No food or drink in the studio

This is a rule that I always find difficult to enforce.  Since switching into contracting mode, I am often at any particular studio once per week or less.  It seems to me, no matter what signs are posted or what words are spoken, the DJ seems to hear; “It is okay to eat and drink in the studio.”

Of course, with that attitude, the inevitable is bound to happen:

RS-18 Millenium console on/off button membrane
RS-18 Millenium console on/off button membrane

To make things worse, this was spilled on the main mic on/off buttons.  These button membranes come in groups of six and are not inexpensive.  The complaint was “The main mic will not turn off.”  Ah well, I am paid to fix things after all.  The DJ’s are only inconveniencing themselves at this point.

Fixing small problems

This happened recently at an AM station we were doing work for. It seems the modulation monitor was not working when connected to the backup transmitter. A quick check of the RG-58 coax showed that I had the correct cable plugged into the monitor selector relay.  Another check with an ohm meter showed the cable was okay.  Then I looked at the connector on the monitor port of the transmitter and saw this:

BNC connector pin  improperly located
BNC connector pin improperly located

Looks like the pin is too far back in the connector. This is an old style BNC connector with a solder in center pin:

BNC connector center pin
BNC connector solder type center pin

The center pin has a blob of solder on it, preventing it from seating properly in the connector body. I could have lopped it off and applied a new crimp on connector, but my crimp tool was in the car. I didn’t feel like walking all the way through the studio building, out into the parking lot and getting it. Therefore, I used a file and filed off the solder blob then reassembled the connector:

BNC connector
BNC connector

The transmitter was installed in 1986, I think the connector had been like that for a long time.

It may seem like a small detail to have the modulation monitor working on the backup transmitter, however, the modulation monitor is also the air monitor for the studio.  Switching to the backup transmitter but not having a working air monitor would likely have caused confusion and the staff might think they are still off the air.  I know in this day and age, a lot of station do not even have backup transmitters, but when something is available, it should work correctly.

I like my cool network analyzer and all that, but sometimes it is the Mark 1, Mod 0 eyeball that gets the job done.

Repairing the Nautel VS2.5 transmitter

The newish Nautel VS2.5 transmitter installed at WJJR had an RF module failure. This particular model transmitter does not have slide in RF modules as other Nautel transmitters do.  To fix this transmitter, it has to be pulled out of the rack, flipped over and opened from the bottom. The module replacement is very straight forward, there are five solder pads that connect to wires carrying the input, output, power supply and bias voltages.

Nautel VS2.5 transmitter RF modules and combiner
Nautel VS2.5 transmitter RF modules and combiner

The troubleshooting guide gives good instructions on how to check the PA MOSFETS with a DVM. I found that 1/2 of the device in PA1 was bad:

Schematic Diagram, NAPA31
Schematic Diagram, NAPA31

All in all, not a very hard repair. This was under warranty, so a replacement RF pallet was sent to the station without charge. The problem is more about where the transmitter is located:

Killington Mountain, Killington, VT
Killington Mountain, Killington, VT

Killington Peak is the second tallest mountain in Vermont, topping out at 4,235 feet (1,291 meters). In the winter, one can take the chair lift to the top. In the summer, the road is drivable with a four wheel drive. In those in between months, access to the top can be very tricky at best. We had a pretty wet spring this year, so the roads up the mountain are just now becoming passable for vehicles.

Even after reaching the parking lot, there is still a 10 minute walk to the peak, another 200 or so feet up a steep, rocky trail.

Further complicating things, this transmitter is wedged into this little shack, which holds; a BE FM3.5A transmitter (defunct WJJR), a Harris HT3 transmitter (WZRT), an ERI combiner, two racks of equipment (STL’s, Exciters, remote controls, etc) a backup QEI transmitter, an Onan generator transfer switch:

Killington Peak fire tower, WJJR WZRT transmitter building
Killington Peak fire tower, WJJR WZRT transmitter building

Both stations run into this ERI half wave spaced antenna:

WJJR WZRT ERI antenna
WJJR WZRT ERI antenna

It is very tight in this transmitter room. There is a new tower on Killington Peak, which is still under construction. At some point, the plan is to move into the larger building next to the new tower.

Killington Peak tower
Killington Peak tower

On a clear day, the view from the top is spectacular. On this day, the peak was in the clouds, so not so much:

Killington Peak view
Killington Peak view

It is a great site, the HAAT is 2590 feet (790 meters) and the stations carry forever on relatively low power outputs.