I switched to using 2 FT240-43 cores in my 49:1 UNUNs. They seem to work better with lower SWRs than a single core. I only run 100 watts. The primary and secondary windings are separate for no common mode current in the coax.
First time making my own unun. I was curious if i was going to eat it up doing ft8 using a stacked 240-43 with 12ga wire, looks like I should be fine. Thanks for the confirmation!
Hi Colin, great video. Your findings with the 140-43 are exactly as I have found (by accident) I built a 49:1 from a kit that was supposed to be 100W. I was a bit startled to see the SWR run away whilst running 80W for 15 minutes or so. I could run 50W for extended periods without issue. I now stack 2 x 140-43’s for my maximum available 100W. Love your work. 👍 Daryl de VK3AWA
Nice to see others with the same experience I built a 49:1 with ft140-43 and it took about 15min as well to overheat on ft8 @100w. I have now just finished building a 2core 49:1 using 2 ft240-43 I wanna be able to run 100-150w ft8 all day if need be
@@HamAround23 100W FT8 is a high average power. My experience is that 3 turn primaries will halve your loss, but make 15m and 10m less efficient. 2 cores will reduce loss as well, significantly. How many turns are you running? What bands? Maybe I can guess at efficiency with 1 and 2 cores - I've lots of testing this last 12 months.
Core heating can be observed in a non-contact method with almost any of the common infrared "thermometers". They are available in price ranges from $20USD to $50USD. Here in the USA, Harbor Freight has 2 different models under $50USD and 2 more between $60USD and $90 USD. I used them in weld shops for years. The core suppliers will have the critical temps in theur specs. I have not looked them up, but I remember seeing them in the past. Good presentation, and thanks for your testing! 73, Keith, WB2VUO here near Buffalo, NY
Liked the video. Keep up the good work. I just built a 49:1 with the same core as the 3rd transformer you showed in the tiny box my ft140-43 transformer was in. Tight fit but it works. I can bring a 100 watt rig portable now with no overheating. 73 KE6VG
Excellent video ! That third core that you tested, is it a Fair-Rite 2643251002 ? I have just started to use those due to the reported higher efficiency.
Measurement gear always helps. Those infrared gadgets would show the exact temp of the core and give you a much better clue as to temp rising and falling. I bought one for $7 ebay a while ago..... Very handy device. You just point it at what you want to measure and it gives you the temp. N6GRG
I have to wonder if the temperature rise is more of a function of wire diameter. If you used a heavier wire perhaps the temp wouldn’t rise until pumping more power through it. Thanks for the thought provoking video! 73- AA4K
With the amplifier engaged, is the Kenwood's SWR meter still showing the SWR of the antenna? Or that of the amplifier's input matching network?!? The latter, I'd presume.
Hello Colin iv been back to the transformer videos you have done a lot of times to reference things and with the 9 to 1 transformer becoming popular too I can't keep wondering what your findings on the 9to1 style I guess you are not much of a fan because of efficiency as I know that's your thing as is mine but I find myself wondering what kind of compromise is the 9to1 and is there a place for it for someone who likes efficiency in there antennas so my question is have you played with the 9to1 and if so I very much think there others who would love to see a video of your findings and opinions and recommendations on how to use these antennas for best performance and recommendations to usecase if any
I think there is some worth in thr 9:1, especially if you have a short length of coax. The Smokin Ape did a back to back test and the losses were really low. Its something I will likely look at in time.
Aw okdoki I didn't realise ape did that comparison I still look forward to see any work on it you do tho and in the mean time I'll go fine apes stuff on it
Have you ever tried 2 Type 61 cores? Lower Initial Permeability than Type 43 and more efficient. G8JNJ likes 61 type but he was testing 9:1 unun's with non-resonant antenna. Not sure if Type 61 can be used for 49:1 for EFHW????
@@MM0OPXFieldRadio FT8 is still only 50% duty cycle at most. FM or other digital modes like PSK31 or RTTY would heat it up a lot more since the transmissions can be much longer than FT8.
This is great, thanks! I think I've been fairly conservative with mine. I have built one based on 2/14 turns on an FT-240-43 for home use and I will run it on 100W SSB but tend to stick to 50W FT8, occasionally going up to 75w for short periods. I have also built one on an FT-140-43 for portable use. I tend to limit that to 50W SSB but I use it more often for 5W QRP. I had thought of making one with a couple of stacked 140-43s for portable use (box size!) in order to be able to run 100W SSB, though you've got me thinking that I might as well buy the "doubled up from the factory" thicker cores, like the other one you recommend, even though I have a couple of spare 140-43s at the moment. Have you tried 2x140-43?
