For calculating the length of a half wave in metres, I use 141 (MHz) for wire elements. After cleaning it up and testing it, I installed it on the side of my house on top of a straight pole. The model results show the need for a not entirely insignificant counterpoise. 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. Copyright 2014-2023. This antenna is only 15m long using 2 loading coils. For Jackson County, please call Western Egyptian Economic Opportunity Council, in Steeleville, at (618) 965-9031. The resistance (real) component of the impedance is right where we want it near 50 ohms. Your article was well written and very informative, thanks. Isn't it? Hi Ajai, Performance of 49:1 Ferrite CoreTransformers, 24 Hour Animated PSK Reporter ReceptionReports. In theory, the examination is supposed to be used to help clarify your medical condition and . It should be no surprise that 80pF is close to optimal. One point of my small-core, compact winding design was to be able to cool the core. Above is a sweep of the roughly compensated transformer. I found it very useful to label the tuner with switch and capacitance positions. These inductances are required in determining the right capacitance values, of which two values are important: the minimal and the maximum capacitance values. Some say you do not need a counterpoise, but that is false. I used the coil inductance calculator at 66pacific.com and after a few tries came up with 83 turns over a length of about 83mm as shown below. The combination of the transformer with the end-fed dipole results in a positive reactance. 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. The previous table already contains these measurements. The point is to get the characteristic time constant for the cooling, which is the reciprocal of the exponent coefficient that Excel shows for the fitting equation. Now I just need to build or acquire a decent radio to utilize this new antenna. The transformer is wound as an autotransformer, 3+21 turns, ie 1:8 turns ratio. 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. 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. What are the advantages and disadvantages of the end-fed half wave antenna? For my build, I started with a waterproof enclosure from the hardware store, a panel mount SO239 connector, an FT240-43 toroid, two 220pf 15KV capacitors, and 14g enameled copper wire, and some hardware to connect it all up. To mitigate the voltage issue mentioned above, I used a couple layers of Kapton tape over the secondary winding. = 258 * 10^-12. For . This is perhaps one of the most hotly debated rookie topics in. Essentially, the matching is done with a tank circuit, which represents the highest impedance when it is tuned to resonance. I ran WSPR at 10mW for about 2 hours and got the results below. 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. 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. The bridge than will measure zero voltage across the bridge, and the LED will turn off. Inverted V Antenna A popular Dipole variant, EMI-RFI and Noise related HF Radio Station performance loss. Krem, rja le, mi a krdse. The real power limit will be core heating. 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. 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. Transmitting on 15 meters was impossible because of RF into the radio. You can start with the links below. No capacitor was installed. I am already seeing interesting things with it, but not enough measurements to make any conclusions yet. xZ Wxi@@=\A,Y1I0E~?)JdWfe.z/|iqLI?>BPo>Pf*w~]WZu.VZZZM5zjO=?`yC^l_-H{q|m|U]21xgS6~ltFGZH}(6FE4n0D9Klx`T/;! I set up an EFHW for field day using a similar transformer with 25 ft. of coax from the box, everything floating, to my battery powered radio. (LogOut/ It does not need any special components; in fact, most of us may have them in our shack drawers already. This will yield the maximum capacity of the variable capacitor. I am building an EFHW antenna for my new MTR3b, but do I need to include the capacitor for 20, 30 and 40 meters? 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. A 100pF silvered mica was connected in shunt with the transformer . (LogOut/ There are two aspects, however that we need to consider: Lets begin with the transformer. 2. 2015. One of the many confusing terms used in Workers' Compensation, "IME" stands for Independent Medical Evaluation or Independent Medical Examination. 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'. I also built one that is heavy-duty handling easily up to 100W for 80/60/40m bands. From that we can find Mismatch Loss. Gut feeling says that should be possible with just a couple of FT114-43 cores, similar to the design by John Oppenheimer, KN5L. 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. Above is a thermograph of the transformer at 20W input at 3.6MHz. I checked the inductance again to make sure this hadnt been overly affected, and it remained unchanged at 109.8H, good enough! Note that the primary winding on the toroid is using the inner lead of an RG-58 coaxial cable. If not a lightning strike, I will write an article about the experience as well. Note that building loss into antenna system components is a legitimate and common method of taming VSWR excursions, eg TTFD, CHA250, many EFHW transformers, but in some applications, users may prioritise radiated power over VSWR. 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. 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. 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. The parasitic reactances near the feed-point also vary between installations. Thank you Gary. Well, in ham radio, everything works. This suggests an inductive reactance. Research salary, company info, career paths, and top skills for Software Engineer - EDI Does your station desperately need a good RF ground to behave properly? One end may even be close to the ground, not yielding the best radiation efficiency, but much activation proved it still operational. 