Apparently, somebody, over the long holiday weekend had a wee bit too much time on their hands. So much so that they decided ripping the doors off of the generator shed at the WGHQ transmitter site was a good idea. And so they did:
Generator shed doors ajar
That, and smash the light fixture.
The good news; thus satisfied with their bit of malfeasance, they left the generator and other contents of the building untouched. It could have been worse.
Perhaps the site could do with some security cameras?
Generator shed door repaired
The local carpenter was called and the door frame was replaced. Truth be told, the wood door frame was a bit past its prime anyway. Once the doors were remounted, I check out the generator and it starts and runs just fine.
Generator
It’s a cute little thing, 23 KW, 4 cylinder diesel engine.
This video shows some of the maintenance required for an HF (AKA Shortwave) broadcast station. It starts with transmission line tensioning, some shots of a curtain array then goes on to show the inside of a transmitter building. Transmitters shown are Harris HF-100 (a 1980’s model tube type PDM design) and Continental 418, but I didn’t see the letter number. They are likely tube-modulated units.
These are from the international service of Australia Broadcasting Corporation (ABC), or Radio Australia International.
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.
As has been widely reported in other places, the NAB (National Association of Broadcasters) has completed its study of AM Radio and recommendations to improve the service. The NAB has taken a cautious, if the not somewhat paternalistic approach of holding the report while they review their options. It seems that the technical nature of such a document would not be understood by us mere mortals.
Some of the AM improvement options that have been bantered about in the past include:
Moving AM stations to the vacant frequencies of TV Channels 5 and 6, see this.
Reducing the number of AM stations on the band, see this.
Increasing transmission power of AM stations, see this.
Converting AM stations to all digital modulation, see this.
There may be a few other options considered also.
It does not take too much analytical prowess to deduce where the NAB’s proposal is going. My prediction is that they will be promoting an all-digital “solution” to the AM broadcasting issue using iBquity’s HD Radio product. I base this prediction on the fact that all of the major radio members of the NAB (Clear Channel, Cumulus, CBS, et al) are heavily invested in the iBquity product. For this reason, the NAB will find (or has found) that digital broadcasting in the medium wave band will solve all of the currently perceived problems with AM and everyone should embrace the technology.
A few numbers to note:
iBiquity and the FCC data base reports that there are currently either 270 or 299 AM stations licensed to operate with HD Radio. Other sources note that several of these stations have been turned off and the actual number using HD Radio is 215.
Currently, HD Radio is transmitted 4-6% of the AM stations in the country.
It costs $25,000 US to license a single HD Radio station through iBiquity. They are, however, discounting that to between $11,500 and 13,500 and have a convenient payment plan (limited time offer, expires December 31, 2012, FCC license fees are extra).
It costs between $75,000 and $150,000 to equip and or modify a single AM station with HD Radio gear.
Unless iBiquity drops all patent claims and licensing fees to use its product, an FCC mandate for AM stations to install HD Radio would be skating dangerously close to corporate fascism (AKA Mussolini Fascism or Corporatism) as one corporate entity would then control broadcast radio by licensing its modulation scheme. And no, the patent is not going to expire.
Digital modulation schemes used in the medium wave band have their own set of technical issues. HD Radio is not the panacea for AM broadcasting’s self inflicted woes.
