Reflecting the state of the economy in Detroit, WDTW went silent on January 1st. Less than two weeks later, the towers come down:
Thanks, Chris R for the video link.
The license has been donated by Clear Channel to MMTC (Minority Media and Telecommunications Council), but not the land or towers. It remains to be seen whether the station will return to the air, however, given the costs involved and the economic conditions in Detroit, that is unlikely.
The station signed on in 1946, moving to 1310 KHz with full-time operation in 1948. Back in the day, it was a flame-throwing top 40 station and is purported to be the source of the “Paul is dead” rumors that surrounded the Beatles in the late 60’s. Much more history at Keener13.com.
Take pictures of your favorite AM stations now because tomorrow, they and all their history may be gone.
After a bit of delay, we were able to return to the WICC transmitter site to install the Wireless LAN link. The installation was pretty straightforward. The studio unit was mounted on an existing STL tower on the top of the elevator room, the transmitter unit was mounted on an existing pipe on the roof of the transmitter building.
M5 Nanobridge mounted on transmitter building with RADOME
I included RADOMEs for a couple of reasons; first, there is a lot of critters around of the two-legged and winged kind. The upright two-legged critters may be attracted to the signal-strength lights at night. This unwanted attention could invite the juvenile delinquent’s bored teenagers to throw various objects found laying around on the ground at the antenna, damaging it. The winged type critter may be inclined to view the feed horn as a good nesting location. The other reason is this site gets a lot of rain, wind, ice, and snow, therefore the RADOMEs afford some protection against the weather.
Aiming the antennas was pretty straightforward, but requires at least two people. Using landmarks, we aligned the dishes in the general direction of each other. Both ends of the system were turned on and we had a -89 dBm signal path, and somewhat surprisingly, the radios linked up and my laptop grabbed an IP address via DHCP. Using the signal strength meter on the side of the antenna, each dish was peaked in turn:
M5 Nanobridge Antenna signal strength meter
Then, somebody on either end went below and looked at the signal strength screen on the web interface while the other end peaked. In the end, we had about -65 dBm signal strength, which is somewhat less than the -58 dBm predicted. I think we can do better, so on the next clear day, I am going to peak the signal again.
The data rate initially reported was over 100 MBPS, however, once I started transferring files back and forth, that dropped to about 50 MBPS. If it is raining, that rate drops to about 35 MBPS, which is still far above what we need this link to do. As a test, I streamed a youtube video, downloaded a Windows update, loaded several web pages, and checked my email simultaneously. There were no issues with the data rate while those tasks were being preformed.
It is quite amazing to me that these little inexpensive radios can work so well. My boss thinks that they will be blown up by lightning during the first thunderstorm of the season. I don’t know. There are several of these units have been installed at mountaintop tower sites and have been working for several years without issue.
Next step, installing the IP cameras and warning signs on the fence, setting up the monitoring software, etc.
Transmitter site security cameras
Cameras mounted on old chimney platform. This is the first set of cameras covering the south, north, and west approaches. A fourth camera will be mounted on the back of the building covering the east approach. Then, under the eves’ cameras will be mounted on all four corners of the building and the generator shed. If anything moves, it will be recorded.
Emergency! The (AM) Transmitter keeps popping off the air and we can’t figure out why! YOU MUST HELP US!!1!!!
Really?
Some problems are easy to spot, difficult to fix
Well, with the ATU mounted about 1/4 inch away from the 90-degree, series-excited tower, I wonder why. It seemed to be especially problematic during rain, snow, and ice storms. When I asked how long this had been going on, I was told “About two years, ever since we put up the new tower!”
You don’t say.
We finally took care of this by moving the ATU back inside the shed after moving the transmitter to a different building. The funny thing is, this was installed by a guy who had a BSEE. I guess he must have been out sick the day they covered this in class.
I am in the process of installing a pair of the Nanobridge M5 units as an IP network link between a transmitter site and the studio location. The path is relatively short, about 1.5 miles over mostly water. The main reason for this is to replace the analog phone lines used for remote control data and backup programming delivery to the transmitter site. One added benefit, we are also installing several IP cameras to keep an eye on the place. We purchased the Nanobridge system for $80.00 per side. The price is pretty good, but the configuration and testing are a bit intensive.
Network Diagram
There are many versions of these spread spectrum radios, some are licensed, and some are license free. These are inexpensive, license-free links that I would count on for short paths or use in non-congested areas. In congested areas, licensed (Part 101) links should be used, especially for critical infrastructure like STLs.
Since I dreamed up this idea, I figured I should make sure it is going to work before recommending it to the powers that be. I have learned the hard way, almost nothing is worse than a failed project with your name on it. Better to over-study something than to go off half-cocked, spend a bunch of money, then realize the idea was flawed from the start. See also: Success has a thousand mothers but failure is an orphan.
Nanobrige path study, 5.8 GHz, moderate noise floor, 1.5 miles
Looks pretty good. 300 MB/s bi-directional which is faster than the Ethernet port on the unit. This will be set up in bridge mode with pretty robust encryption. The transmitter site side is configured in the router mode, creating a second class A network at the remote site.
Nanobridge M5 22 dBi antenna
Next step, configuring the units. The Nanobridge units were set up in a back to back configuration in the engineering room. Each end comes with a default IP address of 192.168.1.20. The units were several steps behind the latest firmware version, therefore the firmware was upgraded first. The default admin user, password, and IP addresses were changed. There is no greater security risk than default user and password. The wireless security feature is enabled using WPA2-AES PSK and a greater than 192-bit access code. The unit allows for any access code length up to 256 bits. With a key of between 192 and 256 bits, the number of possible solutions is between 6.2771 E 57 and 1.1579 E 77, which should be pretty hard to crack. By way of reference, a 192-bit password has 24 ASCII characters and a 256-bit password has 32 ASCII characters.
Air OS main screen
The system requires an access point, which is configured for the studio side making the transmitter site stub network the station side. The access point is configured not to advertise its SSID, thus it should be transparent to anyone sniffing around. The WLAN is configured as a layer two bridge, which will cut down on the data overhead, as layer three framing will not need to be opened between the two units. The transmitter site network is set up with SOHO router function built into the Nanobridge. One static route is needed to get to the main network. Once the security cameras are installed, PAT may need to be used to access individual camera units via the public network.
Ubiquity air os signal strength screen
Next step, deploy the units and aligning antennas. These are 22 dBi gain antennas, which have a pretty tight beam width. Maximum transmit power is 23 dBm, or 200 mW. The transceiver/antenna unit has a handy signal strength meter on the side of the unit, which is good for rough in. The web interface has a more precise meter. In addition to that, there is a java based spectrum analyzer, which is very handy for finding open channels in congested areas. These units can also be used on UNii frequencies with special requirements.
According to the manufacturer, UV-resistant shielded Category 5e cable should be used for outdoor installations. We have several spools of Belden 1300A, which fits the bill. The shielded Cat 5 is necessary for lightning protection as the cable shield offers a ground path for the antenna unit. The antenna mounting structure is also grounded. I did not take the equipment apart to examine, but I believe the POE injector and antenna have 15KV TVSS diodes across all conductors. It will be interesting to see how these units do at the transmitter site, where there are two 300-foot towers that likely get struck by lightning often.
More pictures of the installation when it is completed.
Next step, put the system into service and monitor the link. At the transmitter site, a re-purposed 10/100 Ethernet switch will be installed for the cameras, computer, IP-RS232 converter, and anything else that may need to be added in the future. One thing we may try is an Audio of IP (AoIP) bridge like a Barix or Tieline for program audio and room audio.