I haven't tried the 2 x FT140-43. I opt for the chunky core like you say. Its not all about power handling either but transformer efficiency which you get with the chunky core.
@@MM0OPXFieldRadio I have a vague recollection that at 240 size, two or three stacked 52 material rings had a better efficiency. I know we're into a new world of hurt in terms of money now, but have you tried any other material other than 43?
I have some 52 material here and done one check so far. Its not as good as I thought. It has a much higher currie temp so more power can be run, doesnt make it any more efficient though. th-cam.com/video/TZjY2Jim7fY/w-d-xo.html
Hi Colin. Very informative video. I want to build an 80-10 m antenna based on your improved 100W transformer with 2643251002 Fair-Rite core. Where did you source mounting board for RB1065 box used in your project? Would it make any difference to use 18 AWG silicon wire instead of enamelled one in the context of heat dissipation on the core in wide spaced 2/15 turns with crossover (56:1) and both 150W SSB and 100 W digital scenario? What gauge of antenna silicon wire would you suggest to handle the load specified above? Would you be able to post parts used in your projects in descriptions of your future videos? This way you would not only inspire new HAMs like myself but also help them to build their projects. Great work!
I will try to do this in future videos. The mounting board is custom designed by me and made by JLPCB. Theres not many parts to this really. The silicone wire wont help IMO. The core would hit currie point first. This core is fine for 250w SSB.
Thanks for the good video. Many commercial transformers are rated PEP and their true rating on higher duty cycle modes is much lower. Do you think there is a frequency dimension to this as well? I have found that transformers start to become saturated at lower power levels on higher frequencies especially 10m.
I have the same toroid (the FT140-43)... what gauge of wire did you wrap around it? And what capacitor did you use? Also, great test!!! Very exciting to see!!!
I don't have the space here to test 80m here but will if I can find the space. That wasn't the purpose if this video though, it was to show the difference in core geometry and how it effects power handling back to efficiency. There is only 2g difference in weight on these 2 larger cores but wildly different power handling ability.
don't use either one. I use FT-240-52, 3 cores for 80-10m. It can handle 1500w on 40-10 and 1500w SSB on 80 but maybe 1kw with CW. On 160 I use three or four 290-43. Right now I'm using an 80m horizontal loop anyway.
I don't. The easy way is to buy a myantennas MEF-130-LP which uses the same transformer. I discovered this after Danny commented on a Facebook post I made. The case I used is an RP1065 85x80x55
I use three FT-240-43 cores with 700 watt CW and have never had a problem if i tuned to 1:2 or lower SWR. However, at high initial SWR, the cores my overheat in short order even with 100 wayys. You may want to test your choke also. Thanks for the test!
Thank You for the information. This gives me an idea what I can do with my EFHW. I think I will make one with two 240-43 using number 14 wire doing the 3//21. I am sure that that will handle all that my IC7300 will do without any trouble. 73 de W4DES
My tests were running 100w continuously on FT8, not stopping at all along with using low loss M&P coax. Most people will not transmit continuously like this.
@@MM0OPXFieldRadio Hi Colin, Just wondering if you had any idea the level of power PEP you could safely use the last transformer design you showed in this video, i.e. the one with the chunky core (#2643251002)? You say it's good for 100W data modes. Also I've seen a similar core used by Evil Lair Electronics but with a 61 mix (#2661102022) and his tests showed a slightly better performance between 40 - 10m, with performance dropping off at 80m and below. I'm looking to build one myself and as I have no interest in 80m so maybe 61 mix would be ok for me?
I ran ft8 at 100 watts for 48 hours straight. My single core 240 43 did not even get warm. My 49:1 is made with 14 awg wire also. Tested power out at the 49:1 input showed 100 watts into the 49:1. Loss in coax so low it did not show on my digital meter. Did this on 40m ft8 with a 1.0 swr on the EFHW.@@MM0OPXFieldRadio
I never chose a core based on power handling. Thats always secondary. I dont think you can gereralise either, have you seen the KN5L winding? My previous video looked at efficiency th-cam.com/video/nZ-G4hJCTSM/w-d-xo.html
Excellent "real world" testing. Very informative. Thank you.
