I've watched this video several times. I finally got off my kiester and made it! I had to buy a meter, but wanted one anyhow. I had fin with this project. It works! I still have to tune just a bit... thanks for making this video. Very articulate! Well done kind sir.
Colin: I made a much heavier-duty coil for my 80 meter loading coil. The former was 4" PVC drain line, and the coil was wound with 14-ga insulated stranded wire. 43 turns with a winding length of 6 1/2 inches. It measured out at 103uH. All hardware was stainless steel, 1/4-20 coarse thread, double-nutted with spring lock washers. Beefy! I am glad that I made it heavy-duty as our 2022 Xmas blizzard here near Buffalo, NY had 2 days of winds in excess of 55 mph with peak gusts near 80 mph! The coil came through unharmed. This shortened 80 meter design is the first antenna for the band that fits in my very small urban lot. Great video, very informative. Looking forward to a video of the complete antenna. 73, Keith, WB2VUO here near Buffalo, NY
Your video helped me tremendously. I needed an 80 meter antenna that would fit in a 70 foot long area and this design did it. It works like a dream eventhough it's feed point is just 6 inches off the ground and the coil end is only 22 feet in the air. Thank you!!
I tuned it to 3.975. Typically coiled antennas have a high Q and narrow bandwidth, so if changed frequencies I often had to use my tuner. But it works great across the 20 meter band without a tuner.
Hi Colin! Thanks for sharing! I now have a loading coil for the EFHW I am putting up in the garden. Some tips for others - do use the calculator in the link shared in the information above to make sure the resulting inductance is the 110uH you want. I used thicker wire (1.6mm - because I had it), so of course it won't be 65mm long once I have the right number of turns. I found that 100 turns is about 175mm long. After several iterations with the calculator, I ended up with 110 turns on a 43mm former (+ the wire thickness, since the diameter in the calculator is to the wire centre on the coil) and the coil ended up 19.8 cm long. The third time I cut the former (!!), I left it long, and cut it to length after I finished winding the coil. The final value of inductance on the coil is 0.11mH according to my cheap component checker - so bang on! Now I need to get the wire up and tune it. I assume I tune 40m before adding the coil, then tune the 80m tail? 73, Paul (MW7PAJ)
Got one of these in the garden Colin, works really well and haven’t noticed any depreciation in performance on 80mtr. Best thing is no ATU and can easily change bands without the need to tune up.
I made a similar, much larger coil, using the same calculator using some 110mm plastic waste pipe and some 1.6mm galvanised steel fencing wire I had left over. Can't just remember exactly how many turns but it's around 14" long and can be tapped at any point for a good match. It will easily handle 100w and works well for 80m and also tunes up for 160 although it's very much a compromise for top band. It's size obviously limits it's portability unlike yours which will easily fit in a pocket!👍 Call me a cheapskate but I find experimenting with and building antennas "on the cheap" like this very rewarding.😃.
Definitely. I throw nothing away that I know can be used in an antenna. Eventually you get to a point where you have everything you need, if you can find it that is.
I created my own antenna similar to this one only I used 26 gauge copper wire, around a solid cardboard pipe wrapped about 200 times or more. To get a good signal...I use it for FM reception and it works well.
Hi Colin, I use one of these antennas at my QTH and one for portable ops. They work very well. Another benefit is the ability to tune the 40m and 80m sections as two independent antennas with no interaction between each during tuning. Good video as always. Cheers Daryl de VK3AWA. By the way, I have purchased one of Billy’s antenna switches based on your video on it.
Thanks for letting me know Daryl. The way I see it your not loosing anything but gaining something even if it's not ideal. Billy makes great stuff for the ham radio community. I've known him for years after meeting at a local club. We got licensed around the same time. He is selfless and will help anyone without asking for anything in return.
