Awesome. As soon as you began to talk about the 80M band, it instantly made sense that you were going to say that you could install a capacitor higher up the antenna. Really helpful in helping to “tune” the EFHW antenna to ones personal needs. Thanks....73
Thanks so much for your hard work. Not only testing the antenna, but making a video is hard work. I live in a mobile home park. I was going to put up an open wire fed doublet, but I've decided to use an end fed. Your tutorials have really convinced me to go that way. Especially using an end fed 40meter as a quarter wave inverted L on 80 with your relay addition. Thanks 73
This idea with the coil originally comes from few decades ago and was proposed by the German ham DL7AB and is described in the Karl Rothammel's "Antennenbuch" ( page 185). It was then designed for the EFHW 80-10m "Zeppelin" type of antenna fed by open wire line (the pre - "49:1" transformer era :)). It is still very attractive antenna and I'm glad the coil idea was probably creatively employed by the modern days EFHW manufacturers. 73! Linas LY2H
Very interesting. I found an old version of the book in German and found the article on page 172 however I cannot read it. I can't even copy and paste it in a translator. Maybe I will order the English version for $100. Thank you.
Steve Ellington , there is not much to translate actually :). I'm not any better than Google teanslator but the essence is like this: " The radio ham DL7AB offered a simple way on how to tune the long wire antenna to resonance on all bands. The principal of work is based on the fact that the coil inserted into the antenna wire makes the electrically lengthening effect. The effect is the biggest when the coil is in the Current Antinode ( Strombauch), and this effect diminishes with the Current Nodes ( Stromknoten) approaching the coil. The picture depicts the current distribution in the wire cut to lambda/2 on 80m. When the coil is inserted at the 2.5m point from the beginning the lengthening effect on 10m band is the most since the coil finds irself exactly in the first Current Antinode. On 15 m band the coil finds itself a bit farther from the Current maximum point so its effect deminishes. Thus, with the wavelength getting longer and longer the lengthening effect of the coil getting lesser and lesser. If you choose the length of the antenna wire equal to 40 meters it turns to be a bit too short as a half w/l on 80m. But still, the lengthening effect of the coil is good enough to bring the wire into resonance on 80m band despite the coil finding itself almost in the Current Node. On 40m band the length of the wire turns to be 1,7m too short from resonance and the coil is closer to the Current Antinode and thus makes for the compensation of being too short. Equally on the other bands: on 20m band the wire physically is shorter for 2,3m, and 2,5m on the 15m band. Summarising, the lengthening effect of the coil helps to get the wire electrically correct on all ham bands due to these electrical properties of the coil acting in the float of current in the wire. " Further in the text there is a picture proposing the 5 turns of wire on the 50mm former for the coil with the latter being inserted at the 2,5m point from the beginning. The rest of the text describes the same antenna in the symmetrical dipole version and the way of tuning and pruning the antenna employing the tube type amplifier and its final LC contour checking with the Anode Current change all the way long :). Hope this helps a bit and I take no responsibility for the correctness of this translation! 73 ! Linas LY2H
@@Linas_LY2H Interesting. The modern version of this places the coil 78 inches or 2 meters from the transformer, not at the 10m anti-node. This makes me wonder.... What happens if we used another anti-node along the antenna instead of #1? It is interesting how the change on just one anti-node affects all the others.
Steve Ellington It would surely be interesting to experiment further with the placement of the coil. Some manufacturers put it as "non critical" , the place of the coil but it seems to me that putting it in any other place than the first anti-node on 10m band would seriuosly distort resonance on other bands. I have put mine at abt 2,5m from the begining and have it working fine but I have not tried putting the coil elsewhere. Interestingly, I have tried once to insert the same coil into the 40m band EFHW ( abt 20m length) at the same place of 2,5m and the result was dissapointing since the antenna got it resonances distorted on all bands including the 40 :)). So I don't use this coil on my 40-10 EFHW.
@@Linas_LY2H I think the problem you are having may be the result of installing the coil too far away from the transformer thus too far into the 40m section. The commercial versions all stop at 2 meters and it seems to work on the 40m efhw well. We use 6 turns around a 1 inch form, close spaced, insulated antenna wire.
Lucid, compact, helpful presentation and you have apparently cured your habit of saying ACROSSED when the word "across" is intended. Congratulations de NK7B. Great antenna.
The length should be around 130 feet which will put it on the low end of 80m. Doing that is necessary to make the higher bands fall into place. If you cut it shorter for 75 meters the higher bands will be too high so you need to insert a capacitor at mid point, about 400pf, to raise 80m for the phone band and not affect the higher bands. See my video on EFHW for 75 meters modification.
