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[K4RVN]

I have read in the past where a Bobtail curtain was not worth the effort on 20 meters. I recently read an article by MFJ that one could add a vertical half wave reflector and a director behind and in front of the middle 1/4 wave vertical fed element to enhance the performance of the Bobtail curtain. Anyone have experience with a Bobtail curtain on 20 meters? I am just thinking up an easy winter antenna project and have read about the above mentioned antenna with interest. I have used half squares for years in the past for DX and they worked well but mine were on 40 meters. Of course a half square is not a Bob Tail Curtain. Any comments would be appreciated on the 20 meter application. I would be using an impedance transformer inductor and capacitor to feed the antenna at the bottom of the center vertical. Then 50 ohm coax back to the shack.

Frank

[N2SR]

There was an article in an old 73 magazine back in the 70's where a guy in the Pacific Northwest made some big heavy platform with small wooden poles.  He attached aluminum tubing to the center poles, and wire to the outside poles, and basically made what you are describing.   IIRC, it was for 20 and 15m.   He could manually rotate the whole "contraption," and the claim by the author (not the guy who built the antenna) was that it worked well.   

[K4RVN]

I would just direct it toward VK and ZL land, no relay switching or rotation planned. Not too many Bobtail curtains out there in my experience. Thanks for the comments.

Frank

[WA2VUY]

I've read that MFJ article, didn't make sense to me.

[K4RVN]

I am wondering why the added verticals for a reflector and director for the driven element would be 1/2 wave since the driven element is 1/4 wave. The rest is typical bobtail curtain design. I have not built one yet so have no experience as to how it would perform. I was hoping for some comments from those who have used or considered on and did some studying of the antenna.
Thanks for your comment.
Frank

[K4SAV]

Sure you could build something like this, but the question should be why would you want to.  It will be very complex and will have less gain than a 20 meter EDZ (unless you put it over salt water).  It would have a very narrow beamwidth so it would only be useful for point to point because it unlikely you would be able to rotate it.

Jerry, K4SAV

[W5DXP]

I am wondering why the added verticals for a reflector and director for the driven element would be 1/2 wave since the driven element is 1/4 wave.

Passive reflectors and directors have to be resonant. A 1/4WL passive element is not resonant. Try using a GDO on 1/4WL of wire with no counterpoise.

[K4RVN]

Jerry,
I was looking for a point to point antenna to aim toward VK with a gain close to a two element Yagi.  I already have a Hex beam and a 40 meter homebrew beam that rotate on towers. Just checking into a fixed wire antenna that I have not built before. The Bobtail curtain is not complex in my view as I have an analyzer and pretty good junk box for the LC feed circuit. I have built a number of antennas that only stayed up a short time as they did not work well. Old dude here with time to tinker with wires.

Frank

[K4RVN]

Thanks for info Cecil. I read an article last night of a Bobtail beam made with a reflector duplicate antenna spaced behind the driven antenna bout .25 wavelength and with verticals cut 6% longer. If I build this antenna I may try the single half wave reflector and director mentioned in the MFJ article . If that doesn't work, I'll try the beam I read about. Just having fun with the 500 ft. roll of wire I bought at Lowes.

Frank

[W1FBV]

I am not sure there is much difference in gain between a bobtail and a half square.  I have not seen an article on a bobtail with a director or a reflector, but I have seen articles describing a half square with a reflector.  Google "half square beam." 

Jim, W1FBV

[WB6BYU]

Cebik W4RNL had several articles on beams based on the Bobtail Curtain and the Half-Square.  Generally they
used parasitic elements of similar shape, though you could use a half-wave reflector behind each driven element.
I don't remember how much gain he got from it offhand.

I've made some computer models for 2m antennas, but the complexity generally overcomes any improvement
in gain or pattern over something like a 3-element quad.

So, yes, it can be done, but whether or not it is worthwhile depends on your needs, any other available options,
and the local ground conductivity.

[VK3YE]

My receiving experiments with a bobtail on 432 MHz.

It works but a small yagi gives more gain and directivity.

https://www.youtube.com/watch?v=FgJVuEq5Its

[K4RVN]

Jim,
I have read where there is not much difference between a half square and a Bobtail curtain in gain. I have used and built half squares since the 70s with good results on 40 meters. I have built an array by VA 7 ST for 40 meters. Now that I have a beam that rotates for 40 meters I am shifting my tinkering to 20 meters. I have found the nay sayers  don't always have the same antenna feeds etc. In other words one has to build it and see what happens.
Thanks for your input. Here is the MFJ article on adding parasitics. https://www.mfjenterprises.com/antennatalk3.php

Frank

[K4RVN]

Dale,
Cebik wrote about the two element and 3 element half squares which I printed out and save some years back. He designed for two meters. The two element had a gain of 13 dBI with front to back of 18 dB. Feed point impedance at one corner was 49.4 -1.4 ohms.
The three element added a gain of 1.4 dB not dBI and improved the front to back to 22.6 db The three element had an impedance of 43 ohms at resonance pretty good antenna for 2 meters @ only three elements. I always appreciate your input and thanks.
My three element half square for 20 meters was not as good as my K4KIO hex beam on a side by side comparison to Europe. A real pain to keep in alignment. I took it down and saved the components for another day.

Frank

[K4RVN]

Peter
 I appreciate your reply and had already watched your video. You fed yours another way from what I plan to try.
I am going to feed the center vertical at the bottom with a parallel LC circuit according to Greg VE3NXB's Article. He states at that point the impedance is about 4k ohms. We will see. Some I have seen feed the Bobtail on an end like the half square.
Of course yours was much smaller and mine will be strung on Dacron cord line between two trees. I have lots of trees on my 6.5 acres. I hope to have the proper position to hang a vertical half wave director in front of the driven element and a reflector behind it
on the initial build. It will be pointed at VK land with a compass on the build.

Frank