Dipoles: Wrapping Back Excess Bare or Insulated Wire (

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Let's build some 40m dipoles and install them in a sloper configuration. We will wrap the excess wire back on the dipole in both the bare copper and the insulated wire configuration. The outcome may surprise you!
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Опубликовано:

12 сен 2024

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Комментарии : 36

@dksayt Месяц назад

Hi Dave. I feel I have something to contribute here. It concerns small backyards. When I first got my license I went on 2 meter nets and explained that I had only a 30 x 15 ft backyard. There is also an unhelpful very tall inaccessible spruce tree in the neighboring yard. Declaring this on one of the weekly networks an Elmer showed up. My Elmer suggested an vertical he found on Ebay. It worked somewhat but I noticed that he had an MFJ 1775 rotatable dipole that works for 2 M to 40M. I have that on a mast up about 20 ft. With it I have contacts in Alaska, Eastern Russia, New Zealand, and Tasmania. Also much of South America. Above that on a short piece of mast I have my home brewed seven element 2M horizontal dipole. Local Hams hear me without rotation on that.

@pasixty6510 10 месяцев назад

This experiment should encourage everyone to try adjusting their (isolated) wire antennas just by wrapping back the excess wire. The folded back piece of wire, as long as it’s close enough (and it usually is) to the main wire, takes the RF - inductively coupled - with it and doesn’t affect the expected properties much. It works, that’s all we want. Only if you want to get overly precise, you must take the foldback into consideration as a kind of capacity hat, which makes the antenna electrically a little bit longer. The higher your frequency, the more you will notice that effect. Thank you very much for this highly instructive video! Vy73 DB6YC

@robcarnaroli269 10 месяцев назад

Interesting. I had a fold back on my 80m extension of my EFHW. It caused the lowest point of the dip in the band to only go down to 2:1. As I trimmed and adjust the foldback the SWR kept dropping till it got down to about 1.2:1. KC3SWZ 73.

@bill-2018 10 месяцев назад

Good stuff Dave, once again. In my early days of radio I wondered about insulated or non insulated wire and decided there was no difference. Only an SWR meter back then. I also folded wire back with the same conclusion. Wire is cheap. 20 to 10m so five dipoles in my attic but three coax cables to make tuning easier with less interaction. G4GHB.

@davidhodgson977 10 месяцев назад

Good morning David, I have made both insulated and uninsulated dipoles for 40 and 20 metres. You are quite correct, it does not make any difference if you fold the ends back on themselves. HS0ZQA David Thailand

@cornbread-KO5RN 9 месяцев назад

Dave it’s funny we were walking in the French Quarters N.O. and ran across a street musician playing your song 😂

@r2old636 10 месяцев назад

It is tidbits like this that make life so much easier for many of us that have been hesitant when it came time to make that final bit of tuning for fear of destroying an antenna that looks good on paper, but is just that little bit off.

@CoroPlanesLLC 10 месяцев назад

Love your content. Please keep sharing your knowledge! So much good information! I especially like the antenna content because I need help with both height and space for my antennas (small HOA lot). Any new tricks to improve my antenna in my limited space is well received!

@d3w4yn3 10 месяцев назад

Good question, and good experiment!

@mewrongwayKOCXF 10 месяцев назад

Awesome Dave!! 👍👍👍

@goodnewsfromgod-bybob5710 10 месяцев назад

Thanks Dave!! I put my first wire antenna up last month. 80 meter efhw and I’m having fun experimenting

@OaklynHall 10 месяцев назад

Thank you for sharing this interesting and education video with us. I guess the antenna just "catches the wave" and it's the overall length of the antenna (from end to end) that matters and not how much wire (including "wrapbacks") is in the antenna. What would happen if the "wrapback" went all the way along each leg of the dipole so there was in fact twice the amount of wire but the antenna remained the same overall length? Would the antenna receive a stronger signal with twice the wire?

@davidhodgson977 10 месяцев назад

I made a dipole that I cut for 40 into a 20 dipole and I wrapped it all the way back as I didn't want to destroy the 40 metre dipole, and it worked great. David HS0ZQA Thailand

@everythingelectronic63 6 месяцев назад

I did the same test with a transformer-fed end fed half wave antenna and noted that folding back seems not to shorten that antenna (much) but cutting it will, as KC3SWZ has observed here also. Maybe it's dependent on how tightly the folded back section becomes capacitively shorted toghether, which depends on how close the wires are and what the insulation material permittivity is. 73, OH3WAV

@vladtepes481 10 месяцев назад

Very informative.

