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#1
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help requested for designing 4-square inverted L on 20 meters
Hi,
I am using 4nec2 and ICEPAC to design a 4-square inverted L. I think the far field pattern, SWR, and area coverage are pretty good. I believe most receivers can hear signals down to -120db fairly well. I am modelling not only radials but also a ground system to reduce the SWR and help with the lightning protection. I hacked this out of a standard 4-square for 80 meters. Any of the 4-square people out there who can offer additional pointers, construction details, and other things I have not considered? I'm finding trouble reducing the SWR from 2:1 down to 1:1 NOTE: Distance T is an arbitrary distance between the ground and a planned wooden deck roof to help disguise the system. Distance D is an arbitrarily small distance between the ground system and the dirt. Thanks much! The Eternal Squire CM K6NA - 4-Element W1CF Phased-Vertical Array CE converted with 4nec2 from AO to 4nec2 format on 22-apr-02 SY T = 9 ft SY S = 17.3875 ft SY K = T SY M = 8.69375 ft SY D = 0.1 ft SY W = 8.69375 ft GW 1 5 -S 0 T -S 0 T+W 1in GW 2 5 0 -S T 0 -S T+W 1in GW 3 5 0 S T 0 S T+W 1in GW 4 5 S 0 T S 0 T+W 1in GW 11 5 -S 0 T+W -S+W 0 T+W 1in GW 22 5 0 -S T+W 0 -S+W T+W 1in GW 33 5 0 S T+W 0 S-W T+W 1in GW 44 5 S 0 T+W S-W 0 T+W 1in GW 111 5 -S 0 K -S-M 0 K 0.25in GW 112 5 -S 0 K -S+M 0 K 0.25in GW 113 5 -S 0 K -S M K 0.25in GW 114 5 -S 0 K -S -M K 0.25in GW 211 5 S 0 K S-M 0 K 0.25in GW 212 5 S 0 K S+M 0 K 0.25in GW 213 5 S 0 K S M K 0.25in GW 214 5 S 0 K S -M K 0.25in GW 311 5 0 S K 0 S-M K 0.25in GW 312 5 0 S K 0 S+M K 0.25in GW 313 5 0 S K M S K 0.25in GW 314 5 0 S K -M S K 0.25in GW 411 5 0 -S K 0 -S-M K 0.25in GW 412 5 0 -S K 0 -S+M K 0.25in GW 413 5 0 -S K M -S K 0.25in GW 414 5 0 -S K -M -S K 0.25in GW 51 5 -S 0 0 -S 0 T 2in GW 52 5 0 -S 0 0 -S T 2in GW 53 5 0 S 0 0 S T 2in GW 54 5 S 0 0 S 0 T 2in GW 66 5 -S 0 D 0 0 D 0.25in GW 67 5 0 0 D S 0 D 0.25in GW 68 5 0 -S D 0 0 D 0.25in GW 69 5 0 0 D 0 S D 0.25in GW 70 5 -2S 0 D -S 0 D 0.25in GW 71 5 S 0 D 2S 0 D 0.25in GW 72 5 0 -2S D 0 S D 0.25in GW 73 5 0 S D 0 2S D 0.25in GW 80 5 -1S 0 D -1S -1S D 0.25in GW 81 5 -1S 0 D -1S 1S D 0.25in GW 82 5 1S 0 D 1S -1S D 0.25in GW 83 5 1S 0 D 1S 1S D 0.25in GE 1 SY I1 = 1 SY I23 = 1 SY I4 = 1 SY P1 = 0 SY P23 = -90 SY P4 = -180 EX 6 1 1 00 1.0 0.0 EX 6 2 1 00 .0 -1.0 EX 6 3 1 00 .0 -1.0 EX 6 4 1 00 -1.0 -.0 GN 0 0 0 0 13 0.002 ' FR 0 1 0 0 14.01 EN 'From the arrl antenna anthology, vol. 1. |
#2
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don't worry about the swr, you need to build a phasing system that generates
the required feed currents and that can easily contain a network to bring the output impedance to whatever you want to feed it with. wrote in message oups.com... Hi, I am using 4nec2 and ICEPAC to design a 4-square inverted L. I think the far field pattern, SWR, and area coverage are pretty good. I believe most receivers can hear signals down to -120db fairly well. I am modelling not only radials but also a ground system to reduce the SWR and help with the lightning protection. I hacked this out of a standard 4-square for 80 meters. Any of the 4-square people out there who can offer additional pointers, construction details, and other things I have not considered? I'm finding trouble reducing the SWR from 2:1 down