Long-Distance Phone Microwave Towers

When I started heading south on US-45 after getting off of I-57, I spotted a microwave tower that still had long-distance telephone antennas. Since the road had a full width shoulder and I was doing just 10 mph, it was easy to pull off the road to get a picture. (Facebooked)

(Notes on concrete microwave towers)

20140723-24 0005c

If you did a long-distance phone call in the 1960s or 70s, it probably went through several of these towers. Fiber optic cables have made these towers obsolete, so these will now start disappearing.

safe_image for Vintage Skynet: AT&T's Abandoned "Long Lines" Microwave Tower Network

The towers are spaced so that there is a clear line of sight from an antennae on this tower to an antennae on the next tower. Because of the curvature of the earth, a tower needs to be built about every 25 miles (34-jumps-to-chicago). The antennae is specifically a horn. Originally, it looked like:

But, since metal reflects microwaves, they were able to turn the horn vertically by adding the 45-degree sheet of metal at the end. This made it easier to mount the horn on the tower. I got a closeup of the top of the tower because I could see just one waveguide, not four. The closeup confirms that just the horn farthest from us on the left still has a waveguide attached to it.

So I was wondering if they have started to dismantle this tower. At first I thought a Bing image shows several waveguides are still going from the tower to the building. But now I think the white line between the tower and the building might be a "cable rack" for waveguides. The street-side view was looking at the north side of the tower. This view is looking at the south side. You can see the waveguide coming from the southeast horn.

Bing map

The building contains the electronics needed to amplify the microwaves for the next hop across the country. When microwave communication was first developed, waveguides had not been invented. So the towers were made of concrete so that the electronics could be built on top of the tower next to the horns. I don't know if they are still standing, but in the 1970s I saw two of these towers for the original New York to Chicago link still standing in northern Indiana. Unfortunately, I no longer remember where they were.  I'll have to keep an eye out for them during my next trip across Indiana.


The electronics in the building must have also extracted phone circuits that were terminating in nearby towns. But I don't see any phone cables coming from the building to hook into the local network.  So this tower is no longer doing its function of relaying long-distance calls across the country. It is now just handling long distance calls that terminate in this area because it is not economical to lay a fiber optic cable to this area for a relatively small number of circuits.

I wonder if the waveguides contain precious metal or if they can be used in other applications. What else would justify the labor costs of removing three of the waveguides?

Another strange maintenance issue I noticed while studying a closeup is that the rungs of the ladder have been removed from the top 2/3 of the tower. In the closeup below left you can see the rungs at the bottom, but not at the top. I added a red line in the picture to the right to indicate where the rungs stop.

I've seen rungs missing from the bottom before so that unauthorized people can't easily climb a tower. The maintenance people probably carry a ladder on their truck to climb the lower part. I can't imagine why you would remove rungs from the upper part but leave the lower part intact. The rungs stop too low to use this as a cell-phone tower.

An aerial view of the tower indicates that the direction of the link was a little north of east to a little south of west.

Bing map

The next day, while driving along US 19 in Florida, I spotted another tower. Since I was traveling at highway speeds and the shoulder was about 2 feet, I didn't pull over for a street side picture. But later I was able to find it in an aerial view.

Google map

Note that this tower slightly changes the direction of the next hop. Given what I learned about the Illinois tower by studying the picture---the removal of three waveguides and most of the ladder rungs---I now wish I had turned around and got a picture of the Florida tower.

In Winter Garden, Florida, I noticed that there was a microwave tower without any microwave antennas. There are a few cell-phone antennas.

20140801 0202

The building under the tower is for the phone company. The red-roofed building in front of that building is the old Atlantic Coast Line depot and now a local museum. The parkway this side of the cars is were the ACL tracks came through town. A lady in the museum mentioned she was glad to see the big antennas come down because buzzards used to perch on them.

So fiber optic cables must have been laid to Winter Garden. Since long distance fiber optic cables tend to use the right-of-way of railroads, and there are no longer any railroads serving this town, I wonder where the fiber optic cables were buried. (The only track left in town is a remnant of the Tavares & Gulf Railroad between Winter Garden and Ocoee.) Perhaps the cable is buried in the parkway that was the ACL right-of-way. I wonder if the phone company bought the ACL right-of-way and lets the town use the land. Or if the phone company leases access to the parkway from the town. Or....?

Jeremy Buck Jordan posted two photos with the comment: "These old weather stations are scattered all over the state. Not real sure if the tower still serves a purpose, but the building sure isn't getting any attention."

