tech stuff – Page 26 – Engineering Radio

Servicing the UPS

A client of ours, WDST in Woodstock, NY, has this Best FE7KVA UPS. This unit is several years old and has already been through a couple of battery replacements. These are good units, however, Best Power has been bought up by Eaton/Powerware and they are ~~no longer made~~ apparently are still made.

Regardless of that, the UPS is still functional, but like all UPS’s, it needs battery replacement every so often. This unit has three battery cases, each holding four 75 Ah (20 hour rate) 12 volt sealed lead acid batteries. Each battery is slightly larger than an average car battery. There is one important detail here, the batteries must be gas recombinant because the UPS has a four stage battery charging system. Gel or AGM batteries will not make it past the first or second equalizing charge.

A bit about batteries and battery charging. Most battery chargers are three stage units; bulk, absorption, and float. The rate of charge depends on the voltage of the battery. Bulk charging sends the most current to the battery and for 12 volt cells, this anything below 12.5 volts or so. Absorption stage reduces the charging current and supplies a steady current until the battery reaches full charge of 13.8 volts or so. Float or trickle charging draws very little current, just enough to maintain the battery at full charge.

The forth stage of charging is equalizing which is important for multiple battery series/parallel installations. This is when the batteries are deliberately overcharged for a period of time. The reason for equalizing charges is to intentionally boil off some hydrogen gas and knock any sulfur crystals off of the lead plates. With multiple battery banks in a parallel configuration, it is important to maintain the battery resistances as close as possible so that each bank of batteries is drawn on and charged equally.

In flooded lead acid batteries, this works well and the battery either vents off the hydrogen gas or recombines it will oxygen to make water again. In non-gas recombinant cells, the hydrogen will be released into the room which may pose an explosion hazard. Additionally, the electrolyte level will need to be checked after every equalization charge. With a sealed non-recombinant battery, the case my bulge and split, spilling electrolyte and ruining the battery and battery enclosure. Thus the importance of ordering the correct replacement batteries.

Best Power FE7KVA UPS and battery enclosures

After all, the reason for the UPS is to protect the expensive computer equipment connected to it. It simply will not do to install the wrong stuff and do more damage than if the UPS did not exist at all.

Mounting a new satellite dish

Something that almost every radio station has but no one really thinks about; is the satellite downlink. I think radio stations began installing satellite downlink equipment around 1982. Before that, all network programming was carried hither and yon via Ma Bell’s extensive terrestrial microwave network.

Those early dishes were almost always Scientific Atlanta 9000 series 2.8-meter antenna system, which went with the SA 7300 DATS satellite receiver. Fast forward 31 years and things have changed. The satellite constellation is now spaced at one degree and those old SA 9000 dishes are not one-degree compliant.

Scientific Atlanta 9000 series satellite dish

Therefore, when it came time to re-aim a dish at AMC8, something new was required. A Prodelin 1374 3.7 meter center-fed C band dish was ordered up.

The first thing to do is look at the dish specifications and decide if the suggested mounting procedure is a good one. The soil in this area is sandy loam. The mounting design calls for a six-inch schedule 80 steel pipe at least six feet into the ground. This calls for renting an excavator, digging a six-foot deep hole, buying a 36-inch sono-tube and a 16-foot piece of 6-inch schedule 80 steel pipe, and a couple of yards of concrete from a truck. This work is all being done on the ground system for the WDCD antenna array. All the while, abandoning the old pad and dish in place. Seems like a lot of money and wasted materials. Reusing the old pad and part of the old mount made more sense. I did some rough calculations on paper regarding wind forces, this was the results:

The maximum static force is 1,555 N on the back bolts of the mounting ring into the concrete pad. Maximum wind force is 5,603 N, and a maximum wind from bearing 76° T will exert a force of 7,158 N or 730 Kg force on the back bolts of the mount. The concrete that the mounting bolts is embedded in will withstand 4,267 Kg of force at six inches deep. The the existing pad and 3/4 inch J bolts are well within their rating to handle this load, so it seems like a good design. Putting that to practical use:

Scientific Atlanta 9000 series dish mount

First, we unbolted the azimuth mounting ring and removed the old dish, leaving the bottom of the mount. I drilled down 6 inches into the old concrete pad and inserted 1/2 inch re-bar. These re-bar are somewhat diagonal toward the center of the tube towards the new mounting pole.

Scientific Atlanta 9000 series dish mount reuse

Then, we placed the 6 inch by 8 foot schedule 80 pipe in the center of the tube and attached it to the tube with 1/2 inch all-thread. We used the all thread to adjust the 6-inch pipe to be vertical.