to 1:1 NOTE: Distance T is an arbitrary distance between the ground and a planned wooden deck roof to help disguise the system. Distance D is an arbitrarily small distance between the ground system and the dirt. Thanks much! The Eternal Squire CM K6NA - 4-Element W1CF Phased-Vertical Array CE converted with 4nec2 from AO to 4nec2 format on 22-apr-02 SY T = 9 ft SY S = 17.3875 ft SY K = T SY M = 8.69375 ft SY D = 0.1 ft SY W = 8.69375 ft GW 1 5 -S 0 T -S 0 T+W 1in GW 2 5 0 -S T 0 -S T+W 1in GW 3 5 0 S T 0 S T+W 1in GW 4 5 S 0 T S 0 T+W 1in GW 11 5 -S 0 T+W -S+W 0 T+W 1in GW 22 5 0 -S T+W 0 -S+W T+W 1in GW 33 5 0 S T+W 0 S-W T+W 1in GW 44 5 S 0 T+W S-W 0 T+W 1in GW 111 5 -S 0 K -S-M 0 K 0.25in GW 112 5 -S 0 K -S+M 0 K 0.25in GW 113 5 -S 0 K -S M K 0.25in GW 114 5 -S 0 K -S -M K 0.25in GW 211 5 S 0 K S-M 0 K 0.25in GW 212 5 S 0 K S+M 0 K 0.25in GW 213 5 S 0 K S M K 0.25in GW 214 5 S 0 K S -M K 0.25in GW 311 5 0 S K 0 S-M K 0.25in GW 312 5 0 S K 0 S+M K 0.25in GW 313 5 0 S K M S K 0.25in GW 314 5 0 S K -M S K 0.25in GW 411 5 0 -S K 0 -S-M K 0.25in GW 412 5 0 -S K 0 -S+M K 0.25in GW 413 5 0 -S K M -S K 0.25in GW 414 5 0 -S K -M -S K 0.25in GW 51 5 -S 0 0 -S 0 T 2in GW 52 5 0 -S 0 0 -S T 2in GW 53 5 0 S 0 0 S T 2in GW 54 5 S 0 0 S 0 T 2in GW 66 5 -S 0 D 0 0 D 0.25in GW 67 5 0 0 D S 0 D 0.25in GW 68 5 0 -S D 0 0 D 0.25in GW 69 5 0 0 D 0 S D 0.25in GW 70 5 -2S 0 D -S 0 D 0.25in GW 71 5 S 0 D 2S 0 D 0.25in GW 72 5 0 -2S D 0 S D 0.25in GW 73 5 0 S D 0 2S D 0.25in GW 80 5 -1S 0 D -1S -1S D 0.25in GW 81 5 -1S 0 D -1S 1S D 0.25in GW 82 5 1S 0 D 1S -1S D 0.25in GW 83 5 1S 0 D 1S 1S D 0.25in GE 1 SY I1 = 1 SY I23 = 1 SY I4 = 1 SY P1 = 0 SY P23 = -90 SY P4 = -180 EX 6 1 1 00 1.0 0.0 EX 6 2 1 00 .0 -1.0 EX 6 3 1 00 .0 -1.0 EX 6 4 1 00 -1.0 -.0 GN 0 0 0 0 13 0.002 ' FR 0 1 0 0 14.01 EN 'From the arrl antenna anthology, vol. 1. |
#3
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also, why bother with inverted L's? a full 1/4 wave vertical for 20m is
only about 15' tall, easily built from tubing or pipe and easily supported even free standing. wrote in message oups.com... Hi, I am using 4nec2 and ICEPAC to design a 4-square inverted L. I think the far field pattern, SWR, and area coverage are pretty good. I believe most receivers can hear signals down to -120db fairly well. I am modelling not only radials but also a ground system to reduce the SWR and help with the lightning protection. I hacked this out of a standard 4-square for 80 meters. Any of the 4-square people out there who can offer additional pointers, construction details, and other things I have not considered? I'm finding trouble reducing the SWR from 2:1 down to 1:1 NOTE: Distance T is an arbitrary distance between the ground and a planned wooden deck roof to help disguise the system. Distance D is an arbitrarily small distance between the ground system and the dirt. Thanks much! The Eternal Squire CM K6NA - 4-Element W1CF Phased-Vertical Array CE converted with 4nec2 from AO to 4nec2 format on 22-apr-02 SY T = 9 ft SY S = 17.3875 ft SY K = T SY M = 8.69375 ft SY D = 0.1 ft SY W = 8.69375 ft GW 1 5 -S 0 T -S 0 T+W 1in GW 2 5 0 -S T 0 -S T+W 1in GW 3 5 0 S T 0 S T+W 1in GW 4 5 S 0 T S 0 T+W 1in GW 11 5 -S 0 T+W -S+W 0 T+W 1in GW 22 5 0 -S T+W 0 -S+W T+W 1in GW 33 5 0 S T+W 0 S-W T+W 1in GW 44 5 S 0 T+W S-W 0 T+W 1in GW 111 5 -S 0 K -S-M 0 K 0.25in GW 112 5 -S 0 K -S+M 0 K 0.25in GW 113 5 -S 0 K -S M K 0.25in GW 114 5 -S 