This transmitter is about 10 years old. In ten years of service, there have been no failures. Not one transistor has gone bad. It is connected to a three-tower directional array on 920 KHz.
WGHQ Nautel ND-5 transmitter
Sadly, this model transmitter is no longer made. They were built like tanks, heavy gauge steel cabinets, well-designed, well-grounded circuit boards.
It is dirt simple; RF power MOSFETs on drawers, combined and tuned with the output network. A power supply, exciter, and simple control logic and nothing else. No serial port to plug a computer into, no ethernet ports, no digital read-outs, fancy efficiency optimizing computers, etc. In the meantime, it does what it is supposed to do, stay on the air.
I was reading, with interest, the idea of “energy star” transmitters. I think that good radio station engineers already take electrical efficiency into account when buying a new transmitter. That being said, electrical efficiency is not the only measure of efficiency an engineer should be considering. Reliability, redundancy, and repairability must also be considered. If the station spends an inordinate amount of time on the old backup transmitter while the new, super-efficient main transmitter is off line is counterproductive. Not to mention the time wasted troubleshooting which could be better spent on something else.
Radio stations more and more revolve around networked computers. Engineers need to understand computer networking, especially as it relates to audio distribution and playback. Eventually, I see broadcast engineers being more computer science types rather than electrical engineering majors.
What I have found out about computer networking is this: it is not rocket science. In fact, most of it is pretty easy. Physical networking and cabling are similar to audio and TELOC cabling. Automation computer servers themselves are not difficult to understand as most of them run on some type of Windows program. Other servers such as Apache for WWW and for FTP and streaming run on some type of LINUX OS. LINUX is also not difficult to understand so long as one knows the right command line prompts.
The first part of understanding computers is networking. Without a computer network, a computer is a glorified typewriter. Almost every automation system and or digital editor requires some type of network. Consoles and computers that use AOIP require well-constructed networks in order to operate properly. To that end; cabling choices, network interface devices such as switches and routers, patch panels, and so forth need to be specified and installed with care.
Most often, it is the simple things that will trip an installer up. The one area where I have found the most mistakes made is the pair’s connection to various termination points. There are two basic standards, TIA/EIA T568A and T568B. Neither is better than the other, both are often identified on terminating devices such as jacks and patch panels. The most important aspect of these standards for an installer is to pick one and stick with it.
TIA/EIA 568 color code
When certifying networks, the most common problem I have encountered is crossed pairs. Almost invariably, one end will be punched down with the A standard and the other with the B standard. Jacks are particularly difficult, as the color-coding stickers show both. Many patch panels have a slide-out, reversible card with is an either/or situation. For some reason, I have stuck with the B standard, and on any project I am managing, I get rid of all the A color codes I can find and tell the installers that B is the only acceptable termination standard. That cuts down on a lot of errors and redos during certification. That is good, it saves time and I hate redos.
Cat 5e wall jack set
You can see that this color code marking can lead to confusion. I take a sharpie and cross out all the A markings to avoid installation mistakes.
Incidentally, on any new network installation, Category 6 cable should be used. As more and more data throughput is required for network applications, Category 6 Cabling has better performance specs and will likely have a longer service life than another cable. It may be a little bit more expensive than Cat 5, however, well worth the investment. It would be a great mistake and a waste of money to have to pull out the network and reinstall it in a few years because the cabling doesn’t have the required bandwidth.
Cause the STL receiver to unlock. A quick peak at the thermometer this morning showed -12° F outside. Meanwhile, out on the island, the WICC TFT STL receiver decided that it was just too cold to continue and gave up the ghost. Weak sister. This created quite a bit of hiss on the WICC signal until about 11 AM, when the program director finally called me to tell me of the situation.
Via remote control, we switched over to the backup analog 8 KHz 15 KHz TELCO line, which sounds fine, given the talk radio program material.
Unfortunately, vehicle access to the transmitter site is now gone. I have the option of taking the Bridgeport harbor master boat over to the dock and walking .9 miles, or driving to the Long Beach parking lot and walking 1.3 miles in order to repair it. This will likely be tomorrow, as the weather is supposed to be better, 36°F and light snow. Well, it is what I get paid to do.
Pleasure Beach, Bridgeport, CT
Regarding the analog 8 KHz TELCO line, that is an anomaly. These analog circuits where used to wire the country together, once delivering all of the network programming to affiliate stations before the widespread use of satellites. They require unloaded dry pairs and normally have an equalizer on the Z (far) end. Nowadays everything is digital, try and find a tech to repair one of these circuits when it goes down. Fortunately, this is a short distance circuit.
Satellite dishes have been a part of radio station technical equipment for years. I am surprised at the number of broadcast engineers that do not consider center of box when aiming dishes. As dishes get larger and focal points get smaller, center of box aiming is not a nice thing to do, it is a necessary thing to do. The latest generation of satellite receivers, (AKA XDS) have a somewhat less than lively RF front end, they require higher E/B than the previous generation Starguide receivers to stay locked.
For years, the majority of commercial radio networks were carried on AMC-8 or its predecessors living at 139° W. On the East Coast, particularly in the Northeast, that makes aiming points relatively low to the horizon, anywhere between 8-10° elevation.
3.2 meter COMTECH satellite dish
This all means that precise aiming the satellite receive dish is critical for satisfactory performance. SES Americom owns AMC-8 and thus they have a web page about all of their satellites and important operating information. SES Center of box for AMC-8 is available in one-month blocks, which makes scheduling the aiming chore fairly easy.
Large satellite dish aiming diagram
I have always used a spectrum analyzer through a 3 dB splitter to look at the 950 MHz LNB output. This aiming setup allows the best combination of Azimuth/Elevation/polarization. Using the satellite receiver to confirm and maintain signal lock, peak the waveform that the receiver is locked to. It is pretty crowded up there, so there will be lots of signals on the spectrum analyzer trace.
It is a pain in the rear end to lug all that equipment out to the satellite dish, especially if it is on the roof. That is why it only need be done once; the right way the first time.
Any shortcuts will likely lead to those annoying chirps and dropouts or complete loss programming, particularly when the weather turns bad.
