Modeling the AA2TX Parasitic Lindenblad
Hello folks,
I've been intrigued by Tony's Parasitic Lindenblad ever since I first read about it. I have a center section in CAD, suitable for 3D printing in PET-G, which eliminates the messy gluing, etc. and gives me a chance to use my printer. :-)
However, I'd like to eliminate the requirement for the 0.750" OD aluminum mast and replace it with 0.650" OD (name: 1/2") copper water pipe, which can be readily found in any hardware store. Given the appropriate paint coating, copper pipe has held up well over many years at my QTH when exposed to the elements.
I am using Xnec2c on FreeBSD, but any NEC program should be able to use the deck, to model the antenna. However, my dimensions don't seem to match what Tony came up with. Are there any NEC gurus in the audience?
Here's my sophomore stab at the antenna deck:
CM --- NEC2 Input File created or edited by xnec2c 3.4 --- CM AA2TX Parasitic Lindenblad -- All distances in meters CM Goal is to use 1/2" copper water pipe for dipole element (0.650" OD) instead of 3/4" OD aluminum pole CE --- End Comments --- GW 1 15 0.00000E+00 0.00000E+00 -1.39000E-01 0.00000E+00 0.00000E+00 1.39000E-01 1.58750E-02 GW 2 15 2.58000E-01 8.50000E-02 1.49000E-01 -2.58000E-01 8.50000E-02 -1.49000E-01 1.50000E-03 GW 3 15 -2.58000E-01 -8.50000E-02 1.49000E-01 2.58000E-01 -8.50000E-02 -1.49000E-01 1.50000E-03 GW 4 15 8.50000E-02 2.58000E-01 -1.49000E-01 8.50000E-02 -2.58000E-01 1.49000E-01 1.50000E-03 GW 5 15 -8.50000E-02 2.58000E-01 1.49000E-01 -8.50000E-02 -2.58000E-01 -1.49000E-01 1.50000E-03 GE 0 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 EX 0 1 8 0 1.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 FR 0 20 0 0 4.30000E+02 1.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 NH 0 0 0 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 NE 0 10 1 10 -1.35000E+00 0.00000E+00 -1.35000E+00 3.00000E-01 0.00000E+00 3.00000E-01 RP 0 19 37 1000 0.00000E+00 0.00000E+00 1.00000E+01 1.00000E+01 0.00000E+00 0.00000E+00 EN 0 0 0 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00
Questions that arise from an afternoon of fiddling with this:
1) Should I model the driven element as two wires with the 1/4" gap between them? If so, how would I do this?
2) Will the 0.100" difference in OD make enough of a difference to even go through this exercise?
Any and all comments, especially from NEC gurus, appreciated!
--- Zach N0ZGO
Would HFSS help?
If you have a sketch, then I have someone that can model it at no cost.
-Michelle W5NYV
On Fri, Jul 10, 2020 at 4:05 PM Zach Metzinger via AMSAT-BB < amsat-bb@amsat.org> wrote:
Hello folks,
I've been intrigued by Tony's Parasitic Lindenblad ever since I first read about it. I have a center section in CAD, suitable for 3D printing in PET-G, which eliminates the messy gluing, etc. and gives me a chance to use my printer. :-)
However, I'd like to eliminate the requirement for the 0.750" OD aluminum mast and replace it with 0.650" OD (name: 1/2") copper water pipe, which can be readily found in any hardware store. Given the appropriate paint coating, copper pipe has held up well over many years at my QTH when exposed to the elements.
I am using Xnec2c on FreeBSD, but any NEC program should be able to use the deck, to model the antenna. However, my dimensions don't seem to match what Tony came up with. Are there any NEC gurus in the audience?
