Another example from my blown-up shit collection, pictures archive:
Burned-out harmonic filter, BE FM-30T transmitter
The harmonic filter from a Broadcast Electronics FM-30T. This actually started in the bullet connector to the 3-inch hardline on the output side of the filter.
Burned out 3-inch hard-line section
Again, I did not install this myself, someone else did. Cutting 3-inch hard line is pretty straightforward. When using a field flange, the outer and inner conductors are cut flush. Both conductors should be de-burred and filed smoothly. It only takes a little thing to start an arc with 30 KW of FM power, so once again, attention to detail is key to avoiding these things.
Fortunately, BE sent along replacement parts for the harmonic filter and the line section was replaced.
I developed these checklists for the FM transmitter site based on experience and what needs to be checked, how often it needs to be checked, and what else can go wrong. This checklist is for a generic FM transmitter site with a backup transmitter and an RF STL. Every site is different, so some things on this would likely need to be changed or adapted depending on equipment and other facilities.
BE FM20T transmitter
Enjoy!
Weekly Maintenance:
A. Visit site, Check following:
Check critical transmitter values against last logged value
Check forward/reflected power on main transmitter
Check and reset any overloads
Check generator fuel level
Check the STL signal strength level against last logged value.
General check of building, look in all rooms, inspect for damage from vandalism, Leaking roofs, obvious signs of trouble, take steps to correct.
Monthly Maintenance: B. Visit site, Check following:
Do a full multi-meter log, run backup transmitter into dummy load.
Check line pressure, Check tank pressure and/or desiccant for water
Start and run generator for 5 minutes, check block heater, hoses, belts, oil and antifreeze levels
Calibrate remote control meters with transmitter meters, log it*
Check the tower fence, be sure it is secure and locked.*
Complete Items 3, 4, and 6 under weekly maintenance.
During summer months, be sure the vegetation is cut around building and tower.
Quarterly Maintenance:
C. Visit site, Check following:
Complete 1 through 7 under monthly maintenance.
Check all air filters, clean or replace as needed.
Check frequencies of all exciters, STL receivers, TSL transmitters and log.*
Complete quarterly tower lighting and painting inspection
Bi-yearly Maintenance:
D. Visit site, Check Following:
Complete 1 through 4 under quarterly maintenance.
Clean backup transmitter
Place backup transmitter on air and clean main transmitter.
Yearly Maintenance:
E. Check all licenses and authorizations for accuracy, make sure all license renewal cards are posted and placed in the public inspection file.*
F. Visit site, Check following
Complete 1 through 3 under Bi-yearly maintenance
Complete service of generator
Complete Inspection of tower and antennas, check concrete tower bases, check guy wire anchors, (grounding, turnbuckle safety cable) check property for anything out of the ordinary
Repair driveway as needed
General maintenance that is completed on an as needed basis:
Tube changes on main/backup transmitter.
Sweep antenna with a spectrum analyzer/return loss bridge to make sure it is on frequency and has sufficient bandwidth to pass FM signal.
Look at FM RF mask with spectrum analyzer, check harmonics for proper attenuation.
Sweep transmission line with a spectrum analyzer/return loss generator.
Re-fill fuel generator fuel tank when drops below 1/2
Empty trash, sweep floors, dust.
Paint exterior of building
Replace tower lights*
Paint towers*
*These are FCC inspection items, pay close attention if you do not want a fine.
The .pdf version can be downloaded here. I’ll to an AM directional checklist next week.
One of our stations relies on a T-1 (DS-1) to relay audio from the studio to the transmitter site (STL). This station started as a piece of paper, with no format, no staff, no real estate, and no studio equipment. There was a transmitter and an antenna installed on a leased tower site.
That being said, corners were forcibly cut. Instead of installing a microwave STL system, a T-1 was ordered because we had a T-1 multiplexor. Fast forward several years… The station is now successful, making a decent amount of money and having a popular format.
The station has two T-1 circuits on different cables with an automatic switcher. Yesterday afternoon, the inevitable happened, both T-1s went out, along with most of the other TELCO circuits in the surrounding area. A construction crew cut two 3600-pair cables a mile down the road. The TELCO is racing to restore the service to all of the tenants on that tower by rigging a temporary aerial cable.
Now the mad scramble ensues with conflicting requirements from the wacky program director. Screw it, I grabbed one of the AudioVault express machines and took it to the transmitter site. They are back on the air with a radio station in a box playing music until the T-1 gets fixed.
This site has had numerous problems since we have owned it. In the 5 years since we launched the format, there have been six T-1 outages longer than 24 hours. For backup, we have tried an ISDN line, a 3G wireless card in a computer, and a second T-1 circuit. None of these have proved reliable as most circuit outages involved a cable cut, and multiple circuits were affected.
The real solution is a microwave STL, either a conventional 950 mHz system or a 2.4 or 5.8 gHz last mile system. Either would work better than what we have now. Station ownership, they don’t want to hear it.
Update: This took until Friday, September 4th to repair, for a total outage of 9 days, 2 hours, and 26 minutes. During that time, the station remained on the air with the AudioVault server at the transmitter site and the program director updating it twice per day with voice tracks and commercials.
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:
Gate to transmitter road
Then it goes up the hill:
Transmitter site access road
Some sections are worse than others:
washed out road
Along the way there are some nice views:
City reservoir near the transmitter site
Finally, the gate to the tower farm:
Access gate to transmitter site
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:
view looking north
The reason why we came:
Transmitter room
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.
