August 2012 – Page 2 – Engineering Radio

Out in the Trenches

We fight for every scrap we can get. Sometimes it is not a fair fight. Sometimes the most frustrating thing can be the suits in the corner office. We eat, drink and sleep RF. I have transmitter dirt permanently embedding in my skin. If a thunderstorm passes by, I get my shoes on. Last time I was home during a blizzard, I was in high school, and believe me, that was a long time ago. I’ve been hot, cold, soaking wet, dirty, dusty, hungry and dehydrated all in the same day. Those days can be 8-36 hours long or longer. 240 volts AC is low voltage. Arcs and sparks are a diagnostic tool.

I have clip leaded things, used non-standard parts to get a transmitter back on the air, employed fans on power supplies, filed, cut, bent, tightened, burnished relay contacts, put plate transformers up on a block of wood and crossed my fingers while turned the plate supply on.

My DVM looks like this:

But the best part is, when I walk into a radio station studio, the DJ says “THANK GOD YOU ARE HERE!” I don’t drive a fancy car or wear a fancy suit, but the respect I get is there, even with the young too cool for school guys on the CHR station.

I am a broadcast engineer and I am here to fix your shit.

Now where is that BNC male to N female adaptor

Working with RF can produce some head scratchers. Most transmitter manufactures tend to use the same type of connector for things like exciter RF outputs and composite inputs. Over the years, I have become well stocked with all sorts of BNC and Type N connectors. Satellite equipment uses Type F connectors, Analyzers use Type N, Oscilloscope uses BNC, GPS equipment uses SMA and so on. Except when they don’t. As any good engineer will tell you, when they don’t will be in the middle of the night at some mountain top location while the station is off the air.

After one such incident, I invested in a TPI-3000A adaptor kit. This kit has both the male and female versions of Type N, F, SMA, BNC, TNC, UHF, UHF mini and RCA. They can be mated in any combination using the Universal interface.

On more than one occasion, this little kit has meant the difference of between being back on the air or driving down the mountain to look for an in between series adaptor. A couple of recommended additions include a 7/8″ and 1 5/8″ EIA flange to type N male.

They can be a little pricey, however, I have seen several for sale on eBay for less than $100.00. The key to not loosing the various little parts to this kit is to write a little note detailing the date and location where the adaptor was used, then stuff it in the empty hole. Hopefully, when permanent repairs are made, the adaptor will be retrieved.

Bench Work

Almost every broadcast engineer has to do some type of bench work. While I enjoy a certain amount of bench work, it is not my strong suit. I suppose if I had to do it more often, I would become more proficient. Truth be told, I would rather be at a transmitter site than sitting work chair studying schematic diagrams. It is becoming increasingly difficult to make repairs in the field due to surface mount components. The company I work for has a repair and rework shop where almost anything can be repaired. There is one bench tech, who is pretty proficient with power supplies and RF amplifiers among other things. There is a complete set of test equipment including several Tektronix spectrum analyzers and oscilloscopes.

Likely the most versatile piece of equipment is the IFR 1500 service monitor.

The bench itself is fairly large:

There is also a good stock of spare equipment that can be rented out while repairs are being made:

Repair work includes by is not limited to:

RF repairs; Moseley STL systems, Marti STL and RPU systems, TFT STL systems, most exciters, IPA modules, etc
Transmitter repairs and retuning
Mechanical devices like transmission line dehydrators, transfer switches, etc
Switching and linear power supplies
Uninteruptable power supplies
Remote control equipment; Gentner VRC-2000, Burk ARC16, Moseley MRC-1600
Audio Processing; All Orban equipment, Symetrix, Valley, DBX
Audio equipment; Amplifiers, consoles, reel to reel machines, cassette decks, CD players, DAT machines, etc

I am sure there are many other things that I am leaving out.