General – Page 62 – Engineering Radio

Module swap guys

Gone is the day when the radio station engineer had to troubleshoot down to the component level, often crawling in and out of transmitters to get at the suspected part. I for one, spent many a long night at a transmitter site chasing some weird combination of symptoms down to the $0.34 1N914 diode in the directional coupler (see previous post about the MW-50).

It is a skill set now mostly confined to manufacturers’ repair departments, for which they charge a pretty penny. Nowadays, the technician simply slides out one module or circuit card and slides in another. If that doesn’t fix it, panic ensues. I know of several class C FM radio stations that are now relying on the computer guy to fix transmitters, because, you know, it’s cheaper.

To be fair, most engineers are contractors and many of those simply do not have the time to troubleshoot to the component level. So, they ship everything back to the factory and then pass the cost on to their client.

Then of course, most circuit boards these days are surface mount systems, which are hard to work on if you don’t have the right tools. Normally an expensive temperature-controlled soldering station is required, as well as a magnifying glass.

All of these things combine to make circuit board work something to be outsourced. Unfortunately, a night spent troubleshooting was often a great learning experience. I have done some of my best work when my back was up against a wall and I was out of options.

I make the attempt to fix things locally unless the transmitter or other item is under warranty or not having a spare/attempting to troubleshoot will take the station off the air. I think it is important to keep abreast of technology and keep my troubleshooting skills up to par. Besides, I find it gratifying that at least I can still fix things.

General Electric BT-25-A

This is one of my favorite old transmitter memories. Back when I landed my first Chief job, I was working for an AM/FM combo. The AM station was a 50,000-watt flame thrower that first went on the air in 1947. The original transmitter, a General Electric BT-25-A was still in service as a backup unit. These pictures are from the last night it operated, December 16, 1993. The bank made us remove all of the PCB transformers and capacitors before they would refinance their loan. Of course that was most of the transmitter, the rest of it was scraped or sold for parts.

This is a long transmitter, GE BT-25-A looking from the control cabinet

The transmitter takes up the entire span of the room. There were eight large cabinets, each with its own stage or section. The stages were connected to each other by a wiring trough in the floor. The transmitter used lead-jacketed cable within and between sections.

IPA stage with "multi-meters" — IPA stage with “multi-meters”

The IPA section had been modified to use 833A tubes. This is where the RF was developed and amplified for the final section. It is in the middle cabinets of the transmitter, the audio and control section being to the left, the PA and PA power supply being to the right.

PA section. Those WL 5891 tubes. — PA section. Those are WL 5891 tubes.

Final section. There were three tubes, only two were in use at any given time. The third tube was a spare which could be quickly placed in service by throwing a knife switch and moving those bars on the back wall around. This picture was taken with filament voltage only, we had to close the door to turn on the PA voltage.

The transmitter was cooled by this blower which faces down into the floor. Concrete duct work carried the air to the various stages of the transmitter. The blower is powered by a 2 1/2 HP motor. There were two blowers, one in use and one in standby. Behind this is an air mixing room and filter room. During the winter time, the transmitter waste heat was used to heat the building by closing a series of ducts and opening other ones.

Modulation transformer and modulation reactor

This is in the transformer vault. The unit to the left is a modulation transformer, it was 7 feet tall. Directly in front is the modulation reactor and just out of the picture to the right is the plate transformers. The plate supply was 480 volts 3 phase. The other piece of green equipment is a hydraulic tube jack, to get the 5891 final and PA tubes out of their sockets.

The transformers were what contained most of the PCBs. The modulation transformer contained about 150 gallons of Pyranol, the GE trade name for their transformer oil. Pyranol contained greater than 750,000 parts per million PCB.

It is a shame we had to kill this transmitter, it sounded wonderful on the air. The day we signed it off, there was nothing like it, not the Mw-50B that replaced it, nor the Nautel ND-50 that replaced the MW-50, nor the DX-50 at the competing station across town.

What a shame.

WBCQ The Planet

File under: What I wish I could do, if I had the money.

Imagine, as an engineer, owning and running your very own radio station. Not just any radio station, but a 50,000-watt flame thrower heard over most of the eastern US. Dude! Only one minor detail, it is a Shortwave station, which, by FCC regulation is only supposed to be listened to outside of the US, hence the official FCC name, International Broadcasting. As I said, minor detail.

Anyway, WBCQ is heard at various times on 5110, 7415, 9330, and 15420 kHz both in and outside of the US. Their full schedule here. Last night I was treated to the Lost Discs radio show, featuring rare tracks not often found or heard anywhere. It sounded like they were having a lot of fun and it was entertaining, which is why I continued to listen for well over an hour. Besides this, they played a cover of one of my favorite songs, Wish you were here, as played by Kris McKay.

I put up the video for the song that was in it, and, no, I don’t know who those grainy people are.

It seems that the owner, Mr. Weiner is a fellow radio engineer and long-time radio enthusiast. He was and still is a strong proponent of radio for the good of the public. Most of his earlier attempts to own radio station fell on the other side of the legal line, being not quite sanctioned by any government authority. At first, he did attempt to obtain a license and was turned down by the FCC, prompting him to write this reply (shamelessly lifted from Wikipedia):

…we went about a year ago … to apply for a license. Our attempt proved quite humorous to your employees, who sent us away with word of “Forget it.” Further investigations showed us why our attempt was then so comical. Licenses were so expensive and hard to get that even small stations were being sold for millions. Broadcasting was reserved for power men.

…We are not disputing, however, your right to assign channels and set aside bands for the prevention of interference. We certainly, however, are disputing your right to reserve broadcasting for the well-to-do only.

So, I applaud Allan Weiner and his never say never attitude. Perhaps one day, I’ll apply for an international broadcasting license and do something similar. I wonder if he gets many RFI complaints from people living around his transmitter site. I once had one from somebody who was receiving the radio station on the outlets in their kitchen. Seems Larry King was not their thing…

A trip to the FM transmitter site

A few pictures from my last trip to one of our FM transmitter sites. This is a mountaintop site, in as much as a medium-sized hill is a mountain around here. This site has a 2.3-mile road through the woods that is almost impassable 3-4 months out of the year.

Previous engineers have walked up the hill with a toolbox. I can say this with all honesty; not me. In the past, they have also rented a helicopter, and used a snowcat, snowmobile, or an ATV with snow tracks. I’d do those things provided they are safe and insured. As I get older (and wiser), I realize that the only person who going to look after my well-being is me.

Anyway, the trip starts here, at the gate:

Then it goes up the hill:

Some sections are worse than others:

Along the way there are some nice views:

City reservior near transmitter site — City reservoir near the transmitter site

Finally, the gate to the tower farm:

There are two digital TV stations, several cell phone carriers, some government two-way gear, some FM translators, Media Flow, and us at this site. There are also some Ham radio repeaters off to the side in another building. All in all, a pretty RF-intense site.

The view from the top:

The reason why we came:

That is a 24-year-old BE FM5B transmitter. The backup is a Gates FM5G, which aren’t we glad we have a solid reliable transmitter selection for such a remote site. Actually, we were supposed to put in a new Nautel V-10 here last year, but the money was spent on computers instead. Oh well, good thing there will be no computer crashes when we go off the air.

A standard maintenance trip consists of meter readings, comparing the reading to the last set of readings, changing the air filters, checking the remote control and calibrating it to the transmitter, checking the tower light sensor, etc.

Normally, the backup transmitter would run into the dummy load, but the backup transmitter no longer works. Parts are not available to fix it, so we operate without a net. One of the previous general managers asked if that keeps me awake at night, to which my answer was no, not at all.