Towertalk
[Top] [All Lists]

## Re: [TowerTalk] Fw: [SteppIR] 3El height

 To: "Mark Beckwith" , Re: [TowerTalk] Fw: [SteppIR] 3El height Jim Lux Sat, 29 Jul 2006 20:32:41 -0700
 ```At 04:24 PM 7/29/2006, Mark Beckwith wrote: > > Modeling it is > > simple enough > >I have modeled a lot of antennas for a lot of years, and I have concluded >that varying the yagi height will change the take-off angle much more than >any amount of varying element lengths. I agree. That height parameter so dominates all the others, I think that all you can really do with trying to do beam steering (in the vertical plane) is possibly suppress something that is coming from the "wrong" elevation angle. This is for relatively low (<60ft) installations. Get high enough, and I think it starts to have more value. If you think about it in the "pattern multiplication" scheme for doing array patterns, you'd multiply the elevation pattern of an isotrope at the relevant height by the elevation pattern of your array in free space. The problem is that the "height derived pattern" has such deep nulls, that no amount of directive gain from the array can overcome it. >Varying element lengths may return nickles and dimes; varying the height >will return \$\$\$. If you want to control the take-off angle in a useful way, >then stacked yagi arrays where you can control which antenna gets how much >power at what phase angle will give the greatest control of this variable. And even there, I suspect the big return comes from running the power to the antenna that's at the "right" height. The steering you from phasing them differently is going to be pretty small (a few degrees?). Placing a null is a different matter. You could place a very sharp null at a particular elevation angle, which might be useful. The other case is if your array of SteppIRs is high enough off the ground that you're in the delightful situation of the "ground reflection pattern" being a big broad lobe. Get your array center a lambda or two off the ground, and now you can do some serious fooling around. Jim _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread Re: [TowerTalk] Fw: [SteppIR] 3El height, (continued) Re: [TowerTalk] Fw: [SteppIR] 3El height, K8RI on TowerTalk Re: [TowerTalk] Fw: [SteppIR] 3El height, Jim Lux Re: [TowerTalk] Fw: [SteppIR] 3El height, Bill Re: [TowerTalk] Fw: [SteppIR] 3El height, Jim Lux Re: [TowerTalk] Fw: [SteppIR] 3El height, Tom Osborne Message not availableRe: [TowerTalk] Fw: [SteppIR] 3El height, Tom Osborne Re: [TowerTalk] Fw: [SteppIR] 3El height, N2TK, Tony Re: [TowerTalk] Fw: [SteppIR] 3El height, Red Re: [TowerTalk] Fw: [SteppIR] 3El height, Jim Lux Re: [TowerTalk] Fw: [SteppIR] 3El height, Mark Beckwith Re: [TowerTalk] Fw: [SteppIR] 3El height, Jim Lux <= [TowerTalk] Fw: [SteppIR] 3El height, Howard Klein Re: [TowerTalk] Fw: [SteppIR] 3El height, Jim Lux Re: [TowerTalk] Fw: [SteppIR] 3El height, Jim Lux [TowerTalk] 80' tower in SF Bay area (update), JC Smith Re: [TowerTalk] 80' tower in SF Bay area (update), Alan NV8A Re: [TowerTalk] 80' tower in SF Bay area (update), Michael Baker Re: [TowerTalk] 80' tower in SF Bay area (update), KA9OFM John Garrett Re: [TowerTalk] Fw: [SteppIR] 3El height, Cqtestk4xs Re: [TowerTalk] Fw: [SteppIR] 3El height, john