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## [TowerTalk] Antenna surface area

 To: [TowerTalk] Antenna surface area n3rr@erols.com (Bill Hider) Sun, 10 Jun 2001 03:16:01 +0100
 ```Hummm, I did not see that in his posting. You are just verifying my posting, since, as you say, we must take Gene's calculation and multiply by 0.6 to obtain wind area. That makes sense to me, since Gene said that his calculation resulted in a higher number than the mfrgs said. 0.6 is the multiple for the approximation of the integral I proposed in my posting. Bill, N3RR ----- Original Message ----- From: Michael Tope To: Bill Hider ; EUGENE SMAR ; ; Stu Greene Sent: Sunday, June 10, 2001 3:31 AM Subject: Re: [TowerTalk] Antenna surface area > Bill, > > Gene specifically said that he was calculating projected area without any shape > factors. The projected surface area at right angles to a cylindrical tube is simply > diameter x length. The effective area is computed by including the drag coefficient > of the object. For a cylinder, the drag coefficient is around 0.6. Thus the effective > area of an antenna with round members is about 40% smaller than the projected > area (a round tube of length, L and diameter D, is more aerodynamic than a flat > plate length L and width, D). > > 73 de Mike, W4EF.................... > > > ----- Original Message ----- > From: "Bill Hider" > To: "EUGENE SMAR" ; ; "Stu Greene" > Sent: Saturday, June 09, 2001 6:13 PM > Subject: Re: [TowerTalk] Antenna surface area > > > > The formula Gene proposed is not exactly correct, nor does he precisely > > state what to do with the taper. > > > > Regarding the formula, Gene's thinking is: If you think of the wind as > > hitting the tube broadside (at 90 Deg to the tube), the exposed surface area > > as seen by the wind looks like a rectangle whose length is the length of the > > tube and whose height is the full OUTSIDE diameter of the tube. Hence, L x > > Dia. Unfortunately, it is not that simple. > > > > The tube is a cylinder as seen by the wind, hence the angle that the wind > > *hits* the tube, even if it is perpendicular to the tube, hits at 0 Deg on > > the centerline and then the angle increases to 90 Deg as the wind hits the > > tube away from the centerline (above and below the centerline of the tube > > for a horizontal element). This assumes the wind-front is wider than the > > outside diameter of the tube, which is probably a very good assumption. So, > > the surface area exposed to the wind by the tube is not simply L x Dia. > > It's the exposed tube length times the integral from 0 to Dia of the surface > > area of each tube (Pi x Dia), where Dia is the Outside diameter of the tube. > > Gene, this is why the manufacturer's wind area is less than what you > > calculated, and theirs is correct. [If anyone has trouble picturing this, > > let me know and I'll try to explain it in more detail.] > > > > But, I question the correctness of adding all of these calculations up and > > saying that's the *wind area*. It certainly is the 1/2 of the *surface > > area* if it's done this way, but the wind cannot be simultaneously hitting > > the elements at 90 Deg and the boom at 90 Deg, so it should take that into > > account by specifying the *larger* of both calculations, but not the sum of > > both. > > > > Regarding the taper: each tube should be calculated separately for the > > *exposed* length of the tube *only*. Remember, some tubes are *inside* > > other tubes, causing the taper. > > > > Bill, N3RR > > > > > > ----- Original Message ----- > > From: Stu Greene > > To: EUGENE SMAR ; > > Sent: Sunday, June 10, 2001 2:42 AM > > Subject: Re: [TowerTalk] Antenna surface area > > > > > > > At 09:06 PM 6/9/01 -0400, you wrote: > > > > > > > Area = L X diameter for the exposed surface of each piece of aluminum, > > > > simple as that. > > > > > > > > > > > > Shouldn't the calculation be L X (Diameter X pi) ? Or length times > > > circumference? > > > > > > And this doesn't reflect tapering of the elements. > > > > > > > > > List Sponsor: Are you thinking about installing a tower this summer? Call > > us > > > for information on our fabulous Trylon Titan self-supporting towers - up > > to > > > 96-feet for less than \$2000! at 888-833-3104 > HREF="http://www.ChampionRadio.com";> > > > www.ChampionRadio.com > > > > > > ----- > > > FAQ on WWW: http://www.contesting.com/FAQ/towertalk > > > Submissions: towertalk@contesting.com > > > Administrative requests: towertalk-REQUEST@contesting.com > > > Problems: owner-towertalk@contesting.com > > > > > > > > > List Sponsor: Are you thinking about installing a tower this summer? Call us > > for information on our fabulous Trylon Titan self-supporting towers - up to > > 96-feet for less than \$2000! at 888-833-3104 > > www.ChampionRadio.com > > > > ----- > > FAQ on WWW: http://www.contesting.com/FAQ/towertalk > > Submissions: towertalk@contesting.com > > Administrative requests: towertalk-REQUEST@contesting.com > > Problems: owner-towertalk@contesting.com > > > > > List Sponsor: Are you thinking about installing a tower this summer? Call us > for information on our fabulous Trylon Titan self-supporting towers - up to > 96-feet for less than \$2000! at 888-833-3104 > www.ChampionRadio.com > > ----- > FAQ on WWW: http://www.contesting.com/FAQ/towertalk > Submissions: towertalk@contesting.com > Administrative requests: towertalk-REQUEST@contesting.com > Problems: owner-towertalk@contesting.com > > List Sponsor: Are you thinking about installing a tower this summer? Call us for information on our fabulous Trylon Titan self-supporting towers - up to 96-feet for less than \$2000! at 888-833-3104 www.ChampionRadio.com ----- FAQ on WWW: http://www.contesting.com/FAQ/towertalk Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com ```
 Current Thread [TowerTalk] Antenna database, EUGENE SMAR [TowerTalk] Antenna surface area, Stu Greene [TowerTalk] Antenna surface area, Bill Hider [TowerTalk] Antenna surface area,