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Creating a Folded Inverted-Vee Antenna (031)
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- čas přidán 15. 08. 2024
- In this video I will be showing you how I created a Folded Inverted-Vee Antenna for the 3.5 to 4.0 MHz Amateur Radio 80 meter band.
I will walk you through the whole process so you can create your own for any frequency you choose.
Why do this?
A Folded Dipole or Folded Inverted-Vee antenna has significantly wider bandwidth than its non-folded cousins.
I wanted to increase the bandwidth of my antenna to cover more of the 80m band.
Here is the promised link to the 4NEC2 model:
drive.google.c...
Time Markers for Your Convenience
----------------------------
00:05 Initial Comments & Introductions
01:07 What is an Inverted-Vee Antenna?
01:36 Why use an Inverted-Vee Antenna?
02:14 What are the characteristics of an Inverted-Vee Antenna?
02:45 Why create a Folded Inverted-Vee Antenna?
03:49 How does the current antenna perform?
03:59 Introducing the antenna
04:32 Its performance - the VNA scan results
05:23 Planning the new Antenna
05:27 Starts in 4NEC2 - a Quick Tour of the Model
09:39 The Pieces and Parts
09:45 The Center Support
10:41 The Spreaders
12:19 End Supports, Insulators, Spreaders
12:58 The Wire
14:20 Assembling the Antenna
16:28 Testing & Tuning
17:31 How much wire do I trim to tune?
20:22 The FINAL Performance Results
21:38 Final Comments and Toodle-Oots
-----------------------------
As always, a magister class, Ralph! Thanks a lot, 73. Pancho, LU4DCW
Thank you so much! I am so glad that you found this helpful. You are very welcome! 🙂
Just discovered your channel. As a Tech, I am impressed by your delivery, knowledge and professionalism in your videos. Thank you for teaching us the way you do, making it easier to follow the info. You have a new follower.👍 73
Awesome, thank you! Welcome to the family!
Backing into the length formula to derive the Velocity Factor for your particular wire and configuration is the CORRECT way to achieve accurate adjustments. I’ve seen other CZcamsr antenna makers explain their method which uses the standard factor, and as one might expect, their adjustments never prove to be correct, and in the end, they have to achieve their results by trial and error, which defeats using a formulaic approach in the first place. Kudos for actually educating the community. I really enjoy all of your videos.
Edit: I just remembered, Callum (DX Commander) pointed out that a folded end does not react linearly to changes in length. Im guessing there is an exponential/logarithmic relationship involved. Trial and error may just be the most convenient method after all.
Thank you! I'd like to call it the "educated trial and error method." You are right, there isn't necessarily a *perfectly* linear relationship. But, like so many things in the EE world, if you get close enough, even a non-linear relationship can appear reasonably linear. This is done *all* the time in analysis.
So, we calculate it as a linear entity, trim less than calculated off and then recalculate and trim. We are not, then, trimming blindly or forever trimming small chunks. 🙂
I love your passion for the artform. Keep up the great work.
Thanks, will do! :-)
I made a folded dipole for 40m last year. I made it out of a length of 450R window line. As the feedpoint impedance is close to 300R, I fed it with 300R ladder line down to the balun near the ground, used a 6:1 balun then coax to the shack.
It worked really well, good and quiet too.
I’d imagine yours is wider bandwidth than mine though, as the elements are spaced more.
Yep, the wider the spacing, the wider the bandwidth with the law of diminishing returns in force.
Interesting and really well done! When trimming an antenna to its res freq, my trick is to work out what percentage of the desired freq the actual res freq is; If the res freq is too low then the antenna is too long by that percentage. So cut that percentage off the legs!
Yup! That is exactly the kind of thing I do, but I still purposely cut it a bit longer than those calculations tell me. It's nice that there is that simple inversely proportional formula for antenna length! 🙂
I've played with many dipoles and I finally ended up with a 102' dipole, fed with 450 window-line, on a 48' tower and never looked back.
It has not only able to hit all the HF bands (except 160m and needed because only have TH-7DX) but I get the best signal reports I've ever gotten.
All of my old antennas were coax-fed, some even with baluns but after using balanced feeders I will never go back to coax again!
In addition, we replaced the coax on a FD 40m delta-loop and dramatically increased its performance. 73...
You certainly cannot beat a balanced feedline! 😎Hands down the best way to go ... if you can. Coax provides a LOT of convenience (especially in getting your signal in and out of the shack).
If you have supports available to support the ends of a dipole, too.