Here's my sophomore stab at the antenna deck:
CM --- NEC2 Input File created or edited by xnec2c 3.4 --- CM AA2TX Parasitic Lindenblad -- All distances in meters CM Goal is to use 1/2" copper water pipe for dipole element (0.650" OD) instead of 3/4" OD aluminum pole CE --- End Comments --- GW 1 15 0.00000E+00 0.00000E+00 -1.39000E-01 0.00000E+00 0.00000E+00 1.39000E-01 1.58750E-02 GW 2 15 2.58000E-01 8.50000E-02 1.49000E-01 -2.58000E-01 8.50000E-02 -1.49000E-01 1.50000E-03 GW 3 15 -2.58000E-01 -8.50000E-02 1.49000E-01 2.58000E-01 -8.50000E-02 -1.49000E-01 1.50000E-03 GW 4 15 8.50000E-02 2.58000E-01 -1.49000E-01 8.50000E-02 -2.58000E-01 1.49000E-01 1.50000E-03 GW 5 15 -8.50000E-02 2.58000E-01 1.49000E-01 -8.50000E-02 -2.58000E-01 -1.49000E-01 1.50000E-03 GE 0 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 EX 0 1 8 0 1.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 FR 0 20 0 0 4.30000E+02 1.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 NH 0 0 0 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 NE 0 10 1 10 -1.35000E+00 0.00000E+00 -1.35000E+00 3.00000E-01 0.00000E+00 3.00000E-01 RP 0 19 37 1000 0.00000E+00 0.00000E+00 1.00000E+01 1.00000E+01 0.00000E+00 0.00000E+00 EN 0 0 0 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00
Questions that arise from an afternoon of fiddling with this:
- Should I model the driven element as two wires with the 1/4" gap
between them? If so, how would I do this?
- Will the 0.100" difference in OD make enough of a difference to even
go through this exercise?
Any and all comments, especially from NEC gurus, appreciated!
--- Zach N0ZGO _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Hi Zach,
My intuition is that the relatively small change in the diameter of the radiating element, and material change, will not significantly change the performance of the paralindy antenna.
Increasing the diameter of radiating dipole elements has the effect of broadening an SWR curve, providing more usable bandwidth. Consider a 75-meter dipole comprised of one wire, then increase it's effective diameter by replacing it with a "caged dipole" of four wires separated by a foot or so.
http://www.arrl.org/files/file/Technology/pdf/The%20Cage%20is%20Back%20W1AW....
Furthermore, the change in diameter you're proposing (0.1 in) is a very small fraction of the design wavelength -- so I wouldn't expect to see any significant broadening of the performance vs frequency.
My intuition is guided by a couple of semesters of E&M and a few decades of antenna building and testing. BUT it's only my *intuition*, and I'd be very interested in hearing the results of any modeling!
As an aside, I'm also working to build this antenna with my newly-acquired 3D printer, using PETG in fact! I'm redesigning the 70-cm Lindy as well as 2-m Lindy to use arrow shaft elements. In this manner the antenna will be easy to disassemble and easily portablized. Or transported :)
Curt / K7ZOO
On Fri, Jul 10, 2020 at 4:45 PM Michelle Thompson via AMSAT-BB < amsat-bb@amsat.org> wrote:
Would HFSS help?
If you have a sketch, then I have someone that can model it at no cost.
-Michelle W5NYV
On Fri, Jul 10, 2020 at 4:05 PM Zach Metzinger via AMSAT-BB < amsat-bb@amsat.org> wrote:
Hello folks,
I've been intrigued by Tony's Parasitic Lindenblad ever since I first read about it. I have a center section in CAD, suitable for 3D printing in PET-G, which eliminates the messy gluing, etc. and gives me a chance to use my printer. :-)
However, I'd like to eliminate the requirement for the 0.750" OD aluminum mast and replace it with 0.650" OD (name: 1/2") copper water pipe, which can be readily found in any hardware store. Given the appropriate paint coating, copper pipe has held up well over many years at my QTH when exposed to the elements.
I am using Xnec2c on FreeBSD, but any NEC program should be able to use the deck, to model the antenna. However, my dimensions don't seem to match what Tony came up with. Are there any NEC gurus in the audience?
