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Discussion Starter #1
As suggested by 300ohm I decided to see what kind of improvement can be done to the GH6 gen1 with hat narods and other little changes.

The model from post 29 already added hat narods and narod reflector, so this time I tried two other kinds changes as well.

1) change gaps, reflector positions, shorten wires, etc.. anything that can be done with an existing gen1 model without throwing away any metal pieces. Here is the result:
Code:
  Freq RawGain NetGain     SWR    Real    Imag
================================================
   174  9.7493  9.1295   2.148  229.93 -193.43
   180  9.5993  9.5549  1.2242  250.84 -25.969
   186  9.4093   9.376  1.1915  276.59  44.798
   192  9.2393  9.1567  1.3183  294.27  82.161
   198  9.1076  8.9646   1.439  306.68  110.79
   204  8.9976  8.7758  1.5744  320.41  140.45
   210  8.9076  8.5795  1.7388  342.26  174.48
   216  8.8476  8.3788  1.9406   380.3  213.46
   470  13.956  13.807   1.451  297.97 -111.93
   476  13.766  13.201  2.0743  200.04 -152.97
   482  13.636  13.207  1.8854  192.47 -111.56
   488  13.616  13.336  1.6666  200.23 -77.872
   494  13.618  13.452  1.4806  213.88 -50.918
   500  13.638   13.55  1.3311  230.74 -30.058
   506  13.658  13.618  1.2129  249.29 -14.983
   512  13.678  13.664  1.1199  268.33 -5.4486
   518  13.662   13.66  1.0467  286.67 -1.1577
   524  13.622  13.622  1.0115  303.07 -1.5908
   530  13.562  13.559  1.0578  316.34 -5.7262
   536  13.512  13.503  1.0955  325.84 -12.092
   542  13.478  13.463  1.1243  331.57 -19.228
   548  13.458  13.438  1.1447     334 -26.001
   554  13.448  13.425   1.157  333.71 -31.581
   560  13.448  13.424  1.1615  331.37 -35.325
   566  13.464  13.441  1.1579  327.76  -36.69
   572  13.484  13.464  1.1465  323.92 -35.298
   578  13.514  13.498  1.1291  321.13  -31.22
   584  13.554  13.543  1.1105  320.58 -25.176
   590    13.6   13.59  1.0992  322.99 -18.387
   596   13.65   13.64  1.1034  328.39 -12.165
   602   13.69  13.675  1.1239  336.33 -7.5938
   608   13.72  13.698  1.1547  346.07 -5.4034
   614  13.744  13.711  1.1905  356.79 -6.0271
   620  13.764  13.718  1.2281  367.69 -9.6168
   626  13.774  13.714   1.266  377.95 -16.085
   632  13.784  13.708  1.3033  386.96 -25.145
   638  13.792  13.699  1.3401  394.26 -36.402
   644  13.812  13.701  1.3772  399.67  -49.52
   650  13.852  13.721  1.4156  403.01 -64.363
   656  13.892  13.739   1.457  404.01 -80.976
   662  13.942  13.763  1.5031  402.09 -99.445
   668  14.012  13.802  1.5555  396.26 -119.65
   674  14.082  13.834   1.616  385.22 -140.98
   680  14.162  13.869  1.6866  367.78 -162.01
   686  14.241  13.893  1.7692  343.23 -180.47
   692  14.321  13.905  1.8667  311.87 -193.68
   698  14.391  13.893  1.9824  275.36 -199.02
   704  14.441  13.843  2.1196  236.45 -194.72
nec model
Code:
CM
CM GH6n3 gen1 with moved and/or shortened wires and hat like narods
CM optimized by nikiml
CM covered by GPL v3 or later (http://www.gnu.org/licenses/gpl.txt)
CM see http://www.digitalhome.ca/forum/showpost.php?p=907404&postcount=2
CE


SY radius=0.003175
SY narod_surf_spacing=0.006
SY narod_spacing=0.012

SY feed=0.055' 0.025, 0.055

SY b=0.1392846' 0.1, 0.142
SY a1=0.1272792
SY _G3=feed
SY a2=a1+feed-_G3'this is to avoid self intersection since _G3 is to be > radius+2.5mm
SY a3=a1



