tech stuff – Page 62 – Engineering Radio

Studio Builds, the never ending cycle

The lease is up, it’s time to move! Yay, we get to rip apart the old place and redo it! Again! It seems to be a matter of course that every few years a radio station will move. Such is the case with WKZE in Red Hook (the town, not the area in Brooklyn). Their lease is up on the “Grotto” location, so the owner has decided to move to a new location, closer to the center of town.

The new location was the former thrift shop. I know this because while I am working there, a constant stream of older people stop by and tell so. Once, while working alone doing some pre-move work punching down wires and computer network cables, I had to use the facilities. There I sit, on my porcelain throne, when I hear, “Hello?” in an old shakey voice. A quick glance at the door reveals it is not locked. Oh, NOs! Okay, don’t say anything, she’ll go away.

“Hello?”

“Hello, is anybody here?”

“Hello? Very strange, the doors are open but nobody is here. Hello?”

Oh for the love of Pete, “I’m in the bathroom,” I finally said.

“Where is the bathroom?” said the interloper.

I refused to say anything else and she finally left. She could have taken all my tools if she wanted to.

Anyway, the studios themselves are pretty simple, one production studio and one air studio. A T-1 line to the transmitter site, turned out the be the hardest thing about the entire operation. We moved the old Radio System consoles rather than purchasing new equipment. Radio Systems has a program called a Millennium upgrade, where you buy a new control surface, which replaces all moving parts, for something like $2,300.00 or so. For that, basically, a new console is had.

Radio Systems Former RS-12 now Millennium 12 console

The new production room is long and narrow.

The air studio is large and spacious. They often have live music from this studio, which is really cool. The station uses Prophet Systems automation equipment, although it is live most of the time.

WKZE air studio before furniture is installed — WKZE air studio before the furniture is installed

The main office area is one large room where desks will be located.

We are moving in stages:

Prep work, installing all the computer network cable, phone system cable, pulling all the audio and control wiring. Then the contractor finished up the drywalling and painting. Nice Colors!
Ordering phone lines and T-1 line. Ahhh, the phone company, such a pleasure to deal with, we had to pull a new cable through the underground conduit from the street to the building because the old cable did not have enough pairs. The conduit length is about 75 feet or so.
Removed the old production room console and took it to the shop to rebuild. It was not that difficult really, although a little cumbersome. I throughly cleaned out all the dust dirt and other detreious materials from the console frame and install the new control surface. I also checked all the power supply voltages with an oscilliscope to make sure there was no ripple. The original consoles were made in 1992, not bad for an 18 year old board.
Built a new production room with the rebuilt board.
Tested all computer jacks, audio wiring, etc prior to move.
Move T-1 circuit and all office and studio telco lines to the new location. Fortunately, the phone company is a local company not the big V we have in other cities. They were able to work with us and get things paralleled to the new location, something a large company might not have understood.
On the air from the production room at the new location
Remove the main rack, intact and move it to new location
Remove office phone system and install at new location
Remove and rebuild old air studio console
Install rebuilt air studio console in new studio, wire
Transfer operation to new studio

Right now, we are on step #6. That is going to be done next Tuesday (the day after memorial day) morning I believe. We should have the move completed by the end of the week. I’ll post updates as they become available.

Wire terminations

Radio studios involve quite a bit of wiring. Runs between the console and equipment are pretty straightforward, from whatever the connector required for the equipment to whatever the connector required for the console. When it comes to trunk runs between the rack room and the studio, however, some type of terminating block is required.

alt= — 66 block or M block insulation displacement wire termination

This particular cabling installation is for low-level signaling, contact closures, and the like. It uses a Belden cable with 37 un-twisted wires which do not follow the standard Western Electric color code. The color code can be found here. If it were audio or data, the wires would be terminated differently. That color code can be found here. For more information on color codes and pinouts, see this post.