@@adamjlairepaquibolooc7129 A Dutch or Belgian guy tried it, did all the calculations for coils, impedances, etc. but found it did not work at all well. He also said that it was pretty much impossible to get a good match on more than one band. As soon as he adjusted for one band, any of the others would become unusable. After a week or two tearing his hair out, he gave up on the idea. You could make a multiband delta in the same way you would make a quad (obviously it would be 2 sided, not 4). The outside delta would be the lowest frequency, getting smaller as you move inwards. Adding a loading coil to the delta is where it all goes pear shaped. I've only used a 20m circumference/perimeter delta, fed via a 4:1 balun. This gave a perfect match on 10m (on that band it was a a 2 wavelength loop so would have had some gain). The match on 20m was, as you may suspect, around 2:1, as the Z of a 1 lambda delta is around 100R. That was a pretty good antenna but was only good for 20-10m. I didn't have a decent external atu at that time and the FTdx10 internal atu wouldn't touch it below 14MHz. Now I use an EFHW and will be adding an 80m coil soon. 73, Sean - G4UCJ
If the loading coil is a little low, just cut the end wire a bit longer. It will just give you a wider usable bandwidth in the end. I have a coil loaded Dipole for 80M at my QTH, because my yard is far too small for a big one. I set it up as an inverted U with the horizontals out to the coils and the trailing ends as the vertical elements and it works beautifully. With a tuner I can hit everything in the 80 Meter band, but it's resonant in the voice section.
@@paulsengupta971 I have no way to compare this to an EFHW, but the coils are the same. In the end, the exact impedance is not critical, you make up the difference with the length of the wire. The whole purpose for the coils in the leg is to make them "appear" electrically longer to the radio.
Update to the update. I've discovered that this antenna design also works as a 10, 15, 20, and 40 meters as well using a tuner. No tuner is necessary on 20 meters....amazing.
Hi Colin, good to see another video from you, and of course we will be watching the follow up video, to see how it works. I did something similar, but I added a 7.3mhz trap at the top of my 40m vertical and from the trap I added another 10m length of wire to get 80m and 40m without the loading coil. I also found with a tuner it would work on most bands. Good luck mate, 73 zl3xdj.
Thanks Brian. It will be a compromise but get you on the band at least. Many years ago I also did what you mentioned. This was popularised by Len GM0ONX. It worked but Its location in garden and lack of radials made it far from efficient. In the right location I know it would work well.
You are measuring the inductance at 1kHz and it will be significantly higher in the 80m band. I made an inductor with 80T of 0.9mm wire on a 36mm diameter former and measured it with a NanoVNA. It was 89uH at 90kHz and 110uH at 3.7MHz.
I leave the LCR meter set to auto. The Meter measured almost exactly as the 66 pacific calculator. It doesn't need to be spot on as you cut your wire beyond to 80m resonance.
Quoting someone much smarter than me "Since, inductance is a property, it is a constant and does not depend on any factor and hence does not depend on the frequency. The inductance depends on the make of a conductor. Therefore, the inductance does not depend on the frequency."
Thanks for good information. Given that this antenna should work at 10, 15, 20, 40 and 80 meter band... how do we tune/cut it to lowest swr? I mean, the longer part of antenna...which goes from the transformer to the coil... at what band should we tune it?
Only the bit beyond the coil is for 80m. Tune the wire with only the coil at the far end for 40/20/15/10. Add the remainder on far side of coil for 80m and tune.
Any suggestion on how to make this build resonant on 75 meters? Some content creators insert a capacitor at some defined point, but their build is different. I enjoy this antenna, and it works beautifully. But I'd like better SWR on 75 m. Thanks.
@@MM0OPXFieldRadio I bought one of the commercial ones off someone on e-bay. However I wanted one which fit around my telescopic pole, so I made one using a tube from some silicone sealant, which should fit over the pole. My LCR meter seems way out, but I made my new one to report the same inductance as the commercial one!
I guess the same could be used to add 40m to a 20m EFHW? That would be really cool for portable use, making it possible to have 40m with a relatively short antenna. The coil could even be constructed more compact for use with a small 5 watt radio like the QMX. Do you know what inductance it would need to be?
I have room for an 80m inverted V between the first floor roof of my shack, the 2nd story roof and the roof of a backyard ramada. I am thinking about optimizing 40 and 80 for NCIS allowing the harmonic bands to reach Dx heights (relative to wavelength). I could switch in a coil at the apex with a relay for 160m.
