75 ohm VHF-Low Moxon Rectangle With 2 Directors - Canadian TV, Computing and Home Theatre Forums

 
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post #1 of 3 (permalink) Old 2012-03-07, 08:24 PM Thread Starter
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Posts: 20
75 ohm VHF-Low Moxon Rectangle With 2 Directors

Could someone optimize, my method is to edit a wire in the new editor and calculate a new output to check results. I've cleared the 500 temp limit a dozen times this week, hence my rookie stature. The channel 6 model is just under 6 by 8 feet with a raw gain of about 9 dbi modeled with 1/2" plumbing. Thanks

--------------------------------------------------

CM VHF Channel 2 Moxon Rectangle With 2 Directors
CE
GW 1 5 20.09375 -35.9375 0 33.53125 -35.9375 0 0.30625
GW 2 1 33.53125 -0.375 0 33.53125 0.375 0 0.30625
GW 3 17 33.53125 -35.9375 0 33.53125 -0.375 0 0.30625
GW 4 17 33.53125 0.375 0 33.53125 35.9375 0 0.30625
GW 3 5 33.53125 35.9375 0 20.09375 35.9375 0 0.30625
GW 4 7 17.25 -35.9375 0 0 -35.9375 0 0.30625
GW 5 35 0 -35.9375 0 0 35.9375 0 0.30625
GW 6 7 0 35.9375 0 17.25 35.9375 0 0.30625
GW 1 5 46.25 -35.9375 0 56.71875 -35.9375 0 0.30625
GW 5 35 56.71875 -35.9375 0 56.71875 35.9375 0 0.30625
GW 3 5 56.71875 35.9375 0 46.25 35.9375 0 0.30625
GW 1 5 83.6875 -35.9375 0 94.40625 -35.9375 0 0.30625
GW 5 35 94.40625 -35.9375 0 94.40625 35.9375 0 0.30625
GW 3 5 94.40625 35.9375 0 83.6875 35.9375 0 0.30625
GS 0 0 0.0254
GE 0
LD 5 0 0 0 58000000
GN -1
EK
EX 0 2 1 0 1 0 0
FR 0 0 0 0 57 0
RP 0 181 1 1000 -90 0 1 1
EN

--------------------------------------------------

CM VHF Channel 6 Moxon Rectangle With 2 Directors
CE
GW 1 3 13.6875 -24.3125 0 22.71875 -24.3125 0 0.30625
GW 2 1 22.71875 -0.375 0 22.71875 0.375 0 0.30625
GW 3 12 22.71875 -24.3125 0 22.71875 -0.375 0 0.30625
GW 4 12 22.71875 0.375 0 22.71875 24.3125 0 0.30625
GW 3 3 22.71875 24.3125 0 13.6875 24.3125 0 0.30625
GW 4 3 11.625 -24.3125 0 0 -24.3125 0 0.30625
GW 5 25 0 -24.3125 0 0 24.3125 0 0.30625
GW 6 3 0 24.3125 0 11.625 24.3125 0 0.30625
GW 1 3 31.3125 -24.3125 0 38.375 -24.3125 0 0.30625
GW 5 25 38.375 -24.3125 0 38.375 24.3125 0 0.30625
GW 3 3 38.375 24.3125 0 31.3125 24.3125 0 0.30625
GW 1 3 56.6292575 -24.3125 0 63.90625 -24.3125 0 0.30625
GW 5 25 63.90625 -24.3125 0 63.90625 24.3125 0 0.30625
GW 3 3 63.90625 24.3125 0 56.6292575 24.3125 0 0.30625
GS 0 0 0.0254
GE 0
LD 5 0 0 0 58000000
GN -1
EK
EX 0 2 1 0 1 0 0
FR 0 0 0 0 85 0
RP 0 181 1 1000 -90 0 1 1
EN

