[BC] AMs on top of buildings

[Dan Strassberg]

I believe that there are three in Chicago alone: 820 and 1240 are a diplex
and 950 (days only) is the third with a conventional array at a separate
night site (if you can call any six-tower in-line array conventional--they
are quite rare). In LA, KYPA 1230 had moved off of its 70+ year-old L
rooftop antenna to a diplex from one tower of co-owned 1580's six-tower
array, but that meant moving farther from the target audience (Korean
speakers?) and after complaints about poor reception, the station has
reportedly moved back to its old facilities. KMZT 1510 licensed to Piedmont
CA (near Oakland) has the US's only true rooftop DA (in Oakland), I believe
it's four towers days and five nights (with the fifth "tower" a vertical
wire dropped from a horizontal wire that joins the tops of two of the real
towers). 1020 and 1150 in LA (both 50 kW) have been discussed here more than
once. The five-tower site was originally 1020's; 1150 was added much
later..Long before 1150 moved in but after the array was built, a one-story
warehouse was built over the ground system. The tower bases remain on the
ground and I believe the claim that the ground system was relocated to the
roof of the warehouse was convincingly refuted here.

Something that all of the rooftop AM installations mentioned here have in
common is that the buildings on which they are located are low structures.
It would be interesting to know whether any rooftop AM antennas atop
buildings six or more stories high continue in operation. For many years,
engineers are reported to have toiled unsuccessfully to move KYPA to the Los
Angeles building that had at one time housed the rooftop antenna of KFSG
(post-NARBA, that station shared time on 1150 with KRKD). That building must
be at least eight stories high. I believe that when KFSG used the two
relatively tall towers, they supported a longwire. The engineers gave up on
that building as a site for kYPA (which wanted to use one of the towers as a
grounded-base shunt- or skirt-fed radiator) and chose the 1580 site as a
replacement, only to have to give up on that site after a few months of
operation because of the aforementioned signal problems.

Oh, and doesn't one of the Class C AMs licensed to San Francisco have a
rooftop tower?

--
Dan Strassberg, dan.strassberg at att.net
eFax 707-215-6367