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. Other observations along the way: 4) Tight windings or backwinding over the primary can significantly reduce leakage inductance. I first mounted the SO239 connector to the box. 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. 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. 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 last few years have seen a resurgence of interest in the end fed half-wave wire EFHW antenna. Steps to improve the heat transfer over the present design could make this small transformer work at even higher power levels. I recommend a good reading on this subject by Steve Yates, AA5TB at: www.aa5tb.com/efha.html. Nevertheless, this is a rather curious result that might have derating implications for the 160 and 80 meter bands. End Fed Half Wave Antennas: Is a Primary Capacitor Really Needed? 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. Generally a loading coil has far more inductance and shortens the length of the antenna significantly. 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. Lowest frequency = 7.000 MHz. Why does antenna radiation occur? Refurbishing aluminium antenna parts affected by weather / corrosion. The wire as I strung it up seemed to resist having a good SWR for the 20m band. This could be achieved by: Using thicker wire; increasing the diameter/length ratio; using a low loss former. We need to measure the inductances of the toroid with the tapped coil. I decided to play with this to see what I could accomplish. 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). 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. The impedance matching circuit is essentially a simple parallel resonant LC circuit. The original coil is designed for low power portable applications. 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. The conjugate impedance matching arrangement of this nature is far from perfect resulting in considerable reactive currents on some of the bands. With tension on the antenna wire, you can just roll the coil up/down the wire to try different positions as you are optimizing for a particular band. Can a diode be used to rectify signals smaller than its threshold voltage? CG K/ J/ S/ B to 4-20mA 0-1800 Celsius Thermocouple Converter TC Input 4-20mA Output Head-mounted Temperature Transducer first impressions, Some wisdom that shapes articles on this site, Designing high performance VHF/UHF receive systems, A new impedance calculator for RF inductors on ferrite cores, Calculate ferrite cored inductor (from Al), Calculate VSWR and Return Loss from Zload (or Yload) and Zo, https://owenduffy.net/files/EstimateZFerriteToroidInductor.pdf. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. Basically, the loading coil is operating as a trap. Many people use an inductor placed at the near end to make things level out on the higher bands. . Selecting the variable capacitor that can be varied from this minimum to maximum capacity, will allow tuning to resonance for 40, 30, and 20m bands at each of the switch position of the tuner. 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. The equation in the article is corrected now. The difference here is that the target bands are low frequency. A 100pF silvered mica was connected in shunt with the transformer primary. Start by wrapping the wire around the toroid. To compensate for the antenna connector capacitance, the solution might be to add the appropriate inductance on the wire right near the box. One way or another there is always a counterpoise involved if the antenna is tuned correctly. 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??). The procedure was to run for around 30 minutes starting from the box cool at ambient temperature. Look at the compensation coil slide. High Q, hence low loss. Further if your antenna requires a biggeer counterpoise on some bands, you can increase the size of the radiating element or improve your Tuner by using fine tuning capacitor or altering the coils slightly by varying the coil windings (compressed/spread out) slightly. Home Antenna Wire Antennas Multiband End-fed Half-wave EFHW Antenna. Csatlakozz csapatunkhoz! Im very happy with the result. From experience, I found that with this tuner my SWR was better by simply disconnecting the counterpoise at lower bands. I used four parallel #28 wires (not twisted) for the primary. . I tossed the line as far up as I could in a tree. Ismerje meg a hozzszls adatainak feldolgozst . Can you give me an idea for your 100 W version, you built for 80/60/40 m. 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 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. I used my IC-751As power meter and an in-line Siliconix power meter as well as a voltage probe on the feed cable. So far so good. 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. A Brief Synopsis of the Antenna Features & characteristics, EFHW Antenna Geometry versus Center-Fed Dipole. It is worth experimenting with its length also. An EFHW antenna has a very high impedance at the end point and you need a matching transformer to feed power to it. The EFHW transformer box from outside. Above is a sweep of the uncompensated prototype with a 3220+50 load. Radio amateurs using this antenna might remain oblivious to the presence of many active DX traffic originating from the direction of the shadow regions in the nulls. 