inc. 213 Chesterfield Industrial Blvd Chesterfield, Missouri 63005. Home Antenna Wire Antennas Multiband End-fed Half-wave EFHW Antenna. With such a switch, it is impossible to forget to switch back to operational mode. Being end fed, it needs a transformer to transform the higher impedance of the wire to the 50ish ohms the radio is expecting. From our measurements of the box cooling curve, this would correspond to the box dissipating about 14W in still air. The five primary turns cover about 60% of the secondary winding, leaving the high-side of the secondary not covered. The SWR was measured for each of the three antennas across the CW portion of the bands. Newtons Law of Cooling tells us that heat flow is proportional to the temperature difference. As is often the case, packaging was determined by what boxes I had laying around. Ive been wanting to get back into radio stuff for a while now, but the only antenna that I have up now is a 40 meter dipole. 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. The slim coil is torpedo shaped to prevent it being snagged in trees when deployed in 'the great outdoors'. After doing some research on the internet I eventually came across something about rattling radiating elements in Diamond vertical ant, For several years the EF-10/20/40 MKII EndFedz has been my main station antenna for HF. It tests out well on the antenna analyzer for 3.5 to 29.7 MHz. The 2 coils are 35uh and 90uh. The goal of the temperature characterization is to determine how much temperature difference (core to ambient) there will be for a given level of power dissipation. When you are discussing a distributed capacitance, it is difficult to know exactly what you are measuring. The 6-turn loading coil lowers the resonant frequency into the CW portion of the 80 meter and higher bands. It requires a set distance to hang both ends of the antenna, and that is not always given. This was a little bit of a compromise as the last 20ft of the antenna had to run down a fence to fit it into the garden. It is common to use "compensation" coils of a few turns of the antenna wire to improve the alignment of the bands. It is important to consider the voltages on this tank circuit. For Jackson County, please call Western Egyptian Economic Opportunity Council, in Steeleville, at (618) 965-9031. EFHW Compensation Coil Experiment - YouTube P.S. inductance as one FT240-43 and is able to withstand 1kW 50/50% duty cycle with help of a cooling fan. Multiband End-fed Half-wave EFHW Antenna - VU2NSB.com The photos above show a method that works fairly well. The difference here is that the target bands are low frequency. %PDF-1.4 And of course, a counterpoise with various lengths. Other observations along the way: 4) Tight windings or backwinding over the primary can significantly reduce leakage inductance. The total lenght is about 15mtr only and using 2 coils and a little stub (s) on the 80m coil or/and the 40m coil. The final turns ratio turned out to be 3:29. I ran WSPR at 10mW for about 2 hours and got the results below. My limited experience with these antennas also suggest that one must be cognizant of the RF current pushed onto the feed-line coax. With no counterpoise wire it will be the coaxs shield providing it. 2. Nevertheless, the EFHW antenna had in the past, been rather sparingly used by amateur radio operators due to various reasons. Toll Free 800-532-2645 636-532-1523 Fax: 636-532-8259. = .00 00 00 00 0 258 Above, the magenta curve is measurement of a real transformer from 1-11MHz with nominal resistance load and three compensation options: cyan: 0pF, too little compensation; magenta: 80pF, optimal compensation; and. It is likely that next time the tuning may be set according to the already found positions, and it will not be far off, requiring only slight adjustment. It is quite difficult to satisfy both requirements of achieving proper impedance ratio and resonance of the tank circuit at each tap of the inductance. Intro EFHW Compensation Coil Experiment Steve Ellington 10.3K subscribers Subscribe 29K views 4 years ago The little coil helps place the EFHW resonance points where we want them. The maximum B field in the core is proportional to the imposed voltage, as: where A is the cross sectional area of the core, f is the frequency and N is the number of turns. However, I think I made a good choice with a Hammond 1590A diecast aluminum box. For our transformer at 100W (==> 71 Vrms into 50 ) , the core cross section for the two FT114s is 0.74 cm2 , consider the lowest frequency as 3.5 MHz and our 5-turn primary, then plugging in the numbers we find Bmax = 0.012 T. Lets consider a much more challenging extreme: 1000W and the 160m band. The following is the most up-to-date information related to EFHW Compensation Coil Experiment. One point of my small-core, compact winding design was to be able to cool the core. I use my MFJ-939Y AMU regularly anyway, and it has zero trouble with this setup. Looking at several builds and discussions, such as commercial antennas (e.g. It performed well on both the 2m and 70cm bands. A design by VK3JEG is only 66-ft. long, about the size of a 40m dipole. Since it is a EFHW and not a non-resonant end fed, the wire length for 40m is about 67 feet. I hope to do more experiments with single and multi band EFHW antennas above 20 meters - stay tuned -- The experiments have been performed, check it out! Why does a wire carrying RF current radiates to produce EM waves which travel through, Beware of Skip Zone while working HF radio A good radio amateur friend of mine from Poland sounded quite anxious when he told me that his new antenna was behaving peculiarly. A tutorial on estimating the impedance of a toroidal ferrite cored inductor for radio frequencies, Pulse test of a Hantek 6204BD 4 channel 200MHz USB DSO and supplied probe. Wire antennas with an Un-Un-transformer 1: 9 have become more and more popular.
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