Is the wire for the turns just a separate piece of wire, not hooked up to anything? And you just run the antenna through the PFC pipe? How do you get the coil to stay there? Will using a 1 1/2" piece of PFC work (its what I have sitting around). THank you very much! Dave N9DMS
A question: ..for Steve... with an EFHW in a L (or maybe pretzel as may be the case in "English gardens") shape... will the changing polarization of the incoming or departing RF wave-front(s) not have the effect of cancelling each other out, reducing the efficiency by 3db or more?
Steve, you show how this coil brings the higher bands down into resonance for the CW portion of the bands and suggest a capacitor in the center if you instead want 80 meters moved up into the 75 meter portion. My question is that where i live I am afraid the capacitor would be a very weak point especially if i get any ice loading. Would it be possible to add the compensation coil (I would likely just start with a longer antenna wire and wind through the form for weather resistance) then trim the antenna down to be resonant in 75 meters which should also push the higher bands up into the SSB portion? So in essence bring down the higher bands then raise them all up together by trimming the wire.
If you try cutting the antenna for say 3.8 mhz then 40 meters will be out of band 7.6 mhz and maybe even higher! The compensation coil won't have much effect on 40 through 20 so you're out of luck. Why is the center capacitor a "weak link"? Just solder an insulator in place and jumper it with your capacitor. No strength lost.
Hi Steve, I think you answered this but just to be sure are you extending 134' wire by adding the extra 2 meters or are you shortening your main wire by 2 meters to insure your length is net 134'?
Steve didn't say, but I suspect he's using bare uninsulated wire... insulated wire as used in commercial EFHW antennas has a velocity factor of a couple of percent, so the insulated wire length will be a few feet shorter... the same antenna used by MYAntennas is 130'.. their coil is also at 2 meters. and the results (at least mine are) are similar to Steve's.
That's fine if you want 3.6 mhz then 7.2 then 14.4 then etc etc.... You should cut it for the lowest part of the 80m band and then the harmonics will land in-band. If you want 75 meters you can insert a capacitor at mid point and raise resonance for 80m up to whatever you want depending on the capacitor's value. Higher bands won't be affected.
The problem with doing that is: As you go down in frequency the transformer needs more primary turns. 160m needs 3 primary turns. 80m needs 3 but works ok with only 2 and 40 through 10m needs 2 turns. The big leap is from 80 down to 160m. The 2 turn primary will be lossy and swr high on 160m. The other problem is one of resonance. Do the math. If the wire resonantes on 1.9 mhz the harmonic will be 3.8 (actually higher) then 7.6mhz (woops) then 15.2 etc. You're way out of band and it simply won't work. The 3rd problem is radiation pattern where the 160m wire has a null overhead eliminating regional communications which is usually what you want on 80m then on the higher bands it becomes very directional off the ends. Overall the 160m version is only good on 160.
Hey Jim... I use the rig's internal tuner or if running the amp i use an external tuner. SWR is less than 2;1 without it but 1:1 keeps the current draw lower and fans off plus easier on the rig etc. Only a dummy load would be flat:*)
Steve, thank you for great video! Do you know where I have to put compensation coil If I work with EFHW-4010 transformer and 20m wire length? One meter from trensformer?
Steve, I made some testing. Yes, the coil position and inductance is approximately same on 40-10m version but I have a problem with antenna impedance on resonant frequency. My setup is: - Transformer with 2:16 turns ratio on two stacked FT140-43 cores with 110pF compensation capacitor on primary side, tested with 3k3 resistor (swr is 1.5:1 or better from 3.5MHz to 30MHz). - Antenna length is about 19,2m (63 feet) with compensation coil 2m from transformer. Antena is in inverted vee configuration (center point at 6,5m, end points at 1m) 50m away from trees and other objects. - RigExpert AA-170 antenna analyzer for measuring. I got resonance on 7, 14, 21 and 28MHz inside CW portion of band, but on 7, 14 and 28MHz impedance is about 100 ohms, and on 21MHz is about 35ohms. I'm puzzled with results... Does it mean that antenna impedance is over 6000ohms?! It sounds impossible to me.
Normally the length is 67 feet so your's is really short. I would start out with 67' of wire and no comp coil then check for swr. Add things as you go. I believe the coil should be at 2 meters, not 1. Also FT-140 cores are much more lossy than 240's. I don't know of anyone using those in a stacked cfg. My comp coil is 6' from the xfmr on my 8010 version and I see no reason to deviate from that.
