Special Equipment

This year, winter in the Northeast has been relatively tame (so far). As I type this today, the temperature is 60 degrees F. The average high temperature this time of the year is around 40 F. This is an anomaly due to the strong El Nino currently going on in the Pacific Ocean. Next year will likely be closer to normal.

To that end, one of the problems in winter time is access to mountaintop transmitter sites. Several of the sites we maintain can only be accessed with special equipment such as a snowcat, track machine, or snowmobile. We have two or three sites that are cut off from regular vehicular access for 2-4 months per year. One site in particular has water flowing down the access road from a reservoir creating a 200-foot sheet of ice that is not even walkable.

For many years, I have been on the lookout for some special equipment that will allow us to get there safely and back.

Meet the special equipment:

Polaris Ranger 900 with studded tracks
The wheels were replaced with tracks and we added this stud kit for ice
Polaris Ranger 900

Like other such items, there is a cost associated with owning this. In the past, we have paid a two-way radio company that has a larger snow machine for rides to the top of various mountains. That can get pricey if several trips are needed. We will have to figure out a reasonable fuel surcharge for the operation of this track machine.

Co-located common antenna FM stations

One of our clients needs to move to another transmitter site because their lease is expiring at the old site. We have been working on this for several months now. One of the nice features of this project is the panel antenna.

Kathrein 754154 spec sheet

This is installed in a 2-bay 3-around configuration. I don’t see this particular model in the Kathrein catalog anymore, but there are other cross-polarized panel antennas available from them.

Colocated tower

There are many existing services on this tower including two full-power FM stations, a translator, a VHF TV station, numerous cell carriers, etc. Once the installation is done we will have to check carefully for intermodulation.

Honda Track Machine

Winter in the Northeast; there was just enough snow and slush on the access road that the truck could not make it to the top of the hill. This track machine works great. We have added a Polaris Ranger 900 to our inventory (not this machine) for winter access to several of the more difficult transmitter sites. While I do enjoy the occasional walk in the snow, the key word here is occasional.

AAT branch combiner inputs

The three stations are combined into the panel antenna with this rather nice American Amplifier Technologies C-IR-3-3-30K-N branch combiner.

AAT branch combiner output side

The input filters needed a slight adjustment to compensate for the difference between the test load they were tuned to and the actual antenna load they will be running into

Touching up input filters

Two of the transmitters are Broadcast Electronics STX-10 units. We have had good service from the STX-10 which was installed on Mount Beacon a few years ago.

Pair of BE STX-10 transmitters

We are waiting for the Comrex Bric Link III to come back from the factory after their firmware update. They are to be used for the STL. Once they are returned, we should be good to go for site turn-up.

The Rhode Schwarz THR9 transmitter

This is part I of II.

We are in the process of installing an R&S 40 KW liquid-cooled FM transmitter. My first comment; these are well-built units. A quick look at the machining of the parts indicates attention to detail is a key design feature.

As the price of electricity continues to rise, liquid-cooled transmitters for this power level make a lot of sense.

Rhode Schwarz THR9 VHF transmitter

This installation is for Pamal Broadcasting’s WHUD, Peekskill, New York. The site has undergone major upgrades in the last few years. The original 1958 World Tower Utility 80 was replaced a year ago with this Valmont 60X394. Two cell carriers, two translators, and several E911 services are now colocated on the tower.

Valmont 60X394 tower, WHUD Peekskill, NY

The transmitter building is also the original cinder block structure from 1958. When it signed on, the station had a Gates FM5B 5 KW transmitter, an RCA BFA-7, 7-bay horizontally polarized antenna with an ERP of 20 KW. In 1970, that antenna was changed out to a 6-bay circularly polarized ERI with a Harris FM20H transmitter, increasing the ERP to 50 KW. As of now, the station has a 4-bay ERI SHP-4-A-C main antenna and the TPO is 28 KW for the same 50 KW ERP. As the station’s power increased, the building became a little bit smaller than optimal. We needed to rearrange some equipment to gain space for the pump station and step-up transformer.

Pump Station
Heat Exchanger

Rhode Schwarz recommended installing a step-up transformer for the incoming AC mains. The power supplies run most efficiently with 400 volts AC.

Hammond HPS Sentinel K dry core transformer
The Rhode Schwarz RF connection to an ERI switchless combiner

We decided to reuse the ERI switchless combiner left over from the Nautel V-40 installation. There are two Nautel V-10 transmitters with a hybrid combiner that are to be used as a backup. We won’t be running this as a combined transmitter operation, it is a way to save money rather than install a separate 3-inch coax switch. I will build a simple control panel to move the combiner position either all the way up (THR9) or all the way down (V-10s).

2.5 inch core drilled holes for coolant supply and return

Working on the liquid cooling system. I used a core drill to make the supply and return lines to the outdoor heat exchanger. I made sure that I had the shop vac (with a HEPA filter) running while drilling so that all of the concrete dust was captured. That stuff can get everywhere and has a bad tendency to destroy motor bearings. Whatever plant made these blocks in 1958, they used some hard material. It took a while for my masonry drill to get through them.

De-icer controller

Call it climate change or an unfortunate coincidence; we seem to be getting more icy weather in this area. It used to be this region would see one mild event every one or two years. Recently, however, we are getting two to three moderate to severe events per year.

This can create problems for the utility company. Even if the power stays on, the transmitter may not. Excessive ice on the antenna may cause the transmitter to fold back or shut down completely.

We have several clients that have various FM antennas with electric resistance type de-icers. One client has three such stations however I found there were no automatic controllers at any of them. Back in the day, when there were people working at the station, they probably turned the de-icers on and off manually via the remote control. These days, not so much. When we began servicing these facilities, the previous engineer stated that he turned the de-icer breaker on around Thanksgiving and turned it off around Easter. Not terribly efficient.

As a part of moving into a new transmitter building, I began looking for something that would automatically turn the de-icer on when it is precipitating at or close to freezing temperatures and then turn it off after a couple of hours. That would certainly reduce the electric usage for that transmitter site and keep the transmitter happy.

I found this simple snow melt controller:

ETI LCD-8 snow melt controller

This is sold on Amazon for about $570.00. This has an internal relay that can switch 240 volts at 16 amps. However, that 240-volt heating circuit goes up to the top of the tower where the FM antenna is mounted making it vulnerable to lightning damage. I figured an outboard relay switched on and off by this controller was a better way to go. That way, there is an operating indicating lamp and a bypass switch.

De-icer controller relay

Outdoor icing sensor mounted on the ice bridge.

Now, the de-icer stays off most of the time. When it is needed, it comes on automatically and turns off three hours after the precipitation has stopped. Since installing last fall, it has worked well and the station stayed at full power through at least two ice events.

I measured the current on each leg, which was 2.6 amps or 624 watts. That is the same as it was before. A quick calculation, I estimate the number of hours this system was previously energized when the breaker was left on all winter to be roughly 3,400. Thus 3,400 hours x 624 watts = 2112 kWh. These days, our electric rates are running $0.16 to $0.18 per kWh so the total cost would be $380.00 to run continuously. The control system will pay for itself in less than two years.