Next, we filled the old mount up with 4,000 PSI (280 Kg/square cm) ready-mix concrete and let it cure for one week.

While that was curing, I bolted the new Prodelin 1374 dish together on the ground. Follow the directions closely on this one, there are many pieces of hardware that look the same and are almost the same but will not work if exchanged.

We used a loader with a lifting bar on it to sling the new dish into place. I was going to video tape this evolution, but we were short handed and I ended up helping bolt the dish on the mount once it was placed there.

Once the dish was mounted, I installed the feed horn and LNB.

WDCD Albany, NY, Prodelin 1374 dish installded — WDCD Albany, NY, Prodelin 1374 dish installed

Then there was the aiming; this dish is pointed at AMC-8, for which I found this information from dishpointer.com most helpful:

WDCD AMC-8 information, courtesy of dishpointer.com

This is a crowded neighborhood and finding the right satellite took a bit of trial and error.

New Studio project

It is time, once again, to replace some very old Pacific Recorders BMXII consoles. The Pacific Recorders consoles were very expensive when new, but after 30 years of continuous use, have more than paid for themselves. The replacement console of choice for this installation is a SAS Rubicon. I have installed these units elsewhere and they are the modern equivalent of the PRE BMX.

The heart of the Rubicon system is the 32KD router. Routed audio systems can save a lot of time and effort in a large studio facility installation. Not having to run and terminate multiple analog and digital trunk cables between the rack room and the studio is a huge deal in a six or ten-studio installation project.

The SAS 32KD router and Rubicon console system use a serial TDM bus to communicate and transport audio around. This is a simpler system than packet-switched IP data. Basically, the console surface is a very large, fancy computer control interface. Here are some pictures of the start of the project:

This is the view from the entry door. The furniture was placed last week and the countertop was cut in for the console. The furniture is made by Studio Technology. The pile of yet-to-be-installed equipment:

For monitors, we are using the Tanoy 602p near field monitor placed on the table top above the computer screens. This studio will not have a turret. Turrets used to be necessary to hold things like cart machines and CD players. These days the CD players are used so infrequently that it was decided to put them in the side rack under the counter top. Turrets also take up a lot of counter top space that can be put to better use.

Punch blocks and power connections. The red outlets are isolated ground UPS type, the back outlets are feed by the emergency generator power panel. All electric wiring is inside of the metal conduit. The punch blocks are the inputs to the SAS RIO link unit, one 16-pair analog audio cable and ten category 5e shielded cables. The cat 5e is used for computer and TDM data buss to the router.

The SAS Rubicon console is cut into the counter top and protected by plastic sheets.

Rack room with 32KD routers. This facility has 9 studios total plus a news room with three work areas.

The SAS 32KD router. All audio from the automation systems, satellite feeds and other sources is connected directly to these units. This unit is on line for other studios that have already been converted to the SAS gear.

Category 7 Cable

As data transfer technology progresses, so do cable types. Category 6 UTP copper cable is commonly used today in ethernet installations where 1000BaseT (or gigabit ethernet) systems are required. Cat 6 cable has a certified bandwidth of 250 MHz (500 MHz for Cat6a). Category 6 cable is a newer version of Category 5 and 5e cable wherein the wire pairs are bonded together and there is a separator to keep each pair of wires the same distance apart and in the same relationship to each other. The four twisted pairs in Cat 6 cable is also twisted within the overall cable jacket.

Category 7 cable is much different from its predecessors. It has an overall shield and individual pairs are shielded:

Shields on individual pairs are required to reduce cross-talk (FEXT, NEXT). It also requires special shielded connectors called GG45 plugs and jacks. Pinouts and color codes are the same as gigabit ethernet (Category 5e and 6) however, Category 7 (ISO 11801 Class F) jacks and plugs also have to contact the corners of the connector or jack. This allows better shielding. A small switch in the jack senses when a Category 7 type connector is inserted and switches to the corner contacts, thus keeping jacks and patch panels backward compatible with Category 5/6 cables.

Category 7 GG45 connectors, jack and plug

Category 7 cable is rated for 600 MHz bandwidth (1000 MHz for 7a) which translates to 10 GB ethernet. This was previously the domain of fiber cable. Copper cable has some advantages over fiber; lower propagation delays require less complicated equipment, copper is less expensive than fiber and more durable. It is nice to have the flexibility to use copper cable on 10 GB ethernet for runs of 100 meters or less. Longer runs still require fiber.

Category 7 and 7a cable looks remarkably similar to the older Belden multipair “computer cable” pressed into service as audio trunk cable seen so often in older studio installations.