[BC] WLS dead cxr prob. this a.m. at ~6:50

[Paul Christensen]

> Antenna height diversity has been used by the telco's for years on their 
> microwave hops. Usually 50 ft. spacing is sufficient.

True to a limited degree, but the primary method used by AT&T and it RBOCs 
since the early 1950s was simultaneous frequency-diverse systems on 4, 6 and 
11 GHz links.  That combination of frequencies did a good job at keeping 
100% up-time in the event of rain, fog, or other climatic changes.  A good 
number of these systems are still active today as last-resort back-ups to 
fiber.

Two weeks ago, I was visiting family in Northern Illinois and had a chance 
to stop at the behemoth Norway, Illinois AT&T facility (father worked there 
during the '60s & '70s) and was surprised to see that all the delay-lens and 
horn antennas were intact and active.  If you're ever down that way, it's 
worth the trip into the barren farm lands to see it.  Another site that once 
linked to Norway is located just east of the WLS-AM tower, between LaGrange 
and Harlem Roads on I-80 in Tinley park.

Space-diverse and frequency-diverse systems are both good alternatives to 
path fading and interference problems.

Paul


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Paul Christensen, CPBE, CBNT
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