Here's my sophomore stab at the antenna deck:
CM --- NEC2 Input File created or edited by xnec2c 3.4 --- CM AA2TX Parasitic Lindenblad -- All distances in meters CM Goal is to use 1/2" copper water pipe for dipole element (0.650" OD) instead of 3/4" OD aluminum pole CE --- End Comments --- GW 1 15 0.00000E+00 0.00000E+00 -1.39000E-01 0.00000E+00 0.00000E+00 1.39000E-01 1.58750E-02 GW 2 15 2.58000E-01 8.50000E-02 1.49000E-01 -2.58000E-01 8.50000E-02 -1.49000E-01 1.50000E-03 GW 3 15 -2.58000E-01 -8.50000E-02 1.49000E-01 2.58000E-01 -8.50000E-02 -1.49000E-01 1.50000E-03 GW 4 15 8.50000E-02 2.58000E-01 -1.49000E-01 8.50000E-02 -2.58000E-01 1.49000E-01 1.50000E-03 GW 5 15 -8.50000E-02 2.58000E-01 1.49000E-01 -8.50000E-02 -2.58000E-01 -1.49000E-01 1.50000E-03 GE 0 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 EX 0 1 8 0 1.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 FR 0 20 0 0 4.30000E+02 1.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 NH 0 0 0 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 NE 0 10 1 10 -1.35000E+00 0.00000E+00 -1.35000E+00 3.00000E-01 0.00000E+00 3.00000E-01 RP 0 19 37 1000 0.00000E+00 0.00000E+00 1.00000E+01 1.00000E+01 0.00000E+00 0.00000E+00 EN 0 0 0 0 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00
Questions that arise from an afternoon of fiddling with this:
- Should I model the driven element as two wires with the 1/4" gap
between them? If so, how would I do this?
- Will the 0.100" difference in OD make enough of a difference to even
go through this exercise?
Any and all comments, especially from NEC gurus, appreciated!
--- Zach N0ZGO _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership.
Opinions
expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
On 07/10/20 19:43, Curt Laumann via AMSAT-BB wrote:
My intuition is guided by a couple of semesters of E&M and a few decades of antenna building and testing. BUT it's only my *intuition*, and I'd be very interested in hearing the results of any modeling!
As an aside, I'm also working to build this antenna with my newly-acquired 3D printer, using PETG in fact! I'm redesigning the 70-cm Lindy as well as 2-m Lindy to use arrow shaft elements. In this manner the antenna will be easy to disassemble and easily portablized. Or transported :)
Hello Curt,
Thank you for the encouragement. I wish I recalled enough of my EM Theory class for this, but I think I've repressed it ever since I eeked out of it with a passing grade. Probably because the professor started a class trying to derive something unrelated to homework or exams one day, got to the end, then realized he'd made a mistake in the first 5 minutes. "You can just go back and fix that and it'll all work out."
I'm finishing up the 3D model right now, using openscad, and will kick off the print tonight.
I plan to put the model up on my webpage for any/all to use, modify, contribute back to, etc. once I have it working.
--- Zach N0ZGO
On July 10, 2020 6:41:54 PM CDT, Michelle Thompson mountain.michelle@gmail.com wrote:
Would HFSS help?
Thank you for the offer, but HFSS is commercial and pricey. I have access to similar tools through my workplace, but this exercise should be solvable with nec2, I think. That way, others can build off of it, should they want to.
--- Zach N0ZGO
Yes, it's commercial and pricey. I was able to get a license donated for community use.
The advantage of getting results from software like HFSS is that you have a result to compare results from NEC against. It's not a replacement. It's an additional result. Both/and, not either/or.
We have done this to test open source GSE and DVB-S2X work.
-Michelle W5NYV
On Fri, Jul 10, 2020 at 9:31 PM Zach Metzinger via AMSAT-BB < amsat-bb@amsat.org> wrote:
On July 10, 2020 6:41:54 PM CDT, Michelle Thompson < mountain.michelle@gmail.com> wrote:
Would HFSS help?
Thank you for the offer, but HFSS is commercial and pricey. I have access to similar tools through my workplace, but this exercise should be solvable with nec2, I think. That way, others can build off of it, should they want to.
--- Zach N0ZGO _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
participants (3)
-
Curt Laumann -
Michelle Thompson -
Zach Metzinger