efhw compensation coil

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. Change), You are commenting using your Facebook account. As is often the case, packaging was determined by what boxes I had laying around. I dont have an amplifier, so only need to be able to handle 100W. This is based on random lengths of the antenna, which is transformed with the un-un into a medium-ohmic impedance range with reactive components. Multiband End-fed Half-wave EFHW Antenna - VU2NSB.com End Fed Half Wave Antenna Coupler (EFHW) - M0UKD The EFHW's SWR will be affected by height above ground, type of ground, feed line interaction, and any nearby conductive surfaces. I checked the inductance again to make sure this hadnt been overly affected, and it remained unchanged at 109.8H, good enough! End Fed Half Wave (EFHW) Antenna Upgrade Part 1 - The Matching Transformer. 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. The Truth, ,and Nothing But The Truth (as I've experienced it) I checked the wall brackets and mast, but all the fixings were nice and tight. Does your station desperately need a good RF ground to behave properly? I needed to add an additional coil (approx 12.5 uH) about . 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? Start by wrapping the wire around the toroid. A lot of radio amateurs have made similar antennas to this with larger transformers for higher power handling. The 6-turn loading coil lowers the resonant frequency into the CW portion of the 80 meter and higher bands. 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. used with a load such that the input impedance Zin is approximately 50+j0, Gin=0.02S; Duffy, O. The original coil is designed for low power portable applications. One point of my small-core, compact winding design was to be able to cool the core. Apply for the Job in Software Engineer - EDI at St. Louis, MO. Nevertheless, I will also describe, how it is designed, if one decides to embark on building it for different bands. The SWR was measured for each of the three antennas across the CW portion of the bands. Other observations along the way: 4) Tight windings or backwinding over the primary can significantly reduce leakage inductance. 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. http://www.hamuniverse.com/randomwireantennalengths.html, https://km1ndy.com/diy-491-unun-impedence-transformer-for-end-fed-half-wave-efhw-antenna/. Let's find out! . However, let me write about it from a slightly different perspective that was not very obvious from the articles I read. 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 usual problems of having the multiple band resonances all line up appear here with the end-fed design, similar to the same issue with off-center-fed designs. This happens to place the coil near the peak of a current maximum for the 20m band, which coincidentally appears to have significantly improved the match on that band. Lowest frequency = 7.000 MHz. The wire as I strung it up seemed to resist having a good SWR for the 20m band. However, it has its idiosyncrasies. Accordingly, calculate the capacity for the resonance at the highest frequency to be covered with the highest inductivity taken in consideration. Ez az oldal az Akismet szolgltatst hasznlja a spam cskkentsre. It is basically an end fed half wave dipole on 20m/40m and an end fed full wave dipole on 10m. More designs can be found by Googling "80m loaded dipole.". From this article one may build a 40, 30, 20m end fed half wave antenna, with no special parts needed, or no special skills required. Some of my research showed that a small compensation coil can be added about 2 meters from the transformer to pull down the SWR on the higher bands. How to tune a multi-band EFHW antenna using a loading coil Generally a loading coil has far more inductance and shortens the length of the antenna significantly. This is indeed a classic antenna that is not only, Introduction to Omnidirectional Antennas In the literal sense, an Omnidirectional antenna is an antenna that radiates uniformly in all directions. When the transformer was mounted in its box and the output connected to an antenna connector feedthrough, the observed capacitance increased dramatically to about 6.0 pF. Above is a sweep of the roughly compensated transformer. Thank you for your comment and feedback on the article about the EFHW antenna. This is perhaps one of the most hotly debated rookie topics in. 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. For Jackson County, please call Western Egyptian Economic Opportunity Council, in Steeleville, at (618) 965-9031. The EFHW transformer box from outside. In theory, the examination is supposed to be used to help clarify your medical condition and . Once that's done, the instructions say "adjust the coil as necessary" to bring the other bands into resonance. Energy Assistance (LIHEAP) | Crosswalk Community Action Agency 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. Ismerje meg a hozzszls adatainak feldolgozst . A ktelez mezket * karakterrel jelltk. Can I get away with no capacitor in my design? 