efhw compensation coil

At 5W input the connector at the end of the antenna wire may be up to 160V, and at 15W it may be 270V. Once that's done, the instructions say "adjust the coil as necessary" to bring the other bands into resonance. In comparison to the EFHW antenna, a simple dipole offers a far better prospect. A/l for the chosen core is 3.5 times that of a FT82-43 yet it is only 1.6 times the mass. I went with a 49:1 unun to match the unbalanced antenna to the unbalanced feed line. I got the, http://pa-11019.blogspot.com/2012/04/149-transformer-for-endfed-antennas-35.html, End Fed Half Wave (EFHW) Antenna Upgrade Part 2 - The Loading Coil. PART - 1 : The EFHW antenna as a radiating and receiving element is a decent multi-band antenna with good efficiency on all bands, provided it is driven at its feed-point using a well configured and well-matched driving source. The blue trace above shows the results of adding a 6-turn 2 coil about 6.5 ft. from the box. Thanks for your comments. The slim coil is torpedo shaped to prevent it being snagged in trees when deployed in 'the great outdoors'. Hence, even operating at 1000W on the 160m band, the cores would not saturate with the 5-turn primary. Essentially, the matching is done with a tank circuit, which represents the highest impedance when it is tuned to resonance. It performed well on both the 2m and 70cm bands. I checked the wall brackets and mast, but all the fixings were nice and tight. 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 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. 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. (LogOut/ 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. Cmzett: Weince joseph How can we help? It depends on the selection of the inductance and the capacitor values. The negative effects of local QRM on an, How does antenna radiation occur? 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.) I was a little long on 80m not surprisingly, so folded back about 40cm of wire leaving about 2.1m beyond the coil. The photos above show a method that works fairly well. 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. There could be any number of reasons for that, where I put the bends in the wire, the location of tree branches, etc. It should be no surprise that 80pF is close to optimal. 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. 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. These, in turn, are instrumental Read More, Learn CW Morse Code Lesson Set 2 This is Lesson Set -2 in our multi-part series of CW Morse Code hands-on tutorials where we will introduce numerals and a few important punctuation marks as Read More. (The antenna wire could also be tuned for the lower end of 80 meters without the coil but the . Toll Free 800-532-2645 636-532-1523 Fax: 636-532-8259. The orientation of these lobes varies with the frequency band of operation thus resulting in directional inconsistencies between bands. The antenna is effective and the materials and construction are of a very high quality. I have been searching the internet for a very long time (AA5TB, VK3YE, SOTA Reflector, among MANY others), and your posting finally made clear for me the many questions I have had. This will yield the minimal capacitance of the variable capacitor. Ha elolvasod alapszablyunkat s a benne lertakat elfogadod, akkor nincs ms teendd, mint a ha5kdr@ha5kdr.hu email-cmen, vagy egy klubnapon jelentkezni nlunk! 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. The SWR for 30 meters, 1.05:1, was the lowest of all three antennas since the transformer was tuned for impedance match at 30 meters. I tossed the line as far up as I could in a tree. For . Could it be something to do with the new vertical aerial I had recently installed? coil inductance calculator at 66pacific.com. In fact, this was the second one I had built, as I had also made one for a 30m/15m end fed antenna. No capacitor was installed. I checked the wall brackets and mast, but all the fixings were nice and tight. . Thanks! RC = 2500 x 1.0e-12 = 2.5 nS Now consider the period of a 30 MHz wave. The SWR for the 20 meter EFHW antenna was < 1.2:1 Disclaimer | Privacy Policy | Cookie Policy | Terms of Use. Wow, Gary! 2) Winding capacitance and leakage inductance, especially present as you increase the number of turns, limit the high frequency performance. Research salary, company info, career paths, and top skills for Software Engineer - EDI Next, I started winding the transformer. I first mounted the SO239 connector to the box. This graphical depiction makes it easier to visualize the current and impedance correlation between bands. 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. Consequently, this is how the capacitance values are determined. All Rights Reserved. The highest voltages as well as radiation are also at the end of the antenna wire. 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. From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. Thank you Gary. 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. 3) Total losses are approximately independent of core volume. One possible explanation is that the core losses drop with temperature. The above factors often also lead to unacceptably high CMC on the coaxial cable transmission line thus rendering a rather poor antenna system. The parasitic reactances near the feed-point also vary between installations. Note: Crosswalk CAA administers the LIHEAP in Franklin, Jefferson, and Williamson Counties. This provides proper insulation from the relatively high voltages on the seconder winding. I place a 2 inch coil of the antenna wire with 3 turns (green) or 6 turns (brown) close to the box. One cable is the coax feedline, the second is the supply to the cooling fan and control of relays. Because of the division of power between the 3220 resistor and VNA input, there is effectively an attenuator of -10*log(50/(50+3220))=18.16dB, so |S21| has a component due to this division. I found that sometimes the multimeter that was measuring the temperature would give unreliable information when RF was present, so the off periods provided regular intervals for measuring the temperature. Zin=46.52+j6.72. 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. But before we do, let us look at the insertion and transmission loss that the VNA is reporting. We would like to try to fly a kite with a halfway antenna wire and see what miracle we achieve. My goal was to describe the parameters of an antenna that can be easily build, yet show enough theory for someone to design his or her own antenna and antenna tuner. Select components with good insolating materials and properly chosen, relatively high voltage rated parts. Your article was well written and very informative, thanks. blue: 250pF, to much compensation. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. Tackling both of these issues at once led to a much smaller, lighter, and less costly transformer with better loss characteristics than previous designs. 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. Measurements were made on the unmounted transformer with just a ~2 inch length of lead from the secondary to the 2450 load and sampling resistor (jig connections as shown in the photo above). From our measurements of the box cooling curve, this would correspond to the box dissipating about 14W in still air. VSWR<1.8 over all of HF. It does not need any special components; in fact, most of us may have them in our shack drawers already. With the cooling curve and a good estimate for the heat capacity of the box, now it is just a matter of running some power through the transformer and measuring the the temperature rise from ambient to be able to determine the power that turns to heat in the transformer. I have been offered input VSWR curves for such a configuration, and they are impressive but VSWR curves do not address the question of loss / efficiency. Another design by KB0ZZ is a little longer, but resonates on both 40m and 80m. My question is what is 'higher frequency' specifically? One of the many confusing terms used in Workers' Compensation, "IME" stands for Independent Medical Evaluation or Independent Medical Examination. 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. In my research on End Fed Half Wave (EFHW) antennas I found that nearly all have a capacitor in the primary (rig) side of the transformer. = .000001 / 3868.88 Firstly, bandwidth on 80m is restricted to about 80 kHz at . The technical storage or access that is used exclusively for statistical purposes. Ive been wanting to put together a decent multi-band antenna for a long time and finally settled on an end fed half wave antenna. This antenna is working for 80,40,20,10 and 6m bands. MyAntennas), G0KYA, K1RF, K1TA, K6ARK, N4LQ, W8JI AND WA7ARK; they all have a primary capacitor of 100 pfd to 220 pfd.