Just noticed that autocorrect changed NVIS to NCIS (and just tried three more times). I have since seen that some people bypass the transformer completely to use the wire as a quarter wave at 160m
A 66 foot long end fed, assuming it’s configured as an inverted L or even a low horizontal wire for NVIS type work, can be fed directly from a 50 ohm coax feed line without the usual 9:1 or 49:1 end fed transformer as a quarter wave radiator on 80/75 meters. I keep a nominal 66 foot wire in my mobile kit, and use it as a quarter wave wire when parked as a sloper or inverted L hung from a tree or as a low horizontal wire, connected instead of the normal mobile whip at the mobile antenna’s base at the left rear corner of the truck above the fender line. Like with the mobile whips on 80/75, a small inductive shunt coil or capacitor (500-1000 pf) across the feed point allows my IC-7100, which does not have an internal antenna tuner, achieve a near perfect 1:1 SWR match at resonance. The quarter wave wire works against the truck body as a counterpoise just as the mobile whip would. If desired , improved efficiency can be obtained by deploying some wire ground radials connected to the truck body at the feedpoint. If using a quarter wave wire in the field, you obviously will need to have some wire radials as a counterpoise. I’ve observed that a quarter wave low to ground horizontal wire for NVIS short haul propagation gives at least a 10 dB improvement over a good 75 meter mobile antenna when using just the truck body as the counterpoise in either case. Chris AJ1G Stonington CT
This was my first antenna...worked "OK" ....now my EFHW is full 1/2 wave for 80m as an inverted V configuration supported at the centre on a 9m squid pole strapped to my chimney ...much better! de VK2AOE.
How did it work? Did 75 turns give you a resonant antenna on 80 meters? How much power could you rate this coil? Can one use insulated wire to make a coil?
To be honest I havent put it on the air yet. This is thin wire so guessing 50w or so. Thicker wire needed for 100w+ .Insulated wire will work just as well but will likely need more turns as its effectively wider spacing.
Just made up one of these coils, My inductance meter says its around 100uh, Was originally 110uh, But by the time i put it all together it had dropped to around 100uh, Problem is its resonant around 2.2 Mhz, Taking a few turns off and trimming the pigtail made little difference, My EFHW is only around 5m high, Reckon that's what's causing it to detune on 80m
@@MM0OPXFieldRadio Thanks for the reply, Aye that's what it turned out to be, Last ten feet or so was running down a pole in an inverted vee configuration, Which meant the stub after the coil was only a few feet above ground, Tried another configuration and it now works a treat, 150 Khz of bandwidth on 80m. Coil is only 98 uh so i had to make the stub longer (7 feet) SWR on the other bands is much the same, Infact its reduced my SWR on 10m 😃
I'm curious about opinions from those that got to experiment a little more than me. I made this version some while ago... but I only had 0.7mm wire for the coil... so I ended up with a tight bandwidth on 80m. My question... since I have a really long backyard... wouldn't be better to use a proper 1/2 halfwave on 80m wire ? It should work better and have a better bandwidth I guess right ? 73 Colin. I'm still hunting you for my log )))
@@dxexplorer That's what I've got set up in my GW QTH, a wire slightly longer than 40m total length. If you are into SSB on 80m then a capacitor in the middle of the wire will electrically shorten the wire on 80m to bring up the frequency of resonance on that band. A search will find a variety of ways to do this and capacitance value. I haven't done it yet but I've bought a capacitor ready!
@@MM0OPXFieldRadio not for me. The LCR meter gives me the reactance at like 1kHz. I prefer to see the inductance or capacitance at my operating frequency. The nanoVNA lets me do that. I could be way off with the LCR meter.
I've watched this video several times. I finally got off my kiester and made it! I had to buy a meter, but wanted one anyhow. I had fin with this project. It works! I still have to tune just a bit... thanks for making this video. Very articulate! Well done kind sir.
