[amsat-bb] Modeling the AA2TX Parasitic Lindenblad

[Zach Metzinger]

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