SY x=-0.09599742' -0.12, -0.06
SY g1=0.01889463' 0.002, 0.035
SY g2=0.004276019' 0.002, 0.035
SY g3=0.045
SY l1=0.2865377' 0.205, 0.295
SY l2=0.2906641' 0.216, 0.306
SY l3=0.306' 0.216, 0.306

SY n_h=0.08801093' 0.04, 0.18
SY n_f_dx=0.07538282' 0, 0.1
SY n_top_dy=-0.01370904' -0.06, 0.05
SY n_b_taper=0.001202546' 0, 0.1
SY n_top=_G3+a3+n_top_dy- n_b_taper/2'hat head size
SY n_f=x + n_f_dx'so the hat does not tilt behind the reflectors


SY narod_top = a1+a2+a3+narod_spacing+n_h'want to put 3 reflectors between z=very_small and z=narod_top +/- very_small,  1 reflectors around narod_top and 1 above it
SY z1=0.1046551' 0.0435, 0.1235
SY z2=0.1537644' 0.1405, 0.2605
SY z3=0.4055761' 0.281, 0.48

SY ay1=feed+a1
SY ay2=feed+a1-a2
SY ay3=feed+a1-a2+a3
SY ay4=feed+a1-a2+a3+b
SY az2=a1+a2
SY az3=a1+a2+a3
SY n_b_z=az3+narod_spacing
SY n_b_y1=n_top+n_b_taper
SY n_b_y2=n_b_y1+b

SY n_z_coef=0.8354309' 0.5, 1.4
SY n_zsz=0.4132564' 0.3, 0.55
SY n_0sz=0.4701835' 0.3, 0.6
SY n_x_diff=0.1966167' 0.15, 0.3
SY n_x = x-n_x_diff
SY n_z = narod_top*n_z_coef


GW 1 10 0 feed 0 0 ay1 a1 radius'#00f
GW 2 10 0 ay1 a1 0 ay2 az2 radius'#00f
GW 3 10 0 ay2 az2 0 ay3 az3 radius'#00f
GW 4 7 0 ay3 az3 0 ay4 az3 radius'#00f
GW 5 15 x g1 z1 x l1+g1 z1 radius'#0f0
GW 6 16 x g2 z2 x l2+g2 z2 radius'#0f0
GW 7 16 x g3 z3 x l3+g3 z3 radius'#0f0
GW 11 5 n_f n_top n_b_z+n_h 0 n_b_y1 n_b_z radius'#000
GW 12 7 0 n_b_y1 n_b_z 0 n_b_y2 n_b_z radius'#000
GX	20	010
GW 13 18 n_f -n_top n_b_z+n_h n_f n_top n_b_z+n_h radius'#000
GW 15 44 n_x -n_zsz n_z n_x n_zsz n_z radius'#D00
GX	40	001
GW 16 50 n_x -n_0sz 0 n_x n_0sz 0 radius'#D00
GW 100 9 0 -feed 0 0 feed 0 radius*.8675'#f40
GE	0
LD	5	0	0	0	24900000
GN	-1
EK
EX 0 100 5 0 1
FR	0	0	0	0	800	0
EN