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 am building an EFHW antenna for my new. It is worth experimenting with its length also. My limited experience with these antennas also suggest that one must be cognizant of the RF current pushed onto the feed-line coax. But systems that work better increase the prospects of contacts. Select components with good insolating materials and properly chosen, relatively high voltage rated parts. That does not seem inconsistent with the expectation calculated above of about 10% core loss at 3.6MHz. This gave the RF some place else to go, trapped by the coil and capacitively shunted to ground, rather than on to the transceiver. How badly can high Local Ambient QRM affect HF Radio? We have been in the middle of Storm Arwen and Strom Barra here, so I had the pole down for a few days. For the antenna wire itself, I used 119 feet of 22g stranded hookup wire. Graphed with a log scale, it makes a nice straight line. 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. Hence, even operating at 1000W on the 160m band, the cores would not saturate with the 5-turn primary. In that case, expected efficiency (meaning PowerOut/PowerIn) of the transformer was less than 65% at 3.6MHz. I checked the wall brackets and mast, but all the fixings were nice and tight. It is fun to build them and measure the lower and upper frequency limits and to see how close the calculation was. Because of the turns ratio N, the secondary capacitance will appear N2 larger at the primary and will resonate with the primary magnetizing inductance. The patterns fro the horizontal wire is compared with those of an inverted-V configuration. The impedance per unit length of a lumped transmission line is where L and C are values per unit length. I swept the antenna with a nano vna from 2 to 30MHz and there were nice dips at each band. I wish I had a simple answer, but really this is where some experimentation can pay off. This can then, fed with coaxial cable, in many cases be . 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. Be aware counterpoise or ground radials are required for all hf antennas for better performance. 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. Do I count the six loops around the pvc in the measurement? 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. After acquiring a MTR3b for SOTA activations I decided I needed a different antenna than the End Fed Random Wire (EFRW) or the speaker cable 20 meter dipole I use with my KX2. BG7TBL FA-3-6G frequency meter initial impressions, tinyPFA HP8656B vs Trimble Thunderbolt GPSDO, tinyPFA Trimble Thunderbolt GPSDO vs Leo Bodnar Precision GPSDO, (tr)uSDX unauthorised product and countermeasures, Comparing RF Power Amplifier Tube Performance Computer and Calculate initial load line of valve RF amplifier on the AL811H, Review of inexpensive Chinese thermostat DST1000, Garden environmental telemetry project part 5, Another small efficient matching transformer for an EFHW 2643251002 #5 improved Simsmith model (v1.03), A Simsmith model of a Ruthroff 1:4 voltage balun 2843009902 (BN43-7051), Another small efficient matching transformer for an EFHW 2 x 5943000601 (FT82-43) VK4JJ build and measurement, Another small efficient matching transformer for an EFHW LO1238 VK3PY, VK3TU build and measurement, An improved simple Simsmith model for exploration of a common EFHW transformer designs (v1.03), Modelling an antenna as a simple two terminal resistance is often naive, Garden environmental telemetry project part 4, A simple transformer model of the Guanella 1:4 balun some further observations, A simple transformer model of the Guanella 1:4 balun, An experimental propagation beacon on 144.385MHz part 2, An experimental propagation beacon on 144.385MHz, Another small efficient matching transformer for an EFHW 2643251002 #4 G8GYW build and measurement, Digital directional wattmeter based on G8GYW part 2, Garden environmental telemetry project part 3, Some wooly thinking on Antenna Factor online, Garden environmental telemetry project part 2, LED plate driver failure 24W round plate, Digital directional wattmeter based on G8GYW part 1, Diagnosis of a 9:1 transformer from NanoVNA plot part 2, Diagnosis of a 9:1 transformer from NanoVNA plot, Garden environmental telemetry project part 1, Digital display for DIY 25W dummy load part 4. 101: The Independent Medical Evaluation - "IME" By: Cynthia M. Hennessey Attorney. Could it be something to do with the new vertical aerial I had recently installed? The equation should have a 10^6 and not 10^-6 in the nominator. This graphical depiction makes it easier to visualize the current and impedance correlation between bands. Being end fed, it needs a transformer to transform the higher impedance of the wire to the 50ish ohms the radio is expecting. In this case C~5pF and Z~2450 suggests that the inductance needed should be about 30 H. With very little counterpoise, the antenna is being fed at a high impedance point so a rather large impedance step-up is employed. The blue trace above shows the results of adding a 6-turn 2 coil about 6.5 ft. from the box. Elnzst krnk, de elsikkadt az zenete. Ez az oldal az Akismet szolgltatst hasznlja a spam cskkentsre. In practice, exactly how you wind the primary turns can drastically affect the high frequency behavior of the transformer when measured into a 2450 load. 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. It requires a set distance to hang both ends of the antenna, and that is not always given. 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. I fashioned an antenna connector with washers made from some acrylic rod I had on hand. 2006. Wow, Gary! I started with a small piece of PVC pipe and drilled a few holes in it to run the wire through. The 6-turn loading coil lowers the resonant frequency into the CW portion of the 80 meter and higher bands. You cant really see the antenna wire, but the red line shows the antenna path. The highest voltages as well as radiation are also at the end of the antenna wire. The orientation of these lobes varies with the frequency band of operation thus resulting in directional inconsistencies between bands. These four data points are plotted on the Transmission Losses chart shown below as the yellow squares, all but the 80 meter point coming in a bit lower than expected losses based on the VNA measurements. 100W on a Wire Antenna How far would it reach? 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. It tests out well on the antenna analyzer for 3.5 to 29.7 MHz. 100W on a Wire antenna! A method for estimating the impedance of a ferrite cored toroidal inductor at RF. Tackling both of these issues at once led to a much smaller, lighter, and less costly transformer with better loss characteristics than previous designs. The SWR results are as follows: I wish you lots of productive experimentations and successful portable operations. With no counterpoise wire it will be the coaxs shield providing it. It matches the impedance fairly well to the half-wave antennas high impedance at one of its ends. A week or two later I started to notice an occasional knocking sound inside the house. It uses a coil as a compensation unit, and no counterpoise. The SWR was low, but not unity, so the peak voltage was lower than the 50 ohm match value when measured with the high-Z scope probe. There could be any number of reasons for that, where I put the bends in the wire, the location of tree branches, etc. inductance as one FT240-43 and is able to withstand 1kW 50/50% duty cycle with help of a cooling fan. 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). You can achieve this inductance with half a dozen turns of the antenna wire tied in a small coil. The SWR for the 20 meter EFHW antenna was < 1.2:1 I will publish my findings, but I cannot not promise to complete it until early fall. Being end fed, it needs a transformer to transform the higher impedance of the wire to the 50ish ohms the radio is expecting. I use my MFJ-939Y AMU regularly anyway, and it has zero trouble with this setup. 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. 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? Then I covered the coil in kapton tape to hold it together. The technical storage or access is strictly necessary for the legitimate purpose of enabling the use of a specific service explicitly requested by the subscriber or user, or for the sole purpose of carrying out the transmission of a communication over an electronic communications network. From experience, I found that with this tuner my SWR was better by simply disconnecting the counterpoise at lower bands. Throw one end of the antenna wire, extended with a rope, as high as you can on a three, and walk away with the other end and attach it to the tuner. This article will describe a 40/30/20m band end-fed half wave antenna, focusing on its matching unit. The photos above show a method that works fairly well. 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. (Tvir s tvbeszl gpek s kszlkek) Ksznm. For fun, I attached an 18 clip lead to the secondary output and observed 7.2 pF due to the dangling clip lead. The technical storage or access that is used exclusively for anonymous statistical purposes. I think the idea is to begin by tuning 40m operation, adjusting the wire length as needed. of the wavelength. The 2 coils are 35uh and 90uh. 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! 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. MyAntennas), G0KYA, K1RF, K1TA, K6ARK, N4LQ, W8JI AND WA7ARK; they all have a primary capacitor of 100 pfd to 220 pfd. This is typically a weak spot. Tuning the antenna to its resonance will result in 50 seen at the output of the SWR circuit. RC = 2500 x 1.0e-12 = 2.5 nS Now consider the period of a 30 MHz wave. Then record the change in temperature recorded at the core from the probe, and the elapsed time so I could corrected for not reaching perfect equilibrium. I thought to test this hypothesis by measuring the losses as an oven-heated transformer box cools down. I tried to operate from a hotel, and learned the hard way that this type of antenna is not suitable for such location. I would mention first its ease of installation. Will there be the same performance for single band EFHWs? With a very short counterpoise it is difficult to resonate the fundamental with any drive impedance. As I reexamined my formula, you pointed it out correctly, there is an error in it. If you really want to get the heat out, add some fins to the aluminum box. The cooling rate is more difficult to calculate because it involves how heat moves through the structure, but it is easy to measure. Most informative and appreciated. Having recently built a MTR2 3-band CW transceiver, I was keen to make band switching on a mountain top as simple as possible. 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 This will allow good matching of the half-wave radiating antenna wire to the 50 coaxial cable at virtually any location. When you are discussing a distributed capacitance, it is difficult to know exactly what you are measuring. The final turns ratio turned out to be 3:29. The antennas are set up as a sloper as in my SOTA outings. Hello, a wonderful approach for the problems.. It is basically an end fed half wave dipole on 20m/40m and an end fed full wave dipole on 10m. We would like to try to fly a kite with a halfway antenna wire and see what miracle we achieve. 1. Cmzett: Weince joseph How can we help? Apply for the Job in Software Engineer - EDI at St. Louis, MO. Nothing drastic but likely the SWR on the summit will vary as conditions and the setup change. Show more. 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. Basu Bhattacharya (VU2NSB). i liked it a lot, you give good ideas, many thanks. Yes, indeed EFHW antennas are very useful for SOTA or other field operation. Note: Crosswalk CAA administers the LIHEAP in Franklin, Jefferson, and Williamson Counties. The antenna is up. Or transmitting about 50% of the time, the peak power you would want to run with would be about 300W. 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.
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