Top loaded wire phased vertical-- The MINI CURTAIN

It is amazing to find a little used wire antenna with enormous utility , simplicity and gain. This antenna really has no name. I first read about it on page 57 of the march 2016 antenna issue in the article written by John Hallas, W1ZR. He writes about it in terms of stealthiness but in my opinion it is so much more.

What is it? It is a wire 1 wavelength long ( 1005/fq) fed at the quarter wave from 1 end . The middle half wave is supported as high and flat  as practical and the two quarter wave ends are dropped vertically to about some where above ground. This creates a phased vertical and radiates broadside with phased vertical gain ( 4.5 dbd) WITHOUT RADIALS.!! 
It obviously is top loaded  but guess what? 50 or 75ohm ,no tuner , no balun.  You trim the ends to resonance 1:1!. 

After I read about it I worked a station using one built by a fellow with deed restriction in a two story town house. His wire was literally pinned to the walls.  It was a 20 meter with the vertical ends 17 feet long but 4 feet off the ground. The horizontal half wave was 34 feet long and as high as he could hang it on the eves of the townhouse. It was very loud!! I was really impressed. So, on Christmas vacation in Ruidoso., New Mexico,in a two story  rent house,I hung one on the out side wall above the outside second story deck. I did try to move to out from the wall a few inches . I used # 14 insulated multi-strand wire. You want insulated wire because it may touch the wall or supports in places.   I found that it was high in frequency resonance so I added 8 inches to each end and it went flat on SWR. It was amazing. I made 37 qsos on 20 meters cw in 3 days ( leisurely)   and worked LU VK and XE in horrible conditions. It was impressive.

Now I wanted to fly one at home in free space. I also wanted to use the one I put together is New Mexico. To test it , I had a 34 foot freestanding pole with a pully rope on it and 60 feet away I had a 28 foot pole that I used to tie off my 160 half sloper. 
Using weed eater line to run through the top pulley on the 20 foot pole , I raised that end of the half wave section and let the other ends drop vertically 17 feet. I tied them off to a ground post using non conducting weed eater line.  The other end was hoisted up to 33 feet which had the top corner feed point. So it slopes but who cares. Because of free space and soil differences I had to retrim it to 1:1. I use RG6 72 ohm coax. I did use a one 1:1 Balun but mainly as a coax connector . It will match without it. ( IF YOU TRIM OR EXTEND THE ENDS AS NEEDED)

What is unique about my test was that I actually have ground mounted phased 20 meter verticals to compare with on the Internet Reverse Beacon  Network,  The ground mounted verts have about 40 radials each.  I was able to compare them because they are both broadside east west . I couldn't have had a better test comparison set up. 

I did numerous reverse beacon tests 1 minute apart and on different but close frequencies and while each antenna has different nulls and hot zones my conclusion was that the Mini Curtain was as good or better that the ground mounted phased verts and NO RADIALS!!   The angle of radiation on the Mini Curtain is between 15 and 22 degrees depending on height. ( if you are not familiar with reverse beacon on the internet, see my page dedicated to helping you with that.) 

Also the 20 meter Mini Curtain worked on 15 and 40 with no tuner. Here, I believe it works as a folded OCF and it was not quite as good but surprisingly comparable to my mono band wires for those bands. It was good on 17 with a tuner. 

The killer would be a 30, 40 or 80 mini Curtain.  I need Spring time to come but I will do a 40 or 30.

Now I wanted to try a two band on one feed line !!

Here is the 20 meter Mini Curtain from the above mentions QST article..


It is the ultimate if you are deed restricted and have trees or walls high enough to float the Mini Curtain But do not underestimate to phased vertical gain on the lower bands. NO RADIALS!!  

Now let's see if my theory is correct . " If RF can find resonance in an antenna , it will". Could we put two bands on a single feed line -- two Mini Curtains in one , so to speak. I had a 20 meter Mini  up but could I come inside and drop a 1/4 wave vertical off the 34 foot 20 meter half wave but do it at the 17 meter half wave point?? The halfwave point on the flat top for a 17 meter rf circuit would be on 27.5 feet from the top loaded corner so I measured that point from which I would drop the 17 meter quarter wave vertical wire ( 13.75 feet ) . I simply did a twisted tap at the 27.5 foot mark  on the 34 foot half wave 20 meter flattop. 

