Thanks for the simulation.
Could you please try different feed points to try to improve the SWR?
Looks like I’ll have to learn this software 
Ok, I will run the simulation again to find best feed point, but dont depend too much on software simulations. The results have errors around 5% to 15%, enough to knock down a collinear. These can at best be taken as crude guide. The trial & error method to adjust feed point gives better results. Try 6mm +/- in steps of 2 mm.
OK, here is sweep of feed (tap point) from 2 mm to 22 mm in steps of 2 mm.
Minimum SWR is at 6 mm tap from bottom, and its value is 4.65 
But dont get disappointed, the simulation results cannot be blindly relied upon. Try to adjust feed point manually in steps of 2 or 3 mm.
Would you mind sharing the .NEC? I’m going to spend some more time on this antenna.
The .nec file is on my Desktop, and I am not at home now, replying from my phone. When at home, I will upload it to dropbox and post a link.
I have uploaded following .nec file to dropbox
“J-Pole Collinear halfwave132mm coil turns16 dia5mm length53mm.nec”
You can download it from here:
dropbox.com/s/qtkinnn6twaea … m.nec?dl=0
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Did I miss something?
The 2 elements with the same 148mm irradiating elements gives me 5.2dB of gain and a sweet SWR of 1.09 and a much more regular irratiation pattern.
The simulation I have done was for dimensions given by you (2 vertical radiating elements 132 mm each+ 1 coil+1 stub 64mm). You have re-done the simulation after adding one more coil and an additional upper vertical element of 148mm length. This will sure change drastically the performance.
Did you change the length of lower 2 radiating elements to 148mm or these are still 132mm, and only the extra upper radiating element is 148mm?
Now do the acid-test: built it and put to trial.
All the verticals are 148mm. The other dimensions remained the same.
Both antennas (2 and 3 elements) have almost the same SWR profile, looks like the matching coils are working (at least in theory).
Going to make it today, will update later.
@aldoir
Due to very high SWR given by nec simulation, and very symmetrical shape of radiation curve, I doubted that in simulation I have posted I have made some mistake, as it was done on a working day and I was squeezed for time. Your abnormal simulation results with 3 Radiators also strengthened this doubt.
Today being weekend, I looked at that .nec file, trying to debug, but could not catch the error. I then decided to do it from scratch. So I made new model with 2 radiators, and found it gives results matching with your trial run results. I then made a copy and added one coil and one radiator, so the second model is with 3 radiators. In the new .nec files, I have kept the frequency, radiator length, stub length and feed cable tap as variables (see symbols tab in .nec input file). This will help in optimizing by sweeping any of the above parameters. Also, instead of using coil dia = 5 mm, I have used coil dia = coil inner dia + wire dia = 5 mm + 1.29 mm = 6.29 mm, which is the coil dia from center of wire to center of wire, as required by NEC.
I have uploaded both .nec files to dropbox, and the download links for these files is given below:
**2 radiator 1 coil: (right click and select save link as) **
https://www.dropbox.com/s/j7c25u3agrlf0p8/J-Pole-Collinear_2xRadiators_1xCoil-turns16-inner-dia5mm-length53mm.nec
3 radiator 2 coils: (right click and select save link as)
https://www.dropbox.com/s/ikkyn4lwcnhobwj/J-Pole-Collinear_3xRadiators_2xCoil-turns16-inner-dia5mm-length53mm.nec
SIMULATION 1 of 2
TWO RADIATORS
SIMULATION 2 of 2
THREE RADIATORS
Hi, thanks for further exploring this
I’ve made both and the result is very similar, a great number of messages up to 100nm and then a suddenly drop
Still liked this antenna, very easy to build, slim and debug free, it would be nice to see a real world comparison with your beloved cantenna
Here is today’s result of my Col J-Pole.
3 elements + 20dB amplifier + 75Ohms line + RTL-SDR
Comparison of Super J-Pole and Spider Antennas
Test Setup: Antenna >> 12 ft (4 meters) RG6 Coax >> Generic DVB-T (black) >> Orange PI PC
Image 1 of 4: Message Rate
Image 2 of 4: Super J-Pole
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Image 3 of 4: Quick Spider
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Image 4 of 4: Variants of J-Pole. The design under test is Super J-Pole (3rd from left)
Comparison of Maximum Range Curves of Super J-Pole and Quick Spider
Test set up: Antenna >> 12 ft / 4 meters RG6 coax >> Generic DVB-T (black) >> Orange Pi PC
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Super J-Pole Maximum Range Curve
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Quick Spider Maximum Range Curve
Another batch of tests, the ranking is
- 4 elements Collinear J-Pole ~ 180nm
- 3 elements Collinear J-Pole ~ 150nm
- Slim Jim / 6 (3?) elements RGC213 CoCo (tie) ~ 100nm
- 1/4 ground plane ~ 80nm
The winner is a 4 elements (3 coils) J-Pole Collinear.
The good thing about this antenna is that the results are reproducible, if you make 10 antennas and they will behave equally
The 4 elements is 85cm longer and fits inside a 14mm PVC pipe (~10mm diameter)
Here’s a comparison between 3 and 4 elements J-Pole. These screenshots where taken in different days, as you can see the pattern is consistent, because I’m surrounded by mountains and a building. The clearer view is for south.
3 elements
4 elements
Hello, I want to share my finding here with Vinnant 5db antenna
I bought it here 109005-s and setup with 10m RF400 and AirNav stick and SBC is Orange Pi Plus 2E.
I benchmark it with FA Flightfeeder, which is I consider as top performer.
After serveral round testing, I found my setup beat FA feeder easily (430 vs 394 airplane reported)
But during recent plug-in and out, I accidently let the coil of vinnant dropout, and I found my favorite antenna is just barely a wire collinear with 2 loops, no more.
Despire I have 3 commercial antennas, I still to try with some DIY like spiderman or coco, but it fails as your. Now with new finding I want to go with wire-col.
I suggest you @aldoir to try this.
were those two results recorded at the same time of sequential?
If they were sequential, it doesn’t really tell you much at all
2 Likes
Try this simple-and-easy one - the V-Stub wire collinear:
Construction Details
https://discussions.flightaware.com/t/quick-spider-no-soldering-no-connector/19181/114
Sideby side test with Flightaware antenna
https://discussions.flightaware.com/t/quick-spider-no-soldering-no-connector/19181/70
Gain, SWR, and Radiation Pattern by Simulation
SWR = 1.4
Gain = 4.33 dBi / 3.85 dBi
https://discussions.flightaware.com/t/quick-spider-no-soldering-no-connector/19181/66
Version with 2 radials only
Why are we bumping a five year old topic?
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Serveral round testing at the same time, of course.
1 Like