There could be any number of reasons for that, where I put the bends in the wire, the location of tree branches, etc. Some say you do not need a counterpoise, but that is false. Once that's done, the instructions say "adjust the coil as necessary" to bring the other bands into resonance. The band compensating inductor placed on the wire is another story. End Fed Half Wave Antenna Coupler (EFHW) - M0UKD MyAntennas.com Group | When I'm measuring the half way point on my EFHW Adding an additional 2 meters to the counterpoise did very little to affect the resonant frequencies, much less than adding that length to the main wire would accomplish. The SWR figures were as follows: FT240-43 132ft/100pF capacitor 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. With the entire winding length short, the flux from the primary need not travel all the way around the core to link all of the secondary turns. = 1/30.e6 = 33 nS. The 6-turn loading coil lowers the resonant frequency into the CW portion of the 40 meter and higher bands. Experiments with 160m antennas | VK3IL Blog 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. The coil is just 12 turns of wire wrapped around a 0.7 inch diameter tube, located about 6 feet past the antenna's feedpoint. = 258 * 10^-12. The photos above show a method that works fairly well. The 40-10m EFHW camping antenna is late but done. More info in - reddit Independent Medical Evaluation - IME | Cynthia Hennessey I was curious why this capacitor was added to the transformer. End Fed Half Wave (EFHW) Antenna Upgrade Part 2 - The Loading Coil 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. Also find news related to Efhw Compensation Coil Experiment which is trending today. Of course, you will need to find your tuning positions and apply your own position scale. With the coil and its wire attached I fired up my AA-35 Zoom analyzer from RigExpert and had a look. Elnzst krnk, de elsikkadt az zenete. Note that there is some uncertainty in the measurements, but we can be confident that the loss is no where near the figure estimated for the FT82-43 design. Best results are with 2450 drive impedance and the 3.3m counterpoise, so it is not surprising that 49:1 transformers are the common choice. From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. The real power limit will be core heating. You can see the coil in the picture below (red arrow). A few comments have been made about why the capacitor is needed: 'Improves higher frequency UNUN performance' and 'Compensates for UNUN primary leakage' - K1RF I place a 2 inch coil of the antenna wire with 3 turns (green) or 6 turns (brown) close to the box. I chose to use FT8 transmissions for this test since they generate 100% duty cycle during the transmission period with an average duty cycle of 12.6 sec / 30 sec = 42% overall when including the listening periods. For the transformer, a T130-2 toroid will be sufficient, on which we wind the seconder with multiple taps, as shown in the below table. Your posting put it all together for meTHANK YOU!!!! A short 80m antenna for my lot - KB6NU's Ham Radio Blog This could be achieved by: Using thicker wire; increasing the diameter/length ratio; using a low loss former. = .00 00 00 00 0 258 To explore parameter space a little, I modeled a couple of lengths for the counterpoise and see how the wire is resonant across the band when fed with various impedances at the driven point. The original coil is designed for low power portable applications. Nothing drastic but likely the SWR on the summit will vary as conditions and the setup change. To mitigate the voltage issue mentioned above, I used a couple layers of Kapton tape over the secondary winding. 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. This will allow good matching of the half-wave radiating antenna wire to the 50 coaxial cable at virtually any location. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. Subscribe to our newsletter and receive regular updates on new posts and articles. xZ Wxi@@=\A,Y1I0E~?)JdWfe.z/|iqLI?>BPo>Pf*w~]WZu.VZZZM5zjO=?`yC^l_-H{q|m|U]21xgS6~ltFGZH}(6FE4n0D9Klx`T/;! The high frequency performance was extraordinarily sensitive to anything that could add capacitance to the output lead. This is why we need the impedance transformer from the 50 coaxial feed-line to the several kilo-ohm antenna connections. For a quarter wave that is about 8 nS. Ive spent some time on digital modes over the last week and and my signal reports seem very similar to the pre-80m-extension period, which is good, and I am getting out well past 1000 miles on 20, 40m and 80m digital. Low SSN Why do most Hams find HF Radio so difficult? I recommend a good reading on this subject by Steve Yates, AA5TB at: www.aa5tb.com/efha.html. In this case C~5pF and Z~2450 suggests that the inductance needed should be about 30 H. Isn't it? No wire counterpoise is used to reproduce the SOTA setup. 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. From experience, I found that with this tuner my SWR was better by simply disconnecting the counterpoise at lower bands. The latest news about Efhw Compensation Coil Experiment. I checked the inductance again to make sure this hadnt been overly affected, and it remained unchanged at 109.8H, good enough! Note: More extensive experiments including operation at HF frequencies higher than 20 meters, harmonic versus fundamental operation and transformer efficiency is posted in this blog. 