GatesAir contracted me to go to Utica, NY, and do some repair work. WKTV has a ULXTE-50 UHF transmitter which burned out an RF elbow between the UHF combiner in cabinet 1 and the UHF low pass filter for cabinet 1.
Burned-out RF parts3 Port UHF combiner, cover removed for cleaning
There was a bunch of burned debris in the bottom; little bits of melted metal and plastic.
Bottom of UHF combiner
We first vacuumed out as much stuff as we could get. Then used an air compressor to blow the rest out and wiped everything down with clean rags and Windex.
Once that was done, the unit was reassembled and reinstalled in the transmitter. A new elbow, UHF low pass filter, and direction coupler were installed and the transmitter powered back up.
The transmitter site is actually located north and slightly west of Little Falls, NY. The station has been on the air since 1949 and the original GE transmitter is still in the garage. It was difficult to squeeze in and get a look at the transmitter, however, the operator’s console was out in the open:
GE TV control operator’s console, circa 1949
In most places, this would have been thrown out years ago. Now, it is a museum piece. Lots of interesting history in the Wikipedia article, too.
This thing is on the air! There are still some tidying-up things to finish, but it is up and running and sounds great! Here are some pictures of various stages of the installation work:
Making harmonic measurements
The filing cabinets hold manuals and spare parts. There is not a lot of room left in this building, so workspace is at a premium. The filing cabinet on the left needs some Windex and elbow grease.
Main disconnect and conduit to 400-volt transformerOutdoor coolant run3/0 cables, 240-volt input to Hammond HPS Sentinal K transformer
The transformer does not have a neutral reference to the power company. The neutral for the transmitter is derived from the Y output connection. The transformer is also designed to suppress harmonics from non-linear loads like switching power supplies.
Wiring in Square D I line panelSquare D I-line panel rated for 600 volts#2 SOOW cable feeding upper and lower sections of transmitterWiring to disconnect switch on transmitterPump station during system fillHeat exchanger
The wiring on the pump station and heat exchanger needs a little more work. The client wanted to get this on the air as soon as possible because they are in a book and were running at 50% power. Once things calm down a bit, I will put the backup transmitter on for an afternoon and properly dress the wires.
FM modulation analysis
I found this FM modulation analysis function on my spectrum analyzer very useful. The station deviates slightly more than the allocated 75 KHz because of a subcarrier. Overall, it looks good. I measured the harmonics out to the 10th harmonic, most of them were in the noise floor. A few made a slight appearance, but well within FCC tolerances. It is important to document this, as this site has colocated cellular carriers and several E911 services.
FCC part 73.317 states:
(d) Any emission appearing on a frequency removed from the carrier by more than 600 kHz must be attenuated at least 43 + 10 Log10 (Power, in watts) dB below the level of the unmodulated carrier, or 80 dB, whichever is the lesser attenuation.
47CFR 73.317
WHUD fundamentalWHUD fundamental with two Mini-Circuits NHP-200 high pass filters installed
The rest of the harmonics were measured down to -130 dB with the two NHP-200 high-pass filters in the circuit. The 3rd, 4th, 5th, 6th, and 8th harmonics were unmeasurable. The 8th, 9th, and 10th made slight appearances.
WHUD 6th Harmonic, noise floorWHUD 8th harmonic makes a little appearanceMain antenna VSWRAntenna VSWR according to the transmitter directional coupler
Pretty close, the VNA was inserted at a patch panel, which is the last thing before the transmission line leaves the building. The transmitter goes through an ERI switchless combiner, which probably gives it a slightly better load.
Backup antenna SWR
Aside from the finishing details, I need to keep an eye on this for a week or so and top off the Heat Transfer Fluid as needed. It takes a bit of time to get all of the air out of the coolant loop. Another thing; the operating pressure on this is 4 Bar, which is almost 60 PSI. That is higher than other liquid-cooled transmitter systems I have installed before.
We have been really busy this fall working on multiple projects plus the day-to-day tasks. One thing that is always fun; sweeping antennas with a VNA.
In this case, WVIT Hartford, CT needed to repair a leaking transmission line section just below the antenna. To ensure that there would be no problems with return to the air at full power, we did a before sweep and after sweep.
WVIT is the ATSC 3.0 lighthouse station for the Hartford Market. FCCinfo.com has the station listed as ATSC 3.0.
WVIT Tower, Hartford CT
The WVIT tower is 1,100 feet tall and is located on Rattlesnake Mountain near Farmington, CT. Most of the other Hartford TV stations are on the same hill.
Tower crew, hitching a ride to the topSelfie; return loss looks good
It is always interesting to see new places and meet new people. This site has an auxiliary TV studio, which they were using during COVID.
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 StationHeat 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 transformerThe 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.
