Gladiator Beast Combos, Chase Bank Name Address, Byo Catering Wedding Venues Bay Area, Articles E

Commercial Coils, Inc. 213 Chesterfield Industrial Blvd Chesterfield, Missouri 63005. 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. For the last step, I put together a RF choke to use between the radio and the feedline. The equation should have a 10^6 and not 10^-6 in the nominator. 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. Basu Bhattacharya (VU2NSB). 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 original coil is designed for low power portable applications. I use my MFJ-939Y AMU regularly anyway, and it has zero trouble with this setup. Generally a loading coil has far more inductance and shortens the length of the antenna significantly. The Counterpoise is a short, typically one twentieth (0.05 *. ) If you stare at the above frequency sweeps you will discover a few things. I used a section of 40mm external diameter PVC waste pipe and 1mm diameter enameled magnet wire to make the coil. Home Antenna Wire Antennas Multiband End-fed Half-wave EFHW Antenna. Firstly, lets estimate at 3.6MHz minimum number of turns to ensure that magnetising conductance is less than about 0.002S (for better than 90% core efficiency). The SWR results are as follows: Considering the compromised installation (ends about 2.5-3m above ground, inverted V with peak at 8m) I am pretty happy with this so far. It matches the impedance fairly well to the half-wave antennas high impedance at one of its ends. The in-band SWR improved significantly with this localized inductance to compensate for the boxs capacitance. The 6-turn loading coil lowers the resonant frequency into the CW portion of the 80 meter and higher bands. 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. A design by VK3JEG is only 66-ft. long, about the size of a 40m dipole. Below about 7 MHz, transmission losses increase as the core temperature increases. 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. (LogOut/ . Let's find out! Moreover, this antenna produces several inter-lobe nulls creating multiple band dependant shadow regions in its coverage. 2 0 obj 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. It is hard to wait an infinitely long time for the box to equilibrate to a given power level. 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 It requires a set distance to hang both ends of the antenna, and that is not always given. 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. Elnzst krnk, de elsikkadt az zenete. In theory, the examination is supposed to be used to help clarify your medical condition and . From experience, I found that with this tuner my SWR was better by simply disconnecting the counterpoise at lower bands. I used my IC-751As power meter and an in-line Siliconix power meter as well as a voltage probe on the feed cable. Some say you do not need a counterpoise, but that is false. Increasing the drive impedance tends to move the resonances to slightly higher frequencies. First, note that the transformer has low transmission loss up to nearly 50MHz. With no counterpoise wire it will be the coaxs shield providing it. Hence, we need to move along and start to include the antenna with our testing. However, a key restriction is its 25W power rating, due to the small matching transformer. My favorite SOTA antenna is the End-Fed Half Wave Antenna. 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. 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. The photos above show a method that works fairly well. Basically, the loading coil is operating as a trap. A krdsem az, hogy a knyv elrhet esetleg pdf-ben is? I was a little long on 80m not surprisingly, so folded back about 40cm of wire leaving about 2.1m beyond the coil. A week or two later I started to notice an occasional knocking sound inside the house. This gave me an effective coil diameter of 40.5mm. This can then, fed with coaxial cable, in many cases be . Very interesting design. From that we can find Mismatch Loss. Be sure to take a look for additional analysis and conclusions. Winding the wire manually was a bit tedious but once done I temporarily held the wire with cable ties and checked the inductance. 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. 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. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. View the job description, responsibilities and qualifications for this position. I drilled a couple of holes at each end of the former, a small one for the wire to pass through and a larger one for a bolt and wingnut for wire attachment as I wanted the end result to be portable across different antenna projects. Hence, there is no optimum single-fit solution. It tests out well on the antenna analyzer for 3.5 to 29.7 MHz. I think the idea is to begin by tuning 40m operation, adjusting the wire length as needed. Regards VE9HAM. 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. The 2 coils are 35uh and 90uh. Thank you Gary. The second smallest number I measured was 2.7pF, derived from the self resonance at 2.72 MHz with the magnetizing inductance (measured at 25.8 H) with the secondary open and the output wire folded to a small 1/2 length. 