Ham Radio - A 40 meter folded dipole using window line.
ฝัง
- เผยแพร่เมื่อ 11 พ.ค. 2019
- In all the years I've been playing radio, I've never built a folded dipole. Boy have I been missing out! These are amazing performers.
Link to the 3D part for the center:
www.thingiverse.com/thing:361...
My video on making the 4:1 Balun:
• Ham Radio - Building a...
A few pages with technical info on folded dipoles:
www.electronics-notes.com/art...
www.w8ji.com/folded_dipole.htm
www.qsl.net/w4sat/fdipole.htm
If you like my videos, please subscribe here: th-cam.com/users/loughkb?s...
If you want me to keep making more videos like this, consider becoming my patron at Patreon: / kb9rlw
Discuss this and other videos on Facebook:
/ kb9rlw
The hols in the window line reduce wind load. Interesting and informative video.
Jochen As roy previously explained. The holes in the feeder are there to reduce the velocity factor. That is why open-wire feed line is better with less material in between the pair of wires.( i.e the v.f number goes up).
Great video Kevin. I've built several folded dipoles with similar, great, results. I recall a few years ago when I researched the noise immunity it was due to how the antenna responds to the E and H fields versus a conventional single wire dipole. The folded dipole, being a loop, responds more to the magnetic (H) fields of radio waves. Most man-made noise is electrostatic (E) in nature and less prone to be picked up by magnetic antennas. The use of the current balun, as you mentioned, chokes off common mode currents on the coaxial feedline, so that the feedline isn't as prone to receiving noise as much either. Seems to me some authors called the sensitivity to electrostatic voltages and currents the "antenna effect". Sorry I don't have any citations to back this up, but that's what I recall as an explanation and it seems plausible to me. 73, Sparks.
Thanks for sharing all this information. I must say I am very impressed with your quiet efficient 40 meter folded dipole.
I am a real beginner with ham radio or radio overall.
Last month i made my first crystal radio, and now i am in the process of putting up my first inverted V dipole antenna in my backyard, so i can get on the 20 and/or 40 meter band.
I just wanted to say that Kevins videos has been the most helpful in order to wrap my head around it all.
Next will be to install a long Beverage antenna in the fields around here, so your videos are a tresure for a student
Keep up the good work! de KD5INM
I thought it was Called Ladder Line because it looks a bit like a Ladder..
Great to see it working so well for you Kevin.👍👍..Very well presented and explained...
Take care in the Sun, you are looking very Healthy but a wee bit like a Strawberry hi hi.😊.
Wow! Quite a noise level difference. Thanks for another great video, Kevin.
Yeah. I keep checking against other antennas. It's equally dramatic compared to an end fed wire too. So much quieter. (except for the signals, which get much stronger.)
I wish I'd built one of these years ago.
Great to see Ladder Line being used, I know my late father explained that a lot of the radio operators when they were deployed in the Angolan conflict waaay back when used Ladder Line Antennas.
I have been using a off center fed dipole for many years. When I started out, I did not know so much, but I thought I did. Once I got the full understanding of the off center fed dipole. One of the benefits is the multiple bands it can tune with no tuner. The tuner in your radio can increase bandwidth of some of the wider bands. I have 1.2:1 across 12m, and that is a rather short band, but it also works very well on 20 m, 40 m, and many more. The things I learned in the years leading up to now, are that the feed point impedance is governed by the height of the feed point.. The other thing is the BALUN, it is a 4:1, and I made my first 4:1, and it worked, but not so well. I called Bob at BALUN designs and spoke to him about what I was doing, and he spoke to me for a while, I eventually bought his BALUN that was made for OCFD's. It does handle a lot of power, but I only run 100 watts. There was a marked improvement if the dipole, but still not perfect. The next improvement came when I put ground radials just under the grass line under it. This was a very good step in the right direction. The last improvement came years later, and it was after I had my crank-up fold-over tower crash to the ground. The tower only put my feed point at 28 feet. I then installed a Rohn 25 tower, I did this all by myself, and once I was done, my feed point was at 40 feet. This is when my OCFD took a sharp turn for the better, it was now the antenna that many love, and the one that drives hams toward it. Even if they don't get what I have, many give up and try something else, but the Ham friends in the area who had my input on it, all got the same great antenna, and still use it. The low noise of your folded dipole, might be great for low noise, but when there is no noise, nothing beats my OCFD, unless it is one of the wire antennas that take a football field to assemble and use. i have very small property in Florida, and the antenna is 90on one side, and 45 on the other. one side runs out to the road, right next to a stop sign,. So it is all I can do. I've been using it as my only HF antenna for over 10 years.
