From a practical viewpoint, it is easier to achieve "high" r-f bandwidths in transmitters and transmit antenna systems at higher carrier frequencies because the necessary percentage of bandwidth to do it there is reduced.

Back in the 1960s I had a McIntosh MR-55A AM/FM mono-only tuner. The AM section had selectable r-f bandwidth that enabled nearly flat audio response out to 9.5 kHz, and a 10 kHz "whistle filter" to remove the audio heterodyne from adjacent-channel carriers. It was possible to make an instant A-B swi...

Below is a view of the nighttime skywave contours of WOWO and some of their co-channel competitors these days.

CBS ... hobbled WBBM-AM's signal by reducing its power and moving it to a diplex with WSCR, several miles further from the center of Chicago. ... As it turns out, the WSCR tower is a taller and "more efficient" radiator than the one WBBM used before they diplexed with WSCR. The 42 kW nighttime grou...

WYLL should probably also be on the list. But they are 50 kW Night from a second site in Lockport, IL. ... Here is a list of Chicago AM stations showing their nighttime skywave (50%) fields in Mackinaw City, MI. WSCR: 0.73 mV/m WGN: 0.75 " WBBM 0.67 " WLS: 0.72 " WMVP: 1.1 " WYLL: 1.3 " The value s...

ftballfan wrote: ↑

Tue May 12, 2020 3:07 pm

How does WTMJ perform up there?

Mackinaw City is located considerably off the peak of the narrow main lobe of the nighttime pattern of WTMJ. Their nighttime, 50% field in MC is about 0.36 mV/m.

Below are plots showing the nighttime relative fields serving Mackinaw City, MI radiated by WJR, WFDF and WWJ, based on FCC data and methodologies:

Those are the nighttime skywave fields (50%) for all three stations.

1. WWJ 950 50000 watts, Directional to the North. 2. WFDF 910 25000 watts, