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.
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
Usual disclaimers apply.
AM site Maintenance checklist
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 signal strength on STL against last logged value
Check generator fuel level
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, (includes tower phase angles, loop currents), run backup transmitter into dummy load.
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 all tower fences for integrity and locked gates*
Complete Items 3, 4 and 5 under weekly maintenance.
Quarterly Maintenance:
C. Visit site, Check following:
Complete 1 through 5 under monthly maintenance.
Check all air filters, clean or replace as needed.
Check frequencies of all transmitters, STL receiver, and log.
Complete quarterly tower lighting and painting inspection*
Bi-yearly Maintenance:
D. Visit site, Check Following:
Complete 1 through 5 under quarterly maintenance.
Conduct monitor point readings for all directional antenna patterns*
Check base current readings for day/night towers. Ratio.*
Clean backup transmitter
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.*
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.
Yesterday, I threw out a transmitter. I know there is probably some radio station out there that may have been able to use a 5 KW FM transmitter but believe me, not that one. There are limits to how much you can help out a fellow broadcaster. Donating an FM transmitter that never really worked right in the first place is counterproductive.
Anyway, to demonstrate that I am not a total heel, here is my favorite brand of transmitter, Nautel:
I like Nautel because they are rugged, reliable, and good-looking. Okay, good-looking is low on the list of transmitter attributes, however, you have to admit, it is good looking. It is also good sounding. The night we switched over from the long-in-the-tooth BE FM30A to the Nautel V-40 I noticed a marked improvement in the station’s sound. It was like somebody switched off the background noise generator.
As the caption states, this is 4 V-10 transmitters combined with an ERI magic T combiner. It is set up so that if any one transmitter fails or reduces power, the magic T combiner automatically adjusts for minimum rejected power, then the SC-1 controller turns up the other three transmitters to maintain the station’s Transmitter Power Output (TPO).
TPO 28 KW
In this case the TPO is 28 KW, which is getting into the semi serious range for an FM station. Nautel has updated their transmitter line, which now consists of the NV series transmitter. The differences mainly have to do with the IPA module/PA module interchangeability (not interchangeable in the V series, fully interchangeable in the NV series) and the “Advanced User Interface.” I don’t know, fancy touch screens are optional on FM transmitters as far as I am concerned. It’s the underlying RF generating sections that I am most concerned about.
Nautel V-40 transmitter
Another view. Just for the useless trivia that is in it, the “V” in these transmitter names stands for “Virtuoso.”
