efhw compensation coil

He was afraid that being, Inverted V Antenna - A popular Dipole variant, The Center-fed Half-Wave Dipole Inverted V Antenna An Inverted V antenna is a very popular variant of the standard horizontal dipole. 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. I checked the wall brackets and mast, but all the fixings were nice and tight. The Counterpoise is a short, typically one twentieth (0.05 * ) of the wavelength. It may be one or even five kilo-ohms. Jim, do you mind if I add your email and my answer as a comment to the article? There's seemingly conflicting information out there, such as on QRZ the consensus seems to be to either use no choke on the coax, or choke it some ways away from the feedpoint - WA7ARK recommends .07 wavelength, which is about 9' on 40M. The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user. End Fed Half Wave Antenna Coupler Schematic - 7-30MHz. 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. The EFHW's SWR will be affected by height above ground, type of ground, feed line interaction, and any nearby conductive surfaces. The tests here were using a dummy load on the transformer, and that did allow confirmation of the design and expected loss at 3.6MHz. 'Capacitor flattens SWR at higher frequencies' - WA7ARK. The Counterpoise is a short, typically one twentieth (0.05 *. ) 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. High Q, hence low loss. Radio Transceiver S-Meter Pitfalls to avoid, Atmospheric impact on VHF Radio Propagation, Terrestrial VHF Radio Signal Coverage LOS, Terrestrial VHF Radio Signal Coverage BLOS, HF Surface Wave Propagation (Ground Wave). End Fed Half Wave Antennas: Is a Primary Capacitor Really Needed? Basu Bhattacharya (VU2NSB). Then I covered the coil in kapton tape to hold it together. The cooling rate is more difficult to calculate because it involves how heat moves through the structure, but it is easy to measure. Thank you Gary. . The SWR for the 20 meter EFHW antenna was < 1.2:1 This reveals we only need to compensate for the reactive component. Steps to improve the heat transfer over the present design could make this small transformer work at even higher power levels. 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. This will allow good matching of the half-wave radiating antenna wire to the 50 coaxial cable at virtually any location. At 5W input the connector at the end of the antenna wire may be up to 160V, and at 15W it may be 270V. 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. Looking at several builds and discussions, such as commercial antennas (e.g. 5 Band EFHW Antenna 80m-10m | 49:1 End Fed Half Wave Ham Radio DX 27.1K subscribers 19K views 7 months ago #HamRadio #AmateurRadio #EFHW Here are my experiments and modifications with an EFHW. Next, I started winding the transformer. Let's find out! The EFHW's SWR will be affected by height above ground, type of ground, feed line interaction, and any nearby conductive surfaces. I installed an eyebolt on one end as a pull-point, and a BNC connector on the other. Tuning the antenna to its resonance will result in 50 seen at the output of the SWR circuit. However, a key restriction is its 25W power rating, due to the small matching transformer. The finished tran, End Fed Half Wave (EFHW) Antenna Upgrade Part 1 - The Matching Transformer. Some say you do not need a counterpoise, but that is false. 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. Basically, the loading coil is operating as a trap. . 100W on a Wire Antenna - Is it good enough for DX? Hence, there is no optimum single-fit solution. stream The high frequency performance was extraordinarily sensitive to anything that could add capacitance to the output lead. Why had I not noticed this before? What are the advantages and disadvantages of the end-fed half wave antenna? is the initial disequilibrium temperature, is the equilibration time constant, and is the heat capacity. The original coil is designed for low power portable applications. 2015. Taking the time derivative of the above equation you get the power dissipation. Why does antenna radiation occur? I added some Christmas colored zip ties to hold everything in place. I then used a piece of heat shrink on the outside to hold everything in place. However, to minimize capacitance, you want to spread turns and keep windings apart, so what is the right approach? The last few years have seen a resurgence of interest in the end fed half-wave wire EFHW antenna. It is not necessary to calculate the above; the results are sown in the following table. Since it is a EFHW and not a non-resonant end fed, the wire length for 40m is about 67 feet. However, it has its idiosyncrasies. In the problematic upper bands, the resonant wire significantly improved the in-band SWR compared to the resistively terminate box (purple). We would like to try to fly a kite with a halfway antenna wire and see what miracle we achieve. Regards VE9HAM. Trapped 20/30/40 Meter EFHW Antenna - AI6XG Geeksite The overall lenght is only 15m. End-Fed antennas are useful in many ways, includes easier mounting of cable at one end (freeing the antenna from unnecessary weight of cable) & antenna maintenance in future. MyAntennas), G0KYA, K1RF, K1TA, K6ARK, N4LQ, W8JI AND WA7ARK; they all have a primary capacitor of 100 pfd to 220 pfd. The negative effects of local QRM on an, How does antenna radiation occur? Im very pleased with that indeed. The 40-10m EFHW camping antenna is late but done. More info in - reddit Software Engineer - EDI - salary.com The highest frequency could be14.350MHz. Is it any good? We do not know what the actual impedance will be at the end of the antenna radiator. Im very happy with the result. Below about 7 MHz, transmission losses increase as the core temperature increases. 