Bob Klaus: Not weather stations, but part of the obsolete AT&T microwave LongLines military telephone network built during the Cold War. The giveaway are the cornucopia-shaped horn reflector antenna on top. AT&T sold off the towers in the 1990s. Most are now owned by Heartland Towers. The horn antennas remain unused, but the towers now support modern microwave dishes and cell phone repeaters.

https://99percentinvisible.org/article/vintage-skynet-atts-abandoned-long-lines-microwave-tower-network

https://personal.garrettfuller.org/blog/2018/01/19/att-long-lines-a-forgotten-system/

The tower photos barely indicate how huge the horn reflector antennas are. Compare with the size of the instrument house doorway and stairs in this photo.

In 1965, AT&T engineers Penzias and Wilson were tasked with troubleshooting the source of noise in the antenna. They verified the antenna was not the source. They mounted a horn on a ground swivel and proved the noise originated from our galactic center, and got a Nobel Prize in 1978 for verifying the big bang theory. https://supernova.eso.org/.../penzias-wilson-hornantenna... https://www.pbs.org/wgbh/aso/databank/entries/dp65co.html

Today, the transistor microwave transceivers are integrated into the focus of the small parabolic dishes, and are powered and fed with CAT6 Ethernet cable. When the LandLines system was designed, vacuum tubes were in use. The 6 GHz microwave carriers scooped up by the horn antennas were fed into inch square silver-plated brass wave guides that ran down to a two storey building buried two stories underground to resist a nuke blast. The waveguides were pressurized with dry nitrogen to keep the silver plating bright. The upper story contained racks of vacuum tube electronics - the diplexers, transmitters, receivers, channelizers and modems for a 7 watt 6 GHz signal. The lower storey contained generators, fuel tanks, air handlers, and life support for a 2 man crew to be sealed off underground for 2 weeks during a nuclear attack, if necessary. Everything was mounted on shock-absorbing springs, even the toilet!

The towers were designed to survive a nearby nuke strike, and are sited at optimal hilltops before the later microwave networks, so the old towers are still prized locations!

Travis Baber: Here is a neat documentary about at&t long lines. Did you know these towers also relayed television before satellites? Yup.

https://youtu.be/XWwV4Hc-Nkc?si=_shNDbmZxpd0pdIk

1

2

20150510 1135

I came across the largest collection of microwave antennas I have ever seen south of Chicago. I'm not surprised that a major urban area had a large complex. I am surprised that all of the antennas still seem to be active. There are a lot of railroads near by so I would have thought that fiber optic cables would have made these obsolete quite a while ago.

20141017-20 0084c

I was going along the tracks in McComb, IL looking for grain elevators and interesting old buildings and found their central office. Since there is a university in town and an active BNSF railroad route to town, I assume the town gets service via fiber optics and this tower is providing service for smaller towns in the area. A detail showing the wave guides going into the central office. (Facebooked)

20160811 4088

While driving up Peace Road to the Sycamore Steam Show, I noticed this tower. I turned west on Fairview Drive and took the picture from Macom Drive even though I was in a bit of a hurry to get to the show before the 1:30 Parade of Power. I did make it with some time to spare. (Facebooked)

Satellite

Tommy Lee Fitzwater posted
Dennis Boyd Microwave tower in the background?
Thomas Cain Dennis Boyd this is Barr Street, looking north from Washington. What was News Sentinel building on left (now Unired Way), before 1st Wayne Church built, and after 1910s Market Buildings demolished. Tower in back is GTE, prior to their 1970s renovation. The white box building at rear left is Wolf and Dessauer, where the were moving to about the time of the fire. That's now Citizens Square.
Jack C. Shutt Dennis Boyd Yes. That is the old GTE microwave tower, before the "lighthouse tower" was built on top of the building.
[Fort Wayne had General Telephone Electric instead of AT&T for the phone service.
The stone building in the middle is the Old City Hall.]
John Hume The newest vehicle I see in the photo is a '59 Chevy on the far right. Can't tell what year the Ford Falcon is parked two spaces in front of the Chevy.
Marc Servos I admit I didn't notice the Falcon at first, thanks. Obviously from the 1960-63 model year range, which I assume '60 models being on market in late 1959. But we don't see the front to help pinpoint the model year.

A 1960 map of the broadcast lines connecting the stations. (Source: Long-Lines.net) via personal.garrettfuller

(new window)   And then the YouTube AI offered: TV transmission (radio transmission is at 6:13), long distance (microwave towers at 8:13) and #1 ESS (for my information).