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. application of Kirchhoff's current Law on a typical EFHW antenna configuration. Energy Assistance (LIHEAP) | Crosswalk Community Action Agency I will go back and have the article corrected. So, I embarked on testing it for myself. blue: 250pF, to much compensation. A Smith chart view of EFHW transformer compensation A radio station is as good or as bad as the antenna it has. It is important to consider the voltages on this tank circuit. Basu (VU2NSB), Antenna Bearings Geodesic Map We present automatically rendered Antenna Bearings with Geodesic Paths projected on a Rectangular Map. 100W on a Wire Antenna How far would it reach? I found it very useful to label the tuner with switch and capacitance positions. How badly can high Local Ambient QRM affect HF Radio? Note that the primary winding on the toroid is using the inner lead of an RG-58 coaxial cable. I look at the end-fed as just an extreme example of an off-center-fed antenna. I mentioned in the reference article that the metric A/l captures the geometry, the larger it is, the fewer turns for same inductance / impedance. I was pleasantly surprised that the dips were so perfect across all of the bands and the SWR was low enough to not really need a tuner. 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. This is not an optimal value, benefit may be obtained by exploring small changes to that value. 2006. One end may even be close to the ground, not yielding the best radiation efficiency, but much activation proved it still operational. Un-Uns for Endfed-Antennas (EFHW) by DK7ZB - qsl.net This will yield the minimal capacitance of the variable capacitor. I wish you lots of productive experimentations and successful portable operations. The next important parameter is the parallel resonant circuits resonant frequency. At 5W input the connector at the end of the antenna wire may be up to 160V, and at 15W it may be 270V. y73s de Michael DL9SKY, Visszajelzs: The End-Fed Half Wave Antenna a bit Differently Coventry Amateur Radio Society, Az e-mail cmet nem tesszk kzz. The EFHW transformer box from outside. In fact, this was the second one I had built, as I had also made one for a 30m/15m end fed antenna. Will there be the same performance for single band EFHWs? Why had I not noticed this before? Note the material 43 hysteresis curves shown below for 25 C and 100 C has a smaller open area (and hence lower losses) at the higher temperature. Real end fed antennas operated harmonically do not present a constant impedance, not even in harmonically related bands. Trapped five band EFHW SOTA antenna | VK3IL Blog PDF MANUAL: ENDFEDZ 40-10-KW EFHW 1KW ICAS ANTENNA - Vibroplex Do your own experiments with your own set up, 2019 - 2022 by Dan Koellen AI6XG. During portable operations, I noticed that I forgot the toggle switch in the tuning position, just to discover that no one calls me back to my relentless CQ-ing. 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! 3) Total losses are approximately independent of core volume. A Brief Synopsis of the Antenna Features & characteristics, EFHW Antenna Geometry versus Center-Fed Dipole. Un-Uns for Endfed-Antennas (EFHW) by DK7ZB. Since it is a EFHW and not a non-resonant end fed, the wire length for 40m is about 67 feet. I particularly want to know how counterpoise affects the common mode currents on the coax. The smallest number I measured was 1.6 pF, derived from the self-resonance at 41 MHz with the leakage inductance (measured at 198 nH) when the secondary was shorted. Lets do a quick calculation to see how much an issue is this output capacitance. <> 100W on a Wire antenna! Research salary, company info, career paths, and top skills for Software Engineer - EDI 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. The commonly used primary compensation capacitor does not work very well for this winding method which keeps the leakage inductance as low as it does. It matches the impedance fairly well to the half-wave antennas high impedance at one of its ends. The last few years have seen a resurgence of interest in the end fed half-wave wire EFHW antenna. It is all about getting the heat out. Being end fed, it needs a transformer to transform the higher impedance of the wire to the 50ish ohms the radio is expecting. After doing some research on the internet I eventually came across something about rattling radiating elements in Diamond vertical ant, Once I had upgraded the matching transformer for my EF-10/20/40 MKII "EndFedz" (see Part 1) my thoughts turned to the loading coil. Which begs the question what happens when you attach the antenna? Thanks for your comments. Other observations along the way: 4) Tight windings or backwinding over the primary can significantly reduce leakage inductance. 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. How to tune a multi-band EFHW antenna using a loading coil There is no BIG secret about the EFHW-8010 antenna, it is just a wideband low loss transformer and a piece of wire. Check your inbox or spam folder to confirm your subscription. Change). The transformer was attached to the 30 meter EFHW antenna and turns were removed for best match to 50 ohms. . Inverted V Antenna A popular Dipole variant, EMI-RFI and Noise related HF Radio Station performance loss. %PDF-1.4 The End-Fed Half Wave Antenna a bit Differently This provides proper insulation from the relatively high voltages on the seconder winding. Proudly created withWix.com. Hence, even operating at 1000W on the 160m band, the cores would not saturate with the 5-turn primary. Ismerje meg a hozzszls adatainak feldolgozst . In case you need to perform calculations, use the formula: Where the frequency f is in MHz and the inductance L is in H. In theory, the examination is supposed to be used to help clarify your medical condition and . Yes, indeed EFHW antennas are very useful for SOTA or other field operation. As you look to use this transformer at higher power levels, I can imagine that the bottleneck might be voltage breakdown or corona in the windings. This totally un-rigorous calculation just gives a quick idea of how much you have to be careful. = .000001 / 3868.88 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. Is it any good? 