AM Radio discussion. Directional arrays are FUN!
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Ryan Williams wrote: Is there a component to the transmitter that has weakened over the years, causing increased sensitivity to that range?
Have you checked the LTU Z?
Does the audio sound good on the air? I had a contract client many years ago whose BC5 that would occasionally trip off via plate overload when a certain DJ was working. He had very bad mic habits and many words had a strong ess sound on the end. Almost a whistling sound. On the air, the general sound was pretty good but the esses were really ripped up and ragged. Eventually, one of the unipole skirts was damaged by lightning, The tower had a simple series cap with series inductor to wash out the reactance. I found that the cap was bad and the base R was reasonably close to 50 ohms but had a substantial amount of reactance of which I don't recall the sign. Replacing the cap and retuning to 50j0 didn't fix the DJ's annoying ess sound but it did clean up the ess sound on air (nothing like a good clean ess whistle) and stopped the semi-regular PAOL trips.
I don't have a clue to how this would relate to a DX10 "Supply Fault" but is something to keep in mind.
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They may tell you that there is HPF at 60 or 95, but there is plenty of stuff in that file below 20Hz.
I'd take that file, stick in in an audio editor, apply a 70hz or whatever HPF, and replay that through the tx and see if it cuts out then. my suspicion is that it wont.
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Have you checked with GatesAir about DX10 technical bulletins?
It's been a while, but I recall a TSB from Harris about this problem that closely resembles the symptoms you describe. As with the old Harris SX-line of AM transmitters, there were some large blue capacitors that they recommended replacing if during a maintenance inspection, you removed the caps, shook them and listened for things rattling around inside. At the time Harris was offering replacement of all the caps under warranty, but I'm sure that's long over. Our DX-10 was only about 6 months old at the time, so we just replaced the caps while still covered under warranty.
Skype:kellyalford Twitter: @KellyAlford
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The audio sample you supplied has something in it that makes a spike about 12,470 Hz. Chances are that's not making it to the transmitter but I thought I would point that out.
Mike Shane, CBRE