Great video thanks - I already have a bought antenna for 40 m - but this looks much more fun so I will just have to build one! Very informative piece of work. 73s from England.
Wow. Thanks for review. We use that ladder line in our QSO Party field operations as the feed line for a large loop antenna with 1,000 feet or more wire. I found the same thing with the QRN. It was extremely quiet even compared to a regular dipole. We always twist the ladder line to keep it from flapping around so much in the wind. Very good job, Kevin. Thank you and 73 de K7RMJ Frank
You are very knowable I’m very happy you are sharing it! I learn a lot and your videos are very enjoyable. :) thank you
After watching this video I found free 300 ohm TV twin lead. I made a 20 meter folded dipole and fed with the same into a tuner with balanced input. I strung it up in my living room full of noise sources. About the worst environment you can imagine in a big city. My living is pretty big but the antenna still hangs down the wall from the molding about 1.5 feet.
I had pretty decent results at 5 watts for JS8. I had previously been using an EFHW for the same. The biggest issue I have with this antenna is that it doesn't pack up well. The twin lead is a pain since it doesn't go onto a wire wrapper.
I recently met Kevin on the air and he was using the folded dipole. His
signal was between 10 to 20 db over 59 the entire time. .. .Kevin,
we enjoyed having you check into the Earlybird Net.
Thanks Steve. I'll be checking in there again. 73
Nice video, I might try to build this antenna.
Kevin,
You have mentioned you are building a folded dipole with some (I think what is 450 ohm ) twin lead, window line. You made the comment that you think the window are for using less material. This is mostly correct. the windows also decrease the dielectric constant of the plastic, increasing the impedance of the line and reduce losses. Designing and making your own twin lead using mostly air as a dielectric would reduce the losses. I enjoy your videos, thank you for making them.
73’
KC6WUM Andy
Thanks for this. I never use dipoles because they're too damn big. But this one is much smaller, and apparently works pretty well. Saved to my "Antennas" playlist.
That's a pretty dramatic difference, I'm going to have to give that a try.
Good video Kevin..I used a while back, a folded dipole cut for 40, and it did work very well on 15, and 6.. 6 will be picking up very soon, so keep a listen for the beacons, and the FT8 on 50313 is a good indicator as well of openings...
73
VE6PG
I have a folded dipole for 40m, made from 450R ladder, I feed it with 300R twin, as that's close to the fed point impedance. I then use a 6:1 balun behind the radio. Works great!
Very nice video, excellent and thanks for the content. I'm going to build a HF dipole soon, but using traps as I have space restrictions too.
73 Hayden VK7HH
The bit about even harmonics can be turned into a feature for SO2R or Field Day. With my 80m folded dipole and a 40m dipole mounted less than a foot or so apart at the center, and running the legs parallel, I was able to run 2 radios with very little interference at 100w. I did keep the feedlines for each dipole as separated as possible. Xmit on 80m(3.515) was detectable on the second radio on 40m, but right on the second harmonic the signal was only about S7 on 40m(7.030). Undetectable away from the actual second harmonic. Pretty darn useful feature right there.
That is a potentially extremely useful bit of info. My old club in fort Wayne has been battling station interference forever.
@@loughkb Yes, very useful. The second harmonic from a folded dipole is attenuated down more than most band pass filters. (-50db vs -35-40db) Very useful indeed. Probably more pickup from coax to coax, and I would expect best results using coax rather than ladder line feeders for this purpose. 73 es gl
Hey Kevin awesome video.