5) It is very hard to avoid stray capacitance on the output. I also built one that is heavy-duty handling easily up to 100W for 80/60/40m bands. This will allow good matching of the half-wave radiating antenna wire to the 50 coaxial cable at virtually any location. The highest voltages as well as radiation are also at the end of the antenna wire. Most of the time 5 to 20W will be adequate for activation anyway. (The antenna wire could also be tuned for the lower end of 80 meters without the coil but the . 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. Thanks! Thanks for your comments. Newtons Law of Cooling tells us that heat flow is proportional to the temperature difference. = .00 00 00 00 0 258 Start by wrapping the wire around the toroid. 0 7t8An. }pKumm" t7Vb55nx S;/E}*+RS'|(q&wA;n";&.'KDff9H0^SF7 O0~{h9*QX\Mwk> u)Y h&kvDc%=(]F_$?6!:\EsM4"+>R%;93|"Jn\j+1 z}?>xBaR3 c +U+WLX`\Ld.Q2.VDHh']o.)k;a6*~s" I placed the box in a cool oven and let it get up to about 200 F, soak for a while, and then I took it out, hung it in still air and measured the temperature as time passed and the box cooled. Z8Vq9_@x C\Agv#. Well, in ham radio, everything works. The transformer fits sideways in the box with a few millimeters to spare. I was a little long on 80m not surprisingly, so folded back about 40cm of wire leaving about 2.1m beyond the coil. Change), You are commenting using your Facebook account. Check your inbox or spam folder to confirm your subscription. Nevertheless, the EFHW antenna had in the Read More, SSN, SFI, Solar Data for HF Radio Propagation Here are some of the important Solar activity parametric data that are responsible for influencing the behavior of the Ionosphere on earth. The computation method is also touched on. 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. End Fed Half Wave Antenna Coupler (EFHW) - M0UKD Loss (to mean PowerIn/PowerOut) can be calculated in dB as -|S21|-LoadAttenuator-MismatchLoss=18.64-18.16-0.03=0.450dB, or an efficiency of 10^(-0.45/10)=90.2%. In comparison to the EFHW antenna, a simple dipole offers a far better prospect. I swept the antenna with a nano vna from 2 to 30MHz and there were nice dips at each band. The Truth, ,and Nothing But The Truth (as I've experienced it) How badly can high Local Ambient QRM affect HF Radio? The cooling curve I measured is shown below. (LogOut/ This transformer has more surface area than a FT82-43 based one, so it has higher capacity to dissipate heat, and it is more efficient, so it will have higher power capacity than the FT82-43 based one. IIRC they call it a "compensator". The final turns ratio turned out to be 3:29. It was difficult to work out where it was coming from but I found that it was more noticeable when it was windy outside. 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. So far so good. The following is the most up-to-date information related to EFHW Compensation Coil Experiment. For . 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. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. Research salary, company info, career paths, and top skills for Software Engineer - EDI Can you give me an idea for your 100 W version, you built for 80/60/40 m. One way or another there is always a counterpoise involved if the antenna is tuned correctly. An end fed half wave antenna, or efhw, is a variation of a half wave dipole, but it is fed from one end. The SWR results are as follows: Even at 15W the voltage at the ends may reach 100-200V. |k"^N>F.AnJkJsq'PV}o0I. 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. This can then, fed with coaxial cable, in many cases be . 73! By using traps, the antenna works on all three bands with no operator interaction. Your article was well written and very informative, thanks. Change). So, I embarked on testing it for myself. I also will ask, why didnt it work for you. At FT82-43 matching transformer for an EFHW I wrote about the likely losses at 3.6MHz of a common design using a FT82-43 ferrite core with a 3t primary. I've always had issues with 10m loading up properly so I'll also be adding a compensation coil 78 inches from the feed point on the wire. With most operations you only transmit for 50% of the time, and since a small transformer with four or more primary turns can achieve >90% efficiency, that implies that I really only need to dissipate ~5W. Independent Medical Evaluation - IME | Cynthia Hennessey Hence, we need to move along and start to include the antenna with our testing. But I would caution its usage for higher power than 10-15W. Ive been thinking about getting an antenna up for 80m, and Ive come across a number of options that interest me and would suit the space I have available realistically no matter