Now, I need the other vertical quarter wave at the feed point coming off the other braided side of the coax . I already had the 17 foot vertical dropping there on 20. If  i got the two vertical wires too close it would cause interaction so I pulled them apart about 5 degrees at the apex . 

I was ready for a test. It absolutely worked . I had to trim some of the 17 mini curtain but the 20 stayed resonant.  The reverse beacon tests ( see my page on RBN)  on 17 were great. I have an outstanding 17 meter EDZ at apex 35 feet with 3.3 dbd gain I was able to compare with the new 17 mini curtain . The two antennas were very comparable. The EDZ and the Mini curtain have some lobes and nulls so the testing proved that but head to head the mini curtain was lower noise on RX and very close to the same signal strength. So it worked!!  


THE TWO BAND MINI CURTAIN -- Top loaded phased vertical array. NO RADIALS!!


Ok a blog is a living breathing document so things change. Ice took my two ban 20/17 down so I built a free standing 17 meter . This one is about 28 feet off the ground . It was close to formula 1005/fq although I had to lengthen it to find resonance.This one was on a 1:1 balun with 50 ohm coax. You have to have two structural point to elevate this antenna. Here I used a 30 foot mast and a 30 foot high tree 60 feet apart.  . I use weed eater over the tree and enough excess to reach the half wave tie point on the mini curtain. . Then I hoist it up. This leaves the vertical wire at that end about 9 feet off the ground. Very nice I tie weed eater line to the bottom of the vertical wire at that end and bring it to a tie off point on the ground to keep it from flapping in the breeze.
 On the pole ,I guy the pole with weed eater line -- Hi . I am like the father , Gus Portokalos in My Greek Wedding  ,played by Michael Constantine. He fixes everything with "WD40"!! I use weed eater line for all wire antennas!!  Anyway on the pole ,I use a pulley and rope system but I don't use a pulley. Pulleys bind . I use 1 inch wide eyes on 1/4 inch eye bolts drilled through the top of the mast. NO BINDING once you get the pull line in .

How did it work? Great.I was able to compare on RBN with my 17 meter EDZ, It was right there as it should be with the EDZ having 3.3 dbd again.There are lobes that are better on one antenna than the other.

There was an added bonus.The antenna is really a full wave OCF fed at the Quarter wave.  But as an OCF , mine it loads with good functional SWR on 30, 15, 12, an 10 meters.With auto tuner is works 20 and 40 with decent results.

