SAS studio installation work

I receive several emails a week from interested readers. One noted that the blog seems to be focused on RF. Yes, that is what I do most, but the company does studio installs as well.

This was from a few years ago.

WDST moved out of their Bearsville studio location into the former Methodist Church in West Hurley.

WDST Studios, West Hurley, New York

We installed a new SAS audio router and console system.

Eaton UPS powers rack room and studios
Small Rack Room for NextGen servers and STL equipment
Air Studio, Under Construction
Rack Room
Ethernet Patch Panel
Office area
Live Performance Stage
Rack Room
Back of the racks
WDST Air Studio
WDST Production Studio

Pictures of their old Bearsville studio can be found here:

WDST, Woodstock, New York

If folks are interested, I will post some more pictures of more recent studio-build projects.

Material safety at Transmitter Sites

Recently, while working at a transmitter site built in the early 1940’s I noticed some fluorescent lights were out. Upon closer examination, I noticed that the bi-pin holder on one side of the bulb was damaged. This led to the removal of the fixture for repair, discovering these devices:

General Electric PCB Fluorescent lamp ballast

As this was made in Schenectady, NY, it is almost certainly original to the building. According to the EPA website, each one of these ballasts contains a capacitor with 3-4 ounces of PCB. There were 16 total fixtures, each with one ballast. The ballasts were removed and the fluorescent lamps were replaced with T8 120 Volt LED units. Any defective bi-pin lamp holders were replaced at the same time.

The danger posed by PCBs is minimal unless they leak or there is a fire. Partially burned PCB results in the production of dioxins, which are really bad. The old GE ballasts were properly disposed of.

The PCB capacitors and transformers were removed from the site many years ago. Other things that might have PCBs; are caulking and window glazing compounds.

That made me think; what else is around here? Several things came to mind.

Fluorescent bulbs waiting for disposal

The fluorescent bulbs themselves contain a small amount of mercury. This is not a problem unless the bulb breaks. If the bulb does break, the EPA recommends leaving the room for 15-20 minutes. Then carefully clean up the broken glass and place it in a plastic bag. Smaller particles can be cleaned up with the sticky side of masking tape or duct tape. Do not use a regular vacuum to clean up the broken glass, this will spray mercury around the room.

The fluorescent bulbs should be disposed of as hazardous waste.

Hot water pipes with lagging (insulation)

Asbestos lagging on the hot water/heating pipes. As long as the lagging is intact, there is no problem. All of the pipe lagging in this building is intact and in good shape. With asbestos, the problems start when things are disturbed. Any type of work on those pipes will require a mitigation plan. Something to keep in mind if there are any building modifications being planned.

If old-style pipe lagging like this is falling off or has been partially removed, it is best to have an asbestos survey done. Newer style lagging will be either closed cell foam, open cell foam, or fiberglass insulation with a cardboard cover.

Other things that can have asbestos are floor tiles and siding.

Halon fire supression system

The halon fire suppression system can be hazardous if one is in the building when it discharges. Of course, fire itself is also a hazard. It is something to be aware of if the alarm goes off.

Peeling paint

Since this building was constructed way before 1978, lead paint is likely on the walls. Not a huge problem unless it is chipping off and you accidentally eat the lead paint chips or inhale pulverized lead paint dust. To clean these up, use a vacuum cleaner with a HEPA filter. Alternatively, wear a HEPA filter and use a dustpan and brush. Do not use a regular vacuum cleaner.

If building modification work is being done in areas that may contain lead paint, a properly certified lead paint mitigation contractor should be hired to remove the hazardous material.

None of these situations pose a direct safety threat, however, one should be aware of these potential issues in their work environment.

Part 101, Private Fixed Microwave Service

I have been tasked with installing one of these systems for a sixteen-channel bi-directional STL.  This system was first mentioned here: The 16 channel bi-directional STL system.  As some of you pointed out, the unlicensed 5.8 GHz IP WLAN extension was the weak link in this system.  It was not an interference issue, however, which was creating the problems.  The problem was with layer two transparency in the TCP/IP stack.  Something about those Cambium PTP-250s that the Wheatstone Blade hardware did not like and that created all sorts of noise issues in the audio.   We installed the Wheatstone Edge Routers, which took care of the noise issue at the cost of latency.  It was decided to go ahead and install a licensed link instead of the license-free stuff as a permanent solution.

Thus, a Cambium PTP-820S point-to-point microwave system was purchased and licensed.  The coordination and licensing took about three months to complete.  We also had to make several changes to our network architecture to accommodate the new system.  The PTP-820 series has a mast-mounted radio head, which is the same as the PTP-250 gear.  However, for the new system, we used three different ports on the radio to interface with our other equipment instead of the single port PTP-250 system.  The first is the power port, which takes 48 VDC via a separate power cable instead of POE.  Then there is the traffic port, which uses Multi-Mode fiber.  Finally, there is the management port, which is 1GB Ethernet and the only way to get into the web interface.  The traffic port creates a completely transparent Ethernet bridge, thus eliminating all of the layer two problems previously encountered.  We needed to install fiber transceivers in the Cisco 2900 series switches and get those turned up by the IT wizards in the corporate IT department.

