In an earlier post, W8JI stated that the "Wullenwever antenna was never a
low-noise high performance antenna." Certainly that was true of the World War
II-era German Wullenwever, but the 1960s-era AN/FRD-10 and AN/FLR-9 and other
more recent Wullenweber-like arrays were definitely designed to achieve both
acceptably low noise figure and relatively high dynamic range. Actually
achieving and maintaining high performance was another matter entirely...
The AN/FRD-10 and AN/FLR-9 arrays (without regard to their many performance
degrading but necessary active components) were certainly capable of very high
performance but the arrays couldn't be used for their intended purpose without
many active components (mostly broadband multicouplers) in the signal
distribution paths between the antenna elements and the receivers.
Wullenwever (later known as Wullenweber) DF arrays were originally designed in
Germany during World War II and implemented in large numbers across the USSR in
the 1940s and 1950s. The 1960s-era AN/FRD-10 and AN/FLR-9 arrays as well as a
variety of subsequent lower cost Wullenweber-like arrays were designed and
built to be both high performance DF and receiving arrays.
The FRD-10 and FLR-9 arrays were intended to provide both acceptably low noise
figure and high dynamic range but those performance requirements had to be
compromised in favor of other high priority requirements (e.g., instantaneous
1.5-30 MHz frequency coverage and ability to simultaneously feed hundreds of
receivers each with independently selectable azimuths).
The multitude of difficult performance requirements combined with the
significant limitations of technologies available at the time resulted in many
performance degrading active broadband multicouplers in the signal path between
the antenna elements and the front ends of (mostly) R-390 receivers. The
multicouplers were the main performance limiting components affecting the noise
figure and dynamic range of the antenna system but detecting faults in the
countless thousands of multicouplers, cables and other components in hundreds
of signal processing paths between the antenna elements and receivers always
presented a major difficulty in maintaining the performance of these massive
Modern SDR technology and highly advanced modern DF algorithms running on
powerful computers have made Wullenweber technology totally obsolete in the
21st century. But traces of this obsolete World War II technology remain on
the landscape will continue to do so for many generations yet to come. For
example, the large Wullenweber array at the FCC's Laurel monitoring station
just 12 miles east of my QTH was replaced years ago by a higher performance and
much more compact antenna specifically designed for use with SDRs. But the
footprint of the FCC's old Wullenweber array is likely to survive for
generations to come.
---- Original message ----
>Date: Tue, 5 Feb 2013 21:06:58 -0800
>From: "Lee K7TJR" <firstname.lastname@example.org>
>Subject: Topband: New 160M high performance receiving antenna at W3LPL
>>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.
> 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-.......
>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 48 low band elements were 35 feet tall with a 120 foot tall
>reflecting screen. Each element had a 19dB gain semiconductor amplifier with
>a 7 dB noise figure. I agree also that not all the 48 elements were active
> however the ones that are in a given direction produce some outstanding specs.
> So if I compare usual high performance low noise RX antennas to this
> antenna our directivity specs pale in comparison leading me to believe the RDF
> of the "W" system surely would be greater than anything we could imagine with
> our RX antennas. Nor does noise figure appear to be a concern.
> Or is my thinking corrupt?