My comp coil is 2m from transformer and length of antenna is 63 feet after trimming. At this length I got resonance, but impedance seen by RigExpert is about 100 ohms (100 + j0). I don't have FT240-43 core so I tried with stacked FT140-43. I measured about 1dB loss in this configuration. I have to buy FT240-43. I know, it is better.
H Steve, My 20m end fed worked out at 9.15m length for low SWR at 14.2 but the analyzer put the resonance at 14.6mhz. Low SWR on 10m was 29.2mhz. I think I need to lengthen the antenna and put up with a higher SWR? The antenna is fed as a vertical with the feed point in the clear about 6m off the ground. Looks like the coil would help on 10m but the radiation pattern as a vertical for a full wave radiator does not look good. Any comments?
David. I think the problem could be due to the feed point being 6m from ground. The shield of your coax is just the right length to begin acting as part of the antenna. This upsets the SWR. There are 2 possible cures. Lower the feed point to near ground and ground it there with a simple gnd. rod or put a common mode choke .05 wavelengths from the transformer. For 20m that would be 1 meter or 38 inches from the transformer. That gives the necessary counterpoise while not affecting the SWR much. As for the 10 meter pattern, there is not much you can do. You will have a high angle of radiation from it. It's just one of the disadvantages of multiband verticals. 73
Awesome. As soon as you began to talk about the 80M band, it instantly made sense that you were going to say that you could install a capacitor higher up the antenna. Really helpful in helping to “tune” the EFHW antenna to ones personal needs.
Thanks....73
Thanks so much for your hard work. Not only testing the antenna, but making a video is hard work. I live in a mobile home park. I was going to put up an open wire fed doublet, but I've decided to use an end fed. Your tutorials have really convinced me to go that way. Especially using an end fed 40meter as a quarter wave inverted L on 80 with your relay addition. Thanks 73
Steve thanks you for the all information about this magic antenna !
Great video - thanks for the information!
This idea with the coil originally comes from few decades ago and was proposed by the German ham DL7AB and is described in the Karl Rothammel's "Antennenbuch" ( page 185). It was then designed for the EFHW 80-10m "Zeppelin" type of antenna fed by open wire line (the pre - "49:1" transformer era :)). It is still very attractive antenna and I'm glad the coil idea was probably creatively employed by the modern days EFHW manufacturers. 73! Linas LY2H
Very interesting. I found an old version of the book in German and found the article on page 172 however I cannot read it. I can't even copy and paste it in a translator. Maybe I will order the English version for $100. Thank you.
Steve Ellington , there is not much to translate actually :). I'm not any better than Google teanslator but the essence is like this: " The radio ham DL7AB offered a simple way on how to tune the long wire antenna to resonance on all bands. The principal of work is based on the fact that the coil inserted into the antenna wire makes the electrically lengthening effect. The effect is the biggest when the coil is in the Current Antinode ( Strombauch), and this effect diminishes with the Current Nodes ( Stromknoten) approaching the coil. The picture depicts the current distribution in the wire cut to lambda/2 on 80m. When the coil is inserted at the 2.5m point from the beginning the lengthening effect on 10m band is the most since the coil finds irself exactly in the first Current Antinode. On 15 m band the coil finds itself a bit farther from the Current maximum point so its effect deminishes. Thus, with the wavelength getting longer and longer the lengthening effect of the coil getting lesser and lesser. If you choose the length of the antenna wire equal to 40 meters it turns to be a bit too short as a half w/l on 80m. But still, the lengthening effect of the coil is good enough to bring the wire into resonance on 80m band despite the coil finding itself almost in the Current Node. On 40m band the length of the wire turns to be 1,7m too short from resonance and the coil is closer to the Current Antinode and thus makes for the compensation of being too short. Equally on the other bands: on 20m band the wire physically is shorter for 2,3m, and 2,5m on the 15m band. Summarising, the lengthening effect of the coil helps to get the wire electrically correct on all ham bands due to these electrical properties of the coil acting in the float of current in the wire. " Further in the text there is a picture proposing the 5 turns of wire on the 50mm former for the coil with the latter being inserted at the 2,5m point from the beginning. The rest of the text describes the same antenna in the symmetrical dipole version and the way of tuning and pruning the antenna employing the tube type amplifier and its final LC contour checking with the Anode Current change all the way long :). Hope this helps a bit and I take no responsibility for the correctness of this translation! 73 ! Linas LY2H
@@Linas_LY2H Interesting. The modern version of this places the coil 78 inches or 2 meters from the transformer, not at the 10m anti-node. This makes me wonder.... What happens if we used another anti-node along the antenna instead of #1? It is interesting how the change on just one anti-node affects all the others.