Excellent video... I am going to try to build one of these. I have a lot of noise here on 40. Thank you for sharing! K5NR
Ahh Heck I figured I would just finish watching it now. Nobody around anyways....LOL
Good Job Kevin!!
Hello and thank you, Kevin! So this was the antenna in use when I decoded your signal remotely in Pennsylvania (also here in south Texas). Sounded great on the air! Low noise antennas are the best to use. Receiving a clear signal is half the battle. Speaking of receive antennas, if you feel so inclined, how about doing a Beverage Antenna video? 73 de N0IJK/5.
Good one Kevin. Well explained. Ever compare it to a full wave loop? It is a squashed loop but not much enclosed area.
NICE!! *917*
🤳 Really Great information on radio Waves And How they work with Different Antennas!!! ✍
nice explanetory vid.
what about folded monopole
i.e.vertical been looking for plans but very confusing!73
Good to know. Thanks.
Would it be possible to build a fan folded dipole , hence allowing the same antenna to be used on the desired bands?
Great video. Guess you'll have to make a 20 meter one. I'm using a 40 delta loop in a triangle configuration and love it. Very quiet. Works ok on 20 also. Take care. JJK
Must give it a try.
Great video as always!! Robert K5TPC
I can see a "fan" Dipole experiment for multi band use. Just a brain cramp, Carl
Hi Kevin, as always quite interesting to watch your presentations. Please confirm whether the folder dipole will bring the size down to half. I mean in normal case for instance if the 40 meter require 66feet approx. Will the folded dipole requires 33feet ?
Very informative video Kevin, thanks. Where would I find that window line?
Any number of antenna or amateur radio suppliers. I did a quick search, here's one source.
www.ebay.com/i/153470161443?chn=ps
Thinking on this, would a quadrifilar helix antenna work also? Maybe for 10, 6 and 4M but could it be used in those bands for when DX is open enough for tropospheric times in the summer?
I’d be interested to see how this holds up for RV life. Ladder line isn’t very good at taking down, rolling up, putting back up, rinse, repeat. I still have a roll (50’) left over from a folded dipole I built and used in 2000 or so, I can’t remember what it was called, but I was able to get 160-10 through an MFJ roller inductor tuner with a built in balun.
Thanks for sharing 👍😀
Great tips !!!!
Hi Kevin, huge thanks for this and all your other excellent videos. A new ham, I'm waiting impatiently for my first HF transceiver - a 40m QCX kit - to arrive (I've just watched your video on the assembly of yours for the second time, in fact), and need an affordable antenna. It looks like you've come along with this video at just the right moment !! I've been reading up on dipoles, and was despairing on the need for height - minimum half wavelength is what they say, and that's out of the question for me, so I was about to go with a vertical and wreck my lawn with ground plane radials. As I'll only be on 40 for a while yet, it seems like a folded dipole is the way to go. So my question for you is: what height do you run yours at? It didn't look anything like half wavelength in your picture... I'd like to try DX QRP, but I worry that the radiation pattern won't be suitable.
73, Julian, AJ0S.
p.s. I'm not smart on antennas just yet, but my electrical background is prodding me to agree with you that the low noise from the folded dipole is attributable to common mode rejection, especially as this antenna is so deaf to anything out of band.
Dipoles do work 'best' and radiate better at that half wave length minimum height.
But they do work well much lower. You just start sending more signal up and less out as it begins to act like n NVIS antenna. (as discussed in a previous vid.)
I was running it low, just 17 or so fee up with the ends down to about 6 feet. No choice here. But it still got out great.
Use what you can to put it up and it will work well enough at any height.
Welcome to the hobby and I'm impressed you're diving right in to CW.
Thank you Kevin! i just found this while looking for info on a 30m folded dipole for FT-8. I wonder (two years later) if you still feel the same about folded dipoles? also i already have a 4:1 dual core High power balun, would using it at 50w be lossy or counter productive?