2) only change gaps and reflector spacing Here is the result:
Code:
  Freq RawGain NetGain     SWR    Real    Imag
===============================================
   174  9.5238  8.5407   2.637  174.75 -193.88
   180  9.5538  9.3921  1.4728   204.8 -16.142
   186  9.4038  9.2974  1.3686  240.82  60.567
   192  9.2538  9.1085  1.4432  266.99  99.046
   198  9.1318  8.9312  1.5395  284.98  126.25
   204  9.0418  8.7672  1.6579  301.56  153.67
   210  8.9718  8.5966  1.8077  323.82  185.72
   216  8.9218  8.4123  1.9972  359.89  223.98
   470  13.323  12.264  2.7407  174.99 -205.95
   476  13.383  12.617  2.3462  176.83 -160.63
   482  13.423  12.882  2.0416  182.24 -123.24
   488  13.463   13.09  1.8046  190.36 -92.017
   494  13.509   13.26  1.6185  200.59 -65.887
   500  13.539  13.378  1.4709   212.5 -44.196
   506  13.589   13.49  1.3527  225.68 -26.527
   512  13.639  13.582  1.2573  239.76 -12.605
   518  13.693  13.663  1.1794  254.41 -2.2479
   524  13.733   13.72  1.1154  269.28  4.6109
   530  13.743  13.739  1.0633  283.92  7.8941
   536  13.723  13.722  1.0269  297.57  7.5606
   542  13.708  13.707  1.0337  309.32  3.8822
   548  13.688  13.684  1.0615  318.27 -2.5123
   554  13.678  13.671  1.0869  323.67 -10.698
   560  13.678  13.667  1.1065  324.96 -19.395
   566  13.696  13.682  1.1185  322.11 -26.929
   572  13.716  13.701  1.1214  315.89 -31.506
   578  13.746  13.733  1.1139  308.09   -31.8
   584  13.796  13.786  1.0965     301  -27.67
   590  13.835   13.83  1.0711  296.53 -20.195
   596  13.885  13.884  1.0407   295.6 -11.048
   602  13.925  13.925  1.0084  298.24 -1.7838
   608  13.965  13.965  1.0256  303.98  6.5097
   614   13.99  13.987  1.0603  312.24  13.102
   620   14.01  14.001  1.0961  322.52  17.545
   626   14.04  14.024  1.1327  334.38  19.443
   632   14.06  14.034  1.1702  347.33  18.405
   638  14.067  14.029  1.2087  360.87  14.032
   644  14.087  14.034  1.2486  374.31  5.9129
   650  14.107  14.037  1.2902  386.79   -6.29
   656  14.127  14.038  1.3341  397.22 -22.772
   662  14.145  14.032  1.3811  404.22 -43.462
   668  14.175  14.036  1.4322  406.27 -67.833
   674  14.205  14.034  1.4889  401.83 -94.774
   680  14.255  14.046  1.5532  389.59  -122.5
   686  14.299  14.044  1.6277  368.72 -148.51
   692  14.359  14.046  1.7159  339.45 -169.88
   698  14.429  14.044  1.8221  303.27 -183.67
   704  14.489  14.012  1.9522  262.85 -187.72
nec model:
Code:
CM
CM GH6n3 gen1 with different reflector gaps and spacing and hat like narods
CM optimized by nikiml
CM covered by GPL v3 or later (http://www.gnu.org/licenses/gpl.txt)
CM see http://www.digitalhome.ca/forum/showpost.php?p=907404&postcount=2
CE


SY radius=0.003175
SY narod_surf_spacing=0.006
SY narod_spacing=0.012

SY feed=0.04969166' 0.025, 0.055

SY b=0.142
SY a1=0.1272792
SY _G3=feed
SY a2=a1+feed-_G3'this is to avoid self intersection since _G3 is to be > radius+2.5mm
SY a3=a1



SY x=-0.1042614' -0.12, -0.06
SY g1=0.007552153' 0.002, 0.035
SY g2=0.002
SY g3=0.045
SY l1=0.295
SY l2=0.306
SY l3=0.306

SY n_h=0.1003754' 0.04, 0.18
SY n_f_dx=0.07076099' 0, 0.1
SY n_top_dy=-0.02358553' -0.06, 0.05
SY n_b_taper=0.03925068' 0, 0.1
SY n_top=_G3+a3+n_top_dy- n_b_taper/2'hat head size
SY n_f=x + n_f_dx'so the hat does not tilt behind the reflectors


SY narod_top = a1+a2+a3+narod_spacing+n_h'want to put 3 reflectors between z=very_small and z=narod_top +/- very_small,  1 reflectors around narod_top and 1 above it
SY z1=0.0635
SY z2=0.1905
SY z3=0.381

SY ay1=feed+a1
SY ay2=feed+a1-a2
SY ay3=feed+a1-a2+a3
SY ay4=feed+a1-a2+a3+b
SY az2=a1+a2
SY az3=a1+a2+a3
SY n_b_z=az3+narod_spacing
SY n_b_y1=n_top+n_b_taper
SY n_b_y2=n_b_y1+b