I switched to using 2 FT240-43 cores in my 49:1 UNUNs. They seem to work better with lower SWRs than a single core. I only run 100 watts. The primary and secondary windings are separate for no common mode current in the coax.
Ideal. I did try splitting the wires but didn't notice any difference.
First time making my own unun. I was curious if i was going to eat it up doing ft8 using a stacked 240-43 with 12ga wire, looks like I should be fine. Thanks for the confirmation!
Hi Colin, great video. Your findings with the 140-43 are exactly as I have found (by accident) I built a 49:1 from a kit that was supposed to be 100W. I was a bit startled to see the SWR run away whilst running 80W for 15 minutes or so. I could run 50W for extended periods without issue. I now stack 2 x 140-43’s for my maximum available 100W. Love your work. 👍 Daryl de VK3AWA
Great comment. Same. For VK readers, the Jaycar LO1238 toroid is very close in performance, just watch out for sharp edges. VK3TXD.
Good stuff Daryl. Too much marketing nonsense out there.
Nice to see others with the same experience I built a 49:1 with ft140-43 and it took about 15min as well to overheat on ft8 @100w. I have now just finished building a 2core 49:1 using 2 ft240-43 I wanna be able to run 100-150w ft8 all day if need be
@@HamAround23 100W FT8 is a high average power. My experience is that 3 turn primaries will halve your loss, but make 15m and 10m less efficient. 2 cores will reduce loss as well, significantly. How many turns are you running? What bands? Maybe I can guess at efficiency with 1 and 2 cores - I've lots of testing this last 12 months.
A 100 watt SSB is no problem for an FT-140-43, in FM and digital modes max 25 watts!
Very interesting, keep up the good work.
Core heating can be observed in a non-contact method with almost any of the common infrared "thermometers". They are available in price ranges from $20USD to $50USD. Here in the USA, Harbor Freight has 2 different models under $50USD and 2 more between $60USD and $90 USD. I used them in weld shops for years.
The core suppliers will have the critical temps in theur specs. I have not looked them up, but I remember seeing them in the past.
Good presentation, and thanks for your testing! 73, Keith, WB2VUO here near Buffalo, NY
Yes, it can but you want to check remotely. The the transformer will fail when curie temp is reached for the specific material type.
Really interesting Colin, keep up the good work! Thanks!
Liked the video. Keep up the good work. I just built a 49:1 with the same core as the 3rd transformer you showed in the tiny box my ft140-43 transformer was in. Tight fit but it works. I can bring a 100 watt rig portable now with no overheating. 73 KE6VG
Great Robert. Its a great core, I hope it becomes more popular over the 240-43.
Thanks helpful. I have FT114-43 with 3/21 winding and run 20 watts on FT8. That is about all I would do.
Same here FT114-43 with 3/21 wire is 0.9mm if I remember correctly, and find 40W on CW is OK on 20m, 40m even when weather is hot.
The SWR "creep", core heating, also seems to be frequency dependent. I run about 50 to 150 W FT8 and only notice the swr start to creep up on 28mhz.
Yes, the more loss you have will mean more heat!
I have the same thing with mine
Excellent video ! That third core that you tested, is it a Fair-Rite 2643251002 ? I have just started to use those due to the reported higher efficiency.
Yes, I've made many videos on the 1002 core. Its fast becoming through replacement for the 240-43.
Measurement gear always helps. Those infrared gadgets would show the exact temp of the core and give you a much better clue as to temp rising and falling. I bought one for $7 ebay a while ago..... Very handy device. You just point it at what you want to measure and it gives you the temp. N6GRG
Agreed, ideally a remote temp data logger that poles continually.
What was the toroid type that you showed at the end, the best one? It wasn't mentioned in the video? Thank you.
Thank you for your Video ! It is very intressting !
Thank you 😊
I have to wonder if the temperature rise is more of a function of wire diameter. If you used a heavier wire perhaps the temp wouldn’t rise until pumping more power through it. Thanks for the thought provoking video! 73- AA4K
What I notice is the core is much hotter than the wire so think the wire has a limited effect. Definitely thought provoking though.
@@MM0OPXFieldRadio interesting!
@MM0OPXFieldRadio What is the third core you tested with?
With the amplifier engaged, is the Kenwood's SWR meter still showing the SWR of the antenna? Or that of the amplifier's input matching network?!? The latter, I'd presume.
You presume correct, the latter. Not my first rodeo 😉
Very informative, thank you! 73's
Your welcome.