--------------------------------------------------
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post #2 of 3 (permalink) Old 2012-03-07, 09:48 PM
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Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Quote:
The channel 6 model is just under 6 by 8 feet with a raw gain of about 9 dbi modeled with 1/2" plumbing.
After adjusting for AGT, the Raw Gain is 8.31 with a SWR of 1.18, so the Net Gain is the same. Looks good for a channel 6 antenna of its size.
Adjusted NEC file:
Code:
CM VHF Channel 6 Moxon Rectangle With 2 Directors
CM AGT=1.0 (0db) at 85mhz, Autosegmentation = 21,  75 OHM antenna
CE
GW	1	3	13.6875	-24.3125	0	22.71875	-24.3125	0	0.30625
GW	2	1	22.71875	-0.375	0	22.71875	0.375	0	0.1288
GW	3	7	22.71875	-24.3125	0	22.71875	-0.375	0	0.30625
GW	4	7	22.71875	0.375	0	22.71875	24.3125	0	0.30625
GW	3	3	22.71875	24.3125	0	13.6875	24.3125	0	0.30625
GW	4	5	11.625	-24.3125	0	0	-24.3125	0	0.30625
GW	5	15	0	-24.3125	0	0	24.3125	0	0.30625
GW	6	5	0	24.3125	0	11.625	24.3125	0	0.30625
GW	1	3	31.3125	-24.3125	0	38.375	-24.3125	0	0.30625
GW	5	15	38.375	-24.3125	0	38.375	24.3125	0	0.30625
GW	3	3	38.375	24.3125	0	31.3125	24.3125	0	0.30625
GW	1	3	56.6292575	-24.3125	0	63.90625	-24.3125	0	0.30625
GW	5	15	63.90625	-24.3125	0	63.90625	24.3125	0	0.30625
GW	3	3	63.90625	24.3125	0	56.6292575	24.3125	0	0.30625
GS	0	0	0.0254		' All in in.
GE	0
EK
LD	5	0	0	0	5.8e7	0
EX	0	2	1	0	1	0
GN	-1
FR	0	1	0	0	85	0
RP 0 181 1 1000 -90 0 1 1
Quote:
Could someone optimize, my method is to edit a wire in the new editor and calculate a new output to check results.
Thats one way to do it because it gives you more control in the direction you want to go with the design. I think the temp limit can be adjusted in settings ?

Looking at the freq sweep, it looks pretty optimized now.
To optimize, you have to describe the coordinates of the elements as Symbols in the NEC editor. (warning : Symbols will be lost in a Geometry Edit save) Then use the Optimizer or Evolver in 4nec2 or Nikimls Python scripts.

For example to get you started, heres the above NEC file with the first director Symbolized.
Code:
CM VHF Channel 6 Moxon Rectangle With 2 Directors
CM AGT=1.0 (0db) at 85mhz, Autosegmentation = 21,  75 OHM antenna
CE
SY d1x1=63.90625
SY d1y=24.3125
SY d1x2=56.6292575
GW	1	3	13.6875	-24.3125	0	22.71875	-24.3125	0	0.30625
GW	2	1	22.71875	-0.375	0	22.71875	0.375	0	0.1288
GW	3	7	22.71875	-24.3125	0	22.71875	-0.375	0	0.30625
GW	4	7	22.71875	0.375	0	22.71875	24.3125	0	0.30625
GW	3	3	22.71875	24.3125	0	13.6875	24.3125	0	0.30625
GW	4	5	11.625	-24.3125	0	0	-24.3125	0	0.30625
GW	5	15	0	-24.3125	0	0	24.3125	0	0.30625
GW	6	5	0	24.3125	0	11.625	24.3125	0	0.30625
GW	1	3	31.3125	-24.3125	0	38.375	-24.3125	0	0.30625
GW	5	15	38.375	-24.3125	0	38.375	24.3125	0	0.30625
GW	3	3	38.375	24.3125	0	31.3125	24.3125	0	0.30625
GW	1	3	d1x2	-d1y	0	d1x1	-d1y	0	0.30625
GW	5	15	d1x1	-d1y	0	d1x1	d1y	0	0.30625
GW	3	3	d1x1	d1y	0	d1x2	d1y	0	0.30625
GS	0	0	0.0254		' All in in.
GE	0
EK
LD	5	0	0	0	5.8e7	0
EX	0	2	1	0	1	0
GN	-1
FR	0	1	0	0	85	0
RP 0 181 1 1000 -90 0 1 1
To optimize the first director, just Select Calculate > Start Optimizer, Function Evolve, select all the variables and set SWR and Gain to 100% weight, Click Freq-Sweep, sweep from 82 to 88 mhz step 2, Click Start and watch it go in the Geometry F3 and Pattern screens.

My builds/plans (not the latest models) are located here.
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post #3 of 3 (permalink) Old 2012-03-08, 02:27 AM
 
Join Date: Jun 2011
Location: Central Illinois U.S.
Posts: 108
Scale factor

Just a hint.
With some models you can quickly add variables by declaring a variable (with a SY card) Then in the "new editor" highlight all the xyz fields for all (or just certain ) wires of the model right click and select "multiply same value" (the variable, like 0.95 or 1.05) or use "add same value" to just the x values of one director to adjust spacing.

Even if not using the optimizer this allows quick changes to whole sections or the entire model by changing just the SY variable.

my gain reports and models are here
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