Mike you once said in a video you made talking about tools, “I don’t need a fluke I am an amateur”. Brother this is why you’re not an “amateur” the way people think about it. The trip through the rabbit hole is beautiful, now you own it. What makes it great, you’re sharing it. Your deep dive on the subject and the fact you're sharing what you learned, this collaboration is what I love about being an member of Amateur Radio. Great Job!
Wow! I'm exhausted just listening to this. You said it best at 21:37 -"I don't think it's worth it." Good info though. For me? I'll just throw the tuner in the go bag. It's not that heavy. This is also why I keep a Slidewinder coil, spike, mirror mount, and CHA SS17 in the go box for POTA. Or better yet, your favorite - an ATAS-120 - which I don't own one yet. It's on the list though. My life is complicated enough. Keep it Simple. 😉
The other thing about using a trap for every band is that you then lose the rest of the length of the wire for that band, limiting the length to the first half wave. Tim, G5TM, has videos where he has created a dual band EFHW with a trap, but not a trap with inductance and capacitance, but inductance only. I believe this sort of thing was what Alan was talking about in his e-mail. Tim has his set up for use as a vertical antenna for portable operation. The extra inductance, as mentioned, shortens the overall length somewhat. I think Tim mentions that a trap will throw off the resonance for the whole length, making it non resonant on harmonics...or maybe that was a discussion in the comments - or maybe it was Peter Waters who said that in his videos.
Bravo Mike. This was well done. Aside from the topic of traps, what I really read between the lines is just how important having good Elmers are. Keep digging, learning and sharing. 73 OM
Wow! Just wow on the amount of digging you did on this one! Great information, loved learning about it but I don't know that i would have followed that rabbit for as long as you did. Thanks for the work!
Wow, just wow. My brain exploded around 12:23 into the video. Kudos for chasing this brother. You never cease to provide useful information with a witty delivery...Kudos.
Great video. I like that you just helped a lot of people make their decision. I think your conclusion made sense for most people that want to do "portable" opps. The distinction that you didn't make, was that for a permanent installation, a trapped antenna is a good way for (some) people with limited space to go. In my opinion, the latter is the main reason that someone would consider using a trapped antenna. Thanks for all your work putting these videos together for us.
I put together a 20-30-40 trapped dipole last month. It was more complicated than expected in practice. On the second try,😂😂 I was successful putting over-long wires on the far side of each trap and then tuning and soldering from the feed point out. It was definitely a “everything affects everything” scenario. It was a good learning experience. The tuning a trap part with the VNA was pretty cool. K6ARK should do a build video cause this is a perfect antenna for a tiny 3-band QRP rig.
I swear I saw Alice, White Rabbit, and the Madd Hatter and everyone else. You might have hit China digging that hole. But I did learn a lot Thanks Mike
A minor but important point of confusion needs to be cleared up. Loading coils are not traps. Everything else you covered well but here’s a summary with that point in mind. And an idea for a potential antenna to experiment with. Loading coils allow you to shorten the overall antenna length, getting lower frequencies on shorter antennas at the cost of harmonics and reduced bandwidth. The opposite of that would be a loading capacitor which is the little brother of the trap. In contrast traps won’t physically shorten your antenna but it will appear electrically shorter at specific frequencies, as if a lazy POTA activator had gotten out of their camping chair and disconnected a link ;-P I’ve seen multiple loading coils and multiple traps (not on the same antenna). But if you take into account that a trap is kind of an over engineered capacitive loading device (I.e. the opposite of a loading coil) it’s somewhat counter intuitive to mix in both a device that lowers resonance on a shorter element with a device that raises resonance on a longer element. Not to say that it can’t be done. A coil shortened 40m EFHW (that looses 15m) with a trap for 15m might be a place to start. Don’t know if this will display well in the comments. ---||---=-- matching unit -- elements || trap for 15m = loading coil for 40m You could make this work by linking in the trap and loading coil to an existing linked EFHW though you might need to make the 40m element (2-2.5m) that comes after the loading coil (27-35uH). 73s John
I love that @21:45 you come to the conclusion that, "it just isn't worth it". I feel like I know more now, than if I just skipped to that time code. You explained it so well and with good aids. Thank you.
I tried awhile back, just for fun, and because I liked the idea of a shorter antenna that could be resonant from 40m on up to 10m without having to take it down to put in or take out links. This took a long time just getting the tiny traps built (tiny because it was for QRP-10w). Tunning the thing was a different story... It took awhile... A long while. I was able to get it resonant on 30, 20, 17, 15, 12, and 10. Or maybe I had to ex-ney 12m, I can't really remember as I was trying different things to get 40m to work. I could not. I even used fancy schamncy surface mount mica caps (with 1,000v-500v ratings) for increased stability. I have since shelfed this project until I gather more motivation for winding more tiny toroids. I think I am going to try different mixes of toroids at some point in the distant future among other things. Anyways, it's cool that you spent the time on this one, because I'm sure others have, or will have, this same exact question!
