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Author Topic: Half square antenna for 40 meter DX  (Read 6931 times)
K4RVN
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Posts: 812




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« on: February 16, 2011, 06:21:12 PM »

I presently use a 40 meter half square antenna at 55 ft running about 500 watts. I am pleased with the results in the states, but would like to work DX more often. I bought another identical 40 meter half square and was thinking about trying it as a parasitic reflector by spacing it out about 20 ft from the existing antenna from information on the net by VA7ST. Later I will add relays and stubbs to make it an array as he designed with a reflector that can be switched. Right now I just want a fixed reflector.
Has anyone tried this by just hanging another identical antennna beside the driven one. I thought of using a field strength meter before adding it and then after to see if the gain increased. Is this a good idea? If it works the gain could be around 6dbi. Any input would be appreciated.

Frank
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N4JTE
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« Reply #1 on: February 16, 2011, 06:43:51 PM »

Hi Frank, I never had much success with a half square but probaly due to my lousy ground conditions, it is a vertical antenna, hi.
But if you are not getting the DX you are chasing with it as is, then I'm not sure a reflector would help. The parasitic idea is a sound approach but again, the half square is really a two element phased broadside vertical and is very tied to near and far field conditions as is any vertical, always a hit and miss thing when using verticals, especialy with a phased array with no radials.
good luck,
Bob
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K4RVN
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« Reply #2 on: February 17, 2011, 06:16:16 PM »

Thanks for reply,and comments.
I called CQ tonight on 40 M. and LU3OE gave me a call and report of 56-57. He was about the same. I do get somewhat consistent reports of 59 or over in the states so I am pleased with the phased verticals no radials required. I just like to tinker with improving my antennas so I will add the reflector and make it so I can switch from east to west using relays. I have all the components now so will go ahead and do it while I'm in the mood. I actually talked to another station yesterday running a half square on 40 meters.They have been rare for me over the years. I use a 3 element , 5 band homebrew quad on HF and just got interested in 40 again last year. If you hear me on say hello.

Frank
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WA4FNG
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« Reply #3 on: February 17, 2011, 06:45:11 PM »

Check this out - details of a twin half-square array for 40m.

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=20962

You may also want to try a pair of phased delta loops. Haven't tried them but planning to...

-Milt
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W1NK
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« Reply #4 on: February 17, 2011, 06:48:37 PM »

When making a half-square with a reflector, Cebik recommends keeping the horizontal sections of equal length and altering the length of the vertical elements of the reflector.  The sketch of an 80M parasitic halfsquare on his website has the verticals about 3.25% longer.

(although I have a 40M half square, I haven't tried this.  Just relaying the info  Wink  )

Frank, W1NK
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K4RVN
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« Reply #5 on: February 17, 2011, 07:58:48 PM »

Milt,
I am using that site to make the array. Thanks. I even emailed the writer with questions and he answered them for me. I really appreciated the relay schematic.

Frank
 Thanks also for your comments. I have one antenna up at 55 ft and already have the nylon cords in place at about the same height for the relector.  I will take some doing to get the two spaced properly. The relays will require a wire in addition to the feed line coax adding to the weight. I use RG8X to keep the weight down. Also a half square requires the feed line to run horiz. away from the vertical about a 1/4 wave length to prevent RF interaction. I am thinking of running a third nylon cord into a tree to carry the extra weight of the relays and wiring. I'm having fun, but I hope my efforts pay off with added gain. Later, I may peak it up using my 259 antenna analyser.

Frank
















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W4VR
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« Reply #6 on: February 19, 2011, 08:26:02 AM »

The best way to find out if it will work is to  model it on EZNEC, or on MMNA-GAL which is freeware.  You can download MMNA-GAL from this site: http://mmhamsoft.amateur-radio.ca/pages/mmana-gal.php.  However, I believe that if you intend to use two identical half squares you may want to consider phasing them...again model the array before you go with it.
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K4RVN
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« Reply #7 on: February 19, 2011, 07:49:10 PM »

Thanks for reply. I am using a design by VA7ST who has done all the work for others. All I need to do is the physical work and it is a good thing as I am not into model work for antennas. VA7ST has
patterns, gain, etc. in his article. I'll get to work with my solder gun next week and get the antenna up in place provided this good weather holds and I stay in a work mode.

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=20962



Frank
« Last Edit: February 19, 2011, 07:52:11 PM by K4RVN » Logged
K4RVN
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« Reply #8 on: February 25, 2011, 05:44:38 PM »

Just an update post.
 I completed the VA7ST twin half square array yesterday for 40 meters. I talked to Bugaria last night, and also worked 8 west coast stations in a row while directing the antenna west. If I directed it east, I could not hear them well or not at all so it does have gain in one direction when adding a reflector. A report today gave me two s units gain when directing the antenna that direction. It is also very noticeable on receiving. I was able to have qsos on a very noisy band last night with poor propagation and receive good reports running 500 watts at an antenna height of about 50 ft. This is an excellent antenna for DX or ragchewing with a very good signal using vertical polarization, 50 ohm direct coax feed, no tuner needed and no radials required. Data from VA7ST indicates a gain for the twin halfsquare better than a two element yagi. I have mine oriented so I can switch it east to west with east the default direction.
Thanks for all the comments.



Frank
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W1NK
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« Reply #9 on: February 25, 2011, 09:20:33 PM »

Great!  Now I won't be able to sleep tonite thinking about how I can place another half square in the woods behind the house!  Wink

(Good job Frank!)
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K4RVN
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« Reply #10 on: February 26, 2011, 08:07:00 PM »

Thanks Frank,
I'm emailing you some tips on the install in case you get serious about an array.  They might save you some time. It is still working after two days use and doing a good job on 40 meters for me.

Frank
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W1NK
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« Reply #11 on: February 27, 2011, 06:31:07 AM »

Thanks Frank!  I look forward to receiving the email..  I've thought long and hard about that array for some time!

Frank
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