"David Eduardo" wrote in message
...

"Dan Robbins" wrote in message
...

There's a Franklin at N 41.6 and w 93.3:


http://www.desmoinesbroadcasting.com...use _9867.jpg


I don't know if it still exists, but KELO 1320 used to even advertise it had
a Franklin.

In deference to Steve who says the previous thread is dead, let me answer David's
question about KDKA's "Franklin"....but only to say that KDKA's Franklin wasn't truly
that. A Franklin radiator looks like two self-supporting towers, one inverted on top
the other, fat ends touching. The one such that I remember (and I'd have to think
that most of us have seen the picture) is WLW's tower that participated in the
superpower experiments in the 30s. KDKA's radiator was simply described in the
license as a center-fed vertical radiator, where the base impedance and input power
was determined through quasi-indirect means at the input to the balun necessary to
match the balanced feed point with the unbalanced transmission line (in years past,
this stick was fed with balanced feed line, not unlike VHF twin lead on acid...hams
know this feed line as "ladder" feedline, because of the characteristic cylindrical
insulators placed at regular lengths along the conductors to maintain the correct
separation between those conductors).

KDKA's antenna was fairly broadbanded, which if I remember correctly is a feature of
center-fed radiators. But WLW's Franklin, because of the larger cross-section where
current was higher, had a very nice, minimally-sloped reactance curve, and thus a
very consistent, symmetrical impedance...if you ever heard WLW when they played music
in the 70s, it really sounded great. KDKA's system had, of course, a ground system,
to help pull down the skywave, but due to the fact that my manager (who shall go
nameless to protect the embarassed) let the neighborhood kids ride their BMX
motorcycles on the property (she thought that the presence of life on the transmitter
grounds would deter vandalism), breaking a significant number of radials that were
exposed by rutting after heavy rains dredged out the BMX paths, it didn't work all
that well...on solar max periods, we'd often get fading well within our local metro
coverage area because so much power went skyward and came back down, just slightly
out-of-phase with the ground wave.

The antenna I had direct experience with was replaced in the mid 90s, but from what
I've heard the only thing that was changed was the steel....the basic design was
retained, and the counterpoise was repaired.
--
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