Yes, you have an ideal installation. 🙂
@@eie_for_you well, that begs the question, what would be the advantages (besides the obvious multi-band capability) of your folded dipole if fed with open wire feeders-worth the squeeze?
@@SpinStar1956 You could most certainly feed this thing with open wire feeders (native to its impedance). As I see it, you would not have to deal with the losses associated with coax and the BALUN. But I think that the losses at 3.75 MHz are pretty minimal.
@@eie_for_you well, no I understand that, but I was wondering about the nature of your dipole being folded. The only thing I could see was maybe less tuner excursions per frequency, Delta. Is there any radiation advantage or is it only bandwidth enhancement?
@@SpinStar1956 When I was doing the modeling in 4NEC2, I set the characteristic impedance to the native impedance of the antenna (300 for the folded dipole and 75 for the dipole, as I recall). So, the analysis is quite agnostic of the particular feed method, whether coax, 4:1 BALUN & coax or open-wire feedline. The advantage is mainly in the bandwidth of the antenna The folded dipole will have a wider bandwidth than the dipole and the folded inverted-vee than the inverted vee.
Yes, the radiation pattern is, indeed, different between dipole and inverted-vee. Is there a difference between a folded dipole and a dipole? As I recall ... not really. Is the radiation efficiency higher? I wasn't paying attention to that, so I can not say. All of that is in there in the 4NEC2 simulations, I just didn't notice. Unfortunately I am not in a position to re-open those simulation files to have a look see.
I did provide the link to the 4NEC simulation so you could download that an play with it yourself. If you are not familiar with the FREE 4NEC2 antenna modeling program, here is a link to the first video in my series on the program:
czcams.com/video/Zd6BT558YRA/video.html
It is sooooooo much fun to play with! 🙂
Good stuff, I appreciate the time you put in to put in this video together, for 75/80 M I run inverted L here I have two elevated radials underneath my inverted L antenna inverted L is a single wire I have a toggle switch a double pole double throw toggle switch which toggles between two different sets of radials for one cut for 3790 the other one's cut for 3950 on the high end of 80 m it's a little bit of a trick to walk outside with my 10-ft pole I can throw that toggle switch right at the feed point of the antenna as the elevated wires are up 10 ft in the air but I can easily switch between 3950 and 3790 with a very low 1. 5 or less one to one SWR and I can move all over those two bands so I get the right chew and on the high side and the dxn down on the DX window but yeah I love antennas thank you...
Thanks for the encouragement! I use an inverted L for 160m. I have a trap at the end of it tuned for near the top end of the band. With this I get a double humped SWR response. The bottom dip is with the trap and additional wire working and then the top dip is where the trap blocks.
Have you ever tried doing "virtual" antenna experiments with the FREE 4NEC2 antenna modelling program? I love working through this stuff there, then putting it all into practice. It is amazing how close this simulation is to the real life antenna. I have a video series on 4NEC2 if you need it.
@@eie_for_you I've played a little bit with eznec, part of my problem now is I have so many HF antennas in the yard, and hoping to keep interaction down, in the last few days I have now put up a Vee Beam with 100 ft legs beaming NE, for Europe, trying to get bigger signal for 10/12/15/17 meters, initial results are encouraging, but as usual Murphy's law had this experiment disrupted by the biggest geomagnetic storm in years,which for now has disrupted the excellent propagation we were just having on those Bands hihi. The Vee is 2, 100ft wires , up about 40 feet, apex is 50 degree'ish, aiming Europe (and southwest)
@@jerrym1183 WOW!
Well explained Ralph and a nice design. As you no doubt know, one feature of a folded dipole and other loop style antennas is the inherent DC 'grounding' meaning there is no static build up on the antenna. Such static build up has been known to kill VNA's if the user fails to short the center and braid of the feedline before connecting the instrument. Folded dipole are reputedly 'quieter' than a conventional dipole for this same reason.
Excellent point! Thank you!
You could construct a 3/8 folded inverted Vee antenna with a 9:1 balun and a tuning capacitor at the feed point. This antenna works excellently on multiple frequency bands.
That sounds like a very interesting antenna to put into the 4NEC2 simulator to see what it looks like. Thanks for the idea. 🙂
So you can't extend your tether points into your neighbor's yard another possibility might be to use some inexpensive telescopic fiberglass poles to push up the end of the wire as high as you can get it maybe 10 ft or 15 ft high effectively creating a second angle on the descent that might be a way to improve your SWR even further
I get your idea. It is certainly one to consider. One has to remember, though, that the antenna is not a light antenna requiring a significant amount of tension to keep the "sag" in bounds. I will say, though, it survives sub-zero temperatures with high winds and ice storms this winter. So I am pretty pleased with it mechanical strength.