Thanks Wayne N8KIM
This is a very interesting and useful video, especially for me as I want to build my own antennas and am fortunate to have a long but narrow plot. I have the length for a 160m half wave or a folded dipole but wouldn't be able to get it half a wave high! Hi hi.
Hello Kevin,
Thanks for making these videos. Here are few observation. 1. Assuming you've printed the center part of the dipole with PLA it's worth covering it with a paint or a varnish. There is a good chance that PLA will not live long outdoor otherwise. 2. I wouldn't trust the SWR figure at 50 Mhz much, especially if the measurement was done through a long piece of RG58 coax. As you probably know this cable has relatively high loses, especially at high frequencies, which is especially important when you measure SWR. You have to multiply these losses by two - one time for the original wave and one more time for the reflected wave. Considering other factors, like measurement error, a little miscalibration of the device, etc It's not uncommon to see SWR 2 when it's in fact 6 or more when just 10m of coax is used. You can easyly check this with a vertical antenna (or even a dummy load) by making two measurements - one right at the feed point and another through 3/5/10 meters of the coax. You'll notice that the longer cable gets the more distroded the SWR figure is, and that the SWR gets lower for higher frequencies. 73 de R2AUK
Yeah, PLA might not be the best choice for long term installation. Dollar Store nylon cutting boards make for great material stock for things like this.
I also wouldn't expect such a long antenna to work well on 6 either. Too many lobes, loss in the feed, loss in the balun. It might work, but won't work well.
Good explanation on the phasing relationship doesn’t work on even harmonics.
Nice. I think I’m going to try this. Could you run multiple lengths similar to a multi band dipole to the same center connectors? Eg oine cut for 40! and one for 20?
I'm not sure, but I think that might work. Sort of a fan dipole arrangement but with folded elements. It would be one heavy antenna though.
Thanks Kevin, I will get round to making 1 and see how it performs. 73 2E0KVR
High there Kevin. Over in Germany they used flat twin feed for the T.V line. It was 200 Ohm impedance. All kinds of folded dipoles were made with it with modifications for tuning to length for each band by adding capacitance at each end. I've long since lost all the details. The same material was used for the feeder for these folded dipoles with matching at the shack end. So no expensive/ lossy coax to provide. My Eddystone Rx could be fed direct with twin feeder, so I had no problem.
QRN is vertically polarized, so I'm not surprised the folded dipole is quieter. I'd like to see a comparison between a normal dipole and a folded dipole.
I do like playing around with things like this.
I am interested in how you arrived at the hypothesis that noise is polarized?
I do see the noise on my sloper and NVIS antenna experiments by the way.
I am going to make one of these. Thank you for you video. I have a question. When you tuned it by trimming the ends did you do that by trimming and then connecting the upper wire on the ends to measure the antenna parameters, and then retrim, solder together, and repeat? Or, can you trim to length using only the lower wire and then solder the upper wire once you get a match?
I didn't measure it before connecting the wires at the ends. I think that method should work since the unconnected wire would just be a parasitic element of the same length and characteristics.
I just twisted them together and didn't solder them until I'd found the right length.
@@loughkb Thanks. That is what I was thinking too. It will make trimming easier since you need to raise and lower the antenna each time. Before making the first cut I will scope the antenna with and without the ends tested to check.
I have a lot of local QRM that I am hoping this antenna might let me get a little better performance. Your comparison with the vertical was a dramatic improvement.
Is that 300 ohm line or 450? I see both are available. I just ordered a 3d printed center hanger to give this a try!
I'm going to try a folded dipole. Looks interesting.
If you haven't and get a chance try a double boozka made from coax like RG8U, without any foil between the conductor and braid. They also have an excellent quiet receive quality. I tried one on vertical. The lack of noise compared to others was phenomenal. It also has a DC short. I'm sure that must be the reason.
My gut tells me the bazooka might be quite similar in performance. However, much more complicated to make and you really need a carrier line to hold the antenna under. All those joints along the antenna become potential failure points under the load of it's weight and motion from wind.