what I go for it will be a very compromised antenna, but still much better than none. After cleaning it up and testing it, I installed it on the side of my house on top of a straight pole. http://www.hamuniverse.com/randomwireantennalengths.html, https://km1ndy.com/diy-491-unun-impedence-transformer-for-end-fed-half-wave-efhw-antenna/. A lot of radio amateurs have made similar antennas to this with larger transformers for higher power handling. Essentially, the matching is done with a tank circuit, which represents the highest impedance when it is tuned to resonance. Impressive article and so well done that I may give it a try. Tap and primary high-side are soldered together near the middle of the secondary winding; the ground side of the autotransformer is located over the low-end of the secondary turns. It is clear that the capacitance from just mounting the transformer in its box generates a significant reflection at 30MHz for the 10 meter band. I did struggle with the C in pF calculation..I seem to be getting hung up on the correct decimal placement..for example, for the 40-meter Capacitor requirement, I get .000000000258: C pF = .000001 / [ ( 2 * 3.14 * 7 MHz) ^2 ] * 2 uH Klubunknl folyamatos a tagfelvtel. So, how to construct an end-fed half wave antenna? Engineering the EFHW 49:1 Transformer and Antenna Based on a 2014 survey, the most popular antennas for SOTA (Summit On The Air) activation are the following (see sotabeams.co.uk/blog/5-most-popular-hf-portable-antennas for details): Let us not confuse the End-Fed Half Wave antenna with the Random Length End Fed wire. I've been using a 1:8 ratio transformer successfully in other EFHW antennas, so I planned the same for this one. Two layers of 1mil Kapton tape are placed over the winding. 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. Above is a thermograph of the transformer at 20W input at 3.6MHz. Why had I not noticed this before? That will be the missing resistor in the resistor bridge of the below circuit. We will return to that shortly, but first let us look at the VSWR associated with such added capacitance when driving the 2450 load resistor. Inverted V Antenna A popular Dipole variant, EMI-RFI and Noise related HF Radio Station performance loss. The change in heat content in the box as it cools can be written: where and are the ambient temperature and heat content respectively. 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. 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. The EFHW's SWR will be affected by height above ground, type of ground, feed line interaction, and any nearby conductive surfaces. 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. Thermal gasketing between the cores and the aluminum heat sinks could help a lot, as would a single piece of aluminum rather than the stack up of thin sections I used. 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 is not an optimal value, benefit may be obtained by exploring small changes to that value. Krem, rja le, mi a krdse. 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. To calculate the impedance ratio, use the following equation: A completed tuner is shown here, which depicts the inductance assembly. When you are discussing a distributed capacitance, it is difficult to know exactly what you are measuring. This provides proper insulation from the relatively high voltages on the seconder winding. The worse SWR was 1:1.7 at the top end of 20 meters. The next important parameter is the parallel resonant circuits resonant frequency. Do I count the six loops around the pvc in the measurement? 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. A krdsem az, hogy a knyv elrhet esetleg pdf-ben is? From that we can find Mismatch Loss. 73 Most informative and appreciated. The impedance per unit length of a lumped transmission line is where L and C are values per unit length. The latest news about Efhw Compensation Coil Experiment. 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 conjugate impedance matching arrangement of this nature is far from perfect resulting in considerable reactive currents on some of the bands. High self-resonant frequency. Trapped five band EFHW SOTA antenna. Each geodesic great circle path displayed on the map originates from your location that is derived Read More, The Great Circle Map GCM We present an automatically rendered Great Circle Map GCM based on your location derived from your Internet IP address. I wish you lots of productive experimentations and successful portable operations. It is recommended to use at least 2W non-inductive resistors for this purpose. Nagyon j ez a cikk. nanoVNA-H can firmware be updated if it has a broken USB socket? The EFHW transformer box from outside. From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. How big and where to place it is likely best determined empirically. On the ends of each winding I slip the end under the last turn and pull tight to lock the winding in place. There could be any number of reasons for that, where I put the bends in the wire, the location of tree branches, etc. 5 Band EFHW Antenna 80m-10m | 49:1 End Fed Half Wave - YouTube Current Balun 1. However, let me write about it from a slightly different perspective that was not very obvious from the articles I read. 