| Index | Thread | Archive | Aug-2003 | Archive | Send |
 |
  |
|
   |
|
  |
|
I am in the process of putting together a stack at my QTH in Tomball, Texas. The tower is 150 feet of Rohn 45. There are Phillystran HPTG6700I (6700lb) guys at four points: 150, 113, 76, 38. This is overkill since Rohn specifies EHS 1/4 wire (6000lb) for the top guys and EHS 3/16 (4000lb) for the lower three guys, for 90mph wind loading. If you use Rohn 45G you should be using three guys with 1/4 at the top and 3/16 for the lower two. I have three, five foot above ground, 6 inch metal pipe posts for the ground guy points, at 120 feet from the tower base. These are each set in about 1.5 yard of concrete. A 100 foot tower should have guy ground points 90 feet from the base according to the Rohn catalog. However, be sure to plan the guy design to accommodate the turning radius of the lower antenna. I have developed an Excel spreadsheet to calculate the clearance for my antennas. Let me know if you want a copy to modify for your design. On antenna spacing, be sure to consider wavelength for optimum spacing. I have learned from others that 66 feet is good for 40 meter Yagis and 33 feet is good for 20 meters. My initial plan was to have two C-4XL's on the tower. After talking with Tom N6BT and Jay WX0B I decided to add two C-3's to get 33 feet spacing for 20 meters. So I will have: C-4XL@152, C-3@119, C-4XL@86 and C-3@53. The guy points on the tower had to be varied from the Rohn catalog recommendation to provide for rotation clearance. The recommended maximum vertical guy spacing for Rohn 45 is 40 feet. For antenna rotation I am going with TIC Ringrotors from Array Solutions. You can order direct from TIC but I hear support is somewhat lacking from the factory. I am working directly with Jay WX0B to have his company install the rotors. He is also supplying the StackMatch boxes for my antennas. Jay has been very helpful with the design of my system. Finally, your feedline length requirements are a major concern in terms of RF loss. If you have a sufficient budget, go with Andrew LDF5-50A hardline from the shack to the base of the tower. I am seeing a lot of surplus cable at hamfests, likely from cell phone companies as they have replaced 7/8 with 1.5 Heliax over the past few years. My next choice would be LMR600 from Times Microwave. You can bury both of these cables, but I would use plastic conduit. Texas Towers carries LMR600 and the UHF connectors. From there you can use a switch or StackMatch with RG-8 up to the antennas. My shack is only 30 feet from the tower so I am using Belden 9913 all the way. Good luck. Hope to hear you in upcoming contests. Keith Dutson WD5DXL -----Original Message----- From: Scott Neader KA9FOX [mailto:ka9fox@QTH.com] Sent: Thursday, August 28, 2003 12:34 AM To: force12talk@qth.com Subject: [Force 12 Talk] Stacking C36XR + C31XR I'm building a house on a ridge-top location (5 acres). The bad news is I have CC&Rs to deal with. Fortunately, I'm approved for a single guyed 95 foot Rohn 45/55 tower (plus antennas). I'm starting to think about what antennas I would like on it. It will be a single tower station, so everything will have to be on this tower. I predominately like to do Domestic (USA) contests such as the Sprints, NAQPs, and Sweepstakes (although my baby-making activities have curtailed most contesting in recent years). I also enjoy catching the occasional new band country, busting the piles, etc., as well as 6m/2m openings. So, I'm contemplating a C36XR on top, which will give me 2 ele on 40m, plus 20-15-10. For contesting, a second tribander, perhaps a C31XR somewhere down the tower might be nice. (perhaps 40 ft spacing, obviously need some modelling assistance with that). I'd also need to sneak in 6m and 2m horizontal antennas in the mix, plus some type of wire antennas for 80/160. This is all very preliminary... but what are the group's thoughts regarding a C36XR + C31XR stack? How does one rotate the second antenna? TIC ring? Swinging Gate? The ridge-top location is known to be windy, so I may need 3 sets of guys? It may be hard to get a big antenna to fit down on the tower? Another concern, which can probably be handled with the right feedline, is that the tower has to be in the back 1/3 of the property, which puts it about 275 feet from the shack. With 100 feet up the top, that's a minimum of 375 feet of feedline! Next November, I will qualify for QCAO (Quarter Century Appliance Operator) status, so be easy on me. 73 - Scott KA9FOX --------------------------------------------------------------- Scott Neader KA9FOX (608)788-1234 / FAX (608)787-0100 Free Ham Radio Classified Ads: http://swap.QTH.com Web Hosting Services: http://www.QTH.com/prices Domain Name Registrations: http://www.YourCallSign.com KA9FOX Contesting & DXing Site: http://www.QTH.com/KA9FOX -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force12 Web Site: http://www.force12inc.com To Submit Message to the List: Force12Talk@qth.com To unsubscribe and view the Message Archive: see http://qth.com/force12/list For problems with the list: contact force12@qth.com -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force12 Web Site: http://www.force12inc.com To Submit Message to the List: Force12Talk@qth.com To unsubscribe and view the Message Archive: see http://qth.com/force12/list For problems with the list: contact force12@qth.com |