Very interesting kind of like that . Would you think about making a 40 m loop that way
In a full wave loop, the wire length is slightly longer, but you still need to feed with a 4:1 balun as far as I know.
In this folded dipole, if you unfolded it there would be a total of around 130 feet of wire. In a loop, the online calculator shows 140 feet of wire.
Kevin great video as usual, but what happened to the folded OCF?
I thought I covered that at the beginning. It was just a variant of a folded dipole.
Yes you did, I was not observant. Great video and I am going to build one for myself!
Great video. I'm doing something similar with 450 ohm but creating a linear loaded doublet to try and improve 80m in my small garden. So both doublet legs are not linked like yours but seperate with the ends of each leg shorted. Found info which suggests that you need 70% of the usual halfwave length per leg to create resonance so 46 feet linear loaded 450 ohm (2x23 feet) will get you about 7.1 MHz. Downside is narrower bandwidth for 2:1 SWR but as a multiband non resonant doublet, fed with ladderline / windowline into a tuner it might be worth a try. 73
That might work. But you will need the tuner and it will probably not have the additional noise immunity.
In terms of noise my existing 44 foot doublet is v quiet hence my confidence in the RX aspect of this antenna. 73
I’ll try one on Field Day
Have you experimented with a folded terminated dipole. They are very broadbanded. SWR will be low for the lowest band it is cut for and all bands above it. They are quiet antennas, but you lose a S unit or 2 in receive. You usually make up for the loss in the lower noise floor. I had one that was 65ft long and was usable from 6m up to 40m without a tuner. It does have a matching balun, and a terminated resistor.
what happens if:
1. you connect 2 of them together at the center with one turned 90 degrees? (like a "+")
2. you slant the elements like an inverted V?
I've tried putting two dipoles together in a + configuration. Didn't work well at all.
Great video. I have a bunch of this 450 ohm line. I am going to take down my old 20 meter inverted V and put a folded dipole up in its place. First, I need to build 500 watt balun. The only thing is the wind loading on this window line ? hmm
Put folded dipole on a slope 35-45deg ,works well.Built these for 11-10m bands,yes are quieter.
Hi kevin is there a option to use only coax cable whit the balun 73, pd0cor
Wind the balun with coax? Maybe. It would be big, and heavy though. See my previous vid on winding the balun. It's really quite easy to make.
Nice video, man made noise is typically vertically polarized. That's why a dipole is quieter than a vertical on the lower bands. 73 Douglas
I have heard claims both ways, some that man made noise is horizontally polarized and others share your view. However, I have yet to uncover any real world testing or data to indicate either.
The most probable explanation I have encountered is that verticals are noisier because they are omni-directional. So all noise sources around them contribute energy to the antenna, whereas a dipole has nulls off the ends, reducing the noise sources that it can hear.
This seems to make the most sense to me.
Hello Kevin, horizontal dipoles are omni-directional unless they are 1/2 wavelength above ground. ie: 70 ft on 40 meters, 140 feet on 80 meters.
@@kb9gkc please provide a link to a technical source that verifies this. Everything I find mentions the null off the ends and only the lobes off the sides change with height.
Hello Kevin, EZNEC confirms this in the attached link. Take a look.
www.qsl.net/aa3rl/ant2.html
you got me here
Wondering how this would work if you cut it to length as if you were making a doublite with it. 126' in length ? fed with 25'-30' window line.
That is one of my thoughts also. I have 450 Ohm window line to play with so it might be time to find out.
From what I've read on doublets they are best cut at an odd 1/8 wavelength of the desired lowest frequency ie 5/8 or 3/8. The same with the feedline.
To tune upper band sweep to see if any upper bands are bad match. If so, trim an 1/8 wavelength based upon the upper band.
I understand a tuned doublet for 80m can work on 5 bands.
W4RNL was where I found some better reading.