0 K -S -M K 0.25in GW 211 5 S 0 K S-M 0 K 0.25in GW 212 5 S 0 K S+M 0 K 0.25in GW 213 5 S 0 K S M K 0.25in GW 214 5 S 0 K S -M K 0.25in GW 311 5 0 S K 0 S-M K 0.25in GW 312 5 0 S K 0 S+M K 0.25in GW 313 5 0 S K M S K 0.25in GW 314 5 0 S K -M S K 0.25in GW 411 5 0 -S K 0 -S-M K 0.25in GW 412 5 0 -S K 0 -S+M K 0.25in GW 413 5 0 -S K M -S K 0.25in GW 414 5 0 -S K -M -S K 0.25in GW 51 5 -S 0 0 -S 0 T 2in GW 52 5 0 -S 0 0 -S T 2in GW 53 5 0 S 0 0 S T 2in GW 54 5 S 0 0 S 0 T 2in GW 66 5 -S 0 D 0 0 D 0.25in GW 67 5 0 0 D S 0 D 0.25in GW 68 5 0 -S D 0 0 D 0.25in GW 69 5 0 0 D 0 S D 0.25in GW 70 5 -2S 0 D -S 0 D 0.25in GW 71 5 S 0 D 2S 0 D 0.25in GW 72 5 0 -2S D 0 S D 0.25in GW 73 5 0 S D 0 2S D 0.25in GW 80 5 -1S 0 D -1S -1S D 0.25in GW 81 5 -1S 0 D -1S 1S D 0.25in GW 82 5 1S 0 D 1S -1S D 0.25in GW 83 5 1S 0 D 1S 1S D 0.25in GE 1 SY I1 = 1 SY I23 = 1 SY I4 = 1 SY P1 = 0 SY P23 = -90 SY P4 = -180 EX 6 1 1 00 1.0 0.0 EX 6 2 1 00 .0 -1.0 EX 6 3 1 00 .0 -1.0 EX 6 4 1 00 -1.0 -.0 GN 0 0 0 0 13 0.002 ' FR 0 1 0 0 14.01 EN 'From the arrl antenna anthology, vol. 1. |
#4
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Take a look at the far-field pattern and you'll see why I want it.
Also, it seems that inverted L's rather than verticals lower the SWR from the thousands to something more sensible. The Eternal Squire. |
#5
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The feedpoint SWR will depend heavily on the type of feed system used.
The 4SqTL.EZ example model included with EZNEC, which uses one of the all-transmission line feed systems described by "The Simplest Phased Array Feed System - That Works", shows a 50-ohm SWR of 3.7 at the feedpoint. Other feed systems are possible using this method, each of which produces a different feedpoint impedance. The combination transmission line - L network method described in Chapter 8 of the ARRL Antenna book produces yet other feedpoint impedances, depending on the transmission line Z0s which are chosen. There's no need to settle for a feedpoint SWR in the thousands, and there's no need to alter your array elements as a means of improving it. If you use inverted-L elements for a four square array, it seems to me you'd get a different elevation pattern in the various directions, and that the azimuth pattern would be distorted by the directionality of the elements. Have you modeled the full four element array, with the currents phased as they would be for each of the four readily switchable directions? Roy Lewallen, W7EL wrote: Take a look at the far-field pattern and you'll see why I want it. Also, it seems that inverted L's rather than verticals lower the SWR from the thousands to something more sensible. The Eternal Squire. |
#6
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Roy,
Actually, I have modelled for a single direction, see my original post. I am using 4nec2 for modelling the far field pattern. Would you be interested in checking my work to see if anything better can be done? The Eternal Squire P.S: Do you have experience with 4-square arrays? |
#7
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#8
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I have no problem asking any or all people who might happen to be
4-square enthusiasts. I've been surfing the net and have found only 3 or 4 who talk about it, I have sent them email too. The Eternal Squire |
#10
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