Paul Thurst – Page 33 – Engineering Radio

AM station downgrade

I have been working on another formerly directional class B AM station, this one is in Rutland, VT. WSYB has been on the air since 1931 with the same call letters serving the east-central part of Vermont. In 1931, it was operating on 1500 kc with 100 watts of power. In March 1941 it moved to 1490 kc with 250 watts before settling, a few months later, on 1380 with 1,000 watts, directional night time protecting CKPC in Brantford, Ontario, Canada.

The transmitter site was first located at 80 West Street (now known as BUS US 4), in Rutland. It was moved to its current Dorr Drive (Formerly Creek Road) location in 1938, when the station was requesting a power upgrade to 250 watts. Whilst cleaning out the old transmitter building, a copy of an operating log, dated December 7, 1945 was discovered in the attic above the transmitter room:

Back from the time when readings were required every 30 minutes.

In 1956, WSYB was allowed 5,000 watts daytime non-directional with 1,000 watts nighttime directional.

At some point in the early 1990s, the original towers were replaced with solid-leg Pirod towers, each 195 feet tall.

After that, things went the way things do; AM steadily declined in favor of FM, local programming was mostly replaced by syndicated satellite stuff, there were several transfers of ownership, etc.

A translator on 100.1 MHz was added in 2016; the two-bay Shively antenna was installed at the top of the South West tower. There is local programming on the station from 6 am to noon on weekdays. There may also be some gardening shows and other such programming on weekends.

The current owner has decided like they have done in other markets, that AM directional antenna systems are a maintenance nightmare, the risk of FCC sanctions are high for an out-of-tolerance antenna array, and the ratings and income from the station do not justify the risk/cost. Thus, non-directional nighttime operation was applied for and granted. The station is now a Class D with 25 ass-kickin’ nighttime watts.

WSYB had a two-tower nighttime antenna system. The tower closest to the building (SW) was also the daytime, non-directional tower and it now holds the FM translator antenna and STL antenna. Thus, it was decided to ground that tower and keep those antennas in service. The far tower (NE), which was the second tower of the nighttime array would become the AM antenna. The nighttime ATU was built for less than 1,000 watts of input power, so several components needed to be upgraded for 5,000-watt operation.

I had available these nice vacuum capacitors that came out of another decommissioned antenna system. The vacuum capacitors are great because the voltage/current ratings are much higher than the mica capacitors that were in the circuit before. You can see black goop where one of the Sangamo mica capacitors on the input leg failed several years ago. These vacuum capacitors are rated at 15 KV and the current rating at 1.38 MHz is probably in the 70-80 amp range. I had to move the base current meter from the former daytime (SW) tower out to the NE tower. The day-night switch was taken out of the circuit. The transmission line to the far tower was replaced with 7/8 inch foam dielectric cable. A slight touch-up of the coil on the input leg of the T network was all that was required to bring it into tune.

The electric lines to the tower have been temporarily disconnected. As soon as they are reconnected, I will vacuum out all the mouse crap and other debris. The ATU building also needs some work sealing it up against the elements.

The tower base impedance is 75 ohms, +j95 making the base current 8.6 amps daytime and 0.58 amps night time.

For me, the magic of radio exists at that boundary between the real objects (towers and antennas) and the ether. The transference of electrical voltages and currents into the magnetosphere is something that still fascinates me to this day. Coupling a 5,000-watt medium wave transmitter to a tower and watching it work is something that I will never grow tired of.

The Gibson Bass Guitar

Back in the days of my early adulthood, I found myself in various situations that were neither familiar nor followed any known script. Thankfully, I seemed to manage those things without getting suckered too badly and/or causing too much trouble for myself or others. Thus, when I was living in a barracks building and one of the other guys asked me to loan him $100.00 until payday, I deferred. Lending money to anyone is fraught with danger and in 1983 or 1984, $100.00 was worth quite a bit more than it is today, especially for a junior enlisted guy like I was at the time. A few hours later, the same fellow approached with a different arrangement; I would lend him $100.00 and he in turn would give me his Bass Guitar to hold onto until he paid me back. I looked at the rather nice Gibson Grabber bass complete with road case and said okay.