SY n_z_coef=0.7225789' 0.5, 1.4
SY n_zsz=0.4070839' 0.3, 0.55
SY n_0sz=0.5116345' 0.3, 0.6
SY n_x_diff=0.181007' 0.15, 0.3
SY n_x = x-n_x_diff
SY n_z = narod_top*n_z_coef


GW 1 10 0 feed 0 0 ay1 a1 radius'#00f
GW 2 10 0 ay1 a1 0 ay2 az2 radius'#00f
GW 3 10 0 ay2 az2 0 ay3 az3 radius'#00f
GW 4 8 0 ay3 az3 0 ay4 az3 radius'#00f
GW 5 16 x g1 z1 x l1+g1 z1 radius'#0f0
GW 6 16 x g2 z2 x l2+g2 z2 radius'#0f0
GW 7 16 x g3 z3 x l3+g3 z3 radius'#0f0
GW 11 6 n_f n_top n_b_z+n_h 0 n_b_y1 n_b_z radius'#000
GW 12 8 0 n_b_y1 n_b_z 0 n_b_y2 n_b_z radius'#000
GX	20	010
GW 13 14 n_f -n_top n_b_z+n_h n_f n_top n_b_z+n_h radius'#000
GW 15 43 n_x -n_zsz n_z n_x n_zsz n_z radius'#D00
GX	40	001
GW 16 55 n_x -n_0sz 0 n_x n_0sz 0 radius'#D00
GW 100 7 0 -feed 0 0 feed 0 radius*.8675'#f40
GE	0
LD	5	0	0	0	24900000
GN	-1
EK
EX 0 100 4 0 1
FR	0	0	0	0	800	0
EN
 

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anything that can be done with an existing gen1 model without throwing away any metal pieces.
And its a great earth day contribution to boot. :p

Wow, thats nice. Not quite as good performance as your newer GH6n3, but definately a retro-fit worth doing, especially if additional vhf-hi gain is needed.

2) only change gaps and reflector spacing
Just to clarify for others, that means no rebending or recutting of the existing elements on the SBGH gen1. Just redoing the spacings and adding the additional NARODs and NAROD reflectors. For people who built the SBGH gen1 from the somewhat brittle kind of aluminum, this is the way to go.

Maybe this retro-fit needs its own thread.
 

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thanks for posting I hope I can get the measurement from your data. I may need to learn how to use 4nec2. is there any instruction anywhere that could learn to get the measurement from the retrofit gh6. thanks again.
 

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300ohm's link is probably the best advice, but if it helps here are some crude drawings for the main element and the colinear rod reflectors with the symbols used in nikiml's NEC files.


[In gen1, all the legs of the main element are the same - 127 mm up, 127 mm over.]



I haven't figured out the variables for the top hats yet.
 

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DBGH spacings for option 2 above

After running thru a mess of frequency sweeps, using 2 EX sources, for the above option 2 DBGH version, it looks like the most practical minimum spacing distance is 45 inches, SBGH feedpoint to SBGH feedpoint. That would leave about 6 inches between the bottom NAROD of the top SBGH and the top NAROD of the bottom SBGH, and the overall antenna height would be 84".

While a spacing distance between the two NARODs of 1 inch would be fine for UHF, spacing distances of less than 3 inches severely impact vhf-hi, especially channel 7, performance.
Ideal spacing distances for vhf-hi look to be about 12 to 14 inches between NARODs, but that would make the antenna a bit unwieldy for the marginal increase in gain.