Thank you for confirming my hypothesis that it is much easier and less frustrating to just get up and unlink a wire than to make traps for all these bands. It sounds really cool, but the practicality of it all makes it less than desirable for me. If you ever get it working, we will of course expect a full review of your findings.
Mike, I watched the video on traps versus links and your QMX POTA experience. I am still a little confused on your links as you connect and disconnect segments as you dropped down in the lower bands. The image in my head is that the first segment of your antenna is for 10 m, then you connect to another segment that makes it 17 m, and then another segment that makes it 20 m, and then another segment that makes it long enough for 30 m, and the final segment makes it the full 40 m band. In my way of thinking you should be starting out with the shortest segment, the one for 10 m and then adding segments as you drop down in to the lower amateur bands but in watching your video on the QMX you seem to be adding and at other times removing segments. Maybe I don’t get what you’re trying to say. Please elaborate. Thank you. Dave, K8WE since 1960.
I think I finally understood what you have done when I watched your video on taking the PackTenna 40 m end fed and cutting it into three sections linked together. It makes a little more sense to me now. Thank you so much.
Great video. Yea quite the rabbit hole. I have built a 5-band trapped EFHW for 15-40M. It was a tedious process. Even with trapped tuned spot on on the bench, when the antenna is assembled the traps will interact with one another. This required some slight spreading/compressing of the coil turns on nearly all of them. There was also multiple iterations of doing this until all of them were dialed in. It gets very frustrating. Very cool when done, but I will think hard about my options for building another 5-band one.
One advantage to using the trap is that the lobes are more favorable. On an 80-10 EFHW, there are so many lobes on 10 meters it doesn't perform very well.
Two comments for clarity: Trapped vs. Linked, your analysis is good but misses one vital point - the trapped EFHW is mechanically shorter (albeit heavier due to the traps) and will fit in places where a full-length wire cannot. Also loss in traps will vary depending on their design - and there's some damn well designed traps out there already. Summary - there's a purpose for each type and it's worth it to evaluate needs before settling on one way or the other (says the guy who uses each, interchangeably). Great video Mike and thanks for the shout-out. 73
I like traps on beams, up on towers, where I cannot reach to disconnect links. I like traps on my 4BTV that allows my SDR to receive on multiple bands and the same time. But I have smoked a trap or two due the resistance in the coil winding wire. I am putting the final touches on an otherwise pristine HW-8 to take out to the park. 80, 40, 20 and 15 meters. You have convinced me to try the linked dipole build. Maybe an end fed after that, but most installs I would make have one good support near the rig. Since I am usually out in the daytime, I can leave the 80m add-on section at home.
Nice work, Mike. I guess that I'll summarize my thoughts: Traps are lossy, have weight, and cost significantly more than a link Harmonic resonances are unlikely to be present because of the differing shortening effects of the inductor at the various frequency. As you point out, a trap per band, except for the lowest (so not N but N-1) is potentially required. And even rain can throw these careful tunings off Traps are a good choice for that tri-band beam on top of that 80 feet of Rohn 45. You could use (lots of) treaps on a wire antenna if the installation is hard to lower and too high to reach. In such a case I'd probably go back to my wet dream of a remotely controlled link.
Back in the day George from PackTenna was trying to work on a remotely operated link. That would be so cool! But at the same time, would it be worth all the extra effort?
@@hamradiotube Probably not. As I said, a wet dream. While I could see a latching reed switch as being light enough, I don't know if they exist. Powering the circuitry is already a thorny problem without having to power a non-latching relay. I've never come up with a power scheme. If you have a way to deliver power, then control isn't too hard.
@@KeepEvery1Guessing What about using a reed switch with a magnet on a pole if the antenna is high in the air? It would be a good game, trying to get the magnet in the right place, 7 or 8 metres up using a fishing pole, especially if the wind was blowing.
@@paulsengupta971 I would be interested to hear of your final design. Suitable reed switches maay be a problem, unless you make your own. Voltage ratings may only be suitable for QRP or even QRPP, and you may be wishing for normally closed, opened by the magnet varieties, which I haven't encountered, to avoid having to hang magnets at multiple reeds to have continuity past multiple reeds, though some harmonic design end feds may only require one jumper. Since the tip of your fishing pole is mechanically present at the time of switching, you may do better with a mechanical switch operated by pushing a radial disk one way or another along the wire (this also solves the voltage rating problem). But it still requires you to get up from the operating position and fiddle. You are competing with the ease of temporarily lowering the antenna to be able to play with jumpers. This is particularly easy with an inverted V design, where you probably only need to lower the center support. Have fun.
Interesting video. I looked into traps for a bit, but decided that it would be better for me to start with building linked dipoles before I tackle something that looks to be much more complex to design, build, and tune. Maybe after I get some more experience I'll try a trapped antenna.
