WPON/WCXI harmonics

[k8jd]

Happened to stumble across WCXI's 3rd harmonic this morning , was pretty strong , 5.3 miles from here, measured freq here 3479.990 kHz So checked the 2nd harmonic REAL strong here. Workingback the math, averaging readings etc... fundamental freq would be 1159.9965 KHz.
Checked WPON (same site) and not much harmonic getting here, was on 4379.990 and 2319.993.
Love playing with my new Icom 7300 radio ! Checked It against WWV on all their frequencies and can read out to ONE Hz, and was dead on new and now 6 months later it is STILL dead on.

[Rich F.]

A useful check to see if such harmonics are being produced in the IC7300 receiving environment is to insert a 10 dB r-f attenuator having low SWR(50) across the r-f spectrum being tested into the coax line path from the antenna, at the r-f In/out connector of the IC7300.

Then, if the harmonic values observed are being radiated by the broadcast station under test, those values will drop by 10 dB with the attenuator inserted.* If not, then the receive system may be producing a significant amount of the measured harmonic, itself.

*This assumes that the IC7300 meter is accurately displaying the true values of the r-f voltage at its input terminals, across that spectrum.

[audiophile]

Or try another analog radio.

[k8jd]

Pretty much the same on my TecSun PL880.
Using the internal Attenuator on the iC7300 signal drops as expected !
they are REAL .

[Ben Zonia]

Hypothetically, 80 dB down from 1000 Watts would be .00001 watts, or .00000001 kW radiated.

The field allowed by regulation from a 1/4 wavelength monopole would be SQRT (.00000001) X 308=0.0308 mV/m @ 1 km=30.8 uV/m at 1 km, or 308 uV/m at 328 feet inverse field. A second harmonic would be into a 1/2 wave tower, so it would be 386 mV/m at 328 feet.

[Rich F.]

An important step toward fully and accurately responding to the OP of K8JD would require knowing the GPS coordinates of his receive antenna setup, and its accurate v-pol gain at zero elevation AGL (i.e., Antenna Factor) toward both of those transmit sites, on all sampled frequencies.

[Ben Zonia]

An important step toward fully and accurately responding to the OP of K8JD would require knowing the GPS coordinates of his receive antenna setup, and its accurate v-pol gain at zero elevation AGL (i.e., Antenna Factor) toward both of those transmit sites, on all sampled frequencies.

Not only that, but a reasonably recently calibrated FI Meter would be required for "government work", if you don't want to always compare apples to oranges. The FCC is paring down old meters and getting the FIM-4100/PI-4100, which runs $14000. I don't think they are doing much enforcement these days though, unless it's obvious, and a station complains. The FIM-41 has a second band that goes from 1600 to 5000 kHz, so the 3rd harmonic can be measured except the top of the expanded band.

Some of the ham callsign databases give coordinates for the "home 10-20". fccdata.org has the patterns, and the AM Query can show the distances and azimuth coordinates. Based on radials for WUFL and WDEO proofs, put in 4 mS/m into ground wave graphs, though Winter conditions may cause it to be up somewhat from those measurements. Keep in mind that the harmonic may have a wildly different pattern.