@@eie_for_you sure enjoying your channel! Thanks
@@PatAutrey Thank you! I am glad you are! 🙂
Fascinating, what about a small coil with taps at both ends to facilitate easy tuning, or center frequency shift later if you want to shift down towards the CW section? Presumably it would make it a little more compact.
That sounds like a very interesting idea! It would make for a very interesting experiment. If you do this, I would be very, very interested in the results.
For me, when I want to go to the extreme bottom of the band with my ICOM 7610, its antenna tuner just won't cut the mustard (my TS2000 will, easily!) So, for the low end I tune to the lowest possible frequency that it *will* tune, then just slide down to where I want to be and still have a reasonably low SWR. 🙂
@@eie_for_you My main interest is 160 and below, as an ex maritime radio officer that used the sub-broadcast band frequencies for coastal radio telegraphy I have an unexplainable desire to return to my "old stomping grounds" in a nostalgic and undoubtedly frivolous return to a previous era. Check out the Maritime Radio Station. Museum of KFS in San Francisco for more insight, currently in my top ten bucket list visits. Keep up the interesting work. 73's.
Just a dumb question.? But when you hose clamp coax with out a rubber insulation between the clamp and coax , wouldn't that cause the swr to rise a little bit. Cause I know that when I move my coax around near metal the swr changes a little. And also dumb questio#2 in one of your pictures it looked like the coax was like knotted going through the eye lids. Would that not also cause the swr to rise. Now as for question 1 I may have seen the picture wrong you may not have the coax held down by hose clamps. To me that may seem like it would change the inductance characteristics of the coax. Iam no rf engineer , just mostly a cb radio hobbies. And iam a ham also. But just some things I noticed. I have used sewer pipe clamps with rubber insulation from home depot to put up antennas . Agin I do not know much about engeering antennas. Iam really just a hobbies. And I know that when coax Is looped or tightly knotted it changes the wire resistance inside. Cause it causes the center wire inside to flatten out, changing the resistance and velocity factor. To making it higher witch in turn changes the swr. Agin iam no expert just a cb radio hobbiest. May be straighten out the coax at the eyelids and see if the vswr and swr comes down. Agin like I said iam no expert. I learn from trial and error, cause I know that in electronics everything affects everything.
Be assured, in my mind there are no dumb questions! :-)
The hose clamps are not used on coax. The hose clamps are use on the 12AWG antenna wire. It is insulated wire (black) so it appears like it *could* be coax, but it is just stranded wire with black insulation.
I hope this helps dispell the confusion here.
Thanks for asking.
First of all a very good video well presented well done mate and keep doing such. Now the hard part and that is another stupid question or sound like that to you.
Since the inverted folded vee antenna after trim has achieve that low swr and considering the transceivers you use are 50 ohms, why you need a balun at the top. Is this a real balun or is just a simple feeder.
Thanks in advance for your answer and wish all the best to your projects.
Dimi.
Thank you for the encouragement on the video. I will keep rolling out the videos as long as I have things to talk about. 😎
The balun is a 4:1 balun for impedance matching. The folded dipole has an impedance which is nominally 4 times that of its unfolded cousin. This, the 4:1 balun is required to take this impedance and turn it into my desired 50 Ohms.
12 gauge wire radius is 0.0034' (0.0042 is 10 gauge)
From www.rapidtables.com/calc/wire/wire-gauge-chart.html I get a wire diameter of 0.0808 inches. This gives me a wire radius in feet of 0.0034 feet, so you are right!
I had to check! 🙂
@@eie_for_you Thought the difference had the potential of distorting your results, so I thought I would mention it.
Very good video, by the way. Really enjoyed it.
@Gwen Walcott Fortunately, with this project, the wire gauge actually doesn't make a lot of difference. 🙂
Thanks! Glad you enjoyed the video!
Whats you call sign
WA2PUX since 1971. Before that WN2PUX. Also, in Canada, VE4PUX (Moose Lake, Manitoba).
Make it two miles long 😂😂
LOL!😆😆
terminate it in the middle and cover all the bands
This is not making sense to me. I am not sure what you mean by "terminate in the middle."
termination resistor@@eie_for_you
NOW I GET it! I stumbled across this design elsewhere. I'd like to try it in 4NEC2 to see what it will do (theoretically). It looks like a ~400 Ohm termination. The trick is knowing the power dissipation required.
@@eie_for_you You got it!
@@n0vty873 🙂