30 METER Mini CURTAIN.

With that success I had  a 34 foot mast available after the Ice storm on the certainty wiped out my 20/17 mini curtain. It would be a mono bander on 30. . The 34 footer is 60 feet away from a 28 foot mast that I had to use because of my layout. The much longer top wire 50' would fit but the slope down caused the far end vertical quarter wave to hit the ground ,in fact 3 feet of it hit the ground. . The vertical wire quarter waves are obvious about 25 feet long.  A the low end I took a old 6 inch diameter spool that coax had come on.  It was about 10 inches long and had flanged ends so it would stand up. You could easily buy 6 inch diameter pvc, cut it 1 or two feet long and  glue cross bars on each end so it would stand straight up. Now, I took the 3 foot excess and wrapped it around the spool separating the wires as much as I could on the spool. I placed the spool on the ground and stabilized it with brick on top.  So I still has 22 feet of vertical radiator. plus the 3 foot coil at the bottom,.It absolutely worked great!! The Mini curtain  actually out performed my 160 meter half sloper which is  my best 30 meter antenna over the years. It beats verticals and even a full wave loops. 
Anyway,here is why this coil spool at the bottom is important. When you get to 40, 80 and 160 meters or if you just cant get up that high but want to try this on 20  etc, You can use these coils at the base and still get vertical polarization and phasing. 
Now look at this RBN test . This is the way I can actually know if antenna is a success. I have at least 2 antennas per band. On some band I have 3 or 4, On this reverse beacon test  of my two antennas note the Half sloper antenna is tested at  10.102 at 20:07. Then note below that set the frequency change at 20:06 . That is the 30 meter Mini Curtain at frequency 10.118.  Now look for the same station., for example NO1D. The "SNR" is signal to noise ratio. Think of it as an S meter. On the sloper it shows 24 db. Then drop down to the test of the Mini Curtain and you will see 32 db. That is what you want. Yes, qsb can be a factor but these CQs were called 60 second apart coming from the same receiving station  so that can account for some difference but these signals are coming from all over the open propagation on 30 meters so you are looking for a solid difference. RBN hears you on any band as long as you call cq.  I could have compared with my 30 vertical but it would have been a slaughter. 
The 30 mini works 15 with out auto tuner and 40 with a Tuner !.  It turns out it is a 3/4 wave OCF folded at the ends ad fed at 1/3 wave!  I noted a very close match on 20 meters .With a match auto tune it is by far the best 20 meter wire antenna I have ever seen. I used it in the cqww  as a back side antenna when the beam was in the wrong location. It blew me and the DX station away and Often I forgot the beam.I am not able to tell you why but that 90 foot antenna had gain on 20, no doubt.
So in summary, try one of these phased verticals without radials that I call a "Mini Curtains"and I think you will be super happy.  Send any questions you have to w5zo@arrl.net. 

This is a Post Post post.  I now have 3 freestanding mini curtains. 30, 17 and a new 20.  I want to focus on the 20. Picture the same wire config. What happened  was mind boggling. For reasons irrelevant , I fed the corner with 450 ohm ladder line. I used 35 feet but I really don't think that is important. I then used a 4:1 balun to 72 ohm RG6 ( that stuff is great and the loss is very low) . Now remember . I have no balun on my 30 mini curtain and I have a 1:1  on my 17 meter.  This feed system on the 20 was a hold over on a ZS6BKW that I just didn't like. 
What occurred was astounding  . I have an ICOM 7300 and is has swr plot . I quickly resonated 20. The total length of wore was approx 67 feet . 33 foot flat top and 17 foot verticals ( remember, this antenna is phased wire vertical array. But here is what bands resonated with no tuner.  40,30,20,17,15,12,6. I mean 100% output on a solid state SDR IC 7300. 

I am a lawyer. I don't model things . Have at it. I will also tell you that my 17 meter mini curtain resonated on 40,30,17,15,12,10,and 6. I am talking NO TUNER on all of this.

Now. except for the intended band the bonus bands are OCF folded wires. 
My 30 mini is 36' at the fed corner and sloped down to 20 feet.  My 17 mini is 28' at the fed corner and 22 ' at the far end.  The vertical ends are only a few feet oftf the ground.

My 20 mini is 40' at the fed corner  ans 30' at the other corner. I use weedeater for support lines. 

I tell you guys. These things work great . Mike W5ZO.

1 comment:

  1. I put up a Half-Square for 20 mtrs last fall and never had such a great antenna in my cramped, urban alleyway of an antenna farm. Thanks for the advice about not letting the bare wires touch anything. I had let the feedpoint vertical drop over the feedline, and it had severely scorched the coax. But that didn't prevent me from getting great dx and RBN reports. I used in on 15, 40 and 80 as well with a MFJ portable tuner. RF in the shack on 40 and 80 was a problem. I jumper-clipped at half-wave of insulated wire to the base of the feedpoint vertical and ran it along the wall parallel the top transmission/phasing line. It seems to act like a full wave loop, or a counterpoise at least. I've apparently got a low take-off angle even on the low bands. On 20 the skip zone seems to be 800 miles or so. It's oriented NE to SW (parallel the shoreline of Lake Superior)and RBN spotters in PA, NC, Alberta and Saskachewan love it. I get plenty of ragchewing to CA, AZ and NM--right off the end! I had a long chat with you on it, along with dozens of other Texans. I think their three element yagis and TS 590s receivers are doing all the heavy lifting on those calls. 73, and thanks for the great website. Keith, W0BAV

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