@hamradiotube it really wasn't that hard. In fact i did it twice first time with home made coax traps (they worked well) second time with W2AU traps a little $$ but I was having fun. So first I decided 2 sets of 3 to cover 40 through 10 or 7 bands yes it doesn't divide evenly so one set had extra. Also had to consider 40m will also match 15m bonus. Here we go you take W2AU cheat sheet for his trap dipole and you build it. Tune it cut it half and you have two radials. Then dupe half for the third radial. Do it again for the next band set and done. 6 tuned radials for 7 bands. I made the third one of each band set a tad shorter to give it broader bandwidth.
@@P.SeanCoady That's pretty awesome. I've still not messed with raised radials let alone a raised vertical! I was watching more videos on traps last night. Don't ask me why, glutton for punishment I guess! But one of them mentioned the narrower band width as well. Something I didn't come across in my rabbit hole, but I guess I'm still down there.
Nice video, all the issues I am having. Recently got my license back after 30 years and now have access to HF using pre loved ft818 with a Sotabeam Band hopper 3 as a HA aeria, but it will be 30ft off the ground, so taking it down to change lengths is going to be annoying. I came up with all the same issues, change in the effective length of each section, having to make traps for every band, additional weight.
Ouch that was a rabbit hole that really sucked you in. I had thought about trying traps too. After all they use traps on Beams that are hung up in the air. So it seemed it should work but as you found out it appears it may not with out a whole lot of building and rebuilding traps till you get the magic combo achieved. Thanks for the good video. Vic de KE8JWE
I like the Traps if you are putting the antenna real high permanently. I’ve added 80meters to my 40m EFHW. By just adding a 110uhenry inductor then about 10 ft of wire. Still works on 10,15,&20.
Chameleon emcomm 2. Problem solved. I didn't bother checking 30m, but the internal tuner in the ic7300 easily matched every other band its capable of. 6m through 160m.
TL;DR - The rabbit hole just might be worth it... For anyone who has a few years of their life to dedicate to physics and non-linear circuit analysis... (Concerning LRC circuits) Inductors can be used as low pass filters, capacitors can be used as high pass filters, so each circuit can be configured (as it is frequency dependent) to perform the necessary functionality. So a low-pass, band-pass, notch and high-pass filter are combinations (parallel and series) of impedance, capacitance and inductance. The antenna simply needs to be considered as a system with the various traps being proposed. Sometimes I feel like we believe too much voodoo is involved. Capacitors: voltage leads current Inductors: current leads voltage ...When we look at the antenna pictures with waveforms we always draw the current and the voltage as sinewaves, but we forget (visually), that is exactly what we are influencing with the LRC 'traps, coils, et al'
All this trap stuff is got my brain fried 😂 sounds to me like the squeeze ain’t worth the juice, just rock with the harmonics link system, or whatever, and ham on!
It seems like there's got to be a procedure for tuning each band when using traps. It seems like every trim you make for a section would affect all the others. It seems like there would be a procedure from highest frequency to lowest or lowest frequency to highest frequency when you trim everything? I agree with you as I see a nightmare.
Hey Mike can you go over that again. JK good info I was going to look into all of that myself so thanks for saving me all that torment so now I know traps suck! 73 buddy see you in Dayton
I have an inverted vee for 60m, it was originally for 40m but I later suffered broadband interference so I extended it for 60m where things were quieter. Now it's gone to fibre the QRM has cleared up and I want 40m again but also keep 60m so I'm thinking traps because a link would involve me climbing on the extension roof. There seems to be no details for these frequencies so I'll have to look at a trap calculator. Maybe a variable C to test it. I have five attic dipoles for 20m to 10m. QRP is okay for me, everything here is QRP. G4GHB.
This is what I came across when looking at that a while ago: "VK3IL Blog - Trapped five band EFHW SOTA antenna" for 40/30/20/17/15m. It looked very intriguing, but also finicky to tweak, if you can't use exactly the same parts as VK3IL did. 73 Tobias
Great video, Mike. I could feel the sighs every time you didn't get to your answer. Glad you found Alan explaining it clearly. For your linked EFHW, do you find 20m works better isolated that way (unlink the section beyond 20m) rather than as a harmonic of 40m? Steve/K3SLH
I'm not really sure if it matters one way or another honestly. I've never really compared the two different configurations but I've also never had them all linked and said to myself "man I'm not getting any contacts, let me unlink this" and then made more contacts. Sure you could do WSPR comparisons but there's always going to be the variable of the bands constantly changing. If you did enough over time you may see some different results between the two, but that is a rabbit hole I don't see myself going down any time soon.
Ok, here's another question - you put your 17m link in so that you have a half wave on 17m. What about putting another link in so that you have two half waves at 17m? That way you have the longer antenna (to put in where the space allows) which will still be resonant on 17m. Worth a try?
Great stuff. I look at trap for each band adds some loss in antenna. Having traps for all the bands is a lot of loss. Looking what is out theirs for antenna . I linked antenna is the way to go. The outher choice is use random wire 9:1 or 4:1 . Will have less loss than all them traps. Just need tuner. The Coffee and ham radio Poseidon is a great choice for multi band. Easy to build. 4:1 UNUN easy to wind. Just measure wire cut . Works super great multi band. And most tuners will easy tune for the band you want. A lot less work and works great . 73
The traps change the lenght the same way as a bobbin. I tried and figure out that it is (for me) impossible to build a 10m-12m-15m EFHW antenna, so I compromised with 10m and 15m. Funny enough, I still can operate 12m with an ATU, but I wouldn't try adding traps for every band, as the segment lenghts would become impredictable, and sometimes not possible at all!