Many engineers use the venerable 66 block or M block insulation displacement termination. These terminal blocks were designed by ATT to terminate 25 pair 22 through 26 gauge solid wire. The original design was rated for category 3 (16 MHz or 10 mb/s) communications standards. Newer designs are category 5 or 5e compliant (350 MHz or 100 mb/s). Notice the part about the solid wire. Most audio wire is stranded and as such, the metal fingers on a 66 block will cause stranded wire to spread out losing contact with the terminating finger. This causes intermittent connections and audio dropouts, which I have experienced often (before I knew better, I used 66 blocks when building studios). The way to cure audio dropouts on a 66 block is to heat the termination fingers with a soldering iron. This melts the wire insulation and gets it out of the way. In the long run, it is better to use more suitable terminations.

Krone LSA-PLUS 110 type wire termination block

The 110 block is an updated version of the punch block for high-speed networks. it is also designed for 22 through 26 gauge solid wire. This is the termination used on category 5, 5e, 6 patch panels and RJ-45 jacks. They are also formed into block-type terminations the size of small 66 blocks. The 110 block is designed for 500 MHz (1 gb/s) or greater bandwidth. Krone makes a version of a 110 block called LSA-PLUS which is an acronym that stands for: Lötfrei, Schraubfrei, Abisolierfrei, Preiswert, Leicht zu handhaben, Universell anwendbar, Sicher und schnell. This translates to: no solder, no use of screws, no insulation removal, cost-effective, easy to use, universal application, secure and fast. Unlike a standard 110 block, the Krone block is designed for solid or stranded wire. 110 blocks are acceptable for use with AES/EBU digital audio at sample rates greater than 268 KHz as well as gigabit networks and analog audio.

In very old installations, I have seen Christmas trees. This is a wire wrap system where wires are wrapped around metal fingers that form the shape of a pine tree, hence the name. They were very popular in the fifties and sixties and only work with solid wire. It is also time-consuming work and requires special tools and skills. Wire wrapping is a bit of a lost art.

Christmas Tree wire wrap termination block

Screw barrier strips have been used to terminate audio cables from time to time. I wouldn’t consider this method because it is too time-consuming, takes up too much space, and is difficult to label.

ADC ICON wire termination block

ADC makes a good termination block called ICON (Integrated Cable Organization Network) which uses QCP (Quick Connect Panel) connectors. the connectors are small square devices that are insulation displacement termination (like 66 and 110 blocks) but require a special tool to “punch down.” This particular type of connector is well suited for stranded wire from 22 through 26 AWG. QCP connectors are also used on some of ADC’s patch panels and other audio products. Like any other termination technology, they are only as good as the person punching down the wires. QCP connections are small high-density devices, I have seen them get mangled by someone in a hurry who got his punch-down tool across two of the terminals by accident. ICON blocks can be used for digital audio, however, they do not maintain the 110 ohms impedance of most digital-type audio cables (neither do XLR connectors, by the way). This can lead to some return loss, which on longer cable runs can cause problems.

Radio systems prefer RJ-45 connectors with Category 5 cable, something they call Studio Hub. These are 110 blocks as noted above, but designed primarily for computer networks. Radio Systems discovered that the impedance of most audio cables is very close to that of computer network cables, audio cable is designed for 110-ohm impedance vs. computer network cable which is designed for 100-ohm impedance. Therefore, RJ-45 connectors and shielded or unshielded twisted pair work well with balanced professional audio, either analog or digital.

For analog audio wires, ICON blocks seem to be the best, most secure high-density termination system. In all my years of using them, I have never had a connection go bad. 110 block and other category 5 or 5e systems also work well. For digital audio, Krone blocks or 110 blocks need to be used in order to maintain the full bandwidth characteristics of the cable being used. Using appropriate cable and or terminations in digital audio circuits often leads to impedance mismatches and high return losses in the system.

Copper theft and how to avoid it

One of the unfortunate signs of the times is the increased theft of valuable materials. Copper, while not as expensive as it once was, still fetches a fair amount at the scrap dealer. One local telephone company has been having a difficult time keeping its aerial cables intact in certain areas. For radio stations, the situation is compounded by remote transmitter sites with lots of copper transmission lines and buried ground radials around AM towers. Reduced staffing levels also mean that the weekly trip to the transmitter site is now every two weeks or perhaps once a month or even less.

