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Today's Topics:
1. Spacing at center of K1WA/K3LR array (Mike Smith VE9AA)
2. Re: Spacing at center of K1WA/K3LR array (jimlux)
3. Re: Spacing at center of K1WA/K3LR array (jimlux)
4. four square array tuning (Steve Bookout)
5. Re: four square array tuning (Peter Voelpel)
----------------------------------------------------------------------
Message: 1
Date: Mon, 28 Nov 2016 15:10:55 -0400
From: "Mike Smith VE9AA" <ve9aa@nbnet.nb.ca>
To: <towertalk@contesting.com>
Subject: [TowerTalk] Spacing at center of K1WA/K3LR array
Message-ID: <007f01d249ab$25a8cb20$70fa6160$@nbnet.nb.ca>
Content-Type: text/plain; charset="us-ascii"
Greeting Antenna Gurus,
Put the finishing touches on a 100% homebrew K1WA/(K8UR) K3LR type 5-dipole
sloping dipole (all parasitic) array for 15m only hours before the contest
this weekend and came away quite disappointed.
NE/NW/SE/SW dples are all spaced at 90* from one another but the 5th dipole
(south) is squeezed in between the normal SE and SW directions. Maybe it's
too close. Carib stns were louder when beaming AFRICA than they were when
beaming south. This was all weekend, so I don't think it was an anomaly. I
haven't done field strength pattern testing yet (no time) but I know it
won't be pretty. My little A3S at 24' was usually louder on 15m than the
array. (not 100% of the time, but most of the time.)
This is built almost EXACTLY like Tim's 4-element 160m array at K3LR (or
like his array was in the 1990's anyways - not sure if he still uses it.)
except I used the 5th dipole due south for Caribbean/SA and my 5 radials are
on the ground, and not raised. Phasing lines, tops with ropes, etc. all the
same. Most of the mast is PVC (except the bottom 12'_) and the bottoms of
the dipoles are off the ground maybe 6' (not overlapped at the tower bottom
like Tims). Box and coax grounded, radials attached. All per his article.
What I would like to know from anyone that has either built one for 10-15 or
20m (or any band, and I'll do the math) is what is the actual spacing used
dipole center to dipole center?
Or anyone that knows antenna modeling programs, can you see if this has any
useful gain or F/B with only 6.66' spacing at the centers at 21.1MHz. (which
is roughly 0.142WL I believe)
I went this close because all the hardware was taken from an old 6m array
that I used many moons ago.
I am thinking I should rebuild it with a much larger spacing, maybe around
.25WL(11.6') and ditch the south and extra, 5th dipole.
Tnx
Mike VE9AA
Mike, Coreen & Corey
Keswick Ridge, NB
------------------------------
Message: 2
Date: Mon, 28 Nov 2016 11:34:22 -0800
From: jimlux <jimlux@earthlink.net>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Spacing at center of K1WA/K3LR array
Message-ID: <e6d9d374-72dc-109b-bbb9-127baa9d271d@earthlink.net>
Content-Type: text/plain; charset=windows-1252; format=flowed
On 11/28/16 11:10 AM, Mike Smith VE9AA wrote:
Greeting Antenna Gurus,
Put the finishing touches on a 100% homebrew K1WA/(K8UR) K3LR type 5-dipole
sloping dipole (all parasitic) array for 15m only hours before the contest
this weekend and came away quite disappointed.
NE/NW/SE/SW dples are all spaced at 90* from one another but the 5th dipole
(south) is squeezed in between the normal SE and SW directions. Maybe it's
too close.
What's connected to the unused dipoles? Coax to a double pole switch,
like in the 1994 QST article, so that you basically have a open
circuited stub?
The article comments on the large change in F/B in the model as the
transmission line parameters were changed (which isn't surprising.. it
affects the phase on the "parasitic" elements.
. (not 100% of the time, but most of the time.)
This is built almost EXACTLY like Tim's 4-element 160m array at K3LR (or
like his array was in the 1990's anyways - not sure if he still uses it.)
except I used the 5th dipole due south for Caribbean/SA and my 5 radials are
on the ground, and not raised. Phasing lines, tops with ropes, etc. all the
same. Most of the mast is PVC (except the bottom 12'_)
Since the dipoles are vertical, I would expect that in K3LR's case there
was a fair amount of interaction with the conductive mast. That's
something you'd need to factor in.
and the bottoms of
the dipoles are off the ground maybe 6' (not overlapped at the tower bottom
like Tims). Box and coax grounded, radials attached. All per his article.
What I would like to know from anyone that has either built one for 10-15 or
20m (or any band, and I'll do the math) is what is the actual spacing used
dipole center to dipole center?
In K3LRs, assuming that the angles are all 45s, the distance from the
tower to the feedpoint is 93 ft, and 93 feet from the top of the tower.
That makes the "feedpoint to feedpoint" distance, pretty much the same
as the distance along the hypotenuse from top to feed, 135 feet (41.15
meters)
At 1.84MHz (K3LRs apparent design frequency) the wavelength is 163
meters, so the center to center distance is pretty close to a 1/4
wavelength.
Or anyone that knows antenna modeling programs, can you see if this has any
useful gain or F/B with only 6.66' spacing at the centers at 21.1MHz. (which
is roughly 0.142WL I believe)
That is "very close" and almost certainly interacting.
I went this close because all the hardware was taken from an old 6m array
that I used many moons ago.
I am thinking I should rebuild it with a much larger spacing, maybe around
.25WL(11.6') and ditch the south and extra, 5th dipole.
That would be a start, but this is one of those antennas where some
modeling will help a lot.
Bear in mind that for most arrays, gain is fairly tolerant of phasing
errors, but F/B (null depth) is VERY picky. If the phase in the
parasitic element is off, then the null goes away. That's illustrated in
Figures 3 & 4 in the original article.
