Can The Best 100w End Fed Half Wave Get Any Better?

[@brianspilsbury8953]

this is the 3rd time I have come back to look at this video. Well done Sir. Brian VE3GUE

[@MM0OPXFieldRadio]

Thanks Brian, eventually I will get back tomorrow EFHW experimenting.

[@OffSurfaceAdventures]

Great work! I did start with a FT140-43 because it is the standard, smaller and lighter (I'm QRV portable only). For 100 W SSB perfectly ok and 10-15 % less efficiency doesn't hurt but considering digital modes this Fair-Rite looks like a great upgrade to have less loss and less heat in a bigger core enabling 100 W digital and lower bands in one go. Why not build a 160 m EFHW 😅

[@Howie-wd5oc]

I replaced the FT240-43 49:1 unun on my 40 - 10 meter EFHW with this autotransformer and the SWR readings on the different bands improved by an average of 0.35 swr. Always something new to learn in this hobby. Thanks for the video.👍

[@MM0OPXFieldRadio]

Your welcome. Everyone sees slightly different results.

[@presidentspilot]

Another SUPER idea!! Colin, I rewound my 3ea.-52 mixture toroids, from the older wide-spaced crossover design to your new auto-transformer design, and it works like a great 'bomb'...(i.e. WONDERFULLY!!)!! I also have the single '102' toroid, with your 1 to 56 design, and it also works FANTASTICALLY, and even though it is the older crossover design. I will NOT rewind that one, as it works so darn well as it currently stands! You sure have blazed some great toroid design-trails of late, and THEY ALL WORK SUPERBLY!! In thinking about the losses, the fact that you have fewer losses not only applies to radio transmissions, but also to low-loss signal reception as well!! My thanks to you, Colin!!

[@MM0OPXFieldRadio]

Thanks for the kind feedback. Yes not worth rewinding the 1002 core.

[@johnwest7993]

Note that the type and thickness of plastic you mount a toroid on affects the efficiency. Without doing dielectric analysis of the plastic you can experimentally put them in a microwave for a set period of time and see which type of plastic stays the coolest, and use that to mount the toroid on. BTW, the very best (most efficient,) end-fed half-wave would use an air-core transformer. A toroid based transformer is just the most compact and convenient, and once you get efficiency up over 90% very few hams will find a need to get any more efficient. As a suggestion, on the step-up/step-down efficiency test I'd suggest you turn the transformers 90 degrees to one another to reduce the chance of their fields coupling and affecting the test results.

[@MM0OPXFieldRadio]

Good tips, will do this on future tests.

[@sparky62]

Good stuff! Owen Duffy wrote a 5 part article on this core 2 years ago which confirms your findings vis-a-vis efficiency.

[@MM0OPXFieldRadio]

Yep, I seen that later on. Not seen a bad report on these yet and they are slowly becoming the Standard taking over from the 240-43 for 100w.

[@gregwmanning]

I would like to see how a 2 to 14 (or 2 to 15) transformer, with no connection between primary and secondary windings, compares with the two variations of autotransformers presented here.

[@tofuconfetti]

I have tried 4 iterations of different winds using this toroid and the autotransformer winding technique. I first tried a 49:1 wind and a 120pF capacitor. The upper bands were really high, so i added a coil 2m from the transformer and with 7 winds on 0.75” PVC. It raised the SWR on all the bands but aligned them better. I never could get them satisfactorily aligned with a low SWR. I used 20ga wire and an 8 foot 16ga counterpoise. I tried counterpoise lengths from 4-32feet and 8 gave the best. I then tried a 56:1 wind with a 100pF capacitor and the SWR on 40m dropped, but still could not get the alignment i can get with a 240-43 49:1. With the 56:1, same ga antenna wire and again 8ft counterpoise worked best. So then i tried a 64:1 100pF capacitor, all else the same. Could not tune the upper bands at all, but 40m was great and while not aligned 20m was spectacular. So i made two monoband EFHW antenna wires using the 64:1. On 40m got SWR 1.25 center, arround 1.6 on the ends. On 20m, it was 1.17 on each end and at 14.160-14.195 MHz, the SWR was 1.02! The reactance was really low as well. On the other winds the reactance was comparatively high at the lowest SWR. So I am looking forward to see specifically how you tune yours. I am about to decide that while less efficient, the 240-43 tunes much better, but the new Fair-Rite toroid makes one spectacular monoband EFHW antenna. Going to try an 81:1 on 40 next.