Now, this guy took that $100.00 and for some reason that was never clear, stole his roommate’s car that night and went UA. He was arrested a few days later some distance away near the border to another state. He never returned to me my $100.00 and I never returned to him his guitar.

1978 Gibson Grabber Bass Guitar with original hard road case

Over the ensuing years, I have picked this instrument up and fooled around with it from time to time. I even learned how to plunk along with some easier songs like Louie Louie. It was never serious and for the last twenty or so years, it sat unused in the back of a closet. A few days ago, while cleaning up, I noticed the road case sitting there. A little bit of research reveals that it was made in 1978 at the Gibson Guitar factory in Kalamazoo, MI. As it is in good condition with the original case, appears to be worth a bit of money.

I took some time and cleaned it up. One of the pots was a little scratchy, so I cleaned it with a bit of Deoxit. I took the bridge apart and cleaned it, removed the pickguard and pickups, and cleaned those thoroughly.

Being the curious type, I started fooling around with it again. I then found a few Youtube videos on how to play bass. I watched those along with some other learning tools. I began to practice scales. This turns out to be kind of fun. I do remember how to read music, although I would need to brush up on this skill somewhat if I want to become an actual bass player. I purchased a small Fender Amp, a scale chart, and a clip-on tuner and we are off to the races. I wonder how the electric bass translates to a stand-up bass. I could forgo the Rock ‘n Roll experience completely, but if I get good enough, I’d really like to play in a Jazz band. A boy can dream…

Happy New Year!

After a bit of reflection and a few good conversations over the New Year’s Holiday, I decided that I should continue my work on this blog. I would like to thank all those that have stuck by and waited. I have received numerous emails and messages offline, all of which have been read and appreciated.

Since the abrupt stoppage last July, which was absolutely necessary for me, many things have happened within the business. Fortunately, during the hiatus, I was still taking pictures. After sorting through them, here are a few interesting things that happened:

At one of our client’s AM transmitter sites in Albany, NY a 2.6 Million Watt solar system has been installed.

WROW-AM Steel mounting poles on antenna array field

This project required many steel mounting posts to be driven into the ground around the AM towers. I don’t even know how many, but I would hazard a guess of over three hundred. Each one of those mounting posts was hand-dug down a depth of 6-10 inches to look for ground wires. Where ever a ground wire was found, it was moved out of the way before the post was set.

Basically, the solar array covers about 1/2 of the antenna array field. All of the steel mounting hardware is tied into the ground system, making, what I am sure is a pretty large above-ground counterpoise.

View from the south looking north:

Solar Array installed on WROW antenna array, Glenmont, NY

View from the north, outside of the transmitter building, looking south:

Power company interface and disconnect:

Solar Array utility company disconnect, Glenmont, NY

The utility company had to upgrade the transmission lines to the nearest substation to handle the additional power produced by the solar system. All in all, it was a fun project to watch happen.

At a certain studio building, which is over 150 years old, the roof needed to be replaced. This required that the 3.2-meter satellite dish and non-penetrating roof mount be moved out of the way while that section of the roof was worked on.

Dish was ready to move, and all of the concrete ballast was removed and taken down from the roof. The roofing contractors constructed a caddy and the entire dish and mount were slid forward onto the area in front of it. Since the front part of the roof was not reinforced to hold up the satellite dish, we did not ballast the mount and the XDS receivers ran off of the streaming audio for a couple of days until the dish was put back in its original position.

A couple of other studio projects have been underway in various places. Pictures to follow…

One of our clients sold their radio stations to another one of our clients.

There has also been a bankruptcy of a major radio company here in the good ol’ US of A. Something that was not unexpected, however, the ramifications of which are still being decided on in various board rooms. One of the issues as contractors is whether or not we will get paid for our work. All things considered, it could be much worse.