Andrew VLHP-2-11W 11 GHz microwave antenna
Andrew VHLP-2-11W 11 GHz microwave antenna

The radios mount directly to the back of the 24-inch 11 GHz Andrew antenna (VHLP2-11) with a UBR100 interface.  The waveguide from the radios is a little bit deceptive looking, but I tried not to overthink this too much.  I was careful to use the O ring grease and conductive paste exactly where and when specified.  In the end, it all seemed to be right.

Cambium PTP-820S mounted on antenna
Cambium PTP-820S mounted on Andrew antenna

Not wanting to waste time and money, I decided to do a back-to-back test in the conference room to make sure everything worked right and I had adequately familiarized myself with the ins and outs of the web interface on the Cambium PTP-820 radios.  Once that was done, it was time to call the tower company.

Cambium PTP-820S on studio roof
Cambium PTP-820S on studio roof

One side of these is mounted on the studio building roof, which is a leased space.  I posted RF warning signs around the antennas because the system ERP is 57.7 dBm, which translates to 590 watts at 11 GHz.  I don’t want to fry anybody’s insides, that would be bad.  The rooftop installation involved pulling the MM fiber and power cable through a 1 1/4-inch EMT conduit to the roof.  Some running back and forth, but not terrible work.  I used the existing Ethernet cable for the management port.  This will be left disconnected from the switch most of the time.

Cambium PTP-280S 11 GHz licensed microwave mounted on a skirted AM tower
Cambium PTP-280S 11 GHz licensed microwave mounted on a skirted AM tower

The other side is mounted at about 85 feet AGL on a hot AM tower.  I like the use of fiber here, even though the tower is skirted, the AM station runs 5,000 watts during the daytime.  We made sure the power cables and Ethernet cables had lighting protectors at the top of the run near the dish and at the bottom of the tower as well as in the transmitter room rack.  I know this tower gets struck by lightning often as it is the highest point around for miles.

PTP-820S RSL during aiming process
PTP-820S RSL during the aiming process

Aligning the two dishes was a degree of difficulty greater than the 5.8 GHz units.  The path tolerances are very tight, so the dishes on each end needed to be adjusted in small increments until the best signal level was achieved.  The tower crew was experienced with this and they started by panning the dish to the side until the first side lobe was found.  This ensured that the dish was on the main lobe and we were not chasing our tails.  In the end, we achieved a -38 dBm RSL, the path predicted RSL was -36 dBm so close enough.  This means the system has a 25 dB fade margin, which should be more than adequate.  While were aligning the transmitter site dish, a brief snow squall blew through causing a whiteout and the signal to drop by about 2 dB.  It was kind of cool seeing this happen in real-time, however, strangely enough, the tower crew was not impressed by this at all.  Odd fellows, those are.

Currently brushing up on FCC part 101 rules, part C and H.  It is always good to know the regulatory requirements of any system I am responsible for.  As AOIP equipment becomes more mainstream, I see many of these types of installations happening for various clients.

The Isolated Ground

We get requests to install Isolated Ground outlets from time to time, especially with sensitive equipment. TELCO likes to have isolated grounds on their fiber MUX’s.  It can become an issue with branch circuits in split-phase or three-phase services that share the same ground and neutral conductor.  This can lead to a ground loop between neutral and ground, which will create all sorts of havoc in a broadcast facility.

20 amp, 120 volt Isolated Ground Outlet
20 amp, 120 volt, Isolated Ground Outlet

The National Electrical Code covers Isolated Grounds (IG) and sensitive equipment in several sections.  The first is section 250.146(D), which states that the installation of isolated ground receptacles is permitted.   The grounding conductor connected to such receptacles is permitted to pass through one or more panel boards, boxes, conduit bodies, etc without being bonded to them.  However, said panel boards, metallic boxes, conduit bodies, raceway, etc must also be grounded separately.  That means running two ground conductors, usually, the isolated ground conductor is green with a yellow stripe or spiral.

Studio electrical diagram isolated ground
Studio electrical diagram isolated ground

The second is section 640.9(A), which refers to separately derived power systems.  This section deals specifically with balanced power; 60 volts AC to ground.  In such cases, a separate ground conductor is allowed as outlined in section 250.146(D) and in 647.6(B), which states that the grounding buss should be connected to the grounded conductor on the line side of the separately derived systems disconnecting means.

Other sections of the NEC that may apply to broadcast radio and television facilities:

  • Article 455, Phase converters (rotary phase converters)
  • Article 480, Storage batteries (UPS)
  • Article 520, Theaters, Audience Areas of Motion picture and Television studios, Performance areas, and similar locations
  • Article 640, Audio signal processing, Amplification and Reproduction Equipment (Audio wiring)
  • Article 645, Information Technology Equipment (computer equipment and network wiring)
  • Article 647, Sensitive Electronics Equipment (balanced power 60 volts to ground)
  • Article 702, Optional Standby systems (generators)
  • Article 770, Fiber optic cables
  • Article 810, Radio and Television Equipment (antennas, towers, and grounding)
  • Article 820, Cable TV (CATV)
  • Article 830, Network-powered broadband communications systems (power over ethernet)

If interested, I can do articles on these sections as well.