3rd harmonic complaint Harris DX-15

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Jim Sofonia
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3rd harmonic complaint Harris DX-15

Post by Jim Sofonia » Thu Apr 21, 2016 8:17 pm

I put our spectrum analyzer connected to an un-calibrated antenna (short piece of coax and 4 clip leads. I saw the main carrier and junk all over the band. Suspecting the front end of the SA was overloaded I removed all but the un terminated coax. The entire band cleaned up with still a tall carrier at our licensed freq, 1310. There was nothing visible at 3930. I know a more meaningful measurement would be off the tx sample with calibrated filter to attenuate the carrier without affecting the harmonics. The tx site is only 1.2 miles from the complainant site. I suspect he needs to filter out the licensed carrier as the phantom siginal may be generated in the front end of his receiver. Any comments on this?

ChuckG
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Re: 3rd harmonic complaint Harris DX-15

Post by ChuckG » Thu Apr 21, 2016 8:27 pm

the phantom siginal may be generated in the front end of his receiver. Any comments on this?
If the spectrum is clean when you looked at it, the harmonic has to be generated somewhere else. The front end of a receiver 1.2 miles away from a 15kW AM would seem an opportune spot.
Do you have a way to power the SA sitting in their driveway?
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RGORJANCE
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Re: 3rd harmonic complaint Harris DX-15

Post by RGORJANCE » Fri Apr 22, 2016 6:09 am

I had a nearly eye-dentical situation in Sheboygan, WI about 15 years ago with a 21E. I brought the FIM out and couldn't see anything bad on the 3rd harmonic in our main lobe within rOck throwing distance from the array.. I subsequently located very strong re-radiation from power lines on a huge 3 phase run going North/South East of the site. The 3rd went straight North past the house where the ham lived.

I strongly suspect some re-radiation source. If you have a field meter capable of reading the 3rd harmonic frequency, you might be able to locate the source of the problem.........look at power lines.

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Deep Thought
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Re: 3rd harmonic complaint Harris DX-15

Post by Deep Thought » Fri Apr 22, 2016 11:01 am

You might want to check the complainant's rain gutters too. They make nice antennas for things like harmonics generated by corroded gutter joints.
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Re: 3rd harmonic complaint Harris DX-15

Post by Kelly » Fri Apr 22, 2016 11:55 am

Ugh..Been there, several times. In the interest of disclosure, I'm a ham, but will say that ham's are some of the biggest PITAs about this sort of thing, because many think they know it all and there isn't any way they could have a problem in their shack.

I had one instance, where we received a complaint from a ham who threatened to turn us in to the Commission if we didn't fix his reception issues on 20M. He had the attitude: "I am licensed operator by the FCC and so are you, ergo; we're on the same level." The guy was an insufferable tool. After visiting his home using an FIM 41 and spectrum analyzer, showing there isn't anything wrong with my radio station, he went ahead and filed a complaint anyway. Fortunately I documented the Hell out of everything, including his threats and unwillingness to acknowledge his gear may have been the problem.

Come to find out, the front end of his receiver was being opened up by another station that was closer, but he heard my audio in different places on 20M. We spent hours documenting and showing him the situation, and in the end, had to walk away because he wasn't willing to accept the station wasn't at fault.
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Jim Sofonia
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Re: 3rd harmonic complaint Harris DX-15

Post by Jim Sofonia » Fri Apr 22, 2016 12:29 pm

ChuckG wrote:Do you have a way to power the SA sitting in their driveway?
Yes, I have an inverter and have done it before. I'll have to give that a try.
RGORJANCE wrote:I strongly suspect some re-radiation source. If you have a field meter capable of reading the 3rd harmonic frequency, you might be able to locate the source of the problem.........look at power lines. Fossil W5CFB
My FIM only covers the broadcast band. I was at his house, but he wasn't home, but saw his calls on his van in the drive. He is on the shore of a lake, nice new looking home in an old neighborhood with all overhead wires for the utilities, even some old open 3 wire ac feeds. Funny, no sight of any antennas. I'll have to try a portable Rx and get some idea from the s-meter.
He hasn't replied to a few questions I asked about his operation. I'll let you guys know what becomes of this. Thanks.

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Deep Thought
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Re: 3rd harmonic complaint Harris DX-15

Post by Deep Thought » Sat Apr 23, 2016 8:31 am

WTCM wrote:He hasn't replied to a few questions I asked about his operation. I'll let you guys know what becomes of this. Thanks.
As noted above, document the questions with time and date asked and his (lack of) response, along with everything you've done to troubleshoot this. You'll need it if he opts for the nuclear option and just files an FCC complaint.
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Jim Sofonia
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Re: 3rd harmonic complaint Harris DX-15

Post by Jim Sofonia » Sat Apr 23, 2016 8:15 pm

Deep Thought wrote:As noted above, document the questions with time and date asked and his (lack of) response, along with everything you've done to troubleshoot this. You'll need it if he opts for the nuclear option and just files an FCC complaint.
So noted. Thank you. No reply yet.

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