Colin: I made a much heavier-duty coil for my 80 meter loading coil. The former was 4" PVC drain line, and the coil was wound with 14-ga insulated stranded wire. 43 turns with a winding length of 6 1/2 inches. It measured out at 103uH. All hardware was stainless steel, 1/4-20 coarse thread, double-nutted with spring lock washers. Beefy!
I am glad that I made it heavy-duty as our 2022 Xmas blizzard here near Buffalo, NY had 2 days of winds in excess of 55 mph with peak gusts near 80 mph! The coil came through unharmed. This shortened 80 meter design is the first antenna for the band that fits in my very small urban lot.
Great video, very informative. Looking forward to a video of the complete antenna.
73, Keith, WB2VUO here near Buffalo, NY
Thanks, once the warmer weather is here I will get ot set up to test.
Hey Colin! I wound up a coil like this, and ended up at 108uH and it works pretty well. Your video was the inspiration to make it. Thanks!
Thank you. Honestly this this video was thrown together in 10 minutes as someone asked me and its now my No1 video. Go figure. I'm glad it helped.
Your video helped me tremendously. I needed an 80 meter antenna that would fit in a 70 foot long area and this design did it. It works like a dream eventhough it's feed point is just 6 inches off the ground and the coil end is only 22 feet in the air. Thank you!!
I'm glad its working, I've yet to put mine up.
Just curious as to what part of 80 meters do you get?
I tuned it to 3.975. Typically coiled antennas have a high Q and narrow bandwidth, so if changed frequencies I often had to use my tuner. But it works great across the 20 meter band without a tuner.
Hi Colin! Thanks for sharing! I now have a loading coil for the EFHW I am putting up in the garden. Some tips for others - do use the calculator in the link shared in the information above to make sure the resulting inductance is the 110uH you want. I used thicker wire (1.6mm - because I had it), so of course it won't be 65mm long once I have the right number of turns. I found that 100 turns is about 175mm long. After several iterations with the calculator, I ended up with 110 turns on a 43mm former (+ the wire thickness, since the diameter in the calculator is to the wire centre on the coil) and the coil ended up 19.8 cm long. The third time I cut the former (!!), I left it long, and cut it to length after I finished winding the coil. The final value of inductance on the coil is 0.11mH according to my cheap component checker - so bang on! Now I need to get the wire up and tune it. I assume I tune 40m before adding the coil, then tune the 80m tail? 73, Paul (MW7PAJ)
Yes the inductance can vary due to many factors. I find the LCR meter invaluable.
Got one of these in the garden Colin, works really well and haven’t noticed any depreciation in performance on 80mtr. Best thing is no ATU and can easily change bands without the need to tune up.
Thanks for the feedback. I've yet to set up mine.
I made a similar, much larger coil, using the same calculator using some 110mm plastic waste pipe and some 1.6mm galvanised steel fencing wire I had left over. Can't just remember exactly how many turns but it's around 14" long and can be tapped at any point for a good match. It will easily handle 100w and works well for 80m and also tunes up for 160 although it's very much a compromise for top band. It's size obviously limits it's portability unlike yours which will easily fit in a pocket!👍
Call me a cheapskate but I find experimenting with and building antennas "on the cheap" like this very rewarding.😃.
Definitely. I throw nothing away that I know can be used in an antenna. Eventually you get to a point where you have everything you need, if you can find it that is.
I created my own antenna similar to this one only I used 26 gauge copper wire, around a solid cardboard pipe wrapped about 200 times or more. To get a good signal...I use it for FM reception and it works well.
Another comment. This antenna also works great on 20 meters. Last night, during the DX competition, I had nine contacts at or close to 6,000 miles!
So many people are having great results from a properly constructed EFHW.
Hi Colin, I use one of these antennas at my QTH and one for portable ops. They work very well. Another benefit is the ability to tune the 40m and 80m sections as two independent antennas with no interaction between each during tuning. Good video as always. Cheers Daryl de VK3AWA. By the way, I have purchased one of Billy’s antenna switches based on your video on it.