Dead right Mike walk over to open a link is much easier than wearing out a pair of boots walking around you antenna build with a trap to make it work everywhere else. Thanks for all the ground work though interesting final theory on it all. My link end fed has 1 link with a 1.7 T 1 vswr on 10.1 mhz with the resonate point actually 9.6mhz but a fantastic vswr on 17m where I want it. The harmonic of 10.1 mhz makes the next sweet spot in 19 or 20 mhz not 18mhz. Like you say Vudu at work. regards vk5cz ..
7.023 Mhz 1 watt output. How long do I cut a wire? Does wire guage matter? I think mine is 14Ga 134ft inverted V.. 49:1 homemade unun, no ceramic cap. I tried today, zero reports on reverse beacon network
I have a ridiculously stupid quesiton, feel free to roast the hell out of me for it. Have you ever tried a fan EFHW? Like 10, 12, 15 , 17, 20, and 40m elements all going out of one transformer? I realize it's an awkward solution but I wonder if it works.
Only works if the wires aren't resonant with each other. For instance, if you transmit on 10 meters with such a rascal, the 10m, 20m and 40m wires will all resonate...
I had the same wondering since the phrase "a dipole is a dipole is a dipole" is everywhere, then would a fan work for an EF. I tried a fan dipole project once, thinking an EF design would be easier to cut in. The dxcommander verticals are "fans" as well so maybe those lengths would work in a horizontal run as well?
I suspect if you wanted all those bands you'd have to do one ~66 ft wire for 10/15/20/40 and then one ~18.5ft for 12m and one ~29ft for 17m Suppose 12 and 17 could also be done by putting a mini-trap as demonstrated in the video at the end of the 12m section and then finish it off with enough wire to make it resonate on 17. Since 17 is only 100kHz wide even if its relatively high Q you should still be able to cover the whole band Suppose a coax coil trap would work also, but its also heavier. I kinda feel like trying that out now.
All this talk about traps, and not one mention of Admiral Ackbar. I guess you're just not into Star Trek. I don't bother with traps or links on my portable setup. I carry a manual tuner and a 3' length of coax to put it inline. The tuner can dial in 40 down to 10 with no problem, and I don't even need to get up... although 12 is a little wonky, yet usable... but nobody uses 12 anyway. Props for going through all the nerdery.
Wondering what you have to learn to earn your ham exam over there in the US. Thomson's resonance formula for LC circuits is an absolute basic. 😂 You can use any combination of C an L for your trap that is resonant on your desired band. Just use a cheap calculator and a pencil... I also would encourage you to take a look in antenna simulation with MMANA-GAL (or ezNec) to gain a bit of understanding about resonacese on antenna and the effects of electric shortened antennas. You will be maybe surprised how the radiation pattern of a 40/20/15/10m EFHW differs by band and maybe shocked as it looks on 10m😂
Mike you once said in a video you made talking about tools, “I don’t need a fluke I am an amateur”. Brother this is why you’re not an “amateur” the way people think about it. The trip through the rabbit hole is beautiful, now you own it. What makes it great, you’re sharing it. Your deep dive on the subject and the fact you're sharing what you learned, this collaboration is what I love about being an member of Amateur Radio. Great Job!
I'll second that. Well done Mike. "The effort yields its own rewards" - Data (Star Trek NG)
I didn't go that far down the rabbit hole before I decided on sticking with resonate antennas. Was great hearing your take. 73 K9WWW
Wow! I'm exhausted just listening to this. You said it best at 21:37 -"I don't think it's worth it." Good info though. For me? I'll just throw the tuner in the go bag. It's not that heavy. This is also why I keep a Slidewinder coil, spike, mirror mount, and CHA SS17 in the go box for POTA. Or better yet, your favorite - an ATAS-120 - which I don't own one yet. It's on the list though. My life is complicated enough. Keep it Simple. 😉
The other thing about using a trap for every band is that you then lose the rest of the length of the wire for that band, limiting the length to the first half wave.
Tim, G5TM, has videos where he has created a dual band EFHW with a trap, but not a trap with inductance and capacitance, but inductance only. I believe this sort of thing was what Alan was talking about in his e-mail. Tim has his set up for use as a vertical antenna for portable operation. The extra inductance, as mentioned, shortens the overall length somewhat. I think Tim mentions that a trap will throw off the resonance for the whole length, making it non resonant on harmonics...or maybe that was a discussion in the comments - or maybe it was Peter Waters who said that in his videos.
Great stuff! There really are a lot of smart and helpful hams out there. Thanks for taking us down the rabbit hole on this.