N4VEP
I haven't done this but it seems that some OCF dipole antennas don't work well on 15 meters so a monoband folded dipole may be one solution to have a decent antenna on that band, the same could be said for a monoband antenna for 12 and 17 meters.
An end fed half wave wire, fed with a 49:1 match, cut for 40 meters, 20 m, or 80 m, will work on all the even and odd harmonic bands. Including 15 m.
Wow, that drop in noise is a big attraction for me. Does your folded dipole need a counterpoise? It looks a bit like a big loop antenna so I'm thinking maybe not? Will probably build one after my 20 meter mag loop is up and running.
No counterpoise needed. Its a balanced antenna.
How bout adding an RF choke at the base of you verticle.... maybe a relay to test in and out... DC grounding??? Tnx for the great video ...73
I have done a choke on the vertical upstream from the 9:1. It only helped 'slightly' with the noise. Nowhere near as dramatic of a drop as on the folded dipole.
Kevin, Did you move you feed point? if I remember it is Off Center Feed. Or is it classified as an end feed?
No, it's center fed.
That's the only thing that kills it for me is it's only mono band..
so my 2 antenna i use for camping are all band HF Doublet 10~40 or an off center fed 10~40 meter
I'm experimenting with a vertical setup where there is no treas with an MFJ Ham Stick on a painters pull 20' up with 4 ground radials dubbing as support wires.
little more work if i want to switch bands but it seems to work well with 10 15 20 and 40 whips.
Yeah, it's a trade-off. Any multi-band antenna is going to be a compromise in performance on any one band. A mono-band antenna is tuned for the best performance.
My dream house is a cabin in the woods with lots of trees around so I can put up individual antennas for each band. :-)
Is there any info from those that have tried to do an off-center folded dipole. I would imagine it would require a 9:1 balun. I suspect it would be frequency agile, but perhaps not too efficient. Otherwise there would be literature.
What if you cut different ground lengths to gain that resonance on other bands , but then that maybe changing the directional signal in the lobes.
Has any one built a loop using FM 300 ohm ribbon, it may sound silly I know, such as a triangle or square etc for more for a multi band use, as I was going to make a folded dipole for 40 meters using FM ribbon cable ? for low power.
VK4fpkl
could you put say a 450ohm resistor in the parallel line above your balun and make it a t2fd ?
You could but you then lose most of your power heating the resistor! :-(
Like Brian said, it won't be efficient. The military used that arrangement to get full hf coverage. The cost is loss in the resistor as heat.
@@brianjohn9144 the actual loss is about 30% of your TX power, which can be a worthwhile sacrifice in some circumstances. The T2FD's SWR tend's to yoyo up and down across the spectrum covered by it, so a tuner is a useful thing to have in line. In the old days, before solid state amplifiers, this was not so much of an issue as the TX tank circuit would cope with the mismatch.
On a 40m half wave dipole +- 60 ft is it +-30ft from center on each side and do you solder the center conductor wire to one side and the braided ground to the other side? Have looked all over and havent found a good explanation. I know it seems simple. Please help.
Yes, that's correct. And you want to start with 65 feet total so you can trim it back when tuning it. Mine is around 64ft 7in now and it is perfectly centered on the band.
That's not quite like the folded dipoles I've seen recently made from wire and spacers, but seems like a much easier to make design. The 4:1 balun is also neat and simple. I had to order a couple of toroids to make my own. And that noise drop would be great for an urban noise environment. I hope there will be a performance update in the future.
I hope to hear from a viewer that makes one in urbana.
@@loughkb Where is a good place to buy a bunch of that window line? If I had extra I would make a roll up J-pole, or a Slim-Jim with it too.
@@JohnSmith-bb2np Hamfest is where I get mine, usually the dealers have bargains since they are all competing for your business. You can also make your own using plastic dollar store cutting boards or plastic coat hangers. Cut the plastic and drill holes in it the size of your wire and space it the distance of 450 ohm ladder line or you can use just about any spacing. I have seen ladder line up to 6 inch spacing.