[@MM0OPXFieldRadio]

Really appreciate the detailed feedback. I've saved a copy. Personally I'm not too interested in multiband options. I like to operate as a monoband with my reel system. I will make another video when I do. Thanks again 👍

[@albrowne1035]

I've built one but so far I haven't got to test it yet. My original EFHW was put up last October. It was put up in a hurry and I expected a lot of the weather proofing to have failed but it was a;; still perfect. So for the time being I have left it. As soon as it starts to fail I'll change over the transformer box and let you know how I get on.

[@MM0OPXFieldRadio]

Cool, look forward to your results.

[@KK6USYHamRadioAdventures]

Great work Colin , like to see how it performs when you get a chance to try it out.

[@MM0OPXFieldRadio]

Me too chuck. Horrible weather this week. That Horrible bit between winter and spring.

[@jerrym1183]

Cant believe I have experimenting with Toroids for +1 year now, its an addictive fascinating aspect of the Hobby, have had great success matching, delta loops, and inverted L's too, with the Bonus is the static surge protection is now on the "isolated" antenna side of the transformer and grounded out there away from the house and ham shack, that's an added plus especially with lots of wire up 8n the air as in 80 and 160 meters...

[@MM0OPXFieldRadio]

Yep, its very addictive.

[@Hypercubeaudio]

Hi Colin, I'm using this toroid .. 1002 (49:1 Autotransformer) and it works well. No heating issues during long FT8 sessions at 80 or 90 watts. 73 de 2E0RPS

[@MM0OPXFieldRadio]

Excellent. It will cruise all day and more at that.

[@johnstumm3155]

Colin, I've been dinking with Ferrite antennas for 20+ years, the last 5 making ununs using beads at first and more recently toroids. I've been very successful marketing them with nary a complaint. That said, I've been experimenting with the chunky 2001's since you started espousing them. For some reason I'm not able to achieve good VSWR numbers on a consistent basis across the hf bands (Typically not below 1,7:1.on a given band. Some winding configuration will elicit good numbers on one band but not others. This is using a 40 meter EFHW.. My best performer employs an FT114-43 with a 1:30 impedance ratio, 2:10 winding. Excellent VSWR numbers on all bands 40 thru 10. I stack them up to 3 for more power handling although 1 core will handle 100 watts, If you have one, give it a shot! 73, John, ,kg6zbn

[@presidentspilot]

John, I ALSO AGREE with your findings. I rewound my 3 FT240-52's from a wide space crossover design, to making it an auto transformer design. When finished, I came up with the very same varying results as you found: ( e.g- my lowest SWR was near 1.1 on 14 Mhz, ..BUT much higher on other bands, especially 40 meters!).

[@MM0OPXFieldRadio]

Will have a look John, my 40m SWRnis highest at 1.7, all others are 1.4 or below. I never fret about SWR now.

[@MM0OPXFieldRadio]

Whats high? If you run as a dedicated monoband on 40 what's your SWR?

[@johnstumm3155]

@@MM0OPXFieldRadio Good point Colin. I shouldn't fret over obtaining such low SWR #'s. Modern transceivers have built in tuners that can easily handle the reasonable numbers your's obtain. I appreciate your feedback. Fellow ferrite fan, John

[@acestudioscouk-Ace-G0ACE]

Very useful, thanks Colin. I've never tried winding as an auto transformer but will now. It wins on ease of building if nothing else. 73 G0ACE

[@MM0OPXFieldRadio]

Yes, much easier on the hands. Benefits all round.