Bravo Mike. This was well done. Aside from the topic of traps, what I really read between the lines is just how important having good Elmers are. Keep digging, learning and sharing. 73 OM
Wow! Just wow on the amount of digging you did on this one! Great information, loved learning about it but I don't know that i would have followed that rabbit for as long as you did. Thanks for the work!
All for the love of antennas!
Wow, just wow. My brain exploded around 12:23 into the video. Kudos for chasing this brother. You never cease to provide useful information with a witty delivery...Kudos.
Great video. I like that you just helped a lot of people make their decision. I think your conclusion made sense for most people that want to do "portable" opps. The distinction that you didn't make, was that for a permanent installation, a trapped antenna is a good way for (some) people with limited space to go. In my opinion, the latter is the main reason that someone would consider using a trapped antenna.
Thanks for all your work putting these videos together for us.
Thanks Mike for answering my question. I started going down that same rabbit hole and it scared me! 😂
THANK YOU! You just kept me from going down the rabbit hole myself. Been wanting to figure this out.
Really glad you're talking about traps.
Talking about them, yes. Building them, prob not any time soon.
I sure do like my tuner. I can throw up that EFHW and push a button for each band I work! You have talked me out of building traps!
I put together a 20-30-40 trapped dipole last month. It was more complicated than expected in practice. On the second try,😂😂 I was successful putting over-long wires on the far side of each trap and then tuning and soldering from the feed point out. It was definitely a “everything affects everything” scenario. It was a good learning experience. The tuning a trap part with the VNA was pretty cool.
K6ARK should do a build video cause this is a perfect antenna for a tiny 3-band QRP rig.
I swear I saw Alice, White Rabbit, and the Madd Hatter and everyone else. You might have hit China digging that hole. But I did learn a lot
Thanks Mike
A minor but important point of confusion needs to be cleared up.
Loading coils are not traps.
Everything else you covered well but here’s a summary with that point in mind.
And an idea for a potential antenna to experiment with.
Loading coils allow you to shorten the overall antenna length, getting lower frequencies on shorter antennas at the cost of harmonics and reduced bandwidth.
The opposite of that would be a loading capacitor which is the little brother of the trap.
In contrast traps won’t physically shorten your antenna but it will appear electrically shorter at specific frequencies, as if a lazy POTA activator had gotten out of their camping chair and disconnected a link ;-P
I’ve seen multiple loading coils and multiple traps (not on the same antenna).
But if you take into account that a trap is kind of an over engineered capacitive loading device (I.e. the opposite of a loading coil) it’s somewhat counter intuitive to mix in both a device that lowers resonance on a shorter element with a device that raises resonance on a longer element.
Not to say that it can’t be done.
A coil shortened 40m EFHW (that looses 15m) with a trap for 15m might be a place to start.
Don’t know if this will display well in the comments.
---||---=--
matching unit
-- elements
|| trap for 15m
= loading coil for 40m
You could make this work by linking in the trap and loading coil to an existing linked EFHW though you might need to make the 40m element (2-2.5m) that comes after the loading coil (27-35uH).
73s
John
I love that @21:45 you come to the conclusion that, "it just isn't worth it". I feel like I know more now, than if I just skipped to that time code. You explained it so well and with good aids. Thank you.
That would be great if it only took me 21:45 to figure that all out though lol!
Wow, glad it was you that had to do all that research. Linked or EFHW, that's the way I see it.
Thanks for doing the homework.
Steve, k7ofg.
Toroid Coil Winding Calculator is still alive in the Wayback Machine
Hopefully somebody revives that thing, it was pretty accurate! Sad to see it go.
Good to know. Now I need to go on a deep dive about what is a Wayback Machine lol!
I tried awhile back, just for fun, and because I liked the idea of a shorter antenna that could be resonant from 40m on up to 10m without having to take it down to put in or take out links. This took a long time just getting the tiny traps built (tiny because it was for QRP-10w). Tunning the thing was a different story... It took awhile... A long while. I was able to get it resonant on 30, 20, 17, 15, 12, and 10. Or maybe I had to ex-ney 12m, I can't really remember as I was trying different things to get 40m to work. I could not. I even used fancy schamncy surface mount mica caps (with 1,000v-500v ratings) for increased stability. I have since shelfed this project until I gather more motivation for winding more tiny toroids. I think I am going to try different mixes of toroids at some point in the distant future among other things. Anyways, it's cool that you spent the time on this one, because I'm sure others have, or will have, this same exact question!
Thank you for confirming my hypothesis that it is much easier and less frustrating to just get up and unlink a wire than to make traps for all these bands. It sounds really cool, but the practicality of it all makes it less than desirable for me. If you ever get it working, we will of course expect a full review of your findings.
Mike,
I watched the video on traps versus links and your QMX POTA experience. I am still a little confused on your links as you connect and disconnect segments as you dropped down in the lower bands. The image in my head is that the first segment of your antenna is for 10 m, then you connect to another segment that makes it 17 m, and then another segment that makes it 20 m, and then another segment that makes it long enough for 30 m, and the final segment makes it the full 40 m band. In my way of thinking you should be starting out with the shortest segment, the one for 10 m and then adding segments as you drop down in to the lower amateur bands but in watching your video on the QMX you seem to be adding and at other times removing segments. Maybe I don’t get what you’re trying to say. Please elaborate. Thank you.