Steve Ellington It would surely be interesting to experiment further with the placement of the coil. Some manufacturers put it as "non critical" , the place of the coil but it seems to me that putting it in any other place than the first anti-node on 10m band would seriuosly distort resonance on other bands. I have put mine at abt 2,5m from the begining and have it working fine but I have not tried putting the coil elsewhere. Interestingly, I have tried once to insert the same coil into the 40m band EFHW ( abt 20m length) at the same place of 2,5m and the result was dissapointing since the antenna got it resonances distorted on all bands including the 40 :)). So I don't use this coil on my 40-10 EFHW.
@@Linas_LY2H I think the problem you are having may be the result of installing the coil too far away from the transformer thus too far into the 40m section. The commercial versions all stop at 2 meters and it seems to work on the 40m efhw well. We use 6 turns around a 1 inch form, close spaced, insulated antenna wire.
Lucid, compact, helpful presentation and you have apparently cured your habit of saying ACROSSED when the word "across" is intended. Congratulations de NK7B. Great antenna.
Take a humility pill Mr. M.D.
The length should be around 130 feet which will put it on the low end of 80m. Doing that is necessary to make the higher bands fall into place. If you cut it shorter for 75 meters the higher bands will be too high so you need to insert a capacitor at mid point, about 400pf, to raise 80m for the phone band and not affect the higher bands. See my video on EFHW for 75 meters modification.
Nice simple explanation. Thanks so much de k1oj. dit dit
Is the wire for the turns just a separate piece of wire, not hooked up to anything? And you just run the antenna through the PFC pipe? How do you get the coil to stay there? Will using a 1 1/2" piece of PFC work (its what I have sitting around). THank you very much! Dave N9DMS
Ah right - I now understand why my Hyendfed four band classic has a similarly placed coil. Allows 15m to be resonant perhaps.
what about just shortening the antenna? wouldn't that have the same effect?
A question: ..for Steve... with an EFHW in a L (or maybe pretzel as may be the case in "English gardens") shape... will the changing polarization of the incoming or departing RF wave-front(s) not have the effect of cancelling each other out, reducing the efficiency by 3db or more?
Great!👍
I'd like to see this implemented. Can you put a video showing the coil and capacitor on the antenna? Thanks!! 73 K6TJO
I will have to look at your other videos, but are you running a 49:1 unun into this? Any idea what 30m looks like on this? N1XF
Resonance on 30m is at 10.7 mhz so it's a bit out of band. SWR is about 3:1 so you will need the tuner. Still an easy match and quiet usable.
Steve, you show how this coil brings the higher bands down into resonance for the CW portion of the bands and suggest a capacitor in the center if you instead want 80 meters moved up into the 75 meter portion. My question is that where i live I am afraid the capacitor would be a very weak point especially if i get any ice loading. Would it be possible to add the compensation coil (I would likely just start with a longer antenna wire and wind through the form for weather resistance) then trim the antenna down to be resonant in 75 meters which should also push the higher bands up into the SSB portion? So in essence bring down the higher bands then raise them all up together by trimming the wire.
If you try cutting the antenna for say 3.8 mhz then 40 meters will be out of band 7.6 mhz and maybe even higher! The compensation coil won't have much effect on 40 through 20 so you're out of luck.
Why is the center capacitor a "weak link"? Just solder an insulator in place and jumper it with your capacitor. No strength lost.
Thank You ! 73's
Good to know this, thanks! I may well give it a try.
Hi Steve, I think you answered this but just to be sure are you extending 134' wire by adding the extra 2 meters or are you shortening your main wire by 2 meters to insure your length is net 134'?
If you take a tape measure and stretch it out along side the entire antenna it should indicate 134 feet. Coil or no coil.
Steve didn't say, but I suspect he's using bare uninsulated wire... insulated wire as used in commercial EFHW antennas has a velocity factor of a couple of percent, so the insulated wire length will be a few feet shorter... the same antenna used by MYAntennas is 130'.. their coil is also at 2 meters. and the results (at least mine are) are similar to Steve's.
what voltage rating would be needed for the capacitor??? thanks
I just use a 5kv doorknob type capacitor so I don't need to worry about it. In case of lightning it can take a beating.
Steve, The old standby formula of 468 / resonant frequency desired of 3.6 MHz should be length of 130 ft. Why did you need 134' or more? Just curious.