[@xavierayayaell546]

Hyped for this

[@3dhavok]

Same!

[@K5azz]

Another great Video Colin, Thank you! Did you ever get a chance to test the type 61 material? (2661102002)?

[@MM0OPXFieldRadio]

Not yet, i cant get them locally and need to spend a bit to get them from the US from Mouser or Digikey.

[@kevmscott]

@@MM0OPXFieldRadio I would be happy to send you a couple for testing (if your interested)..

[@mortimersnerd801]

@@MM0OPXFieldRadio ...I'm having a couple muled down from Canada to Mexico soon, gonna order some 120pf TDK caps too... they are appparently useless for 80 (not enuff mu @125), but are champs on 40 and above (credit to the ' Evil Lair'), and when wound 14:2 tapped with an extra turn15:2... should be a good experiment. With 90% to 95% efficiency, I fully believe 100w FT8 and upwards of 250, maybe 300 watts (peak) SSB (35% duty cycle) would be no problema. Unfortunately, 52 material cores in the '002 form factor are not yet avaiable... that would be the perfect mix.

[@N7TWL]

Hi Colin. Thank you for another great video on the EFHW transformer. I really admire how tightly you made your winds on the 1002 core. I have a very difficult time getting mine tight. At 77+ years old, I am guessing my hands do not have the necessary strength in them anymore. If you or anyone reading this has some suggestions as to a winding technique, I would very much appreciate knowing about it.

[@MM0OPXFieldRadio]

Kudos for keeping on going. As a 42 year old I do feel it in my hands after winding a pair. You made a good suggestion for a video, I will ad it to the list.

[@timg5tm941]

Great analysis.. look forward to the test

[@MM0OPXFieldRadio]

Thanks mate. Me too.

[@Tom-cw6xy]

As you said, you won't see the 5% improvement on-air. However you may be able to run a little bit more power with the same or less core heating. Thanks for the video Colin.

[@MM0OPXFieldRadio]

Thats a good point. May well help with heat.

[@WILLIAMPERRELLI]

I hv an 80-10 efhw with a 49/1, 130 feet long. My antennas brand. Very good on all bands. Adding a counterpoise off of the ground rod, I am able to work 160 decently! If I put up a 173 or 202 foot 9-1, wld it gv me better results on the bands, especially 80 n 160?? Ps…I am running an Mfj 998 tuner. Thanku. William

[@stylerxxl1]

i have build one with that core as autotransformer 49:1 … swr on my most liked band (40m) is 1.7 and 2.0 at the end… i think i Must go to 1:56 or 1:64 … but how good is the effectivity then?

[@MM0OPXFieldRadio]

Good feedback. Try the 56:1. The answer is no. It won't effect efficiency that much. I will likely need to do this too.

[@neily6294]

Nice one Colin, wonder if you could apply the same auto transformer approach to your efficient QRP core and make some further improvements to that - think they were all high but yellow. Really enjoy following your experimentation and findings.

[@MM0OPXFieldRadio]

Thats the plan. I had to comprimise slightly on that core as I couldn't get 40m to match. I need to buy some more first.

[@dylanschulz2404]

I would like to see what the difference would be between a transformer like this and different kinds of matching networks. Also radiation strength of an endfed vs a center fed antenna system. That being said, a lot of this might be splitting hairs as the ground losses with the way antennas are deployed in the field is usually knocking off a few DB. Thanks for the videos!

[@MM0OPXFieldRadio]

So would I! Yes splitting hairs and very difficult to measure.

[@theunexcitingfailedattempt]

so as a budding transformer builder, how do you modify your transformer designs to handle higher wattages? For example, if you wanted to build a 49:1 that would handle 500w digital, how do you go about picking the core(s) to use in this situation?

