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Author Topic: Dbl Bazooka hung V or Inverted V. Which way is b  (Read 2607 times)
KW4CQ
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Posts: 129




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« on: October 20, 2003, 05:14:58 PM »

I have an 80 meter Double Bazooka antenna from IAC which I would like to hang in a "V" configuration, i.e. the feedpoint (apex) low and the ends high.  This is opposite from the inverted V configurtion that IAC recommends in their literature.  How would hanging it in a V configuration affect the feed point impedance and radiation pattern coveage on different bands?  Has anyone been able to model this configuration using one of the antenna modeling software tools?
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WB2WIK
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« Reply #1 on: October 20, 2003, 06:29:58 PM »

The reason the "vee" (rather than inverted vee) configuration is rarely used in the lower HF spectrum is that this creates a high radiation angle which can be useful for very local work (like an NVIS antenna) but is not good for DXing, at all.

Remember, most of the useful work of a dipole (or double bazooka!) is performed near the antenna's feedpoint, where the current is highest.  It matters little where the "ends" of the antenna are, as there is almost no current, and thus no power, there.

So, a "vee" configured antenna with its feedpoint say ten feet above ground behaves much like a dipole whose height is ten feet above ground: A very high-angle antenna, likely to be rather detuned by the earth beneath it.  The reason the "inverted vee" configuration is popular is that it allows the doublet to behave in a similar manner to a dipole installed at the apex height.

At higher frequencies, e.g., 28 MHz or 50 MHz (or above), it's easy to get an antenna more than 1/2 wavelength above ground; so it doesn't matter a lot if the vee is "rightside up" or "inverted."  It's high enough, either way, if you get the feedpoint up 18 feet above ground or so.  But at 3.5 MHz, I'd shoot for the conventional "inverted vee" configuration for best results.

WB2WIK/6
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KW4CQ
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« Reply #2 on: October 23, 2003, 07:58:31 AM »

Actually, I was planning on having the feed point at 35 feet and the ends at about 60 feet.  I would operate the double bazooka mostly on 40/20/17 meter bands and only now and then on 80m.  Forty meters is my main band for this antenna with mostly daytime contacts, i.e., local rag chewing up to 500-600 miles.  Not interested in chasing DX.  Since the feed point would be at least a 1/4 wave above ground on 40 I would think the feed point impedance might be within the range of 100 ohms, i.e., a 2:1 match, and not too unreasonable to handle with my tuner.  Unfortunately, they say you cannot measure impedance with a MJF-250B antenna analyzer )too many complex impedances I guess) or I would give that a try along the way.  Anyway, this is just an experiment and if the results don't pan out I can always hang it as an inverted V.  I will let you know how this works out in a few weeks if you are interested in the results.
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WB2WIK
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« Reply #3 on: October 23, 2003, 12:28:47 PM »

Sure, I'll bet several will be interested in the results; however, results are only very roughly estimated until you try both configurations and see which one is better!

(Like the "my antenna works great!" comments from people who only have one antenna; they actually have no idea how it works, since they have nothing to compare it to.)

I'm surprised about using an 80m double bazooka on bands other than 80m.  Normally, coaxial dipoles are considered single-band antennas because the compensation that occurs by using quarter-wave stubs only occurs on the single band where the stubs are a quarter wavelength; also, a double bazooka is normally fed with coax (I suppose it could be fed otherwise, but I've never seen that).  Using a coaxial feedline for an 80m doublet, and then using that doublet on 40m, normally doesn't work at all because the feedpoint Z of an 80m dipole on 40m is thousands of Ohms...creating such high coaxial cable losses that the antenna becomes a virtual dummy load.  Without using ladder line or open wire line (and a good, balanced line tuner) to feed an 80m dipole, I've never had one work on 40m worth a darn.

WB2WIK/6
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K5KOY
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« Reply #4 on: December 25, 2003, 11:58:42 PM »

I really have nothing to add to this topic, but would like to expand on it. I just got a 40m double bazooka, and was curious if anyone has worked up some figures on ideal apex height/leg height and ideal length of feedline to get the most out of the antenna.
 Anyone?
Koy-K5KOY
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W4WLZ
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Posts: 6




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« Reply #5 on: February 09, 2004, 05:26:51 PM »

I wholeheartedly agree with the comments by wik he has all the elements that come to play in a double bazooka antenna.. Usually always are monobanded, I am not familular with any other configuration that that.
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W4WLZ
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« Reply #6 on: February 09, 2004, 05:27:49 PM »

I wholeheartedly agree with the comments by wb2wik/6 he has all the elements that come to play in a double bazooka antenna.. Usually always are monobanded, I am not familular with any other configuration that that.
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WD8QBQ
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« Reply #7 on: May 22, 2011, 04:46:00 PM »

KW4CQ, you didn't post your results in a few weeks as you said?

There's people still waiting.

JIM
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