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Mystery Antenna or 135' doublet... Need results
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by N8NSN on April 3, 2009
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With the weather getting warmer I am considering trying out a few other antenna designs over the spring and summer months. One in particular I want to try is the "W5GI Mystery Antenna".
Here is just some history on what 'multi-band' wire I am currently using... It works so I am just seeking experimental fodder. Who knows I may like something else better than the current one.
The pulley and outrigger system at the tower top facilitates the experimenting ease when I get the bug. Along with a few other HF antennas in the line up; I have been running a 135' center fed doublet as a multi-band as a main stay antenna for about 5 years. I have tried several other antennas through those years such as the cobra type arrangements, inverted L, Fan dipoles and some different variations of the W6RCA pennant loop. Always end up going back to the 135' doublet.
The arrangement used for the doublet is from the 1970 ARRL Antenna Book. Initially the antenna was set up in the flat top configuration but now is in the inverted vee configuration. This caused definable differences in characteristic performance including T.O. Angles, Gain lobes and nulls and impedance among a few others. The antenna is fed with 42 feet of 450 ohm windowed line. In the ARRL book the antenna line (450 ohm) goes directly to a link coupled tuner. I deviated from this design by placing a balun at the base of the tower and a short (9 ft.) section of RG-8 coming into a home brew roller inductor tuner in the shack. This antenna performs well on HF bands from 80 - 10 meters. I can bypass the tuner all together on the 30 and 17 meter bands and still maintain an acceptable SWR. I am not hung up on having the lowest SWR possible in using parallel feeder fed antenna systems... The tuner keeps the rigs happy with the 50 ohm impedance requirements and the low loss (even under high SWR conditions) offered with the parallel feeders are adequate as well.
Here is my question for the Forum...
I have been reading some information on the W5GI Mystery Antenna. It appears as if the performance is fairly comparable to the 135' doublet. This is only according to "opinions" due to the fact that the Mystery Antenna obtained it's name from the lack of "verifiable data" derived from many Antenna Modeling Programs. The applied principles in theory would suggest that the antenna is primarily designed for use on 20 meters per the W5GI design. Doing the math in making a collinear array for any band is easy enough using the same design and "hardware" used for the 20 meter design. So, I guess my main questions would be...
*How effective of a multi-band antenna (80 - 10) is the W5GI Mystery Antenna in it's principal 20 meter design?
*Have you tried one out and what is your opinion on your results?
*Have you made and used a lower band version using the Mystery Antenna design parameters? ...and tried it multi-band?
*Have you ever used a 135' doublet?
*How did the antennas compare in performance?
I know this was a very long post. I enjoy learning from others as well as my own experiments. My stock pile of available antenna stock has me limited to using only what I can use in the expectations that the antenna will perform well at this point in my fun.
I will be looking forward to responses. Thanks.
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RE: Mystery Antenna or 135' doublet... Need result
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by VK1OD on April 3, 2009
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James,
An understanding the W5GI Mystery Antenna operation goes to the heart understanding cophased collinear arrays.
My article "An exploration of a cophased collinear array with coax phasing stubs" at http://www.vk1od.net/antenna/ccps/index.htm might interest you.
IMHO, that background permits sane analysis of the W5GI Mystery Antenna, see "De-mystifying the W5GI Mystery Antenna" at http://www.vk1od.net/antenna/W5GI/index.htm .
Make up your own mind.
Owen
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RE: Mystery Antenna or 135' doublet... Need result
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by N8NSN on April 3, 2009
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Excellent reply Owen Thank you I am going to go to both links right now. :-D
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RE: Mystery Antenna or 135' doublet... Need result
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by W5DXP on April 4, 2009
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> KC8BYF wrote: *Have you ever used a 135' doublet? <
http://www.w5dxp.com/notuner.htm
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RE: Mystery Antenna or 135' doublet... Need result
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by KW4N on April 4, 2009
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Go with the doublet. See my review in eham on the W5GI.
W5GI antenna is a disguise for his personal stimulus package.
73's, Dave
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RE: Mystery Antenna or 135' doublet... Need result
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by N4JTE on April 4, 2009
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To answer your question directly I have used both antennas in question. The mystery antenna was an interesting experiment and worked well on 40 and above and seemed like a keeper until I ran a simple 135 ft laddeline fed doublet as a referance AB test antenna, besides the simplicty of the doublet, the performance exceeded the mystery antenna about 90% of the time. This was in my early days of wire experiments and did not keep my usual records, just going from memory but I think you will be disappointed with the mystery ant due to your obvious understanding of antenna basics. I use to also use a 1 to 1 balun at the shack window to facilitate coax to tuner but I abandoned that and went direct to tuner using some pvc shield thru window, made a huge differance and improvement in my case.
Good luck hope that helped.
Bob
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RE: Mystery Antenna or 135' doublet... Need result
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by K9FON on April 4, 2009
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The good old 135' doublet is very hard to beat. I have a 270' doublet that tunes 160- 40 meters and most of the time if I cant work someone with my other antennas I can rely on the doublet! :-) It has never failed me.
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RE: Mystery Antenna or 135' doublet... Need result
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by N8NSN on April 4, 2009
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Those were the responses I dreaded yet, expected all the same. The 135' doublet has been up and down many times to try other stuff. Always winds up right back where it was.
I know, "Don't fix it if it isn't broken..." I was just getting the hankerin' to play with some wire. As well, I sure would appreciate a quieter antenna. This doublet picks up man made noise very well.
My lot is only about 40 feet front to back and about 170 feet side to side. The tower was planted just where it needed to be with my end supports just in the right place for the doublet. I lucked out. This orientation happens to facilitate enough to lay out the 135 foot doublet for most of the lobes on the bands to be in good places. The antenna spans from about 340 degrees to 160 degrees.
Anyone have any antenna ideas with a similar results and size perimeters or smaller than the 135' doublet that would offer a relatively quiet noise floor and not exhibit too much directional difference from the doublet?
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RE: Mystery Antenna or 135' doublet... Need result
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by VK1OD on April 4, 2009
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James,
If you have a horizontal dipole, rigged so that it is orthogonal to aerial power lines, as far as you can get from building wiring and power lines, using an effective balun to mimimise pickup by the feedline, and its main lobes favour your preferred paths, you have done about as well as you can on 80m for receiving on a suburban block.
An exception is where you have a dominant noise source from a particular direction. In that case, a directional antenna that reduces that noise may help.
Otherwise, if you get less noise power from another antenna, it is probably because it is inefficient.
I am always suspicious of people's claims that they have S1 noise on 80m, it should be higher than that.
At the end of the day, S/N is what counts on *your* receive, but inefficient antennas cripple S/N at the other end of the QSO.
Don't overlook separate receiving and transmitting antennas on the lower bands. It was common practice once, faded out almost completely with black box transceivers, but is still a valid technique.
Owen
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RE: Mystery Antenna or 135' doublet... Need result
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by K3JVB on April 4, 2009
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Keep the doublet for 75-80 meters for sure.
..the mystery antenna may have an edge from 40 on up.
But It is hard to beat "more wire" in the air for 80 meters. The only draw back for the doublet is has many lobes for 20-15-17 and up. But they still play pretty well. But the fun of ham radio is palying with antenna's. Try it ! Home brew will cost very little.
And , as you said, warm weather is on the way.
Let us know how it works out. Good luck !
73
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