Thanks for letting me know Daryl. The way I see it your not loosing anything but gaining something even if it's not ideal. Billy makes great stuff for the ham radio community. I've known him for years after meeting at a local club. We got licensed around the same time. He is selfless and will help anyone without asking for anything in return.
@@MM0OPXFieldRadio hey can you make a shortened delta loop antenna
You can but loading it up will likely prevent it from being multiband.
@@adamjlairepaquibolooc7129 A Dutch or Belgian guy tried it, did all the calculations for coils, impedances, etc. but found it did not work at all well. He also said that it was pretty much impossible to get a good match on more than one band. As soon as he adjusted for one band, any of the others would become unusable. After a week or two tearing his hair out, he gave up on the idea. You could make a multiband delta in the same way you would make a quad (obviously it would be 2 sided, not 4). The outside delta would be the lowest frequency, getting smaller as you move inwards. Adding a loading coil to the delta is where it all goes pear shaped. I've only used a 20m circumference/perimeter delta, fed via a 4:1 balun. This gave a perfect match on 10m (on that band it was a a 2 wavelength loop so would have had some gain). The match on 20m was, as you may suspect, around 2:1, as the Z of a 1 lambda delta is around 100R. That was a pretty good antenna but was only good for 20-10m. I didn't have a decent external atu at that time and the FTdx10 internal atu wouldn't touch it below 14MHz. Now I use an EFHW and will be adding an 80m coil soon. 73, Sean - G4UCJ
@@scarlettgilbert1388 Are you suggesting a fan delta? Interesting. I'll let someone else try it!
Great instructions. You simplified this enough I was able to follow along. I bookmarked this for future reference. Thank you.
Thank you. This was my intention. It will never be a video that will get a lot of views but useful to those who need a guide.
@@MM0OPXFieldRadio 45k views so far! 🙂
Very helpful. I just finished making my EFHW. Question: What SWR are you seeing along the 80 meter band? I'm getting 1: 2.4 to 1:2.7.
Beautifully and simple built, Colin! 💯👍🙋♂
Thank you for the kind words UG 🙏
@@MM0OPXFieldRadio You welcome
Excellent video. Very neat construction too. Cheers.
If the loading coil is a little low, just cut the end wire a bit longer. It will just give you a wider usable bandwidth in the end. I have a coil loaded Dipole for 80M at my QTH, because my yard is far too small for a big one. I set it up as an inverted U with the horizontals out to the coils and the trailing ends as the vertical elements and it works beautifully. With a tuner I can hit everything in the 80 Meter band, but it's resonant in the voice section.
Excellent hint 👌
Are the two coils both 110uH? i.e. are they the same as for a single legged EFHW?
@@paulsengupta971 I have no way to compare this to an EFHW, but the coils are the same. In the end, the exact impedance is not critical, you make up the difference with the length of the wire. The whole purpose for the coils in the leg is to make them "appear" electrically longer to the radio.
Update to the update. I've discovered that this antenna design also works as a 10, 15, 20, and 40 meters as well using a tuner. No tuner is necessary on 20 meters....amazing.
The magic of radio 📻 ✨️
The point of this antenna is that no tuner should be necessary on any of those bands. It may need a compensation coil and/or capacitance.
Hi Colin, good to see another video from you, and of course we will be watching the follow up video, to see how it works.
I did something similar, but I added a 7.3mhz trap at the top of my 40m vertical and from the trap I added another 10m length of wire to get 80m and 40m without the loading coil.
I also found with a tuner it would work on most bands.
Good luck mate, 73 zl3xdj.
Thanks Brian. It will be a compromise but get you on the band at least. Many years ago I also did what you mentioned. This was popularised by Len GM0ONX. It worked but Its location in garden and lack of radials made it far from efficient. In the right location I know it would work well.
Great video. I noticed that you used 0.63 mm enameled wire. What is the max transmitting power (watts) that this coil can handle?
Depends on duty cycle a lot. I haven't ran at 100w SSB but would give it a go.
