[grc] KLLG's Chief Engineer reaches out...

[Lanny Cotler]

GRC’ers:

The following is from KLLG’s Chief Engineer, Roger Wilson. He’s reaching out for tech advice.

Any suggestions?

Thanks,

Lanny


Gentlemen,
       I wanted to take a moment and thank you all for the ideas and suggestions I have been getting from you; via Lanny.
Dealing with the station EAS system took all my time.  Now that I have that working, I can go back to our station signal 97.9 being “heard” on speakers setup on a stage.  Yes, voice & music is clearly heard.  Plus annoying buzz, hum and some “crackling” sound. It happened twice with two different setups.

After I turned off the station transmitter the first time; a light hum was STILL heard.  Bundling together the many (6+) power cords on stage made that hum disappear.
It is most likely that we have two different problems.

Problem #1 ground loop induced AC hum & noise.

the situation in more detail is this. There is a main PG&E drop into the buildin. It comes into the basement. There is only one old ground rod and three different main service drops (3 metered panels.) The station and transmitter are on panel B.  The stage is on panel C.  (Same ground rod in the basement)
the stage is powered from a sub-panel that has ground and neutral tied together.

(main panel > sub-panel > sub-panel(this one has ground/neutral tied together > Stage panel
the audio mixing board is powered from an outlet in the middle of the Hall.  Not on the same circuit as the stage.  probably not even going to the same main panel. (the building is 80+ years old. Post & Knob wiring is live in the attic.)

Solution A
  Talk the Grange (owners of the building) into spending $1000-2000 to have the wiring corrected (And maybe still having ground loops)

Solution B
       I found and bought a Tripp-Lite Isobar power outlet box. (25ft cord, 8 outlets $75) They are supposed to isolate the circuits (while retaining the safety ground.)  I am hoping that it will resolve the bad grounding problems. (By isolating the equipment. Yes, we may need to buy a second one for the mixer sitting in the middle of the Hall.)  A very cheap solution versus rewiring the stage.

Problem #2
      The broadcast antenna is 60 feet up a tower that is about 50 feet from the stage.  So the entire stage is within 100 feet of the 100 Watt antenna output.  Hearing the actual voices and music from the speakers on stage suggests RFI.  Cheap (and/or old) audio equipment seems to be picking up and demodulating the FM signal. Blocking the RF from the mic lines, guitar cables and speaker lines seems required. (No, I cannot tell the bands to buy better equipment.)
Solution C

        I am looking at ferrite beads (and coils) and in-line mic cable RF filters to resolve this.  Any suggestions of what brands you have used (that work).
   Yes, I know that we will need perhaps 3 beads/coils on EACH cable.

Thank you for the ideas and possibilities. When the problems are solved; I will post the real answers that finally worked.

roger wilson
310.245-4821















KLLG-LP ~ 97.9 FM
Lanny Cotler, General Manager
A Project of Little Lake Grange #670
Willits Hometown Radio—Low Power, High Energy
P.O Box 820, Willits, CA 95490
707-367-1812
LANNY at KLLG.ORG
WWW.KLLG.ORG