Link to the 2643251002 core on Mouser www.mouser.co.... Link to the spreadsheet of results docs.google.co... How to measure core efficiency with the back to back method • How to measure Insersi...
I work ten meters with two stacked 240-43 cores and found them to be quite suitable for 100Watts of SSB. Thanks very much for this video. You are really filling a hole of information that needs filling. Your research is making the EFHW anttenna more viable and efficient, especially for multiple band operation.
Colin filming in his garage when it is -10°C inside and even colder outside 😂 Good job Colin. I didn't realise the ft240-43 cores were good for 70W. I always stop at 50. I'll definitely look at your suggestions for a higher power set up. FYI I have worked 10m SSB qrp DX with the EFHW on more than one occasion. Cheers, Fraser MM0EFI
Thank goodness it is getting milder. I wasn't doubting your efficiency calculations for 10m. I think I just got lucky. When 10m is open, a bit of wet string can sometimes do the job. 😊
I've built a 2/14 closewind, at tapped, 100pf using Fair-Rite - 2643102002, using similar test rig I get results inline with the Fair-Rite - 2643251002 and Fair-Rite - 2643625002. I've been using it for POTA w/ 20m~ of wire and it's been matching/surpassing my results from ft-140-43 I was using for 10-100w (usually I activate 10 or 50w)
For reference I was using a single 240-43 as a 9:1 for a Random Wire and had the 70W limit hit me ..not imediately but after a good dose of FT8 also the operation at 10m again seems a bit off.. nice to see that your figures approximate to my setup done independantly!!
@@MM0OPXFieldRadio I would say from the time it takes you are not Saturating the core significantly but enough to slowly heat it near the Curie point at which the performance drops and you are forced to back off to the sustainable level!!
FWIW I have used 2 T240-43 stacked in an EFHW at 400 watts SSB and it has survived 3 years now. I used 10 guage magnet wire for the 49:1 windings. Cheers.
Hi Colin, I'll be making a couple of antennas up with the 2x2643251002 cores stacked and giving them a good test on FT8. Also also 3xT290-43 with 3xT140-43 slipped inside, should be interesting to measure the efficiency of a very large transformer. Have you tried 2643101902? I have done some test on these and with 49:1 wide spaced the efficiency look about 90%+ from 80m-10m and is looking like a good option to replace the T140-43 cores from my products in the future. 73 M0VUE
Hi Chris, I would be very curious for your results. Theres still lots of experimenting out there to do. I havent tried the 1902 core. Its good to see a UK seller selling the 1002 core. Not easy to get hold of this side of the pond.
@@MM0OPXFieldRadio Hi Colin, send me your address and I'll post you a couple of 1902's. I've tested 80,40,20,15,10 my measurements were 93%, 92%, 92%,93% 90% efficiency using 49:1 wide and back to back with my Nano VNA. Would be good to see how close you get to these numbers as well.
I’ve become addicted to half wave end fed mono-band verticals for the higher bands!! I’m using ladder line to create a quarter wave shorted stub to give me a match! I find it a nice alternative to using a transformer when looking for DX!!
@@Gabaab It’s essentially operating as a j-pole! What’s nice is that the losses are low - the only area of high current being around the shorted end of the ladder line. So quite efficient!
@@Gabaab It's worth a try - easy to make and v effective. For 10m I've always thought getting the 5 m wire as high as possible on a 10m pole helps - Height is might etc etc!!!!
This video is semi helpful :-) I have been playing with magnetic loop antennas made with 1” x 1/16” aluminium bar. Using FT240-43 core as a 1:x matching transformer, I have 40m and 20m working exceptionally well with both 8m and 5m circumference loops. However, using the smaller 3 and 4m loops for 10-15m the turns ratio drops and the coupling efficiency seems to die off Stacking cores helps a bit and I grabbed some type 52, 61 and 77 material. Not much difference. Strangely enough the throw together 10m loop I poke out the window made from 2.5m of RG6 with a capacitor made of the same, fed by some random EMI filter cores I found in a computer case is around 12-15 dog biscuits better to the local RBN I’m considering the core efficiency vs the skin effect issues of a flat bar vs round Might look at other coupling and matching methods. Small loop, gamma match. See what works. Sadly these cores you’ve used are too narrow for the strap. Back to the experimenting….
@@MM0OPXFieldRadio they are magic. The noise drops from S7 to S3 on 40m with the 8m circumference loop bs the 33’ vertical. That’s what you get for living in an inner city QRM jungle. Seems quieter since they took away the overhead cable service amp from out front. It’s the coupling that I’m working on. I’ve seen a few of your videos on materials v frequency and they have been very helpful. I think it’s because the loops are almost too long and with a single turn through the core the impedance at resonance is too high and I don’t get a tight enough coupling with so few turns. The match is good, but the energy transfer is crap. That said, I don’t see heat in the core. Back to the drawing board and more experiments. But I have succeeded in a _Poke-Out-The-Window-Tenna™️_ that covers 20m and 40m so I can test radios from my test bench
@@MM0OPXFieldRadio I have managed to drive 100W into this current design. Works well and no capacitor flash over. Trick with mag loops is don’t expect them to cover more than an octave of frequency. 7-14. 14-28. You can certainly tune them down there but their efficiency drops significantly below the first octave, and you can hit self resonance up top. Efficiency is proportional to the surface area so circles and octagons tend to beat squares. Radiating Element surface area is significant to a point. But skin effect is your friend. You can get away with tape, either aluminium or copper. Much cheaper than copper pipe, though if you’re happy to slip a dude a $50 he can take a $30 aluminium pole and bend it into an almost circle for you. Friend has one that he can tune 7-21MHz that performs OK on 7 but really kicks some at 14MHz Finally, you only need a small amount of variable capacitance to cover any band. Makes it cheap to build a mono band loop and change bands by paralleling fixed capacitance across the variable cap. Probably stuff you already know, but someone may come across the thread. :-)
I build a 49:1 with 1 fair rite core and I'm allready amazed with the results of it. I got it now up and running for 3 weeks ..... ok yes you got the changing band conditions but overall ... it does now allready do a much better job then the 240-43 core for sure.
