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Author Topic: Minimum angle & height for inverted-v antennas  (Read 5007 times)
KE8HH
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Posts: 2




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« on: November 17, 2002, 07:17:07 PM »

  I have a very space-limited setting and would like to use an inverted-v antenna (ideally the Yaesu YA-30 or an equivalent short dipole) as my primary station antenna.

  Because of space constraints, the base points for the legs of the antenna will be only about 13-20' above the ground and spaced 12' apart (max). The "v" can be at approximately 40' and up to 45-50' from the leg anchors.

  My question (obviously) is: will this allow a sufficient angle of separation between the two legs of the antenna (which, if it's significant, will have the "v" due East and the legs anchored due West--no alternative exists to this configuration), or will I lose the effectiveness (and benefits) of the dipole with this configuration?

  A second question, if anyone can answer it, is how good of an antenna the YA-30 actually is. I've been unable to find any reviews/info on the antenna on the web but, being a devout Yaesu fan (so nobody's perfect!) with a number of Yaesu rigs (my primary rig is an FT-920), if the antenna is comparible to other brands I'd prefer it. If not--and if anyone has other suggestions (or alternatives to the inverted-v that would fit the space and allow at least 10m-160m operation [6m would be a real plus] without extensive use of a tuner), pointers or tips would be greatly appreciated. Verticals are out, btw, as I cannot install radials at my site (I own the home but rent the lot--which is 23'x60'--and it has a LOT of restrictions).

  Thanks in advance for any help.

  73 de KE8HH, Rick
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AB5Q
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Posts: 202




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« Reply #1 on: November 17, 2002, 08:59:52 PM »

Keep the legs between 90-120 degrees.  A height of 40-50' at the apex is great!  Although not an ideal scenario, an inverted-vee with the apex as little as 30-35' will provide satisfactory results 10-160m (QRO on 160m).  Granted you will not be the biggest gun however I think you will be pleasantly surprised at the performance.  Not everyone has the real-estate or means to put their 80-160m antenna up 150'-200' so their must be a compromise.

Before trying to design/purchase an antenna that does it all, try to figure out which bands are most important to you.  Then figure out what design fits that criteria and go for it.  From a simple but effective standpoint, I would choose a homebrew fan dipole or center-fed Zepp.  The CF Zepp would require 450-ohm ladder line and tuner.  Also, look at what W9INN has in regards to antennas.  He seems to come up with some clever ideas for restricted space antennas.
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KF4ZGZ
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Posts: 286


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« Reply #2 on: November 18, 2002, 06:44:13 AM »

Did I read that right....?  The ends of the dipole are going to be 12 feet apart?  If so, you are pretty much going to end up with a vertical, and with the wires that close you may get a lot of cancelation and end up with a poor performing ant. That being said...if you have no choice, try it, you really never know , it might work.
as for the length, if you can get 44 ft. on each leg of the dipole for a total of 88ft. you be at about the minimum for 80m. with a tuner. It is a workable ant. on 80m and fair performer on the other bands in an inv. vee configuration.I use the 88 ft. dipole as a portable ant. with good results.

 73 es good luck de Matt, kf4zgz

" The best antenna is the one you build yourself!"
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NZ5L
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Posts: 220




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« Reply #3 on: November 18, 2002, 11:21:26 AM »

If you have a 50' potential height but only 24' of horizantal possible, you would be wise to forget the inverted vee approach because, as one poster already noted, the legs most be AT LEAST 90* apart in order to prevent cancellation. With 24' you could put up an inverted vee for 20 Mtrs, but the apex could only be 16-18' high to keep the proper angle.  This is much too low unless you are a rare DX station! Why not a vertical wire antenna using commercial traps?  Check out SPI-RO or Van Gorden.  Your base area may be just enough to accomodate some folded multi-band radials.  Alternatively, a half wave end-fed antenna for 40 would be only about 65' high. you could swing the extra 15' off to the side, inverted L style.  With this arrangement, use a tuning network at the base to step down the high impedance.  There are a lot of possibilities here, but in your situation, the inverted vee approach should be way, way down on the list.  
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W9WHE
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Posts: 254




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« Reply #4 on: November 19, 2002, 12:11:43 PM »

Think about a vertical. It will work alot better than an inverted vee, with the legs too close together!
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