You are measuring the inductance at 1kHz and it will be significantly higher in the 80m band. I made an inductor with 80T of 0.9mm wire on a 36mm diameter former and measured it with a NanoVNA. It was 89uH at 90kHz and 110uH at 3.7MHz.
I leave the LCR meter set to auto. The Meter measured almost exactly as the 66 pacific calculator. It doesn't need to be spot on as you cut your wire beyond to 80m resonance.
Quoting someone much smarter than me "Since, inductance is a property, it is a constant and does not depend on any factor and hence does not depend on the frequency. The inductance depends on the make of a conductor.
Therefore, the inductance does not depend on the frequency."
Thanks for good information. Given that this antenna should work at 10, 15, 20, 40 and 80 meter band... how do we tune/cut it to lowest swr? I mean, the longer part of antenna...which goes from the transformer to the coil... at what band should we tune it?
Only the bit beyond the coil is for 80m. Tune the wire with only the coil at the far end for 40/20/15/10. Add the remainder on far side of coil for 80m and tune.
Any suggestion on how to make this build resonant on 75 meters? Some content creators insert a capacitor at some defined point, but their build is different. I enjoy this antenna, and it works beautifully. But I'd like better SWR on 75 m. Thanks.
To get both 75 and 80 I think you will be toiling. The bands are just too close together. We dont have 75m here.
@@MM0OPXFieldRadio Thanks!
I build similar and found it worked quite well, also. I was happy. Enjoyed the video. Ta.
Thanks Richard. I see there is a few commercial ones and these seem to be wound on smaller longer formers.
@@MM0OPXFieldRadio I bought one of the commercial ones off someone on e-bay. However I wanted one which fit around my telescopic pole, so I made one using a tube from some silicone sealant, which should fit over the pole. My LCR meter seems way out, but I made my new one to report the same inductance as the commercial one!
I guess the same could be used to add 40m to a 20m EFHW? That would be really cool for portable use, making it possible to have 40m with a relatively short antenna. The coil could even be constructed more compact for use with a small 5 watt radio like the QMX. Do you know what inductance it would need to be?
Correct. It has been done but not by me. I think Tim G5TM made some videos on this.
@@MM0OPXFieldRadio ok cool I'll check him out, thanks!!!
I have room for an 80m inverted V between the first floor roof of my shack, the 2nd story roof and the roof of a backyard ramada. I am thinking about optimizing 40 and 80 for NCIS allowing the harmonic bands to reach Dx heights (relative to wavelength). I could switch in a coil at the apex with a relay for 160m.
Yeah thats an option. You could have another trap but bandwidth on 160 would be very narrow.
Just noticed that autocorrect changed NVIS to NCIS (and just tried three more times). I have since seen that some people bypass the transformer completely to use the wire as a quarter wave at 160m
Yes seen that. You need a big radial field tho. Not difficult to install a SPDT relay and switch it remotely.
Great video, gave me confidence to have a go
Thats what it's all about 👍
Hi! does it have to be an air coil to work properly, or can it be with a core to wind fewer turns? if only air, why? 73
You can wind it on a solid former if you wish as long as its non conductive. What matters is the inductive value.
110uh coil for good SWR 3.600 khz ?
80 uh coil swr for 3.750 khz ?
No, remember you have a piece of wire that extends beyond the coil. Make it 110uh and fine tune by lengthening or shortening the wire.
A 66 foot long end fed, assuming it’s configured as an inverted L or even a low horizontal wire for NVIS type work, can be fed directly from a 50 ohm coax feed line without the usual 9:1 or 49:1 end fed transformer as a quarter wave radiator on 80/75 meters. I keep a nominal 66 foot wire in my mobile kit, and use it as a quarter wave wire when parked as a sloper or inverted L hung from a tree or as a low horizontal wire, connected instead of the normal mobile whip at the mobile antenna’s base at the left rear corner of the truck above the fender line. Like with the mobile whips on 80/75, a small inductive shunt coil or capacitor (500-1000
pf) across the feed point allows my IC-7100, which does not have an internal antenna tuner, achieve a near perfect 1:1 SWR match at resonance. The quarter wave wire works against the truck body as a counterpoise just as the mobile whip would. If desired , improved efficiency can be obtained by deploying some wire ground radials connected to the truck body at the feedpoint. If using a quarter wave wire in the field, you obviously will need to have some wire radials as a counterpoise. I’ve observed that a quarter wave low to ground horizontal wire for NVIS short haul propagation gives at least a 10 dB improvement over a good 75 meter mobile antenna when using just the truck body as the counterpoise in either case.