Another well done job~! have you ever tried a double bazooka? de w3les.....AND posted to my W3LES fb pg
My gut tells me the bazooka might be quite similar in performance. However, much more complicated to make and you really need a carrier line to hold the antenna under. All those joints along the antenna become potential failure points under the load of it's weight and motion from wind.
How much coax loss do you have? How much balun loss do you have? How much better (worse) would your dipole work with open wire line and a well designed tuner?
what is the length that you used ?
65 feet. As shown in the diagram later in the vid.
Hi....can we reduce the length by using loading coils...?
I don't believe so. It's a closed system and you lose efficiency and bandwidth when you use loading anyway.
You are comparing apples to oranges. A proper comparison would be single wire horizontal dipole to Horizontal folded dipole. Any horizontal should be quieter than a vertical. Good video, I agree on all other aspects of your dialog. I will give it a try as soon as possible for my NVIS use.
Silly question but with the window line twisting on the main element does that affect the performance or radiation pattern
Not that I could tell. There were times when the wind was spinning it and signals remained strong and steady.
Bandwidth and low noise. What more could you ask for?
Only issue is stealth but a good performer
One quick question. Out of curiousity, what is your antenna height?
The apex is about 20 feet up and the ends were 6-8 feet up. Best I could do with where I am.
I’m not well versed in antennas, ok so what’s the advantage of the antenna you built( closed loop) with some other folded dipoles I see on TH-cam, with (open loop)?
I think it's quieter. Less susceptible to some types of local noise. As far as it being opened or closed, the secondary element acts like a parasitic element anyway.
One more question: Can you fold a folded dipole thus making it take up half the space?
No. The physical length will dictate the resonant freq.
@@loughkb What about making a 80 meter or 160 meter folded dipole and shorting it at the 40, 20 and 10 meter points, example if a 40 meter is 56 feet then make it 80 meters length and put a switch at the shorting point for 80 meters and switches at the 40 meter point and opening 80 meter switch and closing 40 meter switch.???? Would that then act as a 40 meter dipole?
So, the length you get from 468/freq, should that be the total length of the window line (end to end) or do you cut that in half because you are folding it back basically?
Total length. The folded part mirrors the other electrically, so it still needs to be a half wave total length.
@@loughkb Thanks! I am going to be giving this a try at some point!
Hi, if you are using anycubic i3 mega (wich looks like it) what settings do you have on Cura pls? My prints tend to wrap on one side. Thanks
Mostly the defaults cura provides for the prusa I3. I never print hotter than 200c with the bed at 60c
@@loughkb I have tried the same and for the first 5 prints it was fantastic but than I could never come back as the warping started, furthermore some websites say it is due to fan so now will be looking for the circular one. Great videos btw, really enjoyed every one of it. Passed the radio licence in UK not too long ago and loads to learn and explore. M7OTG 73
@@MrCrystan If you're talking about warping of the bottom off the bed, you may need to clean the ultrabase. Heat the bed to 60c and then use a lint-free cloth and alcohol to wipe the bed clean.
Kevin when we built these for TV reception we would make for lowest frequency then wrap about 6 inches of tin foil on each leg. By sliding this wrap closer to feed we could resonate on the higher channels. I am trying to think of a way of tuning down to 20 ect. A capicative "short" so to speak.
I expect that any hack to trap it for use down on 20 would mess with the total length for 40 and probably reduce any gains in performance you get on the antenna as described.
Build two. One for 40, one for 20. Maybe they can share a feedline/balun and work as a fan of two folded dipoles. It would get pretty heavy though.
@@loughkb I don't think you understood what I was saying it wouldn't be multi banded but could be changed to a higher band by sliding the wrap from the ends to the 20 meter point. The antenna might have to be lowered but shouldn't have to be cut.
Wether you use an inline coil as a trap, or a capacitive 'short', it still leads to change in the whole system. I'm certain there would be loss in efficiency and performance. Gut instinct.
@@loughkb this is a method that can can only be used on a folded dipole. I have only seen it used for reception but it worked well for that. It wouldn't hurt the antenna on the design frequency at all as they wrap would be shorted all the way back to the already shorted ends.