Code:
CM GH6n3 gen1 with different reflector gaps and spacing and hat like narods
CM optimized by nikiml
CM Double Bay version spacing distance experiment 6 inches between NARODs
CM covered by GPL v3 or later (http://www.gnu.org/licenses/gpl.txt)
CM see http://www.digitalhome.ca/forum/showpost.php?p=907404&postcount=2
CE
GW	1	21	0	1.9564	-22.4997	0	6.96739213	-17.488708	0.125
GW	2	21	0	6.96739213	-17.488708	0	1.9564	-12.477716	0.125
GW	3	21	0	1.9564	-12.477716	0	6.96739213	-7.4667236	0.125
GW	4	17	0	6.96739213	-7.4667236	0	12.5579433	-7.4667236	0.125
GW	5	33	-4.1047638	0.29736457	-19.9997	-4.1047638	11.9115378	-19.9997	0.125
GW	6	35	-4.1047638	0.07877402	-14.9997	-4.1047638	12.1260181	-14.9997	0.125
GW	7	35	-4.1047638	1.7716874	-7.4997	-4.1047638	13.8189315	-7.4997	0.125
GW	11	13	-1.3188976	5.26617559	-3.0424953	0	6.81147874	-6.9942827	0.125
GW	12	17	0	6.81147874	-6.9942827	0	12.4020299	-6.9942827	0.125
GW	21	21	0	-1.9563323	-22.4997	0	-6.9673244	-17.488708	0.125
GW	22	21	0	-6.9673244	-17.488708	0	-1.9563323	-12.477716	0.125
GW	23	21	0	-1.9563323	-12.477716	0	-6.9673244	-7.4667236	0.125
GW	24	17	0	-6.9673244	-7.4667236	0	-12.557876	-7.4667236	0.125
GW	25	33	-4.1047638	-0.2972969	-19.9997	-4.1047638	-11.91147	-19.9997	0.125
GW	26	35	-4.1047638	-0.0787063	-14.9997	-4.1047638	-12.12595	-14.9997	0.125
GW	27	35	-4.1047638	-1.7716197	-7.4997	-4.1047638	-13.818864	-7.4997	0.125
GW	31	13	-1.3188976	-5.2661079	-3.0424953	0	-6.811411	-6.9942827	0.125
GW	32	17	0	-6.811411	-6.9942827	0	-12.401962	-6.9942827	0.125
GW	13	31	-1.318898	-5.266108	-3.042495	-1.318898	5.2661756	-3.042495	0.125
GW	15	91	-11.23102	-16.0269	-8.440334	-11.23102	16.026959	-8.440334	0.125
GW	41	21	0	1.9564	-22.4997	0	6.96739213	-27.510692	0.125
GW	42	21	0	6.96739213	-27.510692	0	1.9564	-32.521684	0.125
GW	43	21	0	1.9564	-32.521684	0	6.96739213	-37.532676	0.125
GW	44	17	0	6.96739213	-37.532676	0	12.5579433	-37.532676	0.125
GW	45	33	-4.104764	0.2973646	-24.9997	-4.104764	11.911538	-24.9997	0.125
GW	46	35	-4.104764	0.078774	-29.9997	-4.104764	12.126018	-29.9997	0.125
GW	47	35	-4.1047638	1.7716874	-37.4997	-4.1047638	13.8189315	-37.4997	0.125
GW	51	13	-1.3188976	5.26617559	-41.956905	0	6.81147874	-38.005117	0.125
GW	52	17	0	6.81147874	-38.005117	0	12.4020299	-38.005117	0.125
GW	61	21	0	-1.9563323	-22.4997	0	-6.9673244	-27.510692	0.125
GW	62	21	0	-6.9673244	-27.510692	0	-1.9563323	-32.521684	0.125
GW	63	21	0	-1.9563323	-32.521684	0	-6.9673244	-37.532676	0.125
GW	64	17	0	-6.9673244	-37.532676	0	-12.557876	-37.532676	0.125
GW	65	33	-4.1047638	-0.2972969	-24.9997	-4.1047638	-11.91147	-24.9997	0.125
GW	66	35	-4.1047638	-0.0787063	-29.9997	-4.1047638	-12.12595	-29.9997	0.125
GW	67	35	-4.104764	-1.77162	-37.4997	-4.104764	-13.81886	-37.4997	0.125
GW	71	13	-1.3188976	-5.2661079	-41.956905	0	-6.811411	-38.005117	0.125
GW	72	17	0	-6.811411	-38.005117	0	-12.401962	-38.005117	0.125
GW	53	31	-1.318898	-5.266108	-41.9569	-1.318898	5.2661756	-41.9569	0.125
GW	55	91	-11.23102	-16.0269	-36.55907	-11.23102	16.026959	-36.55907	0.125