Learned a valuable lesson about mice chewed wires on generator battery chargers. I noticed that the battery charger seemed to be dead, therefore, I reached down to make sure the AC plug was in all the way. A loud pop and flash followed and this was the result:

My hand felt a bit warm for a while. The fourth digit suffered some minor burns. There is at least one guy I know that would be threatening a lawsuit right now. Me, not so much… All of the high voltage stuff we work on; power supplies that can go to 25 KV, and a simple 120 VAC plug is the thing that gets me.

The return of the rotary phase maker.

Rotary phase maker, Kay Industries T-10000-A

Mechanically derived 3rd phase used when the old tube type transmitter cannot be converted to single phase service.

Those are just a few of the things I have been working on. I will generate some posts on current projects underway. Those projects include a 2 KW FM transmitter installation, another studio project, repair work on a Harris Z16HD transmitter, etc

It is good to be back!

The GatesAir FLX-40 transmitter

The GatesAir FLX-40 transmitter is my first liquid cooled transmitter installation. Previously, I have installed an air cooled Nautel NV-40, a V-40 and a couple of BE FM-35T/20T units. The WEBE transmitter site in Bridgeport, Connecticut is an interesting facility.

Smoke Stack, Bridgeport Energy, Bridgeport, CT

This coal fired power plant smoke stack which currently holds up the six bay, half wave spaced Shively antenna. The old BE FM35A transmitters are getting little bit long in the tooth. Thus, we picked one to scrap, the other will be kept for backup service.

Scraping 34 year old BE FM30A transmitter

We saved a whole bunch of parts to keep the other FM35A on the air in backup service.

The power supply cabinet with that 500 pound plate transformer was the last to go.

On second thought, that plate supply transformer is a good spare to have

The FLX-40 came on a large truck. Fortunately, we were able to open the side gate at the power plant and get the truck to the front door of the transmitter building easily. The transmitter consists of two large cabinets, each with two 10 kilowatt power blocks. There is also a pump station and an outdoor heat exchanger.

FLX-40 in place, cabinets bolted together

This transmitter design is based on the Harris digital TV transmitters.

The pump station and heat exchanger are the same systems used for TV transmitters. Liquid cooled units require a bit more planning on the installation end. The coolant piping should have a high spot from which everything else slopes down hill.

I put a 1/4 to 12 inch pitch on everything. Of course, there are several low points, the heat exchanger, pump station and bottom power blocks.

Holding steady at 18 PSI for 24 hours — Holding steady at 16 PSI for 24 hours

After assembling the cooling system, we pressure tested it for 24 hours.

Installation debris in the coolant line strainer

Following that, we flushed the system with distilled water for several hours before we filled it with 40/60 glycol/water mix. Record low temperature in Bridgeport is -7 F (-22 C), thus a 40/60 mix will give protection down to -15 F (-26 C). The more water in the coolant, the better heat transfer capacity it has.

At the highest point in the system, there is a sight glass and an air purge valve

The pump station is controlled by the transmitter, which speeds up the pumps according to how much heat needs to be moved. In turn, the pump station control the fan speed on the heat exchanger outside.

The pump station runs with one motor most of the time. The other pump motor will run in the event of failure or if there is not enough flow through the power blocks. Each of the four power blocks has a flow rate meter on the return line.

Heat Exchanger Fan motor controllers, Variable Frequency Drive modules

Variable Frequency Drive (VFD) fan motor controllers show them running at half speed.

GatesAir 50 KW heat exchanger mounted on concrete pad behind the building. Air flows out from the motor side.

One of several shipping containers with modules and other parts for the FLX-40

As with most things, some assembly required. The RF modules needed to be placed in the power blocks according to their serial numbers on the test data sheet. This insures that the information on the test data sheet matches the installed transmitter configuration. The power combiner between the two cabinets as well as the reject load and directional coupler all need to be installed.

RF modules with large aluminium heat spreaders. Coolant flows through each module.

On the air!

We ran the transmitter for several hours into the antenna yesterday afternoon. The coolant system is still purging air, so we periodically needed to add water/antifreeze to the pump station to keep the pressure between 12-18 PSI. Eventually, the TPO will be 34 KW with the HD carrier(s).

All in all, I would say that this was a fun project. The liquid cooled transmitter had a few extra steps during the installation process, but not too difficult.