|
Title: Delta Loop -OK- Forgot my Geometry Post by: Bill, KD0HG on August 04, 2012, 08:49:13 PM OK...Assume a delta loop, top apex high on a tower at ~80 feet.
Each leg of triangular loop is 88' long. Each apex is 120 degrees. How far off the ground would the bottom horizontal leg be?? Bill Title: Re: Delta Loop -OK- Forgot my Geometry Post by: Ralph W3GL on August 04, 2012, 09:39:57 PM Bill,
Won't go into the math (hint, it's a TRIG function)... Just pull out some graft paper, you know the stuff with all the little squares on it, give each square a value, draw your design and you should be able to see the base to surface distance at a glance with a scale/ruler... I've done this on many antenna/tower setups... GL... Title: Re: Delta Loop -OK- Forgot my Geometry Post by: KF1Z on August 04, 2012, 10:18:21 PM 3.8 feet off the ground
h = √3 / 2 * a h= height a= equilateral leg length ( 0.866 ) * 88 = 76.2 80 - 76.2 = 3.8 Title: Re: Delta Loop -OK- Forgot my Geometry Post by: Bill, KD0HG on August 05, 2012, 10:18:01 AM Thank you, gents.
Didn't have any gridded paper handy- LOL Bill Title: Re: Delta Loop -OK- Forgot my Geometry Post by: Steve - K4HX on August 05, 2012, 09:30:05 PM Nice calculator here.
http://mysite.verizon.net/ka1fsb/loopcalc.html Title: Re: Delta Loop -OK- Forgot my Geometry Post by: WA1GFZ on August 05, 2012, 10:22:58 PM good chance it won't work worth a crap. Better off an inverted Vee with the ends pulled out as far as possible.
Title: Re: Delta Loop -OK- Forgot my Geometry Post by: aa5wg on August 06, 2012, 09:46:27 AM Bill:
KF1Z nailed it. His calculations match mine. 3.8 feet or exactly 3.790 feet or 3 feet 9.48 inches above the ground (3 feet 9 and 1/2 inches). Chuck Title: Re: Delta Loop -OK- Forgot my Geometry Post by: W3RSW on August 06, 2012, 10:06:35 AM You all nailed it if the apex angle is 60 degrees. ;D
Title: Re: Delta Loop -OK- Forgot my Geometry Post by: KF1Z on August 06, 2012, 10:43:02 AM You all nailed it if the apex angle is 60 degrees. ;D He said "Each leg of triangular loop is 88' long." If all the legs are the same length, then all three angles have to be the same. ;D Yes, different calculation for isosceles or scalene triangles. Title: Re: Delta Loop -OK- Forgot my Geometry Post by: WA1GFZ on August 08, 2012, 04:28:58 PM I've never had any luck using a loop with the base close to the ground. Wasted too many hours trying.
Title: Re: Delta Loop -OK- Forgot my Geometry Post by: W3RSW on August 09, 2012, 04:59:48 PM can you turn it upside down and be somewhat more effective?
-or is the whole thing too close to the ground? Title: Re: Delta Loop -OK- Forgot my Geometry Post by: N4zed on August 09, 2012, 08:24:28 PM Or you can bring two of the points up to match the upper most one....
http://home.comcast.net/~n4zed/site/?/page/N4zed_Loop_2/&PHPSESSID=59c1012508dfe4016757f514c2c43f53 (http://home.comcast.net/~n4zed/site/?/page/N4zed_Loop_2/&PHPSESSID=59c1012508dfe4016757f514c2c43f53) Ken N4zed Title: Re: Delta Loop -OK- Forgot my Geometry Post by: Steve - K4HX on August 12, 2012, 09:16:03 PM The average height is greater with the inverted delta loop and there is less coupling to the ground. This is the config I use on my 40 meter loops. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
S can you turn it upside down and be somewhat more effective? -or is the whole thing too close to the ground? |