Dave, K8WE since 1960.
I think I finally understood what you have done when I watched your video on taking the PackTenna 40 m end fed and cutting it into three sections linked together. It makes a little more sense to me now. Thank you so much.
holy cow, that was an entire nest of bunnies down that rabbit hole!
Love it when rabbit holes suck ya in like that. Learning things like this is FUN!!
Great video. Yea quite the rabbit hole. I have built a 5-band trapped EFHW for 15-40M. It was a tedious process. Even with trapped tuned spot on on the bench, when the antenna is assembled the traps will interact with one another. This required some slight spreading/compressing of the coil turns on nearly all of them. There was also multiple iterations of doing this until all of them were dialed in. It gets very frustrating. Very cool when done, but I will think hard about my options for building another 5-band one.
One advantage to using the trap is that the lobes are more favorable. On an 80-10 EFHW, there are so many lobes on 10 meters it doesn't perform very well.
It depends. Having all those lobes makes it more omni-directional than just broadside to the antenna.
Two comments for clarity: Trapped vs. Linked, your analysis is good but misses one vital point - the trapped EFHW is mechanically shorter (albeit heavier due to the traps) and will fit in places where a full-length wire cannot. Also loss in traps will vary depending on their design - and there's some damn well designed traps out there already. Summary - there's a purpose for each type and it's worth it to evaluate needs before settling on one way or the other (says the guy who uses each, interchangeably).
Great video Mike and thanks for the shout-out. 73
I said all of those things!! Thanks again for all your help with this!
Thanks, Mike, that was really helpful. I'm one of the lucky ones who doesn't lack for space, so I'll stick with the long wires resonant on many bands.
Thanks and yeah that was a rabbit hole
This was a GOOD video. Thanks for making it.
I like traps on beams, up on towers, where I cannot reach to disconnect links.
I like traps on my 4BTV that allows my SDR to receive on multiple bands and the same time. But I have smoked a trap or two due the resistance in the coil winding wire.
I am putting the final touches on an otherwise pristine HW-8 to take out to the park. 80, 40, 20 and 15 meters. You have convinced me to try the linked dipole build. Maybe an end fed after that, but most installs I would make have one good support near the rig. Since I am usually out in the daytime, I can leave the 80m add-on section at home.
Well-done and very well-explained Mike. #HamSmarter!
Nice work, Mike.
I guess that I'll summarize my thoughts: Traps are lossy, have weight, and cost significantly more than a link Harmonic resonances are unlikely to be present because of the differing shortening effects of the inductor at the various frequency. As you point out, a trap per band, except for the lowest (so not N but N-1) is potentially required. And even rain can throw these careful tunings off Traps are a good choice for that tri-band beam on top of that 80 feet of Rohn 45. You could use (lots of) treaps on a wire antenna if the installation is hard to lower and too high to reach. In such a case I'd probably go back to my wet dream of a remotely controlled link.
Back in the day George from PackTenna was trying to work on a remotely operated link. That would be so cool! But at the same time, would it be worth all the extra effort?
@@hamradiotube Probably not. As I said, a wet dream. While I could see a latching reed switch as being light enough, I don't know if they exist. Powering the circuitry is already a thorny problem without having to power a non-latching relay. I've never come up with a power scheme. If you have a way to deliver power, then control isn't too hard.
@@KeepEvery1Guessing What about using a reed switch with a magnet on a pole if the antenna is high in the air? It would be a good game, trying to get the magnet in the right place, 7 or 8 metres up using a fishing pole, especially if the wind was blowing.
@@paulsengupta971 I would be interested to hear of your final design. Suitable reed switches maay be a problem, unless you make your own. Voltage ratings may only be suitable for QRP or even QRPP, and you may be wishing for normally closed, opened by the magnet varieties, which I haven't encountered, to avoid having to hang magnets at multiple reeds to have continuity past multiple reeds, though some harmonic design end feds may only require one jumper.
Since the tip of your fishing pole is mechanically present at the time of switching, you may do better with a mechanical switch operated by pushing a radial disk one way or another along the wire (this also solves the voltage rating problem).
But it still requires you to get up from the operating position and fiddle. You are competing with the ease of temporarily lowering the antenna to be able to play with jumpers. This is particularly easy with an inverted V design, where you probably only need to lower the center support.
Have fun.
Interesting video. I looked into traps for a bit, but decided that it would be better for me to start with building linked dipoles before I tackle something that looks to be much more complex to design, build, and tune. Maybe after I get some more experience I'll try a trapped antenna.
Thank you for this!
That makes a whole lot of sense! Thank you!
Another disadvantage of using traps is narrow bandwidth of target frequency.
Enjoyed the rabbit hole with you.
