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I have been an amateur for a couple of years but until recently lived in an appartment block so my antenna possibilities were severely restricted. Now at last I have moved into my own house, complete with a medium sized garden (yard). Time to play antennas :) I enjoy contesting and so would like to put up a "reasonable" antenna system for 40/20/15/10. I think 40m will be particularly important over the next few years as the solar index declines. Since budget and space are limited, I can't have everything I want. However although I will probably end up with the inexpensive and simple option - a C4S - the other alternative I'm playing with is to stack a EF240S 2-element 40m dipole above or below a C19XS tribander, at about 60 ft. Since I'm very new to towers, rotators and stacked antennas, I would appreciate any input you can give me on the following questions: 1. Which antenna should be on top? I would think the EF240S since the wavelength is longer, so height is more critical for it, but I may be missing something. 2. How far apart (vertically) would the EF240S and C19XR have to be to avoid problems caused by interactions between them? (Bear in mind that 15m is the 3rd harmonic of 40m, so interactions here may be quite strong). 3. Can I just put both antennas on one pole driven using a single rotator, or do I need seperate rotators for the two antennas? (I don't intend to use them simultaneously in different directions!) 4. If I add the "Mast Torque" figures for these antennas I get 360 in-lbs, which is only 30 ft-lbs. The Yaesu G-800DXA rotator is rated at a "F-factor" of 1302 ft-lbs so on this basis there should be no problem. However if I do Yaesu's suggested calculation, which is to multiply turning radius by weight for each antenna and add them together, I get a total of 1671.8 ft-lbs for the two antennas together, which exceeds the rating for the G-800DXA (and it's bigger brother, the G-1000DXA). Which method is right, and can I turn the proposed stack using the G-800DXA rotator? 5. Do you have any better suggestions (remember my contsrained budget!) Many thanks for the help, Andrew ZS1AN Andrew Roos Technical Director, ExiNet Tel: (021) 448-4678 Fax: (021) 448-4620 -------------------------------------------- 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 n4zr@qth.com |
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