Topband: New 160M high performance receiving antenna at W3LPL

[Tom W8JI]

I said:

> >The "Wullenwever" antenna was never a low-noise high performance antenna.
> It was simply a system designed to find direction over a very wide 
> frequency
> range. The multitude of elements increased bandwidth, but the physical 
> width
> in wavelengths is the primary determinant of directivity.

Lee said:

>    While I will agree that the Wullenweber antenna was never designed to 
> be a
> low noise antenna, I fail to see why it is not. My copy of TM32-....... 
> manual
> on the US version shows some pretty good directivity specs. On the low 
> band
> starting at 2 MHZ the beamwidth was 11 degrees with the side lobes down a
> minimum of 18dB. The maximum elevation was 30 degrees. Also the range
> specified was 4000 nautical miles. And its outer element diameter was
> 1116 feet.

The sharpness comes from the wide area.

>The 48 low band elements were 35 feet tall with a 120 foot tall
> reflecting screen.

The 48 elements primarily give it bandwidth. With an 1100-foot array width, 
the 160 meter element spacing only needs to be about 300-400 feet. That's 
only three to four elements necessary, with three to four more (spaced 
35-130 feet back) to make it unidirectional.

160-80 meters would double the number of elements.

It is the broadside area that gives us a narrow pattern, and the number of 
elements in that area that gives us the bandwidth. We can't let spacing get 
too wide between broadside elements. There is a chart here:

http://www.w8ji.com/stacking_broadside_collinear.htm

The more elements we use, the wider the allowable spacing in wavelengths.

Our limitation, at least for low-band use, is our available space and the 
phase differences in signals a few wavelengths apart along the ground. 
Watching phase difference between elements spaced 2-wavelengths apart is 
interesting. I've found it quite possible to have an array too large for 160 
meter skywave because of constantly changing phase differences at wide 
spacings.

I'm sure a 1200-foot wide array would not be nearly as useful as the pattern 
might lead us to believe. I have to break things spaced that wide into cells 
that I run in stereo.

73 Tom