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A linear (gapless) reflector design.

6K views 33 replies 9 participants last post by  wildwillie 
#1 ·
Here is a new design that utilizes a reflector made from 12 linear
rods. Since there are no gaps to deal with, it I believe that it
should be a bit easier to build. The predicted performance is decent
falling somewhere between my GH8 and GH10 rev2 versions. The net-gain
figures in the following table have been AGT corrected.
Code:
 freq[MHz]        SWR    RawGain    NetGain        F/B
    471.25    1.16007    14.2453    14.2214       6.59
    477.25     1.1704    14.3855    14.3587       7.48
    483.25    1.16439    14.4658    14.4406       8.36
    489.25      1.148    14.5061    14.4854        9.2
    495.25    1.12668    14.5165    14.5011       9.97
    501.25    1.10532    14.4969     14.486      10.67
    507.25     1.0889    14.4773    14.4694      11.29
    513.25    1.08241    14.4376    14.4308      11.83
    519.25    1.08828     14.398    14.3902      12.29
    525.25    1.10422    14.3482    14.3375      12.68
    531.25    1.12623    14.2985    14.2831      13.05
    537.25    1.15131    14.2586    14.2371      13.43
    543.25    1.17739    14.2388    14.2098      13.81
    549.25    1.20262    14.2689     14.232       14.1
    555.25    1.22604     14.329     14.284      14.12
    561.25    1.24836    14.3991    14.3457      13.93
    567.25    1.27054    14.4591     14.397      13.68
    573.25    1.29284    14.4991    14.4276      13.43
    579.25    1.31518     14.539    14.4577      13.22
    585.25    1.33745    14.5889    14.4974      13.04
    591.25    1.35961    14.6288    14.5267      12.87
    597.25    1.38165    14.6886    14.5756      12.72
    603.25    1.40365    14.7484    14.6242      12.59
    609.25    1.42568    14.8083    14.6724      12.46
    615.25    1.44784    14.8881    14.7402      12.35
    621.25    1.47029    14.9579    14.7975      12.25
    627.25    1.49315    15.0476    14.8743      12.17
    633.25    1.51662    15.1274    14.9404      12.09
    639.25     1.5409    15.2171    15.0157      12.02
    645.25    1.56619    15.3168    15.1001      11.96
    651.25    1.59273    15.4065    15.1734      11.88
    657.25    1.62077    15.4862    15.2355      11.78
    663.25    1.65067     15.546    15.2761      11.67
    669.25    1.68281    15.5758    15.2849      11.55
    675.25    1.71756    15.5656    15.2517      11.42
    681.25    1.75531    15.5155    15.1762      11.28
    687.25    1.79649    15.3954     15.028      11.07
    693.25    1.84182    15.2055    14.8067       10.8
The design calls for 7mm (about 1/4") diameter rods, and a zigzag made
from #6 AWG wire. I do not yet have a detailed drawing of it. I will
work on a web-page for it later tonight or tomorrow. In the meantime,
here is the NEC file:

Code:
CM hov15-hovzz3-RdipoleN12z2_D7mm_diffevol
CE
GW 1 7 0 -0.0355994 0 0 0.0355994 0 0.00205769
GW 2 25 0 -0.0355994 0 0 -0.196095 0.160496 0.00205769
GW 3 25 0 -0.0355994 0 0 -0.196095 -0.160496 0.00205769
GW 4 25 0 0.0355994 0 0 0.196095 0.160496 0.00205769
GW 5 25 0 0.0355994 0 0 0.196095 -0.160496 0.00205769
GW 6 21 0 -0.196095 0.160496 0 -0.0588342 0.297757 0.00205769
GW 7 21 0 -0.196095 -0.160496 0 -0.0588342 -0.297757 0.00205769
GW 8 21 0 0.196095 0.160496 0 0.0588342 0.297757 0.00205769
GW 9 21 0 0.196095 -0.160496 0 0.0588342 -0.297757 0.00205769
GW 10 19 0 -0.0588342 0.297757 0 -0.183872 0.422795 0.00205769
GW 11 19 0 -0.0588342 -0.297757 0 -0.183872 -0.422795 0.00205769
GW 12 19 0 0.0588342 0.297757 0 0.183872 0.422795 0.00205769
GW 13 19 0 0.0588342 -0.297757 0 0.183872 -0.422795 0.00205769
GW 14 13 0 -0.183872 0.422795 0 -0.307663 0.422795 0.00205769
GW 15 13 0 -0.183872 -0.422795 0 -0.307663 -0.422795 0.00205769
GW 16 13 0 0.183872 0.422795 0 0.307663 0.422795 0.00205769
GW 17 13 0 0.183872 -0.422795 0 0.307663 -0.422795 0.00205769
GW 18 31 -0.0848289 -0.143109 -0.681404 -0.0848289 0.143109 -0.681404 0.0035
GW 19 117 -0.0848289 -0.557066 -0.538873 -0.0848289 0.557066 -0.538873 0.0035
GW 20 81 -0.0848289 -0.381754 -0.417804 -0.0848289 0.381754 -0.417804 0.0035
GW 21 105 -0.0848289 -0.496393 -0.307146 -0.0848289 0.496393 -0.307146 0.0035
GW 22 103 -0.0848289 -0.488764 -0.19585 -0.0848289 0.488764 -0.19585 0.0035
GW 23 31 -0.0848289 -0.147602 -0.0728634 -0.0848289 0.147602 -0.0728634 0.0035
GW 24 31 -0.0848289 -0.147602 0.0728634 -0.0848289 0.147602 0.0728634 0.0035
GW 25 103 -0.0848289 -0.488764 0.19585 -0.0848289 0.488764 0.19585 0.0035
GW 26 105 -0.0848289 -0.496393 0.307146 -0.0848289 0.496393 0.307146 0.0035
GW 27 81 -0.0848289 -0.381754 0.417804 -0.0848289 0.381754 0.417804 0.0035
GW 28 117 -0.0848289 -0.557066 0.538873 -0.0848289 0.557066 0.538873 0.0035
GW 29 31 -0.0848289 -0.143109 0.681404 -0.0848289 0.143109 0.681404 0.0035
GE 0
LD 5 0 0 0 2.49e+07
EK 0
FR 0 6 0 0 475 45
EX 0 1 4 0 1
GN -1 0 0 0 0.0 0.0  0.0  0.0  0.0  0.0
RP 0 1 36 1001 90 0 5.0 10 10000 0
EN
 
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#31 ·
Hi was getting ready to build a DBGH (GH10) antenna when I came across this thread.

I am completely new to antenna building. I have one question, according to John's drawing, does "D" represent the gap between the zig-zag antenna and the rear rods?

I was thinking of going to Metal Supermarket and getting some .25" aluminum solid rod for the rods and also for the zig-zag antenna. Is aluminum a good enough "conductor" or is copper a better choice? What about solid vs. hollow rod - does that make a difference?

Finally, I live in the Mississauga area at around Winston Churchill and Dundas - based on what I have been reading this antenna design looks like it will work well to pickup all of the Buffalo and Toronto based channels without the need of a pre-amp - is this an accurate statement?

Many Thanks in advance!!!

Steve
 
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