Sites that are not visited or monitored very often are prime targets for copper theft. Forget asking the local constabulary to patrol more often, the few times I tried that I was met with a blank stare.

A few common sense type things that I have learned over the years may keep your site intact:

Keep up appearances. A neglected transmitter site is more likely to attract the wrong type of attention from the wrong type of people. Clean up any rubbish, dead equipment, keep the weeds and trees cut down, etc. If a site looks well tended and is often visited, a thief may think twice about lifting valuable metals.
Along with #1, keep things buttoned up. Secure all transmission lines to ice bridges, remove any deadlines, etc. If there are ground radials poking out bury them, same with ground screens, copper straps, etc. Out of sight, out of mind, leaving this stuff exposed is asking for somebody to come along and give a tug.
Fences and locks. Towers are required to be fenced and locked to prevent electric shock hazards. It is also a good idea to fence the building, generator, and fuel tank if possible.
Post all sorts of warning signs, RF warning, high voltage, no trespassing, under video surveillance, pretty much anything to deter trespassing and vandalism.
Add video cameras with a video recording device since most theft occurs during non-working hours. Last year, the company I used to work for traded a video surveillance system for the studio location.
Compensate a neighbor to keep an eye on the place and call you if they see any suspicious activity. It doesn’t even have to be money, I once worked out a deal with a neighbor for some T-shirts and CDs. That was the best alarm system we ever had.

In the long run, keeping all the copper parts where they belong is a great way to avoid those annoying “the station is off the air” phone calls not to mention the expense of replacing damaged transmission and ground systems.

Delta Current Sample Toroid

Another example from my blown-up shit collection, artifacts division:

Delta TCT-1HV current sample toroid destroyed by lightning

This is a Delta TCT-1HV current sample toroid that was pretty well destroyed during a thunderstorm. I mounted it on a piece of plexiglass because I think it looks cool. This unit was installed at the base of the WGY transmitting tower. One June evening, I received a call from the station operator (back when they had live operators) that the air signal sounded kind of “funny.” So I turned on the radio and sure enough, if one thinks a radio station that sounds like a motorboat is funny, then, why yes indeed, it did sound funny.

Since I only lived a few miles away from the site, I jumped in the trusty truck and headed over. Upon arrival, I found the MW50B on the air at full power, with the carrier power swinging wildly from 20-90 KW with modulation. Hmmmm, bad power supply? Turned the transmitter off and tried to place the backup transmitter on the air. Now the old Gates BC5P had never been super reliable in the first place, but it was odd that it would not even run at all.

Then I had a hunch, let’s walk out to the tower I said to my assistant who had shown up to help. When we got to the ATU building it was filled with blue smoke. Ah ha! Somebody let the magic smoke out of one of the components! I was expecting a capacitor blown in half but was surprised to find the copper tubing that connected the ATU to the tower melted in half. Lightning must have caused an arc between the tubing and the toroid and for some reason, the transmitter kept on running while it was arcing. The copper tubing in the picture with the toroid is only missing about six inches, the way the system was mounted at the tower base, fourteen inches of copper tubing was missing, or rather melted into a puddle on the bottom of the ATU.

I quickly found another piece of 1/2-inch copper, cut it to length, flattened out the ends with a hammer, and drilled mounting holes. Luckily I was able to get everything back in order quickly and the station returned to the air about an hour or so after it went off.

Everything has a cause. Investigation showed that the VSWR circuit on the MW50 had been disconnected from the directional coupler. The lead was un-soldered and taped off, so it was quite intentional. I spoke briefly with two of the three prior engineers that had serviced the MW50 over the years, they both blamed the other one. I surmise this; The WGY tower was prone to lightning strikes because of its height. Even if the tower was not directly struck by lightning, oftentimes the guy wires would arc across the insulators, causing the MW50 to momentarily interrupt the PDM signal and drop the carrier for about a second. Some programming people at the station did not like this, it sounded bad on the air, so one of those guys undid the VSWR circuit, and voila! No more momentary outages during a thunderstorm! Brilliant! Except for the 60-90 minute outage one night…

Sometimes it is better to tell the program directors that their idea is not good, then move on.