KNBR is a 50KW "Class A" (formerly "clear channel") mediumwave (AM) rado station broadcasting on 680 KHz, serving the San Francisco Bay area (and, at night, most of the west coast of the US). Opened in 1922, It was originally known as KPO, (later KNBC, and still later KNBR), and soon became the flagship station for the National Broadcasting Company (NBC)'s new western radio network. It is currently owned by Cumulus Media and now broadcasts a sports format.
Comments
Displaying 0 of 3 comments
Matt Blaze
In response to this postMediumwave (AM) broadcast radio uses lower frequencies than other modern broadcasting and so requires much larger antennas (generally getting larger and larger as the frequency gets lower on the dial). This often entails highly customized antenna designs engineered for the particular site and station frequencies. For most radio stations (FM, TV, etc), the towers are there simply to get the relatively small antennas up high, but for AM stations like KNBR, the towers generally ARE the antennas.
The taller tower (550 feet) at right is the main KNBR antenna, built in 1949. It employs an unusual "pseudo-Franklin" design; it's actually an array of two antennas stacked atop one another. The 400 foot lower section is insulated from the ground. The upper 150 foot section is insulated from the lower section. The large (50 foot) diameter "capacitance hat" at the top (reminiscent of the Parachute Jump at Coney Island) electrically lengthens the top section, saving 250 feet of additional height.
by Matt Blaze ;
Likes: 0
Replies: 1
Boosts: 1
JamieGC 🏴 🏳️🌈 🖖
In response to this post@mattblaze St. Louis has one and it has been in continuous operation since 1925 (KMOX).
Mentions: @mattblaze@federate.social
Likes: 0
Replies: 0
Boosts: 0
Garrett Wollman
In response to this post@mattblaze Back in 2010, this was KNBR's main transmitter. No pictures of the towers because it was dark when I visited (lots of pictures of the obstruction lighting but I didn't have a tripod and can't handhold nighttime photography worth a damn). This must have been installed some time in the 1990s (it would be a newer model from the 2000s and probably a Nautel instead of a Harris if it had been actually new at the time of my visit).
@wollman Neat! According to the license, it was replaced with a Gates 3DX-50 in 2016.
by Matt Blaze ;
Mentions: @mattblaze@federate.social
Likes: 0
Replies: 1
Boosts: 0