Chris AJ1G Stonington CT
There are videos of the 80m EFHW (132ft wire) acting as a quarter wave on 160m (with radials). There's relay box to switch the transformer in and out.
Would a 220uh coil give you 160m ?
I dont think so. Logical thinking but but more to it. Possible to do though but you will lose 80m.
A great little vid. What is the wire for the inductor, link possibly? Cheers, Gary, 2E0IGD.
Of course, here you go brocott.co.uk/0-63mm-enamelled-copper-winding-wire-250g/
This was my first antenna...worked "OK" ....now my EFHW is full 1/2 wave for 80m as an inverted V configuration supported at the centre on a 9m squid pole strapped to my chimney ...much better! de VK2AOE.
Any antenna on 80m has got to be bettet than none.
Excellent much appreciated
How did it work? Did 75 turns give you a resonant antenna on 80 meters? How much power could you rate this coil? Can one use insulated wire to make a coil?
To be honest I havent put it on the air yet. This is thin wire so guessing 50w or so. Thicker wire needed for 100w+ .Insulated wire will work just as well but will likely need more turns as its effectively wider spacing.
Just made up one of these coils, My inductance meter says its around 100uh, Was originally 110uh, But by the time i put it all together it had dropped to around 100uh, Problem is its resonant around 2.2 Mhz, Taking a few turns off and trimming the pigtail made little difference, My EFHW is only around 5m high, Reckon that's what's causing it to detune on 80m
Ground effect can make a massive difference. Sounds like something is interacting.
@@MM0OPXFieldRadio Thanks for the reply, Aye that's what it turned out to be, Last ten feet or so was running down a pole in an inverted vee configuration, Which meant the stub after the coil was only a few feet above ground, Tried another configuration and it now works a treat, 150 Khz of bandwidth on 80m. Coil is only 98 uh so i had to make the stub longer (7 feet) SWR on the other bands is much the same, Infact its reduced my SWR on 10m 😃
Glad you got it resolved.
I'm curious about opinions from those that got to experiment a little more than me. I made this version some while ago... but I only had 0.7mm wire for the coil... so I ended up with a tight bandwidth on 80m. My question... since I have a really long backyard... wouldn't be better to use a proper 1/2 halfwave on 80m wire ? It should work better and have a better bandwidth I guess right ? 73 Colin. I'm still hunting you for my log )))
Your thinking is correct. You will however have huge nulls and lobes using such a long wire on the higher bands. Give it a go, could be great.
@@MM0OPXFieldRadio I will do it this coming week and see the results. I'm curious 😁
@@dxexplorer That's what I've got set up in my GW QTH, a wire slightly longer than 40m total length. If you are into SSB on 80m then a capacitor in the middle of the wire will electrically shorten the wire on 80m to bring up the frequency of resonance on that band. A search will find a variety of ways to do this and capacitance value. I haven't done it yet but I've bought a capacitor ready!
We used to buy LCR meters because we couldn't afford ~$10,000 for a VNA. Now VNAs are so cheap, we no longer need LCR meters.
Your right but tje LCR meter is so convenient to use.
@@MM0OPXFieldRadio not for me. The LCR meter gives me the reactance at like 1kHz. I prefer to see the inductance or capacitance at my operating frequency. The nanoVNA lets me do that. I could be way off with the LCR meter.
excellent
Thanks 👍
I think it was a design from GM0ONX if I remember correctly.
I'm not sure. Are you maybe thinking of the trapped inverted L for 40/80 that Len is well known for?
Use a magnetic loop instead of
I need to make another one of these.
Your meter leads are long adds to inductance
The meter is calibration with these fitted so dont see any real issue.