That's fine if you want 3.6 mhz then 7.2 then 14.4 then etc etc.... You should cut it for the lowest part of the 80m band and then the harmonics will land in-band. If you want 75 meters you can insert a capacitor at mid point and raise resonance for 80m up to whatever you want depending on the capacitor's value. Higher bands won't be affected.
Would it be possible to extend given efhw antenna ( with compensation coil ) for 160-10m?
The problem with doing that is: As you go down in frequency the transformer needs more primary turns. 160m needs 3 primary turns. 80m needs 3 but works ok with only 2 and 40 through 10m needs 2 turns. The big leap is from 80 down to 160m. The 2 turn primary will be lossy and swr high on 160m. The other problem is one of resonance. Do the math. If the wire resonantes on 1.9 mhz the harmonic will be 3.8 (actually higher) then 7.6mhz (woops) then 15.2 etc. You're way out of band and it simply won't work. The 3rd problem is radiation pattern where the 160m wire has a null overhead eliminating regional communications which is usually what you want on 80m then on the higher bands it becomes very directional off the ends. Overall the 160m version is only good on 160.
@@n4lq tu fer ur advice, 73.
Can this antenna be fine adjusted ? I mean like making it shorter/longer on 80 improving swr?
Do you have an swr problem?
@@n4lq Not yet. Thinking about building one. Just wondering, given that an ordinary efhw can be fine tuned by cutting.
So you are not using a antenna tuner at all with this? This might be a good antenna for my new QTH.
Hey Jim... I use the rig's internal tuner or if running the amp i use an external tuner. SWR is less than 2;1 without it but 1:1 keeps the current draw lower and fans off plus easier on the rig etc. Only a dummy load would be flat:*)
Steve, thank you for great video! Do you know where I have to put compensation coil If I work with EFHW-4010 transformer and 20m wire length? One meter from trensformer?
I have not tried this but seems that your coil would be located at the same distance from the transformer as the 80-10 version.
I will try. Thank you!
73 de 9A5CZI
Steve, I made some testing. Yes, the coil position and inductance is approximately same on 40-10m version but I have a problem with antenna impedance on resonant frequency.
My setup is:
- Transformer with 2:16 turns ratio on two stacked FT140-43 cores with 110pF compensation capacitor on primary side, tested with 3k3 resistor (swr is 1.5:1 or better from 3.5MHz to 30MHz).
- Antenna length is about 19,2m (63 feet) with compensation coil 2m from transformer. Antena is in inverted vee configuration (center point at 6,5m, end points at 1m) 50m away from trees and other objects.
- RigExpert AA-170 antenna analyzer for measuring.
I got resonance on 7, 14, 21 and 28MHz inside CW portion of band, but on 7, 14 and 28MHz impedance is about 100 ohms, and on 21MHz is about 35ohms.
I'm puzzled with results... Does it mean that antenna impedance is over 6000ohms?! It sounds impossible to me.
Normally the length is 67 feet so your's is really short. I would start out with 67' of wire and no comp coil then check for swr. Add things as you go. I believe the coil should be at 2 meters, not 1. Also FT-140 cores are much more lossy than 240's. I don't know of anyone using those in a stacked cfg. My comp coil is 6' from the xfmr on my 8010 version and I see no reason to deviate from that.
My comp coil is 2m from transformer and length of antenna is 63 feet after trimming. At this length I got resonance, but impedance seen by RigExpert is about 100 ohms (100 + j0).
I don't have FT240-43 core so I tried with stacked FT140-43. I measured about 1dB loss in this configuration.
I have to buy FT240-43. I know, it is better.
H Steve, My 20m end fed worked out at 9.15m length for low SWR at 14.2 but the analyzer put the resonance at 14.6mhz. Low SWR on 10m was 29.2mhz. I think I need to lengthen the antenna and put up with a higher SWR? The antenna is fed as a vertical with the feed point in the clear about 6m off the ground. Looks like the coil would help on 10m but the radiation pattern as a vertical for a full wave radiator does not look good. Any comments?
David. I think the problem could be due to the feed point being 6m from ground. The shield of your coax is just the right length to begin acting as part of the antenna. This upsets the SWR. There are 2 possible cures. Lower the feed point to near ground and ground it there with a simple gnd. rod or put a common mode choke .05 wavelengths from the transformer. For 20m that would be 1 meter or 38 inches from the transformer. That gives the necessary counterpoise while not affecting the SWR much.
As for the 10 meter pattern, there is not much you can do. You will have a high angle of radiation from it. It's just one of the disadvantages of multiband verticals. 73