[@MM0OPXFieldRadio]

3 stack of 240-52 will handle this with ease 👍

[@robcarnaroli269]

Good timing. I bought the stuff for some 15/2 but hadn't made them yet. So I'll wait to see of the auto works good.

[@MM0OPXFieldRadio]

I think it will. You got thrle right core either way.

[@robcarnaroli269]

@@MM0OPXFieldRadio Just put two together and did the back to back VNA test. Almost identical results. I'm going to swap it for my unknown unun and check out how it works. Thanks!

[@MM0OPXFieldRadio]

@robcarnaroli269 I've done a back to back with a 2 stack too as a standard 49:1. It was poor on 15 and 10. Great for low bands though. This core is a no brainer.

[@paulsengupta971]

I made one as an auto transformer, 56:1 with a crossover. The inside windings are very close together. I haven't tried it yet. Soon. I have a problem with my knee stopping me going up in the attic to wire it all up at the moment. Oh, I will add that in order to make the auto transformer, I didn't solder on another lead, after two turns I took the wire out and back again, and twisted it together, before carrying on the winding. The sticking out bit is then a twin twisted wire.

[@MM0OPXFieldRadio]

Good tips, thanks 😊

[@paulsengupta971]

@@MM0OPXFieldRadio It might be not quite as good, but I thought I'd give it a go...

[@ea2re]

Thanks for the video What material and thickness do you recommend for the radiant wire (20 meters)?

[@MM0OPXFieldRadio]

0.75mm2 is more than ample. Thats what I use.

[@thehamradiotutor]

My son and I have made one of these per your process. We will be hooking it up to some wire this weekend. I plan on trying about 140 foot of wire and seeing if I can tune it as a spooler antenna. We considered doing it as a linked, but want to see if spooling it in and out will serve to get resonance on the bands.

[@MM0OPXFieldRadio]

Let me know how it goes. Spooling in and out will work but does depend on the configuration depending which side the reel is and if the wire is bare. Been there and done it.

[@thehamradiotutor]

@@MM0OPXFieldRadio we had mixed results. Some bands tuned well, mainly 20m and 40m. 80m isn’t doing better than 3.5:1. SWR also climbs as you approach 10m. We then measured out 133 feet and started to tune by cutting to tune to 80m (no spooling) and then checked for resonance on the other bands. We are still having problems getting 80m to tune below 3:1.

[@darz3]

Thanks Colin, will have a go at the auto transformer

[@MM0OPXFieldRadio]

If it ever stops raining here I will get a wire on this.

[@walterblizzard]

Would it help or be of any benefit to adding some glass cloth electrical tape under the windings?

[@MM0OPXFieldRadio]

Not really, the core will still heat up with too much power. Wont do any harm tho.

[@Andy-up6li]

Can we stack two of these for more power with the same turns?

[@MM0OPXFieldRadio]

Yes but will lose efficiency 20m up while efficiency on the lower bands will improve marginally.

[@VE9ASN]

Would you stack 3 of those cores for high power as you did with the 240 shape cores? 73.

[@MM0OPXFieldRadio]

You could but above 20m its so inefficient you lose more than half your power.

[@VE9ASN]

@MM0OPXFieldRadio ok, I'll stick to the 240's for this, 73.

[@MM0OPXFieldRadio]

Yep 240-52's

[@wimtel]

I think it is not fair to change the winding ratio from 2:15 to 2:14. This reduces the impedance level at the interconnect. This may change the capacitive loss in the core. I would love to see the results for the same turns ratio. besides this, 90% efficiency is really good for a high impedance device.

[@MM0OPXFieldRadio]

If you have seen any of my precious videos you will have seen I have done a 2/14 standard winding. The whole point is seeing what we can get out of this core. As far as improving efficiency above 90% its negligible gains yes but why not try just for the sake of it.