I've used traps on radials for a elevated vertical. Worked well vertical was 30feet above ground
Good lord, how was that for tuning all the different wires and traps? And would you do it again?
@hamradiotube it really wasn't that hard. In fact i did it twice first time with home made coax traps (they worked well) second time with W2AU traps a little $$ but I was having fun. So first I decided 2 sets of 3 to cover 40 through 10 or 7 bands yes it doesn't divide evenly so one set had extra. Also had to consider 40m will also match 15m bonus. Here we go you take W2AU cheat sheet for his trap dipole and you build it. Tune it cut it half and you have two radials. Then dupe half for the third radial. Do it again for the next band set and done. 6 tuned radials for 7 bands. I made the third one of each band set a tad shorter to give it broader bandwidth.
@@P.SeanCoady That's pretty awesome. I've still not messed with raised radials let alone a raised vertical! I was watching more videos on traps last night. Don't ask me why, glutton for punishment I guess! But one of them mentioned the narrower band width as well. Something I didn't come across in my rabbit hole, but I guess I'm still down there.
Nice video, all the issues I am having. Recently got my license back after 30 years and now have access to HF using pre loved ft818 with a Sotabeam Band hopper 3 as a HA aeria, but it will be 30ft off the ground, so taking it down to change lengths is going to be annoying. I came up with all the same issues, change in the effective length of each section, having to make traps for every band, additional weight.
Ouch that was a rabbit hole that really sucked you in. I had thought about trying traps too. After all they use traps on Beams that are hung up in the air. So it seemed it should work but as you found out it appears it may not with out a whole lot of building and rebuilding traps till you get the magic combo achieved. Thanks for the good video. Vic de KE8JWE
I like the Traps if you are putting the antenna real high permanently.
I’ve added 80meters to my 40m EFHW. By just adding a 110uhenry inductor then about 10 ft of wire. Still works on 10,15,&20.
Chameleon emcomm 2. Problem solved. I didn't bother checking 30m, but the internal tuner in the ic7300 easily matched every other band its capable of. 6m through 160m.
I am waiting for Adam, K6ARK, to put out a kit for this exact build.
Yeah but he's so evil he'd prob make it with the tiniest parts in the world lol!
TL;DR - The rabbit hole just might be worth it...
For anyone who has a few years of their life to dedicate to physics and non-linear circuit analysis... (Concerning LRC circuits) Inductors can be used as low pass filters, capacitors can be used as high pass filters, so each circuit can be configured (as it is frequency dependent) to perform the necessary functionality. So a low-pass, band-pass, notch and high-pass filter are combinations (parallel and series) of impedance, capacitance and inductance. The antenna simply needs to be considered as a system with the various traps being proposed.
Sometimes I feel like we believe too much voodoo is involved.
Capacitors: voltage leads current
Inductors: current leads voltage
...When we look at the antenna pictures with waveforms we always draw the current and the voltage as sinewaves, but we forget (visually), that is exactly what we are influencing with the LRC 'traps, coils, et al'
Wow thanks Mike!!!
Another good source for antenna info is the ARRL antenna manual
I did read a couple articles from old issues of QST. That could have been a separate rabbit hole all of it's own.
All this trap stuff is got my brain fried 😂 sounds to me like the squeeze ain’t worth the juice, just rock with the harmonics link system, or whatever, and ham on!
It seems like there's got to be a procedure for tuning each band when using traps. It seems like every trim you make for a section would affect all the others. It seems like there would be a procedure from highest frequency to lowest or lowest frequency to highest frequency when you trim everything? I agree with you as I see a nightmare.
Hey Mike can you go over that again. JK good info I was going to look into all of that myself so thanks for saving me all that torment so now I know traps suck! 73 buddy see you in Dayton
Oh you got jokes lol!
100% : KISS
The only part of KISS I get is the last S 🤣
I have an inverted vee for 60m, it was originally for 40m but I later suffered broadband interference so I extended it for 60m where things were quieter.
Now it's gone to fibre the QRM has cleared up and I want 40m again but also keep 60m so I'm thinking traps because a link would involve me climbing on the extension roof. There seems to be no details for these frequencies so I'll have to look at a trap calculator. Maybe a variable C to test it.
I have five attic dipoles for 20m to 10m.
QRP is okay for me, everything here is QRP.
G4GHB.
This is what I came across when looking at that a while ago:
"VK3IL Blog - Trapped five band EFHW SOTA antenna" for 40/30/20/17/15m.
It looked very intriguing, but also finicky to tweak, if you can't use exactly the same parts as VK3IL did.
73 Tobias
Great video, Mike. I could feel the sighs every time you didn't get to your answer. Glad you found Alan explaining it clearly.
For your linked EFHW, do you find 20m works better isolated that way (unlink the section beyond 20m) rather than as a harmonic of 40m?
Steve/K3SLH
I'm not really sure if it matters one way or another honestly. I've never really compared the two different configurations but I've also never had them all linked and said to myself "man I'm not getting any contacts, let me unlink this" and then made more contacts. Sure you could do WSPR comparisons but there's always going to be the variable of the bands constantly changing. If you did enough over time you may see some different results between the two, but that is a rabbit hole I don't see myself going down any time soon.
