New Nautel V 7.5 FM transmitter

Behold, I do not work for Clear Channel.  I do not work for Cumulus, or Citadel.  The company I work for is not about to go bankrupt, in fact, we have purchased a brand new FM transmitter for the wretched mountain top transmitter site featured here.

Nautel V 7.5 FM transmitter
Nautel V 7.5 FM transmitter

Am I happy?  Oh yes I am. New transmitter = fewer midnight phone calls thus better quality of life for me and my family.  A solid state Nautel transmitter means fewer unscheduled trips to the transmitter site and better reliability.

As a result of consolidation and smaller engineering departments, almost my entire work day is now scheduled weeks in advance.  One little hiccup in the schedule can throw things off for days, resulting in many apologies, phone calls to reschedule, and general wasted time.

This is a V 7.5 FM transmitter, very likely the last V series transmitter Nautel ever makes.  They have moved on to the NV series.

It is replacing the Broadcast Electronics FM5A, which is 24 years old.  The BE has been a good transmitter, we lost a few rectifier stacks due to lightning over the years, but over all, it has been reliable and easy to repair when problems did arise.  This transmitter will be going into standby service.

The new transmitter, it sounds awesome.

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 straight forward.  When using a field flange, the outer and inner conductors are cut flush.  Both conductors should be de-burred and filed smooth.  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.

FM transmitter site maintenance check list

I developed these check lists for 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 back up 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


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 check list next week.

T-1 outage

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, no format, no staff, no real estate, 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.

TELCO trucks, courtesy of <a href=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 back up, 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 effected.

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.