[@mortimersnerd801]

....going 56:1 instead of 49:1 makes sense, you get a way better match resulting in less loss... trying 49:1 on a 17m EFHW I got 1:1.62 vswr on the NanoVna... OK but it could be better ... I then rewound the core just as you did, auto transformer style 56:1 (15:2) and I got 1:1.04 at resonanance (18.15mhz), that's nearly perfect... I then went key down for 1 minuite 100 watts (didn't want to ruin my rig, the fan was spinning pretty good) and because I could easily access the core I walked over (2 steps) and immediately felt it... it still felt cold. Now I know nothing is 100% efficient but this was plenty good enough for my pay grade.... with that kind of efficiency I feel my 2643251002 core could easy handle well over 250 watts SSB. Colin it doesn't get much better than that...Oh my core is not in a box but attached directly to the antenna; zap strapped to an insulator.. Remember though, we are still (end) feeding a dipole, not a pileup buster, but when not being beaten down by the 2KW big guns.. even with 100 watts, sometimes only 20 watts from my Xeigu G90, you'll work many if not most of the DX stations you hear... I have two EFHW's up in the air...Richard VA7AA/XE1

[@MM0OPXFieldRadio]

Great feedback, especially the last bit. It only a dipole at the end of the day and many forget this. This is why I'm building a Hexbeam.

[@fotografm]

Excllent video. What AWG enamelled copper wire do you use ?

[@MM0OPXFieldRadio]

This was 1.12mm diameter.

[@fotografm]

@@MM0OPXFieldRadio Thanks !

[@janvelter3253]

Hi Colin. What I realy want to know from your perspective is how much power the 1002 core in both configurations could max handle ? I'm planning to go a bit QRO but not realy legal power with it. Say max 600 watts. It's the max my LDG autotuner can handle. Thx 73 de ON1JV

[@MM0OPXFieldRadio]

250w SSB or 100w FT8

[@IncognitaLabs]

Great video! I just got ten of these toroids in from Mouser.. cost me like 63 dollars. Also got some TDK 100pf caps. I am going the autotransformer route... the efficiency looks good 160-10. Now I just need to 3D print something to mount them on. I have quite a few 240-43 toroids but have decided to not use them as I don't run more than 100w anyway.. may make up some stacks of three 240-43 just to see how they test out compared to these nicer toroids.. These are heavy and chunky, they feel good in the hand..lol

[@MM0OPXFieldRadio]

Excellent, the 1002 core is fast becoming the core if choice for 100w I'm happy to see.

[@1kc1981]

Are these for sale? I dont trust myself making one. Just want it to work

[@MM0OPXFieldRadio]

Unfortunately no. I just dont have the time. I need to make a how to video sometime.

[@jamesemery1]

Hi, I'm new to the hobby glad i found your channel and the excellent research that you have done on the best cores for EFHW transformers. I will be definitely making my own 49:1 using the core you suggest and auto transformer winding as it's so straight forward to make. Long story short I will also need a common mode choke to stop the very short run of coax being used as the counterpoise rather than the actual counterpoise, do you have a recommendation of the best core for the choke. Thanks in advance

[@MM0OPXFieldRadio]

Thanks. Yes I do. I recommend the GM3SEK choke. Look it up. Also research G3TXQ who did a lot of work on this.

[@johnstumm3155]

Sorry, I meant to say 1002 cores. I guess my point is what real world numbers are you seeing when attached to a resonant long wire.? I like getting low VSWR on all bands and making the transmitter "happy". I'm wondering if there's a trade off, efficiency vs tune-ability? for lack of a better term. I know your waiting on better weather for this particular configuration, but previous tests? Thanks, John

[@MM0OPXFieldRadio]

Your right, there is a trade off and I've said this many times before. Just because its efficient doesn't mean its going to have an acceptable VSWR. For one thing its easier to wind and thats a winner for me if it works on air.

[@rainer4380]

hello colin, I rebuilt the balun with the 2643251002 and it works well with my endfed antenna. However, I can't get any resonance in the 6m band. It works with the 140/43. Is the 2643251002 not suitable for 6m?