GW	16	115	-11.23102	-20.14308	-22.4997	-11.23102	20.143124	-22.4997	0.125
GW	100	11	0	-1.9563441	-22.4997	0	1.9564	-22.4997	0.10843701
GW	101	21	0	1.9564	22.5	0	6.96739213	27.5109921	0.125
GW	102	21	0	6.96739213	27.5109921	0	1.9564	32.5219843	0.125
GW	103	21	0	1.9564	32.5219843	0	6.96739213	37.5329764	0.125
GW	104	17	0	6.96739213	37.5329764	0	12.5579433	37.5329764	0.125
GW	105	33	-4.1047638	0.29736457	25	-4.1047638	11.9115378	25	0.125
GW	106	35	-4.1047638	0.07877402	30	-4.1047638	12.1260181	30	0.125
GW	107	35	-4.1047638	1.7716874	37.5	-4.1047638	13.8189315	37.5	0.125
GW	108	13	-1.3188976	5.26617559	41.9572047	0	6.81147874	38.0054173	0.125
GW	109	17	0	6.81147874	38.0054173	0	12.4020299	38.0054173	0.125
GW	110	21	0	-1.9563323	22.5	0	-6.9673244	27.5109921	0.125
GW	111	21	0	-6.9673244	27.5109921	0	-1.9563323	32.5219843	0.125
GW	112	21	0	-1.9563323	32.5219843	0	-6.9673244	37.5329764	0.125
GW	113	17	0	-6.9673244	37.5329764	0	-12.557876	37.5329764	0.125
GW	114	33	-4.1047638	-0.2972969	25	-4.1047638	-11.91147	25	0.125
GW	115	35	-4.1047638	-0.0787063	30	-4.1047638	-12.12595	30	0.125
GW	116	35	-4.1047638	-1.7716197	37.5	-4.1047638	-13.818864	37.5	0.125
GW	117	13	-1.3188976	-5.2661079	41.9572047	0	-6.811411	38.0054173	0.125
GW	118	17	0	-6.811411	38.0054173	0	-12.401962	38.0054173	0.125
GW	119	31	-1.318898	-5.266108	41.957205	-1.318898	5.2661756	41.957205	0.125
GW	120	91	-11.23102	-16.0269	36.559366	-11.23102	16.026959	36.559366	0.125
GW	121	21	0	1.9564	22.5	0	6.96739213	17.4890079	0.125
GW	122	21	0	6.96739213	17.4890079	0	1.9564	12.4780157	0.125
GW	123	21	0	1.9564	12.4780157	0	6.96739213	7.46702362	0.125
GW	124	17	0	6.96739213	7.46702362	0	12.5579433	7.46702362	0.125
GW	125	33	-4.1047638	0.29736457	20	-4.1047638	11.9115378	20	0.125
GW	126	35	-4.1047638	0.07877402	15	-4.1047638	12.1260181	15	0.125
GW	127	35	-4.1047638	1.7716874	7.5	-4.1047638	13.8189315	7.5	0.125
GW	128	13	-1.3188976	5.26617559	3.04279528	0	6.81147874	6.99458268	0.125
GW	129	17	0	6.81147874	6.99458268	0	12.4020299	6.99458268	0.125
GW	130	21	0	-1.9563323	22.5	0	-6.9673244	17.4890079	0.125
GW	131	21	0	-6.9673244	17.4890079	0	-1.9563323	12.4780157	0.125
GW	132	21	0	-1.9563323	12.4780157	0	-6.9673244	7.46702362	0.125
GW	133	17	0	-6.9673244	7.46702362	0	-12.557876	7.46702362	0.125
GW	134	33	-4.1047638	-0.2972969	20	-4.1047638	-11.91147	20	0.125
GW	135	35	-4.1047638	-0.0787063	15	-4.1047638	-12.12595	15	0.125
GW	136	35	-4.1047638	-1.7716197	7.5	-4.1047638	-13.818864	7.5	0.125
GW	137	13	-1.3188976	-5.2661079	3.04279528	0	-6.811411	6.99458268	0.125
GW	138	17	0	-6.811411	6.99458268	0	-12.401962	6.99458268	0.125
GW	139	31	-1.318898	-5.266108	3.0427953	-1.318898	5.2661756	3.0427953	0.125
GW	140	91	-11.23102	-16.0269	8.4406339	-11.23102	16.026959	8.4406339	0.125
GW	141	115	-11.231024	-20.143076	22.5	-11.231024	20.1431244	22.5	0.125
GW	142	11	0	-1.9563441	22.5	0	1.9564	22.5	0.10843701
GS	0	0	0.0254		' All in in.
GE	0
EK
LD	5	0	0	0	2.49e7	0
EX	0	100	6	0	1	0
EX	0	142	6	0	1	0
GN	-1
FR	0	1	0	0	800	0
Now to play around with the phasing lines.
 