Ok, here's another question - you put your 17m link in so that you have a half wave on 17m. What about putting another link in so that you have two half waves at 17m? That way you have the longer antenna (to put in where the space allows) which will still be resonant on 17m. Worth a try?
Great stuff. I look at trap for each band adds some loss in antenna. Having traps for all the bands is a lot of loss. Looking what is out theirs for antenna . I linked antenna is the way to go. The outher choice is use random wire 9:1 or 4:1 . Will have less loss than all them traps. Just need tuner. The Coffee and ham radio Poseidon is a great choice for multi band. Easy to build. 4:1 UNUN easy to wind. Just measure wire cut . Works super great multi band. And most tuners will easy tune for the band you want. A lot less work and works great . 73
Wow thanks....I won't get trapped
Pastor Mike, Preaching the antenna gospel!
I mean, I am an ordained minister...
@ Excellent! 😆
Shocked that anyone still checks Yahoo! 😅
Leave no stone unturned 🤣
The traps change the lenght the same way as a bobbin. I tried and figure out that it is (for me) impossible to build a 10m-12m-15m EFHW antenna, so I compromised with 10m and 15m. Funny enough, I still can operate 12m with an ATU, but I wouldn't try adding traps for every band, as the segment lenghts would become impredictable, and sometimes not possible at all!
For those curious: I have single band EFHW antennas for my very limited space!
I think for POTA, traps may not make sense. I do have a trapped dipole for 40/80m at my QTH, that I use for day/night NVIS.
Dead right Mike walk over to open a link is much easier than wearing out a pair of boots walking around you antenna build with a trap to make it work everywhere else. Thanks for all the ground work though interesting final theory on it all. My link end fed has 1 link with a 1.7 T 1 vswr on 10.1 mhz with the resonate point actually 9.6mhz but a fantastic vswr on 17m where I want it. The harmonic of 10.1 mhz makes the next sweet spot in 19 or 20 mhz not 18mhz. Like you say Vudu at work. regards vk5cz ..
7.023 Mhz 1 watt output.
How long do I cut a wire?
Does wire guage matter? I think mine is 14Ga 134ft inverted V.. 49:1 homemade unun, no ceramic cap. I tried today, zero reports on reverse beacon network
Anyone wonder what he was printing?
Excellent job of research and explaining the application and design and consideration of traps. Keep up the good work, it is appreciated. Ed KK7UNA
I have a ridiculously stupid quesiton, feel free to roast the hell out of me for it. Have you ever tried a fan EFHW? Like 10, 12, 15 , 17, 20, and 40m elements all going out of one transformer? I realize it's an awkward solution but I wonder if it works.
Only works if the wires aren't resonant with each other. For instance, if you transmit on 10 meters with such a rascal, the 10m, 20m and 40m wires will all resonate...
I had the same wondering since the phrase "a dipole is a dipole is a dipole" is everywhere, then would a fan work for an EF. I tried a fan dipole project once, thinking an EF design would be easier to cut in. The dxcommander verticals are "fans" as well so maybe those lengths would work in a horizontal run as well?
@@RicksHamShack good point. Though it would be a nice f-u to an HOA
I suspect if you wanted all those bands you'd have to do one ~66 ft wire for 10/15/20/40 and then one ~18.5ft for 12m and one ~29ft for 17m
Suppose 12 and 17 could also be done by putting a mini-trap as demonstrated in the video at the end of the 12m section and then finish it off with enough wire to make it resonate on 17.
Since 17 is only 100kHz wide even if its relatively high Q you should still be able to cover the whole band
Suppose a coax coil trap would work also, but its also heavier.
I kinda feel like trying that out now.
Try it and you'll realize that it won't work, mainly because of the high feedpoint impedance, compared to a center fed dipole.
best video ever. 73
Six minute intro to topic?
🙂👍
All this talk about traps, and not one mention of Admiral Ackbar. I guess you're just not into Star Trek.
I don't bother with traps or links on my portable setup. I carry a manual tuner and a 3' length of coax to put it inline. The tuner can dial in 40 down to 10 with no problem, and I don't even need to get up... although 12 is a little wonky, yet usable... but nobody uses 12 anyway.
Props for going through all the nerdery.
It's a trap!
sounds way to many $$$$
Wondering what you have to learn to earn your ham exam over there in the US. Thomson's resonance formula for LC circuits is an absolute basic. 😂 You can use any combination of C an L for your trap that is resonant on your desired band. Just use a cheap calculator and a pencil... I also would encourage you to take a look in antenna simulation with MMANA-GAL (or ezNec) to gain a bit of understanding about resonacese on antenna and the effects of electric shortened antennas. You will be maybe surprised how the radiation pattern of a 40/20/15/10m EFHW differs by band and maybe shocked as it looks on 10m😂
Yes, we have to learn it to get Extra.
Its not a requirement that we remember it, especially since its not something we'll use every day.