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. Nevertheless, the EFHW antenna had in the past, been rather sparingly used by amateur radio operators due to various reasons. Now I just need to build or acquire a decent radio to utilize this new antenna. The bridge than will measure zero voltage across the bridge, and the LED will turn off. 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. First, note that the transformer has low transmission loss up to nearly 50MHz. Not the ideal antenna, but convenient! Best regards and thanks again for your comment. Ez az oldal az Akismet szolgltatst hasznlja a spam cskkentsre. I used the 14g enameled wire and wound it on the FT240-43. The technical storage or access that is used exclusively for statistical purposes. Therefore, I picked a momentary push button to switch the operational mode to tuning mode while tuning up. It is worth experimenting with its length also. The above data from K1RF shows that the SWR for 20 meters (my dark red markings - SWR scales differ in each graph) is about the same with or without a capacitor in the transformer primary. Below is the schematic of the final build. Looking at several builds and discussions, such as commercial antennas (e.g. It was difficult to work out where it was coming from but I found that it was more noticeable when it was windy outside. If the antenna is not tuned properly, and it represents other than 50, the diode will rectify the current flowing across the bridge and the LED will light up. 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 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. Lowest frequency = 7.000 MHz. 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. 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. 100W on a Wire Antenna - Is it good enough for DX? One point of my small-core, compact winding design was to be able to cool the core. The finished tran, End Fed Half Wave (EFHW) Antenna Upgrade Part 1 - The Matching Transformer. This graphical depiction makes it easier to visualize the current and impedance correlation between bands. These dimensions were derived from modelling the antenna in EZNEC. Im very happy with the result. The toroid with its many taps may be soldered directly on a multi-position switch. Thanks again Jim. of the wavelength. The End-Fed Half Wave Antenna a bit Differently, The End-Fed Half Wave Antenna a bit Differently Coventry Amateur Radio Society, Ismerje meg a hozzszls adatainak feldolgozst, 40 M R/7E azaz a kirlyi ejternysk rdillomsa, jra megy az SSTV tjtsz 144,500 MHz-en. Pocket-tenna core is finally done! Wire and compensation coil being There are two aspects, however that we need to consider: Lets begin with the transformer. If we wish to limit the ferrite temperature to 130 C, then assuming ambient temperature of 30 C, we can tolerate a 100 C temperature rise. 1. Well, in ham radio, everything works. The technical storage or access is required to create user profiles to send advertising, or to track the user on a website or across several websites for similar marketing purposes. This gave me an effective coil diameter of 40.5mm. In an urban area we are much more restricted, especially if we need to be stealth about it. Without a subpoena, voluntary compliance on the part of your Internet Service Provider, or additional records from a third party, information stored or retrieved for this purpose alone cannot usually be used to identify you. In the case of the EFHW 49:1 transformer, the major shortcomings of the most popular current designs are excessive leakage inductance and poor heat transfer from the ferrite material to the environment. The highest frequency could be14.350MHz. Connected to the packaged transformer, I ran some SWR sweeps with just the bare wire and various configurations of small coils to act as band-tuning compensation. The technical storage or access that is used exclusively for anonymous statistical purposes. If you need to change it, is necessary to recalculate the secondary turns, and the resonance frequency needs to be adjusted also. Generally a loading coil has far more inductance and shortens the length of the antenna significantly. This is typically a weak spot. Im a hundred watt guy, so do not have a lot of experience with high voltage RF, but I know that ~5kV peak-to-peak RF voltage that you would expect at the 2450 output at kilowatt power levels could begin to cause you some trouble. Refurbishing aluminium antenna parts affected by weather / corrosion. To further improve the flux linkage, I wound the primary on top of the secondary. The difference here is that the target bands are low frequency. Commercial Coils, Inc. 213 Chesterfield Industrial Blvd Chesterfield, Missouri 63005. This could be achieved by increasing the spacing of the windings, hence reducing the interwinding capacitance. Ambient temperature is 20, and the core temperature increased by 5 over 120s @ 20W continuous input. Efhw Compensation Coil Experiment - Local Search Denver Post The five primary turns cover about 60% of the secondary winding, leaving the high-side of the secondary not covered. EFHW Compensation Coil Experiment - YouTube Having recently built a MTR2 3-band CW transceiver, I was keen to make band switching on a mountain top as simple as possible. An EFHW antenna has a very high impedance at the end point and you need a matching transformer to feed power to it. From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. Multiband End-fed Half-wave EFHW Antenna - VU2NSB.com Therefore, installation is quite easy, and its tuner circuit is rather simple as well. Another design by KB0ZZ is a little longer, but resonates on both 40m and 80m. With very little counterpoise, the antenna is being fed at a high impedance point so a rather large impedance step-up is employed. High self-resonant frequency. Simulating the end-fed half-wave (EFHW) dipole antenna It does not need any special components; in fact, most of us may have them in our shack drawers already. A krdsem az, hogy a knyv elrhet esetleg pdf-ben is?