Nice and informative. Thanks de Joe W1HFF
Your welcome 👍
Hello Colin iv been back to the transformer videos you have done a lot of times to reference things and with the 9 to 1 transformer becoming popular too I can't keep wondering what your findings on the 9to1 style I guess you are not much of a fan because of efficiency as I know that's your thing as is mine but I find myself wondering what kind of compromise is the 9to1 and is there a place for it for someone who likes efficiency in there antennas so my question is have you played with the 9to1 and if so I very much think there others who would love to see a video of your findings and opinions and recommendations on how to use these antennas for best performance and recommendations to usecase if any
I think there is some worth in thr 9:1, especially if you have a short length of coax. The Smokin Ape did a back to back test and the losses were really low. Its something I will likely look at in time.
Aw okdoki I didn't realise ape did that comparison I still look forward to see any work on it you do tho and in the mean time I'll go fine apes stuff on it
Have you ever tried 2 Type 61 cores? Lower Initial Permeability than Type 43 and more efficient. G8JNJ likes 61 type but he was testing 9:1 unun's with non-resonant antenna. Not sure if Type 61 can be used for 49:1 for EFHW????
I haven't but I do have ot noted. Evil Lair has been experimenting with 61 with very promising results.
It would be interesting to look at cores with an IR camera... All the Best! 73 DE W8LV BILL
Yes, ideally you have a data logger polling every few seconds so you can monitor and track the curve.
Depends hugely on the duty cycle of the mode.
100%, this is why I am testing with FT8 as its likely worst case.
@@MM0OPXFieldRadio FT8 is still only 50% duty cycle at most. FM or other digital modes like PSK31 or RTTY would heat it up a lot more since the transmissions can be much longer than FT8.
This is great, thanks! I think I've been fairly conservative with mine. I have built one based on 2/14 turns on an FT-240-43 for home use and I will run it on 100W SSB but tend to stick to 50W FT8, occasionally going up to 75w for short periods. I have also built one on an FT-140-43 for portable use. I tend to limit that to 50W SSB but I use it more often for 5W QRP.
I had thought of making one with a couple of stacked 140-43s for portable use (box size!) in order to be able to run 100W SSB, though you've got me thinking that I might as well buy the "doubled up from the factory" thicker cores, like the other one you recommend, even though I have a couple of spare 140-43s at the moment. Have you tried 2x140-43?
I haven't tried the 2 x FT140-43. I opt for the chunky core like you say. Its not all about power handling either but transformer efficiency which you get with the chunky core.
@@MM0OPXFieldRadio I have a vague recollection that at 240 size, two or three stacked 52 material rings had a better efficiency. I know we're into a new world of hurt in terms of money now, but have you tried any other material other than 43?
I have some 52 material here and done one check so far. Its not as good as I thought. It has a much higher currie temp so more power can be run, doesnt make it any more efficient though. th-cam.com/video/TZjY2Jim7fY/w-d-xo.html
Hi Colin. Very informative video. I want to build an 80-10 m antenna based on your improved 100W transformer with 2643251002 Fair-Rite core. Where did you source mounting board for RB1065 box used in your project? Would it make any difference to use 18 AWG silicon wire instead of enamelled one in the context of heat dissipation on the core in wide spaced 2/15 turns with crossover (56:1) and both 150W SSB and 100 W digital scenario? What gauge of antenna silicon wire would you suggest to handle the load specified above? Would you be able to post parts used in your projects in descriptions of your future videos? This way you would not only inspire new HAMs like myself but also help them to build their projects. Great work!
I will try to do this in future videos. The mounting board is custom designed by me and made by JLPCB. Theres not many parts to this really. The silicone wire wont help IMO. The core would hit currie point first. This core is fine for 250w SSB.
Great Channel !!!
Thank you 😊
Thanks for the good video. Many commercial transformers are rated PEP and their true rating on higher duty cycle modes is much lower. Do you think there is a frequency dimension to this as well? I have found that transformers start to become saturated at lower power levels on higher frequencies especially 10m.
Yes your spot on I think. It is frequency dependent too. If my garden was bigger I would have tested 40m instead.
I have the same toroid (the FT140-43)... what gauge of wire did you wrap around it? And what capacitor did you use? Also, great test!!! Very exciting to see!!!
I think it was 16ga and I use a 3kv 100pf as thats ample for 100w digimodes.
Hi Colin, any suggestions on where you sourced your 3kv 100pf capacitor for the FT140-43 100W version? I've heard there are some dodgy ones out there
I used Mouser when I had placed an order for other things. These are TDK. You can also try Digikey or RS Components.
