Area 51 for Antenna Modelers & Builders (See Post #1)

[300ohm]

The 3D pattern at 201mhz, channel 11 :



The 2d horizontal pattern at 201mhz, channel 11:



The Raw Gain at 201mhz is 5.41 dbi with a SWR of 1.33, Net Gain of about 5.26 dbi. Not too shabby also ! (of course, for the vhf-hi channels, you would need to mount it a little off center to the station)

This antenna certainly deserves further investigation, heh !

[RamKat]

Wow! What an antenna! One will probably need a building permit to get one of those up in the backyard

[300ohm]

Ross Anderson says Kraus invented it. Its a scaled down version of his Big Ear antenna.

Neil Armstrong autographed picture of the Big Ear antenna:



Thats about the size you should make it for channel 2 reception, heh. As you can see, not only will it take up your yard, but the whole neighborhood too, heh. (or even a small town !) That house in the off center is the balun connection point.

[Xauto]

300ohm: Is there 182 cells that are 23 3/6" tall by 9 1/4"per cell? Not that I'm in a rush to make this one.

[300ohm]

I didnt count the cells, heh. But most of them are 9.33 inches by 23.63 inches, except for the ones on the ends and in the middle, which are narrower.

[firimari]

My next plan for massive amounts of computer time is to better optimize the 2x4 mesh Reflector Single Bay Grey Hoverman.

My current idea is that, like in the model that 300ohm posted, I have 'tails' hanging off the ends of the cells, and work to find the best lengths for those.

For extra bonus points, does anyone know the conductivity (that LD 5 tag value) for galvanized steel wire that makes up the reflectors (welded wire mesh, supposedly it has other uses.) we can buy at Lowe's?

[Xauto]

firimari: Take your cu. value and divide it by 5.77. About 10 *10^6 mhos.

[firimari]

Thanks!

Also, I feel that I should mention that the 'descriptive image' above has had no optimization done, so I highly doubt it will look like that, even though it's pretty.
At 25 variables to optimize over and an evaluation time in the 15-20 minute range (464 - 704 MHz step size of 24 MHz. Outside the range of UHF just so it's an increment of the step size), this is going to take forever.

[300ohm]

My current idea is that, like in the model that 300ohm posted, I have 'tails' hanging off the ends of the cells, and work to find the best lengths for those.

Yeah, I build like that because it makes cutting the slit in the middle easy, heh. Also I can wrap the tails around the pvc for more structural stability. On my Baltimore bowtie model, I modeled the wrapping too. It made squat in difference as far as gain goes.

For extra bonus points, does anyone know the conductivity (that LD 5 tag value) for galvanized steel wire that makes up the reflectors (welded wire mesh, supposedly it has other uses.) we can buy at Lowe's?

The stuff at Lowes nowadays is a lot lower quality than the 2 X 4 mesh 10 gauge heavy galvanized that I use. Ive always been puzzled about that too. I suppose due to the surface effect, the conductivity of zinc should be used.

[firimari]

Where do you get your 10 gauge stuff? I found some 12 gauge on the web, but it's a lot more expensive than the 14 gauge.

As for wrapping the ends, I was going to drill holes through the frame to slide them into (yeah, I know, you shouldn't cover your reflectors in pvc...) and then affix the mesh with black plastic ties.

[300ohm]

I got a 6 ft high roll of the stuff from a house I inherited, heh. I was using it to hold up my grape tomato plants for well over a decade outside. Its still almost like new, heh.

[stampeder]

firimari, do a search for "corn crib" wire or mesh and you'll find the right stuff, but hopefully 10AWG.

[Xauto]

Conductivity of Al. 37800000; Zn. 17000000; Silvers is the best 63000000

[300ohm]

My current idea is that, like in the model that 300ohm posted, I have 'tails' hanging off the ends of the cells, and work to find the best lengths for those.

Yeah, I also tried that curved look to the tails like the picture above. I didnt get any better results with it than by having them straight. But I didnt model the curves in the middle section. See how that will come out.

[firimari]

Alas, the straight optimizer didn't do much to improve the reception results.



While I can provide anyone who wants this version of the NEC file, I think I'm going to try and do some more work optimizing this design before I post it. I would like to see if I can work on the low channel fall-off and those dips in the middle, frankly.