Month: October 2009

Harmonic Filter for BE FM-30T

Another example from my blown-up shit collection, pictures archive:

Burned out harmonic filter, BE FM-30T transmitter
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
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.

AM transmitter site maintenance check list

As promised, here is the AM transmitter site maintenance checklist.  This is for a generic directional AM station with a backup transmitter, generator, and an RF STL.

Broadcast Electronics AM6A transmitter
Broadcast Electronics AM6A transmitter

Usual disclaimers apply.

AM site Maintenance checklist

Weekly Maintenance:

A.  Visit site, Check following:

  1. Check critical transmitter values against last logged value
  2. Check forward/reflected power on main transmitter
  3. Check and reset any overloads
  4. Check signal strength on STL against last logged value
  5. Check generator fuel level
  6. 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:

  1. Do a full multi-meter log, (includes tower phase angles, loop currents), run backup transmitter into dummy load.
  2. Start and run generator for 5 minutes, check block heater, hoses, belts, oil and antifreeze levels
  3. Calibrate remote control meters with transmitter meters, log it*
  4. Check all tower fences for integrity and locked gates*
  5. Complete Items 3, 4 and 5 under weekly maintenance.

Quarterly Maintenance:

C.  Visit site, Check following:

  1. Complete 1 through 5 under monthly maintenance.
  2. Check all air filters, clean or replace as needed.
  3. Check frequencies of all transmitters, STL receiver, and log.
  4. Complete quarterly tower lighting and painting inspection*

Bi-yearly Maintenance:

D.  Visit site, Check Following:

  1. Complete 1 through 5 under quarterly maintenance.
  2. Conduct monitor point readings for all directional antenna patterns*
  3. Check base current readings for day/night towers.  Ratio.*
  4. Clean backup transmitter
  5. Place backup transmitter on air and clean main transmitter.

Yearly Maintenance:

E.  Check all licenses and authorizations for accuracy. Make sure that all renewal cards etc are in public file and are posted at control point.*

F.  Visit site, Check following

  1. Complete 1 through 5 under Bi-yearly maintenance
  2. Equipment performance measurements (NRSC, Harmonics, frequency)*
  3. Complete service of generator
  4. Complete Inspection of towers, check for vertical and plumb, check guy wire tensions, retension as needed.
  5. Check property for anything out of the ordinary
  6. Repair driveway as needed

General maintenance that is completed on an as needed basis

  1. Re-fill fuel generator fuel tank when drops below 50 percent
  2. Empty trash, sweep floors, dust.
  3. Cut/remove vegetation inside tower fences, spray herbicide as needed
  4. Water proof tower fences every 2 years
  5. Paint exterior of building
  6. Replace tower lights*
  7. Paint towers*

*These are FCC inspection items, pay close attention if you do not want a fine.

That is it, a .pdf version of this file can be downloaded here.

BE AM5E power supply problem

This is from my burned-out shit collection, pictures section:

Broadcast Electronics AM5E power supply
Broadcast Electronics AM5E power supply

It is a power supply from a Broadcast Electronics AM5E transmitter.  Here is another view:

Broadcast Electronics AM5E power supply mating connector
Broadcast Electronics AM5E power supply mating connector

As you can see, there was a small fire started in the mating connector for the transmitter wiring harness.  I did not install this unit so I have no way to know for sure what happened, but I suspect that the mating connector was not pushed all the way in during installation.  In this business, really in all engineering fields, it is the little details that will catch up with you.

I know that one of the stations I used to work at had a fire at their electrical service panel at the FM transmitter site after they installed a new transmitter.  This happened after I departed for greener pastures.  In any case, it is very important to torque the connections on any service disconnect or circuit breaker to the panel manufacturer’s specifications.  I also check the lugs every so often with a Fluke 62 mini IR temperature meter. Any loose connections will show up as hot spots, which can be fixed before the fire breaks out.

All current-carrying electrical connections should be double-checked for solid connections before the transmitter is turned on, then check periodically thereafter for heat buildup and or heat damage.

FM transmitter site maintenance check list

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
BE FM20T transmitter

Enjoy!

Weekly Maintenance:

A.  Visit site, Check following:

  1. Check critical transmitter values against last logged value
  2. Check forward/reflected power on main transmitter
  3. Check and reset any overloads
  4. Check generator fuel level
  5. Check the STL signal strength level against last logged value.
  6. 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:

  1. Do a full multi-meter log, run backup transmitter into dummy load.
  2. Check line pressure, Check tank pressure and/or desiccant for water
  3. Start and run generator for 5 minutes, check block heater, hoses, belts, oil and antifreeze levels
  4. Calibrate remote control meters with transmitter meters, log it*
  5. Check the tower fence, be sure it is secure and locked.*
  6. Complete Items 3, 4, and 6 under weekly maintenance.
  7. During summer months, be sure the vegetation is cut around building and tower.

Quarterly Maintenance:

C.  Visit site, Check following:

  1. Complete 1 through 7 under monthly maintenance.
  2. Check all air filters, clean or replace as needed.
  3. Check frequencies of all exciters, STL receivers, TSL transmitters and log.*
  4. Complete quarterly tower lighting and painting inspection

Bi-yearly Maintenance:

D.  Visit site, Check Following:

  1. Complete 1 through 4 under quarterly maintenance.
  2. Clean backup transmitter
  3. 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

  1. Complete 1 through 3 under Bi-yearly maintenance
  2. Complete service of generator
  3. 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
  4. Repair driveway as needed

General maintenance that is completed on an as needed basis:

  1. Tube changes on main/backup transmitter.
  2. Sweep antenna with a spectrum analyzer/return loss bridge to make sure it is on frequency and has sufficient bandwidth to pass FM signal.
  3. Look at FM RF mask with spectrum analyzer, check harmonics for proper attenuation.
  4. Sweep transmission line with a spectrum analyzer/return loss generator.
  5. Re-fill fuel generator fuel tank when drops below 1/2
  6. Empty trash, sweep floors, dust.
  7. Paint exterior of building
  8. Replace tower lights*
  9. 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.