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. PART - 2 : Most EFHW antenna configurations resort to the use of broadband impedance transformers at the feed-point to attain acceptable SWR on all operational bands. Thirty turns #28 are wound on the two FT114-43 cores. Yes, indeed EFHW antennas are very useful for SOTA or other field operation. In the open-box image above you can see the thermal probe I used to measure the ferrite core temperature for a thermal characterizations. Why had I not noticed this before? The blue trace above shows the results of adding a 6-turn 2 coil about 6.5 ft. from the box. Is FT8 popularity growing at the cost of SSB Phone and CW? VK1OD.net (offline). With the coil and its wire attached I fired up my AA-35 Zoom analyzer from RigExpert and had a look. The capacitor makes very little difference to the low frequency behavior, but it reduces the input VSWR significantly at the high end. This is why we need the impedance transformer from the 50 coaxial feed-line to the several kilo-ohm antenna connections. Im very happy with the result. PDF shortened multi-band End-Fed Half Wave (EFHW) antenna for 80-10m Hello, a wonderful approach for the problems.. Trapped five band EFHW SOTA antenna | VK3IL Blog This can then, fed with coaxial cable, in many cases be . The impedance per unit length of a lumped transmission line is where L and C are values per unit length. A 100pF silvered mica was connected in shunt with the transformer primary. For a quarter wave that is about 8 nS. The impedance matching circuit is essentially a simple parallel resonant LC circuit. Being end fed, it needs a transformer to transform the higher impedance of the wire to the 50ish ohms the radio is expecting. Interpretation of S-Meter Noise Floor in HF Radio Receivers. Replacing your AC evaporator or condenser coil might, on average, cost around $1,200, with the typical cost range between $800 and $2,400 depending on the brand, your region and other factors . The conjugate impedance matching arrangement of this nature is far from perfect resulting in considerable reactive currents on some of the bands. Check your inbox or spam folder to confirm your subscription. 100W on a Wire antenna! High self-resonant frequency. Proudly created withWix.com. The bottomline, your putting the relationships of 1) Toroid windings and to measure their inductance together with 2) the required capacitance calculation is exactly what I needed to move forward with my specific design plans. Looking at several builds and discussions, such as commercial antennas (e.g. Csatlakozz csapatunkhoz! Un-Uns for Endfed-Antennas (EFHW) by DK7ZB - qsl.net I built one that you see in the article, another one that is much smaller and lighter for SOTA outings. 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. 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. I made one quite similar to it but 3T Primary with #16 speaker wire (2 parallel wires) and 15T Secondary close wound just using about one-third of the circumference of the 2 inch toroid. (The antenna wire could also be tuned for the lower end of 80 meters without the coil but the . On the ends of each winding I slip the end under the last turn and pull tight to lock the winding in place. This could be achieved by increasing the spacing of the windings, hence reducing the interwinding capacitance. For the antenna wire itself, I used 119 feet of 22g stranded hookup wire. 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. In comparison to the EFHW antenna, a simple dipole offers a far better prospect. 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. 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. The toroid with its many taps may be soldered directly on a multi-position switch. 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. Commercial Coils, Inc. 213 Chesterfield Industrial Blvd Chesterfield, Missouri 63005. 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With a very short counterpoise it is difficult to resonate the fundamental with any drive impedance. You can see the coil in the picture below (red arrow). (Tvir s tvbeszl gpek s kszlkek) Ksznm. The 40-10m EFHW camping antenna is late but done. More info in - reddit The technical storage or access that is used exclusively for statistical purposes. It uses a coil as a compensation unit, and no counterpoise. 5 Band EFHW Antenna 80m-10m | 49:1 End Fed Half Wave - YouTube Tackling both of these issues at once led to a much smaller, lighter, and less costly transformer with better loss characteristics than previous designs. : I see you were able to post your comment now, so I just copied my email answer here for others to see. How-To: Make a Multiband EFHWA for Amateur Ham Radio The results are shown below. Is it any good? These inductances are required in determining the right capacitance values, of which two values are important: the minimal and the maximum capacitance values. Another completed tuner, which is more compact then the pervious one shown, also it is lighter, more suitable for portable operations. 