@AC3HT 10 месяцев назад

Thanks Dave. Very interesting experiment and results. Would be curious though if the insulated wire wrapped back, if in a tighter coil configuration and greater extended length, might influence the resonant frequency more readily. Not sure if the insulated tighter wire coil would actually shield the signal, add capacitance or simply exhibit parasitic coupling. Obviously, cutting off the extreme excess of wire would be the solution of course, but my response/question is more theoretic in nature and a pondering point. 73, Dave, AC3HT

@davecasler 9 месяцев назад

Hi Dave, I don't think it would make much difference. 73, Dave, KEØOG

@g0fvt 10 месяцев назад

The foldback of insulated wire result conflicts with some other observations, it has been said that for example if you foldback a significant length of insulated wire the resonant frequency does not go up as high as it would if the wire had been cut. I should try some small scale examples with a VNA ... thank you for the video 73

@godarklight 10 месяцев назад

Something I learned from DXCommander - when you wrap back a decent amount of insulated wire (say 1-2m extra wire), you actually pull the 3rd harmonic down more than the fundamental, so you can get both 40 and 15 to be perfect. It's worth doing this experiment to see if it works for you too.

@BartVanAllen 10 месяцев назад

Excellent, thank you sir

@timmcilraith8762 10 месяцев назад

Thanks Dave. I've often wondered about that. Now tell me, would two or more antenna wires of equal length running parallel to each other, only being connected at each end, result in more signal strength into the receiver?

@davecasler 9 месяцев назад

Probably not. However, if the two wires are connected only at the tips of the antenna (and not in the middle), you have constructed a folded dipole. The feedpoint impedance will be considerably higher. To get a predictable folded dipole, you need a constant spread for the whole length of the antenna. There are numerous resources on the Internet and in the ARRL antenna book.

@timmcilraith8762 9 месяцев назад

Thanks Dave.

@DustyTrailCFDA 10 месяцев назад

informative as usual. Thanks

@richardcallihan9746 10 месяцев назад

What about a full-wave circular loop made from small copper tubing on 10 meters using rg-59 coax matching stub, could you electrically shorten it by re-soldering one end progressively to tune, and folding excess inward?

@glenmartin2437 10 месяцев назад

Thank you, again, Dave. Grazie. N0QFT

@ButtonsKing 10 месяцев назад

Hi Dave, you did a nice experiment. But you made a mistake, which did not change the results, but may confuse some hams. See 6:35! The wire is in direct contact with the rope, the insulator is useless. It might matter during transmitting, if the rope was wet.

@alexjh47 10 месяцев назад

I built a Moxon antenna with the wire connected via paracord, tuned up great in the dry weather, and was terrible in the rain. I need to put some insulators on there if we get a sunny day.

@bill-2018 10 месяцев назад

Okay for a test in dry weather as you say G4GHB.

@davecasler 9 месяцев назад

Good point

@user-zk2yd6xm8s 10 месяцев назад

Did not see where you explained the law for capacitance reactance Xc = 1/2Pi * FC. As you wrap a insulated wire back onto itself you are making a capacitor.. Thus RF will see it as one wire in spite of it being two since the RF passes through the capacitor before it reaches the end

@aurtisanminer2827 9 месяцев назад

If you wrap back a decent amount of insulated wire for tuning you need to leave the excess attached afterward. I wrapped a couple feet of excess insulated wire back on a 75 meter dipole to get the tune I wanted. After getting it all tuned I snipped off the excess. Then my antenna was too short! This shouldn’t be an issue with bare wire since it shorts back onto itself but the insulated wire is still an extended antenna while wrapped back, just not as much as if it were extended all the way outward.

@criscross6591 10 месяцев назад

👍👍

@clems6989 10 месяцев назад

Where is comparison between bare copoer wire dipole with ends folded back vs ends trimmed up ? I didnt see that in video ?

@davecasler 9 месяцев назад

The folded back bare copper wire is shorted to the main wire, hence will not make any difference as long as it is wrapped reasonably tightly. 73, Dave, KEØOG