Tnx
Mike VE9AA
Mike, Coreen & Corey
Keswick Ridge, NB
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------------------------------
Message: 3
Date: Mon, 28 Nov 2016 12:46:02 -0800
From: jimlux <jimlux@earthlink.net>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Spacing at center of K1WA/K3LR array
Message-ID: <3130d07e-f756-d5f8-00f1-9fd2233100a1@earthlink.net>
Content-Type: text/plain; charset=windows-1252; format=flowed
On 11/28/16 11:34 AM, jimlux wrote:
On 11/28/16 11:10 AM, Mike Smith VE9AA wrote:
Greeting Antenna Gurus,
Here's the model
CM Tower with 4 vertical V dipoles ' Comment cards
CM based on K3LR's article in 1994 QST
CE
' End of comment
'
SY TH=190/3.28'tower height
SY TR=1/3.28 'Tower Radius
SY DL=131/3.28 'Dipole element length
SY DA=45 'dipole angle
SY DR=.001 'Dipole radius (1mm)
SY DS=95/3.28 'Spacing from tower for center of dipole
SY DH=95/3.28 'height of dipole center above ground
SY FL=175/.78/3.28 'Feedline length
GW 101 101 -sin(DA)*DL 0
cos(DA)*DL 0 0 .1 DR
' Wire 1, upper part
GW 111 101 0 0 -0.1
-sin(DA)*DL 0 -cos(DA)*DL DR
GW 121 1 0 0 0.1
0 0 -0.1 DR 'feedpoint
GW 122 1 1 0 0.05
1 0 -0.05 .001
GM 0 0 0 0 0
DS 0 DH 0
'move dipole away from tower and up to height
GM 100 3 0 0 90
0 0 0 'make 4 copies
GW 900 100 0 0 0
0 0 th tr 'tower
GE 1
'
GN 2 0 0 0
13 0.005
EX 0 122 1 00 1
0
' Voltage source (1+j0) at wire 1 segment 51
TL 121 1 122 1 50
FL 'transmission line
TL 221 1 222 1 50
FL
TL 321 1 322 1 50
FL
TL 421 1 422 1 50
FL
LD 5 0 0 0
58000000 '20% of copper (steel)
LD 5 900 0 0
37700000 'Tower
LD 0 222 1 1 1e6
LD 0 322 1 1 1e6
LD 0 422 1 1 1e6
'
FR 0 1 0 0
1.84 0
' Set design frequency (300 Mc).
'
EN
------------------------------
Message: 4
Date: Mon, 28 Nov 2016 17:27:52 -0500
From: Steve Bookout <steve@nr4m.com>
Cc: towertalk@contesting.com
Subject: [TowerTalk] four square array tuning
Message-ID: <ac33556d-1cc8-2946-e3fc-7fb1022ff146@nr4m.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Hello all,
Over the last few years, I have added four square arrays for 40 meters
and 80 meters, and both work really outstanding.
Recently, I added a third one for 20 meters and am having a difficult
time with it.
Short version is I resonated each antenna individually, with the others
shorted with clip leads to gnd, to 13.9 MHz +/-. The array, as a whole,
doesn't show a suitable SWR until 15.6 MHz! Like the others I had
installed, I was expecting a 150 KHz, or so, rise in frequency to
resonance. I do understand that it's really all about the power being
dumped to the dummy load, but the amp is not going to tolerate a 3.5 to
1 SWR.
Cables were cut using an AIM antenna analyzer and were double checked.
All other cable/parts were checked out and shown to be correct.
80 ground mounted radials under each antenna.
Built just like I did the other two.
Gonna look at it with an O-scope tomorrow and check phase vs freq. My
gut feeling is an incorrect value component.
My gut feeling aside, I would appreciate any ideas.
73 de Steve, NR4M
------------------------------
Message: 5
Date: Mon, 28 Nov 2016 23:36:04 +0100
From: "Peter Voelpel" <dj7ww@t-online.de>
To: "'Steve Bookout'" <steve@nr4m.com>
Cc: <towertalk@contesting.com>
Subject: Re: [TowerTalk] four square array tuning
Message-ID: <526922D7450D42F2953133F45AA279DB@SHACK>
Content-Type: text/plain; charset="us-ascii"
Hi Steve,
You need to OPEN the unused radiators while you adjust one at the time!
If connected to ground they couple to the radiator in tune.
73
Peter, DJ7WW
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Steve
Bookout
Sent: Montag, 28. November 2016 23:28
Cc: towertalk@contesting.com
Subject: [TowerTalk] four square array tuning
Hello all,
Over the last few years, I have added four square arrays for 40 meters
and 80 meters, and both work really outstanding.
Recently, I added a third one for 20 meters and am having a difficult
time with it.
Short version is I resonated each antenna individually, with the others
shorted with clip leads to gnd, to 13.9 MHz +/-. The array, as a whole,
doesn't show a suitable SWR until 15.6 MHz! Like the others I had
installed, I was expecting a 150 KHz, or so, rise in frequency to
resonance. I do understand that it's really all about the power being
dumped to the dummy load, but the amp is not going to tolerate a 3.5 to
1 SWR.
Cables were cut using an AIM antenna analyzer and were double checked.
All other cable/parts were checked out and shown to be correct.
80 ground mounted radials under each antenna.
Built just like I did the other two.
Gonna look at it with an O-scope tomorrow and check phase vs freq. My
gut feeling is an incorrect value component.
My gut feeling aside, I would appreciate any ideas.
73 de Steve, NR4M
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------------------------------
Subject: Digest Footer
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------------------------------
End of TowerTalk Digest, Vol 167, Issue 56
******************************************