[@MM0OPXFieldRadio]

I think what your perhaps seeing is the 140-43 is much more lossy than the 1002 so the SWR looks so much better. I would need to investigate further though.

[@rainer4380]

@@MM0OPXFieldRadio Yes,please.perhaps you can find something.thanks

[@ulliBG]

Does the Autotransformer also run with the FT240/43 ?

[@MM0OPXFieldRadio]

Yep, no problem.

[@ulliBG]

@@MM0OPXFieldRadio Thanks for your answer !👍 I will try it soon🙂

[@Rainer-c4k]

​@@ulliBGIT works very well with the 140/43,i have tested.try IT Out!

[@geirha75]

Thanks for interesting information. I understand there are 14 turns with the auto transformer. According to your table. Will you test swr in your next test?

[@MM0OPXFieldRadio]

Yes, when I get a wire on it in the better weather.

[@geirha75]

@@MM0OPXFieldRadio I wonder how well this core would preform if designed and assembled based on 64:1 unun ( 3 primary/24 total ). Do you think it would matter Collin?

[@carypeaden4147]

What makes an "autotransformer"? Why is the 56:1 a standard transformer and the 49:1 an autotransformer?

[@MM0OPXFieldRadio]

An Autotransformer is a single coil tapped at a certain point to provide impedance transformation. More commonly you see the twisted primary. On my 56:1 I've used a twisted primary but will he testing as an Autotransformer.

[@G5STU]

good stuff Colin

[@MM0OPXFieldRadio]

Thanks mate 👍

[@juliopereyra7422]

Thanks very good, video, congratulation Colin. 😊

[@MM0OPXFieldRadio]

Thanks 👍

[@JayN4GO]

A cutting board ey. Why didn’t I think of that. I have plenty around. Tnx Colin.

[@MM0OPXFieldRadio]

Yeah I learned from someone else. Its a bit floppy but good enough for these type of things.

[@charlieoscar09]

Colin will there be an Higher Power version using this core. I really like the efficiency of this setup but often run 400w

[@MM0OPXFieldRadio]

You need the 3 stack of 240-52 as an Autotransformer. Unfortunately more than 3 times price for the cores alone.

[@charlieoscar09]

@@MM0OPXFieldRadio Thankyou for the reply and all noted

[@scottcarter9975]

Thanks Colin. Great videos. Yesterday I built the 56:1 wide wound on the 1002 and I just tested and trimmed the radiator. I'd be so grateful if you would comment on these results because I'm wondering if I should change it to 49:1. I used 1mm enamel wire on the toroid and 18g on the 67' radiator. SWR dipped to lowest at 6.830, 14.050, 21.150 and 28.100. 6.830 got 1.0:1. 7.050 got 1.4:1. 28.100 only dipped to 1.9. What do you think? Thanks, Scott in NC

[@MM0OPXFieldRadio]

Antenna orientation, ground effect can have a massive effect on this. They seem to be fine. You wont see super low dips across all bands but as long as its less than 2:1 dont worry, I dont. I found best results as an inverted V with both ends well off the ground. With the transformer close to the grounds it was always worse.

[@scottcarter9975]

@@MM0OPXFieldRadio Thanks! I have seen two opposing views on deploying the transformer near the ground. I just installed mine about 2' up with a short wire to my grounding system per Steve Ellington N4LQ's videos. I gather you would not do that. If you're willing, tell me your preferred distance and whether you would do the grounding or any kind of a counterpoise. I am using a 67' wire in an inverted L/sloper kind of setup. I could do the inverted vee though. Thanks again, Scott NZ4R

[@MM0OPXFieldRadio]

@scottcarter9975 I found the ground effects tuning massively and when you want multiple bands to tie is it can be difficiult. My feed point is at least 4ft off the ground which I find helps. Remember this is a dipole, just fed at the end. Height is always might.

[@The0nionKnight]

What size AWG magnet wire did you use for your build?