100W on a Wire Antenna How far would it reach? End Fed Half Wave (EFHW) Antenna Upgrade Part 2 - The Loading Coil They will be adjusted for resonance at or close to the CW portion of the bands. 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. 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. The coil came out at 89mm in length rather than the theoretical 83mm not surprisingly, but the inductance was bang on at just over 109H. To further improve the flux linkage, I wound the primary on top of the secondary. If not a lightning strike, I will write an article about the experience as well. 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. Hence, there is no optimum single-fit solution. This illustration provides a graphical view of approximate comparative difference in expected Common-Mode-Current (CMC) that could flow on the transmission line to undermine the overall performance of the antenna system. If you really want to get the heat out, add some fins to the aluminum box. is the initial disequilibrium temperature, is the equilibration time constant, and is the heat capacity. Can a diode be used to rectify signals smaller than its threshold voltage? I can give a link if you need. 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. Therefore, I picked a momentary push button to switch the operational mode to tuning mode while tuning up. You can achieve this inductance with half a dozen turns of the antenna wire tied in a small coil. 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. However, the insertion loss of the packaged transformer would be intolerable on the 10 meter band if it appeared the same way with an antenna wire connected. But before we do, let us look at the insertion and transmission loss that the VNA is reporting. (The antenna wire could also be tuned for the lower end of 80 meters without the coil but the . Change). The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user. Z8Vq9_@x C\Agv#. It tests out well on the antenna analyzer for 3.5 to 29.7 MHz. Being conservative, assume we are just 90% efficient, then the average power level we could support would be about 140W. Although the original loading coil is very well engineered, I thought I could make a more efficient version given that I did not need to make it 'trail friendly'. The SWR results are as follows: Assuming, most of us use the 40/30/20m band for HF SOTA activation, so the following table shows the SOTA frequencies, and the calculated half wave radiator wire of the antenna. The previous table already contains these measurements. 5) It is very hard to avoid stray capacitance on the output. 101: The Independent Medical Evaluation - "IME" By: Cynthia M. Hennessey Attorney. I wish you lots of productive experimentations and successful portable operations. 2. Pocket-tenna core is finally done! Wire and compensation coil being I tossed the line as far up as I could in a tree. It is better to build one for 160 and 80m, perhaps add 17m to the design described in this article, and for higher bands it is easier to use a linked dipole. A Smith chart view of EFHW transformer compensation 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. I look at the end-fed as just an extreme example of an off-center-fed antenna. One way or another there is always a counterpoise involved if the antenna is tuned correctly. From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. Note that the resonances do not necessarily line up harmonically, there is commonly some enharmonic effect. This gave the RF some place else to go, trapped by the coil and capacitively shunted to ground, rather than on to the transceiver. If you really wanted to push this design, you could include thermal grease or thermal pads in the stack-up to improve the heat transfer, but I chose to keep it clean and see how it would do without any special effort. Do your own experiments with your own set up, 2019 - 2022 by Dan Koellen AI6XG. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Enter your email address to subscribe to this blog and receive notifications of new posts by email. I was curious why this capacitor was added to the transformer. Your posting put it all together for meTHANK YOU!!!! EFHW 80m extension - MI0KXX I use shock cord to connect the insulator at the end of the wire to my fence. The five primary turns cover about 60% of the secondary winding, leaving the high-side of the secondary not covered. Although the original loading coil is very well engineered, I thought I could make a more efficient version given that I did not need to make it 'trail friendly'. This provides proper insulation from the relatively high voltages on the seconder winding. Transmitting on 15 meters was impossible because of RF into the radio.

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