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. Most of the time 5 to 20W will be adequate for activation anyway. 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. Hence after about 3pF of output capacitance, the source will have a hard time charging up that capacitance before it is time to start discharging it. 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. Research salary, company info, career paths, and top skills for Software Engineer - EDI The 1:64 transformer is wound on 3 stacked FT240-52 toroids, this provides same. This gave the RF some place else to go, trapped by the coil and capacitively shunted to ground, rather than on to the transceiver. Csatlakozz csapatunkhoz! 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. One end is about 5 meters high on an extended fishing pole. of the wavelength. This will also be handling 100W. The finished tran, End Fed Half Wave (EFHW) Antenna Upgrade Part 1 - The Matching Transformer. 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. I settled on a compact secondary using #28 wire. % Looking at several builds and discussions, such as commercial antennas (e.g. The difference here is that the target bands are low frequency. The previous table already contains these measurements. inductance as one FT240-43 and is able to withstand 1kW 50/50% duty cycle with help of a cooling fan. You can find more info here: https://km1ndy.com/diy-491-unun-impedence-transformer-for-end-fed-half-wave-efhw-antenna/. As is often the case, packaging was determined by what boxes I had laying around. Thanks! 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. A transformer was wound on a FT50-43 toroid with 3 bifilar turns followed by another 31 turns of #26 enameled magnetic wire. The negative effects of local QRM on an, How does antenna radiation occur? = 258 * 10^-12. Do your own experiments with your own set up, 2019 - 2022 by Dan Koellen AI6XG. Payment: If you are eligible, Crosswalk CAA will make the appropriate payment to your energy provider (s) on your behalf. Wow, Gary! In that case, expected efficiency (meaning PowerOut/PowerIn) of the transformer was less than 65% at 3.6MHz. = .00 00 00 00 0 258 Thirty turns #28 are wound on the two FT114-43 cores. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. It may be one or even five kilo-ohms. As you stated early in your posting, I also have found 99.99% of all posting on the internet tell you WHAT they did.not HOW they determined the specific design criteria. How to get started on ISS Cross band Repeater? The radiation pattern of this antenna on most bands produces multiple lobes. Krem, rja le, mi a krdse. The orientation of these lobes varies with the frequency band of operation thus resulting in directional inconsistencies between bands. 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. The parasitic reactances near the feed-point also vary between installations. 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. (LogOut/ 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. 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. What kind of balun is this? The slim coil is torpedo shaped to prevent it being snagged in trees when deployed in 'the great outdoors'. Ez az oldal az Akismet szolgltatst hasznlja a spam cskkentsre. = 1/30.e6 = 33 nS. I also built one that is heavy-duty handling easily up to 100W for 80/60/40m bands. 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. 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. I tried to operate from a hotel, and learned the hard way that this type of antenna is not suitable for such location. Update: Full size 132ft EFHW For one month I replaced the 66ft wire and loading coil and replaced it with a full 132ft of wire, connected to the FT240-43 balun. 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. Most informative and appreciated. Yes, there is a coil a few feet from the box but it is NOT TRAP, it is no secret as well, actually, everything in this antenna was published and patented by few people a long ago. 101: The Independent Medical Evaluation - "IME" By: Cynthia M. Hennessey Attorney. Graphed with a log scale, it makes a nice straight line. (The antenna wire could also be tuned for the lower end of 80 meters without the coil but the . When you are discussing a distributed capacitance, it is difficult to know exactly what you are measuring. 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. 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. On the ends of each winding I slip the end under the last turn and pull tight to lock the winding in place. Although it is simple to build and is a multiband antenna, it has several attributes that . MyAntennas), G0KYA, K1RF, K1TA, K6ARK, N4LQ, W8JI AND WA7ARK; they all have a primary capacitor of 100 pfd to 220 pfd. = .000001 / 3868.88 Also find news related to Efhw Compensation Coil Experiment which is trending today. Thanks for your comments. nanoVNA-H can firmware be updated if it has a broken USB socket? For . 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. The EFHW's SWR will be affected by height above ground, type of ground, feed line interaction, and any nearby conductive surfaces. On the transformer, I added a few wingnuts to tighten down the antenna wire. The coil uses 26 AWG (27 SWG) enamelled copper wire close wound on a machined plastic former. To mitigate the voltage issue mentioned above, I used a couple layers of Kapton tape over the secondary winding. As I reexamined my formula, you pointed it out correctly, there is an error in it. 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. More designs can be found by Googling "80m loaded dipole.". 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. Consequently, this is how the capacitance values are determined. It performed well on both the 2m and 70cm bands. 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. Now I just need to build or acquire a decent radio to utilize this new antenna. I mounted the transformer on a tree for testing. 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. 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). These inductances are required in determining the right capacitance values, of which two values are important: the minimal and the maximum capacitance values. From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. What are its disadvantages? Hi Ajai, I would mention first its ease of installation. However, let me write about it from a slightly different perspective that was not very obvious from the articles I read. Note: If we change the primary number of turns, the impedance ratios will considerable change also. Do I count the six loops around the pvc in the measurement? I used four parallel #28 wires (not twisted) for the primary. 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. This could be achieved by increasing the spacing of the windings, hence reducing the interwinding capacitance. Accordingly, calculate the capacity for the resonance at the highest frequency to be covered with the highest inductivity taken in consideration. The results are shown below. After cleaning it up and testing it, I installed it on the side of my house on top of a straight pole. This article will not address that antenna type. Nevertheless, the EFHW antenna had in the past, been rather sparingly used by amateur radio operators due to various reasons. Nothing drastic but likely the SWR on the summit will vary as conditions and the setup change. I swept the antenna with a nano vna from 2 to 30MHz and there were nice dips at each band. With such a switch, it is impossible to forget to switch back to operational mode. I went with a 49:1 unun to match the unbalanced antenna to the unbalanced feed line. Therefore, installation is quite easy, and its tuner circuit is rather simple as well. However, a key restriction is its 25W power rating, due to the small matching transformer. This is perhaps one of the most hotly debated rookie topics in. Fill in your details below or click an icon to log in: You are commenting using your WordPress.com account. This antenna is only 15m long using 2 loading coils. The band compensating inductor placed on the wire is another story. Frank VK1VK. Can you give me an idea for your 100 W version, you built for 80/60/40 m. This provides proper insulation from the relatively high voltages on the seconder winding. At this point, I'm leaning towards the EFHW, but any of these antennas seem . So the differences I see in the data sheets hysteresis curves are not the correct explanation. 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. I particularly want to know how counterpoise affects the common mode currents on the coax. I first mounted the SO239 connector to the box. I can give a link if you need. The transformer fits sideways in the box with a few millimeters to spare. Hence, even operating at 1000W on the 160m band, the cores would not saturate with the 5-turn primary. 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. It is worth experimenting with its length also. The blue trace above shows the results of adding a 6-turn 2 coil about 6.5 ft. from the box. A/l for the chosen core is 3.5 times that of a FT82-43 yet it is only 1.6 times the mass. Finally the tank circuits specification is complete, which is sown below. 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. 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. You cant really see the antenna wire, but the red line shows the antenna path. The final turns ratio turned out to be 3:29. Essentially, the matching is done with a tank circuit, which represents the highest impedance when it is tuned to resonance. One possible explanation is that the core losses drop with temperature. 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. It is recommended to use at least 2W non-inductive resistors for this purpose. The following describes such a transformer using a Fair-rite 2643625002 core (16.257.2914.3mm #43). The cooling curve I measured is shown below. The permeability rapidly goes away above the Curie temperature, about 160 C on the data sheet. If not a lightning strike, I will write an article about the experience as well. All Rights Reserved. Instead, this shifts everything down and makes it very easy to tune 10m. Z8Vq9_@x C\Agv#. Many people use an inductor placed at the near end to make things level out on the higher bands. 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. 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 found it very useful to label the tuner with switch and capacitance positions. Change). The other end, attached to the transformer and antenna analyzer, is about 1 meter above the ground. There is much more that can be written about this antenna and its matching, but that was not my aim. My question is what is 'higher frequency' specifically? 2. 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. It is common to use compensation coils of a few turns of the antenna wire to improve the alignment of the bands. 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. Newtons Law of Cooling tells us that heat flow is proportional to the temperature difference. In the open-box image above you can see the thermal probe I used to measure the ferrite core temperature for a thermal characterizations. Lowest frequency = 7.000 MHz. This will allow good matching of the half-wave radiating antenna wire to the 50 coaxial cable at virtually any location. This condition is rarely met in typical amateur radio EFHW antenna deployments leading to compromised overall antenna system performance. 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. 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. I used the 14g enameled wire and wound it on the FT240-43. 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. How big and where to place it is likely best determined empirically. It will have six turns around a 1.25" diameter PVC fitting that will bump the 10m resonance down about MHz. It is basically an end fed half wave dipole on 20m/40m and an end fed full wave dipole on 10m. So far so good. 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. 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. Note: Crosswalk CAA administers the LIHEAP in Franklin, Jefferson, and Williamson Counties. There are many good descriptions on the net about this type of antenna. 1) More primary turns and primary inductance improve the transformer efficiency and low end performance. SWR for 80-10 meter EFHW with no capacitor, SWR for 80-10 meter EFHW with 100 pfd capacitor, The above data from K1RF shows that the SWR for 20 meters (my dark red markings -, I hope to do more experiments with single and multi band EFHW antennas above 20 meters - stay tuned, 40 meter and 20 meter (full wave) SWR with no cap. http://www.hamuniverse.com/randomwireantennalengths.html, https://km1ndy.com/diy-491-unun-impedence-transformer-for-end-fed-half-wave-efhw-antenna/. 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. 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. After some internet research, I settled on making the former from a paint roller. Change), You are commenting using your Twitter account. The patterns fro the horizontal wire is compared with those of an inverted-V configuration. End Fed Half Wave (EFHW) Antenna Upgrade Part 1 - The Matching Transformer. A method for estimating the impedance of a ferrite cored toroidal inductor at RF. The transformer is wound as an autotransformer, 3+21 turns, ie 1:8 turns ratio. The above factors often also lead to unacceptably high CMC on the coaxial cable transmission line thus rendering a rather poor antenna system. I installed an eyebolt on one end as a pull-point, and a BNC connector on the other. 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. The transformer was attached to the 30 meter EFHW antenna and turns were removed for best match to 50 ohms. We need to measure the inductances of the toroid with the tapped coil. For Jackson County, please call Western Egyptian Economic Opportunity Council, in Steeleville, at (618) 965-9031. Klubunknl folyamatos a tagfelvtel. 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. 5) It is very hard to avoid stray capacitance on the output. The slim coil is torpedo shaped to prevent it being snagged in trees when deployed in 'the great outdoors'. . 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. clear. It performed well on both the 2m and 70cm bands. Why does antenna radiation occur? Transmitting on 15 meters was impossible because of RF into the radio. 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. Copyright 2014-2023. My design objectives were: 1. The last few years have seen a resurgence of interest in the end fed half-wave wire EFHW antenna. 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 totally un-rigorous calculation just gives a quick idea of how much you have to be careful. This is not an optimal value, benefit may be obtained by exploring small changes to that value. I thought to test this hypothesis by measuring the losses as an oven-heated transformer box cools down. 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. 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. 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. coil inductance calculator at 66pacific.com. stream The real power limit will be core heating. It is all about getting the heat out. Another completed tuner, which is more compact then the pervious one shown, also it is lighter, more suitable for portable operations. It is not necessary to calculate the above; the results are sown in the following table. From the condition, it looked like it had been installed outdoors for a few years, so I got it at a good price. I have also had SSB QSOs in Europe, USA and Canada on 20m so havent seen any degradation in performance on that band. 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.