[@MM0OPXFieldRadio]

This 1.12mm diameter.

[@The0nionKnight]

@@MM0OPXFieldRadio Thanks!

[@G1VNB]

very helpfull video and well explaned

[@MM0OPXFieldRadio]

Your welcome 👍

[@PD5RM_Robin]

Great video again. I want to rewind my own core. This is 1.25mm wire isn’t it?

[@MM0OPXFieldRadio]

I wouldn't bother unless you really want to. I'm using 1.18mm wire here. I've just received a 1kg roll of 1.12mm wire. Use what you have to hand.

[@PD5RM_Robin]

@@MM0OPXFieldRadio that would be 1mm or 1.25mm😉 for the qrp one would it be 0.5mm or 0.75mm.

[@PD5RM_Robin]

Have made this transformer yesterday end did an activation today. A halfwave lengt for 40m, 40m at the long side 1.18 at 7.180. 20 is good and on 10 had a reel high swr, wire to long… Does make a 15:2 a better match?

[@MM0OPXFieldRadio]

@@PD5RM_Robin potentially, where was is resonant on 10m?

[@thehamradiotutor]

Is this a 100pf 2kV capacitor?

[@MM0OPXFieldRadio]

Its 3kV but your 2kV is more than ample.

[@johnarcher9480]

Waiting to see a 56:1 auto-transformer on that core 😉

[@MM0OPXFieldRadio]

May not need to if this matches ok

[@geirha75]

@@MM0OPXFieldRadio I'm really looking forward to your results with 49:1.

[@ifell3]

Sorry is that using an antenna tuner?

[@jomckarth4836]

of course not, all bands 1:1

[@ifell3]

@@jomckarth4836 brilliant so my next question is going to be will the auto transformer be better than the other winding on a tuned antenna.

[@MM0OPXFieldRadio]

No Tuner needed.

[@ifell3]

@@MM0OPXFieldRadio awesome, for a tuned antenna which transformer would be more efficient?

[@MM0OPXFieldRadio]

@ifell3 I dont quite understand what your asking? What do you mean by tuned.

[@bitemykrank1970]

Can you stop experimenting on these bloody things....just when I decide to try one, you improve the bloody thing again......STOP PLEASE...your driving me insane....and it's a VERY short trip.

[@chublez]

Just make one. You'll never notice 5% heck You'll likely never notice 20%. Remember you have tou double yer power to gain half an s-unit or see 50% loss to loose half an s-unit...however you want to look at it. Assuming a standard 100w radio and the first design here with a SWR under 2:1 yer gonna get 80 or so watts out. That last 20w(impossible to get 100% of) would at best represent a 25% gain ore 1/8 of an s-unit...not even enough to notice on a small anolog gauge or be represented on a segmented digital one. Your time is far better spent building a moxon you can aim wich would net you 3db over the efhw or the same as doubling yer power and getting that full half s-unit with the bonus of the front to back ratio giving you rear rejection of noise etc. Basically chasing that last few percent on an efhw is a fools errand and the times better spent making a secondary directional antenna to play with. Heck even a simple 1/4 vertical like the DX comander will get you some DX gain over a efhw due to take of angle and ditch toroidal losses. Comercialy costs more but diy doesn't.

[@chublez]

I guess my point is, don't miss months an months of the peak of this solar cycle agonizing over getting it perfect when the difference between good enough and theoretically impossibly perfect are virtually impossible to tell in actual practice. Get a wire up and play!

[@bitemykrank1970]

@@chublezI wasn't commenting on it because it's bad....I was commenting the same thing you have added, but with more brevity.

[@jomckarth4836]

he just dont know anything else....!

[@MM0OPXFieldRadio]

Yes its quite addictive.

[@jomf8929]

Makes zero difference in real world application.

[@MM0OPXFieldRadio]

In comparison to what? If I can wind an Autotransformer easier to the traditional twisted primary and its more efficient then its a no brainer.