If it worked it would change the resonant frequency of the antenna. Closest coarision I can make is the Step IR
For most of us that don't have a printer I think a plastic coat hanger should work.
So, could this antenna be made of standard 75 Ohm "TV twinlead"? Only ask because of the plenitude of this antenna conductor. Where are the cutoff's for its use? VHF/UHF? 73!
The physical form of a folded dipole is used in products throughout the industry and spectrum. The little wifi yagi I picked up for my extender project has a folded dipole for it's active element.
You could probably build one with the old twinlead. I'd be interested in what the measured impedance is at the center feedpoint. It might need a different balun design.
Due to local physical restrictions, I won't by xmiting.. but due to tremendous noise 'quiet' interests me immencely.
I know the xmit efficiency on other bands is objectionable.. my question is how does it RECEIVE on unintended bands?
In my advanced years I have been allocated to the ranks of SWL..
.
Where it didn't TX well, it also didn't RX too well.
@@loughkb thank u sir.. I was afraid that might be the case..
Yo Kevin:
As USUAL, GREAT video! I would like to see a variant on this video. Two items. A) video on a MULTI band version (& cross member version? : ) & B) a STEALTH version for HOA impacted folks (would be VERY much appreciated I am sure! : ).
Again GREAT video!
de seeker/Jeff WA7LFP
The "Twisted Pair" make an appearance...
Thanks for the video. But I do not have a 3D printer. But do know how to use cheap plastic cutting boards for same thing. Can you just give me the measurements?
Not critical. Just cut something to fit for your application.
Unless you're talking about the antenna measurements. But those are in the diagram shown in the video.
Lightning would be vertically polarized, wouldn't it? Maybe that's why the vertical picked up all that noise? I read the comments.
Well, lightning is mostly cloud-to-cloud, or Cloud to ground at an angle, so it's certainly not vertically polarized. Also, the noise that you heard that went away, was hash noise from electronic devices. Lightning makes loud short crackling sounds. Electrically generated interference is usually a whooshing sound.
Clarifies things a bit. Now, got any tips on learning Morse? I'm building a qrp CW set, and it'll be my first time on the air, too. SWL forever, though.
Learn the code by listening to the rhythm of the letters, don't count dots and dashes. If you learn by counting, you'll hit a wall around 12 WPM where your brain just has too much work to do to decode letters.
I have a couple of vids on CW, learning and proper sending. Search for my call and CW to find them.
Thanks :)
Hi...Kevin!
Noise is more related to Vertical vs Horizontal.
Would love to see the comparison of std dipole vs folded.
My full wave loop is much quieter then my dipole. I agree, a shorted loop is better for noise.
Is it possible to make a folded doublet
You could feed a folded dipole with window line, but it wouldn't be considered a doublet then. Doublet just refers to a symmetrical dipole that's usually non-resonant and fed with parallel feed line.
@@loughkb Thought so many thanks
If you’re connecting to BNC over coax, wouldn’t you want a 6:1 balun?
The type of connector doesn't change the impedance of the coax.
@@loughkb agreed, that was an irrelevant part of my comment. What I meant was, aren’t radios and coax generally 50ohm? Connecting to a 300ohm antenna would then need a 6:1 balun, otherwise you’re baseline moves to 1:1.5 SWR minimum.
@@jtmcfarland3512 impedance on the folded dipole is generally 450
@@loughkb well Gosh, if you’re using standard 450 ohm ladder instead of 300 ohm [which I thought you specified in the video] then that would be a regular 9:1 balun, wouldn’t it? Sorry, I’m new to this and just trying to understand. Thanks!
The impedance of the ladder line only counts when it's being used as feed line. Using it as a folded dipole the actual impedance of the feed line itself doesn't matter. It's not being used as a feed line in that point
You should make or buy a double bazooka very similar antenna only no balun 50 ohm feedpoint the same pro's
AA4CP Chuck Patterson
Port Salerno FL USA