Great work Colin... I wanted to try a 49:1 2 stack 52 core, which I don't think you have shown, and which I think will work better on 12 and 10 meters... am only interested in 40 and up. I only had a single FT 240 52 core. Looking at most winding profiles, sans the crossover which is NOT necessary; so you have a winding profile uses less than 1/2 the core mass... the rest on the other side is wasted.... or is it? Carefully using an angle cutter I chopped the core in half, you do this carefully, score the first side down 1/4 then do the other side, it'll fracture apart, clean it up.... and then glue the 2 halves together. Since size matters, I now have double the mass under the windings; that's what you really want. I only run 100 watts SSB max, most of the time it's only 20 watts from my Xeigu G90.... Preliminary results are positive....seems to work well, VSWR is less than 1.5 on all bands, 20 and up including 12 m ... until you get to 40 where it went a bit askew and resonates a bit high in the band... 80 is useless, which I kinda expected. Worked a guy in Kentucky on 10...got a 5X5, but more checks are needed.
Thats a really interesting idea. I would need to do a back to back with chopped cores to see if if makes a difference. I doubt I will though as these are not my cores.
Hi Colin. Great videos. I"m in the process of winding 2 stack of 1002 toroids. Looking at you chart it refers to "14/2 turns wide spaced" I wasn't clear if that differed from the tightly wound and spaced auto transformer. I might be missing something but I've not seen "wide spaced" demonstrated in any of your videos. Clarification would be appreciated...thanks.
I still have some updating of the spreadsheet yet. Wide spaced means just evenly spaced out windings. Your 2 stack of 1002 will be very good low down but become very lossy above 20m. Let me know how it goes for you.
I’m very interested in your work. I would like to build a transformer that does 80, 40, and 20 at least and with full legal US 1500w power on SSB for use in our ham radio club for possible emergency communications. I have subscribed.
Ive made a more recent video on this. You need a 3 stack of 240-52 wound as an Autotransformer. Its as efficient at this (maybe slightly better) and will handle your power.
For this test I used 0.66mm wire as it's easier on the fingers. For use as an antenna use something about 1mm in diameter. I have 1.12mm and 1.18mm here also.
Not on youtube so much hence why I made this. If you look hard enough you will numerous others on facebook groups and Twitter have done this and coroborated results, particularly on the 1002 core. Look at this ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-liobaos7nhs.htmlsi=lQRqyNHX8fgLeSBi
Thank you for supplying your viewers with such amazing data. I am building a EFHW now and putting my 240 43 cores aside, 100 watts max to include SSB and Digital. Ordering the new cores, but now confused with the best way to go, single core or stacked?
Hi Colin, got another question .... Have you ever considered to try and test a 9:1 comparison between the 240-43 and the Fair Rite ....1002 core for the EFRW / EFLW users between us ? Will the efficiency of the 1002 core be as good there too ? I'm gonna build and antenna like that. Goal is to get on the warc bands too.
No, I havent. Thesmokinape has done some videos on this and a 9:1 is pretry good 90% plus. Of course you have SWR losses. It would appear the less the impedance transformation the less the efficiency losses.
Two questions: 1. Is it possible that using a larger value shunting capacitor to negate some the high inductive reactance at 10m ...could decrease that really bad -4.55dB loss? Or does that merely change the total impedance at 10m? 2. Would it be ridculous to think about a hybrid core combo? Since that actual transformation is occuring in the core of the toroids, maybe trying a single 1002 core centered and sitting squarely on top of an FT240-43? Or would one core just take all the loss anyhow? A 4.5dB loss on 10m with two 1002 cores would be excessive and the core heating would be unbearable. I'd rather just use an antenna switch and go to a different antenna on 10m.
1. Possibly but think it would adversely affect the match as as antenna. 2. Not at all. I think its a possibility. Can only try. 3. Agreed, there are many better antennas for 10m.
why so much power on ft8 i worked the world on 10 watts. running your radio to 100watts or amplifiers on ft8 will kill your output transistors. better antenna less power.
I agree in general. To he clear, FT8 is a weak signal mode, not a low power mode. There will be times you need to raise the power but yes usually if the band is open a few watts will do. I wouldnt run more than 30w from my rig on a digimode. My amplifier however would run all day and some at 400w. Its rated 1kw full duty cycle and I know a friend whe had an NOV and ran his on 1kw RTTY without issue which has a higher duty cycle over FT8.
Knew a bloke who during the recent sunspot minimum worked Australia to east coast Russia on 10m using _Russian QRP_ which was around 2KW to get through on FT8 I guess you do what it takes :-) LDMOS has made it easier :-)
Ready? A 240-43, 2primary 16secondary, as close as possible, (obviously no cross over crap), tapped not bifiller, 100 pf, I got the 5t on 1" former inductor 2m from the box, then a few hundred pf cap directly in the middle of the wire for the 75mod, feed it with 75ohm coax Most wonderful end fed I've ever made,
