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Old September 17th 05, 07:55 PM
 
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Default 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.

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Old September 17th 05, 08:11 PM
Dave
 
Posts: n/a
Default

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   Report Post  
Old September 17th 05, 08:13 PM
Dave
 
Posts: n/a
Default

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.



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Old September 18th 05, 03:22 AM
 
Posts: n/a
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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.

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Old September 18th 05, 03:59 AM
Roy Lewallen
 
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Default

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.



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Old September 18th 05, 04:14 AM
 
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Default

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?

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Old September 18th 05, 05:00 AM
 
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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

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Old September 18th 05, 05:26 AM
Richard Clark
 
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On 17 Sep 2005 21:00:13 -0700, wrote:

I have no problem asking any or all people who might happen to be
4-square enthusiasts.


That's been demonstrated, but why didn't you read and respond to his
answer to your question the first time thru?

You can make a 4 square from any kind of element. EZNEC can tell you
what effect the element shape will have. I strongly recommend against
designing the antenna to get the best or easiest match. Design the
antenna for the best performance, then design whatever matching
arrangement you need in order to match it. An exception to this general
rule is that antennas with an exceptionally low resistance or high
reactance might not be practical because of the problem of matching
system loss, so such an antenna might need redesign in order to be
practical.

2) Where can I find or build a reasonably inexpensive phase box?


Chapter 8 of the ARRL Antenna Book describes how to design one. See also
"The Simplest Phased Array Feed System - That Works" and accompanying
program Simpfeed, available from
http://eznec.com/Amateur/Articles/.

3) For the vertical part, I am wanting to a dig a hole 2 foot across by
3 foot down, and fill with concrete. Into this I would insert a 5
foot length of 1 1/2 inch steel support pipe about midway, so that 2
1/2 feet are above ground. Into this I would mount a 10 foot length
of 3/4 inch steel pipe with a 2 1/2 foot insulated overlap of PVC
pipe. The 3/4 inch steel pipe would be the bottom of the actual
driven element. Into this I would mount a 10 foot length of 1/2 inch
aluminum pipe with a 2 foot metallic contact overlap, and then I would
finish with rod for vertical or wire for inverted L.


Wow, for a 20 meter 4-square? For each element on 40, I drove a 1-1/4" 8
foot galvanized chain link fence line pole 4 feet into the ground. (Our
soil is clay.) I cut a piece of heavy wall PVC pipe lengthwise into
quarters for insulators, and clamped the element to the line pole with
muffler clamps with a couple of pieces of the split PVC pipe in between.
The elements are three pieces of telescoping 6061-T6 tubing, beginning
with, as I recall, 1-1/8" at the bottom. They've been up for around 20
years now and survived a couple of pretty strong wind storms.


Question: how would the 2 1/2 foot overlap of a non-grounded metal
support pipe interfere with radiation of the vertical element?


Any shunt impedance will reduce the null depth if the array is adjusted
for the correct base current ratio. This is because a different fraction
of the current will be diverted from each element because of their
differing base impedances. However, I've found that the 4 foot overlap I
have doesn't reduce it noticeably. But my overlapping pipes are parallel
and, if I understand your description, yours will be coaxial. That'll
result in a lot more shunt capacitance, and a correspondingly greater
effect on the null. The main lobe won't be affected much.

Roy Lewallen, W7EL


To simply blow through that response to then ask:
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?

this hardly [doesn't] acknowledges all the effort that went before it.
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