80 meters is where you run into heat problems. Higher bands are not much problem. Try your experiment on 80m.
I don't have the space here to test 80m here but will if I can find the space. That wasn't the purpose if this video though, it was to show the difference in core geometry and how it effects power handling back to efficiency. There is only 2g difference in weight on these 2 larger cores but wildly different power handling ability.
don't use either one. I use FT-240-52, 3 cores for 80-10m. It can handle 1500w on 40-10 and 1500w SSB on 80 but maybe 1kw with CW. On 160 I use three or four 290-43.
Right now I'm using an 80m horizontal loop anyway.
Love the 80m loop. Had one at the old QTH and was very impressed, especially performance on 40m where it worked into the Pacific with ease.
A big Thumbs up from YFUG. I really like this Documentary Video, Colin... 💯👍👍👍🙋♂
Thank you for the kind words my friend 😊
What are the 2 wing nuts for on the ft240-43 for?
One is the antenna connection and the other is a counterpoise wire connection.
@@MM0OPXFieldRadio Cheers ,I'm new to radio do you need a counterpoise wire on the antenna? and what does it do?
Question if you mix cores can you get full coverage of 160- 10 bands also.what is the result on 6 meters as most hf radios are 6- 160 band
Possibly but using 80m of wire on 6m is a waste of time IMO.
Do you sell kits? Where can I get enclosure that fit the last toroid you showed?
I don't. The easy way is to buy a myantennas MEF-130-LP which uses the same transformer. I discovered this after Danny commented on a Facebook post I made. The case I used is an RP1065 85x80x55
Enclosures can be found at hardware stores. Waterproof electrical box. Don't waste your money on kits. Buy your own parts for 1/2 the money.
What is the exact wire length pls ? Thx
Depends what band. For 40m its around 20.55m. 20m is going to be half that. Leave it longer than this then trim to size.
Do you know what the Temperature of the toroid's were when they started to fail?
43 material has a currie point at >130c. I couldn't measure but it would be up around here.
I use three FT-240-43 cores with 700 watt CW and have never had a problem if i tuned to 1:2 or lower SWR. However, at high initial SWR, the cores my overheat in short order even with 100 wayys. You may want to test your choke also. Thanks for the test!
Thank You for the information. This gives me an idea what I can do with my EFHW. I think I will make one with two 240-43 using number 14 wire doing the 3//21. I am sure that that will handle all that my IC7300 will do without any trouble. 73 de W4DES
Double the torroids or even triple. Dissipated power should be much lower because of better efficiancy.
Maybe try immersing core in mineral oil or penut oil?
Yes it would work to keep it cooler but doesn't negate the losses.
Cose HARP start working
I have never had my 240-43 single core 49:1 unun do that at 100 watts. All I run. I run a lot of digital.
My tests were running 100w continuously on FT8, not stopping at all along with using low loss M&P coax. Most people will not transmit continuously like this.
@@MM0OPXFieldRadio Hi Colin, Just wondering if you had any idea the level of power PEP you could safely use the last transformer design you showed in this video, i.e. the one with the chunky core (#2643251002)? You say it's good for 100W data modes. Also I've seen a similar core used by Evil Lair Electronics but with a 61 mix (#2661102022) and his tests showed a slightly better performance between 40 - 10m, with performance dropping off at 80m and below. I'm looking to build one myself and as I have no interest in 80m so maybe 61 mix would be ok for me?
My antennas recommended 250w with identical core and winding.
Many thanks for the reply Colin. 73 de M0ZMT
I ran ft8 at 100 watts for 48 hours straight. My single core 240 43 did not even get warm. My 49:1 is made with 14 awg wire also. Tested power out at the 49:1 input showed 100 watts into the 49:1. Loss in coax so low it did not show on my digital meter. Did this on 40m ft8 with a 1.0 swr on the EFHW.@@MM0OPXFieldRadio
Selecting a core based on power handling capacity is OK, but selecting for loss is also important. A larger core generally has lower losses. DE WA1KLI
I never chose a core based on power handling. Thats always secondary. I dont think you can gereralise either, have you seen the KN5L winding? My previous video looked at efficiency th-cam.com/video/nZ-G4hJCTSM/w-d-xo.html
You will see an entirely different result at the exact point of resonance.
Brilliant to see real world testing. VK3TXD.
Thanks Richard. Can't believe no one has done it already and documented it here.