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Hopefully I will not add to the confusion. Using keef's drawing. Reflectors @-3.78" z1 4.12 g1 1.49 L1 11.28 for a total of 24.05"; z2 6.05 g2 0.34 L2 11.44 for a total of 23.22"; z3 15.97 g3 3.54 L3 12.05 for a total of 27.64". There a 3 NAROD reflectors @-11.52, z0 L=37.02" and z1=15.85 L=32.54. The top hat has a center of 13.26" with leggs 3.56 to the stubs 5.48. The top hat has a tilt from zero at stubs to -0.81" at the top. Note the feed gap on DE is 4.33" this is more than I used on my SBGH.
 

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Discussion Starter #13
After running thru a mess of frequency sweeps
300ohm,

if you want to speed up you sweeps you can use my scripts (provided you still have them installed), it is very easy:

1) create a batch file, lets say evaluate_uV.bat
Code:
set PATH=%PATH%;c:\4nec2\exe
c:\Python26\python -m nec.eval --engine=nec2dxs3k0.exe -uV --num=10 -a10 --cleanup %1 
pause
You may have to edit the path to python and/or 4nec2

2) Right click on a nec file and select Open With -> Choose Program, and browse and select the evaluate_uV.bat file ( and OK your way out).

3) that is it. the -a10 parameter is for autosegmentation of 10. -a0 disables autosegmentation. You can also have multiple batch files.
The best part is that they will stick to the Open With section when you right click a nec file.

Not only this will be faster then sweeping with 4nec2, but it will also automatically calculate net gain and apply AGT gain correction.
Plus it sweeps both UHF and VHF-hi simultaneously.
 

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A couple more drawings for anyone that finds them helpful.





Note that n_top, n_zsz and n_0sz are measures from center.

As far as I can tell, n_top and n_z have no simpler representations. They are computed, and I didn't want to try to put the formula into the drawings. The formula are in the NEC listings so they shouldn't be too hard to compute - or you can follow 300ohm's advice and use 4NEC2.
 

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Discussion Starter #15
Just to complicate things a bit more, the n_h is the narod height but only in z direction and since the hat is tilted backwards it is not exactly the height of the hat that one would measure when it is laying flat.

the real hat height H is
Code:
          --------------------------
    \    /   2               2
H =  \  / n_h  + (x + n_f_dx)
      \/
As keef said the hat parameters are mostly calcualted.
But if you open the model in 4nec2 and from the Geometry(F3) windows select from the menu View-> SYmbol conversion it will show a printout of all parameters with their calcualted values.
 

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Good point. Maybe this is better - the lengths of the tophat segments ("bending" dimension, if you will).



For mod 1
s1: 139.28 mm
s2: 90.4 mm
s3: 335.94 mm
s4: 90.4 mm
s5: 139.28 mm
d1: 338.4 mm

For mod 2
s1: 142 mm
s2: 112.86 mm
s3: 267.52 mm
s4: 112.86 mm
s5: 142 mm
d1: 346 mm

[I've tried to choose variables not already used elsewhere - 's' for segment length, 'd' for distance. I pulled the lengths from 4nec2 so they should be accurate (hopefully free of human error). These are scalar lengths, largely independent of x,y,z coordinated.]
 

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For what it's worth.

Mod 1:


Mod 2:


If you find errors, they are mine; please let me know.
And if anyone knows a good place to host Inkscape SVG drawings or PDFs anonymously (without creating yet another account) please let me know.
 
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