I found this promotional picture in an old NAB conference technical papers book dating to 1969:
RCA TT-30FL promotional picture
So here we see an obviously qualified and appropriately dressed technician gesturing to all the components she is about to install in the transmitter behind her. I wish I worked there. No, wait, I wish I had that transmitter and perhaps this fetching young woman would come and work at my station. Well, hell, I don’t need a TV transmitter, just the woman.
Sigh.
I wonder how many of these rigs RCA sold before the broadcast division went out of business.
By way of reference, the RCA TT-30FL is a VHF television transmitter, 30 KW peak visual power, 7.5 KW peak audio power, air-cooled.
We were notified that the WFAS-AM tower lights were out, thus, it was time to investigate. This problem was easy to find. Upon removing the waterproof cover on the tower light flasher box, I found this:
melted SSAC B-KON tower light flasher, damaged by lightning
As soon as loosened the screws on the cover, I smelled the unmistakable odor of burned electronics and plastic. I disconnected the flasher and covered the photocell, which turned the side markers on. Of course, the top flashing beacon was dark, therefore, it was time to report the outage to the FAA. The nationwide number to report tower light outages is (877) 487-6867. That number is for an automated system, however, eventually, it leads to a live person. Since the new reporting system was established, the only required information is the tower ASRN. From that information, the operator will access a database and have all the required information to issue a NOTAM. In the past, many questions were usually asked; what is the nearest airport, how far away is the airport, how tall is the obstruction, what is the position, etc? Therefore, things have become slightly easier than before.
Once the outage is reported and a NOTAM is issued, the tower owner generally has fifteen days to correct the problem.
Short, but interesting video tour of an FM transmitter site in Germany. The analog transmitters are 10 KW Telefunken solid-state units, 5 main transmitters, and two reserve units into an antenna combiner. At approximately the 35-second mark, the video shows a Rhode & Schartz DAB transmitter. Germany uses DAB+ in band III (174-240 MHz).
It is always interesting to see how others are broadcasting.
One of the issues that I have seen at many transmitter sites is inadequate cooling. Time was, when mostly tube transmitters were in use, a simple fan connected to a thermostat was all that was used to cool most transmitter sites. Even then, however, that setup was lacking for several reasons.
Those reasons are:
The amount of cooling provided was limited by the amount of heat in the outside air. On cool winter days, this is not a problem, but on hot, sticky summer days it could be.
No removal of humidity from the transmitter room was possible. This often leads to excess oxidation, corrosion of metal parts, and so on.
No matter how much filtering was used, bugs, dirt, and other debris were sucked into the fan, making transmitter room cleaning a chore.
With solid-state transmitters, air conditioning is required. Solid-state transmitter devices are far less rugged than tubes when it comes to heat. In a high-heat situation, a tube transmitter will keep running until its control circuits malfunction, or it catches on fire. A solid-state transmitter will crash long before either of those things happen.
Air conditioners should be adequately sized for the heat load plus a little extra. That information can be found in a previous post: A tale of two air conditioners.
As we all know, equipment malfunctions. When an air conditioning system goes bad at a transmitter site, things start to happen fast if there is no backup. That is when a backup cooling fan can save the day. A good rule of thumb for sizing a cooling fan is to exchange the total volume of the transmitter room every two minutes accounting for resistance from louvers and intake openings.
3200 CFM cooling fan, WHUD transmitter site
This fan is connected to a 120-volt contact on a thermostat attached to the ceiling of the transmitter room. The thermostat is set to 90 degrees, which gives a good bit of headroom for the air conditioners to maintain the room temperature while turning the fan on before the room gets too hot. It is also important to monitor the room temperature via remote control. Having an alarm contact connected to the fan thermostat is also a good idea.
There is no such thing as too much backup. Installing a louvered cooling fan affords a little bit of extra insurance.