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. = 258 * 10^-12. 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. It is important to consider the voltages on this tank circuit. Let me review the salient observations from the previous work. Another completed tuner, which is more compact then the pervious one shown, also it is lighter, more suitable for portable operations. The difference here is that the target bands are low frequency. . There are many good descriptions on the net about this type of antenna. 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. Toll Free 800-532-2645 636-532-1523 Fax: 636-532-8259. 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. Elnzst krnk, de elsikkadt az zenete. On one end, I added a ring terminal to connect it to the transformer and on the other end, I connected an electric fence insulator. I have an EFHW and the SWR is acceptable on all the bands with the exception of the WARC bands which is to be expected since the harmonic relationship is different. I use shock cord to connect the insulator at the end of the wire to my fence. Thank you for your comment and feedback on the article about the EFHW antenna. 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. The slim coil is torpedo shaped to prevent it being snagged in trees when deployed in 'the great outdoors'. It is hard to wait an infinitely long time for the box to equilibrate to a given power level. (30 votes, Rating: 5.00) - Please vote the article with your valuable star rating. Copyright 2014-2023. How-To: Make a Multiband EFHWA for Amateur Ham Radio Another design by KB0ZZ is a little longer, but resonates on both 40m and 80m. end fed half wave antenna - awsh.org The effect of the capacitor is very apparent for 17 meters and above, flattening and lowering the SWR curve through 10 meters. From experience, I found that with this tuner my SWR was better by simply disconnecting the counterpoise at lower bands. 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. Consequently, this is how the capacitance values are determined. 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. Functioning as an, HF Wire Antennas - A Primer When we speak about wire antennas, the first and foremost thought that comes to mind is the 1/2 Dipole antenna. Payment: If you are eligible, Crosswalk CAA will make the appropriate payment to your energy provider (s) on your behalf. They will be adjusted for resonance at or close to the CW portion of the bands. The model results show the need for a not entirely insignificant counterpoise. Saturation of a warm core happens near 0.2 T (2000 g) and if you dont want to deal with significantly reduced permeability, then better to limit to 0.1T. I am building an EFHW antenna for my new. With no counterpoise wire it will be the coaxs shield providing it. Instead, this shifts everything down and makes it very easy to tune 10m. The low end of the secondary, which will be the tap, is bent back over to the center of the winding and covered with a small piece of Kapton tape, and then the primary is wound over the tape (and the secondary tap wire). 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. Wideband RF components ultimately succumb to the non-ideal behavior of materials and assembly methods. Since the tuners location is best if it is handy for the operator, one end of the end-fed antenna is also close to the operator. My limited experience with these antennas also suggest that one must be cognizant of the RF current pushed onto the feed-line coax. On the transformer, I added a few wingnuts to tighten down the antenna wire. End Fed Half Wave (EFHW) Antenna Upgrade Part 1 - The Matching Transformer 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. The results are shown below. PDF MANUAL: ENDFEDZ ALLBAND-KW 80-10 EFHW 1KW ICAS ANTENNA - Vibroplex It is all about getting the heat out. P.S. A Brief Synopsis of the Antenna Features & characteristics, EFHW Antenna Geometry versus Center-Fed Dipole. The disadvantage of this switch is that one needs one hand to hold it, another to key down, and yet another to tune the capacitor. Scaling the small core to higher power levels would mean that the flux level in the ferrite core would increase. I found it very useful to label the tuner with switch and capacitance positions. Best regards and thanks again for your comment. It not a loading coil. 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. A method for estimating the impedance of a ferrite cored toroidal inductor at RF. 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. Typically the IC-751A would read about 60W on its power bridge, the Siliconix would show >50W on the 50W scale and 45W on the 500W scale, so there is ~20% uncertainty. As I reexamined my formula, you pointed it out correctly, there is an error in it. Low SSN Why do most Hams find HF Radio so difficult? : I see you were able to post your comment now, so I just copied my email answer here for others to see. The capacitor makes very little difference to the low frequency behavior, but it reduces the input VSWR significantly at the high end. I recommend a good reading on this subject by Steve Yates, AA5TB at: www.aa5tb.com/efha.html.

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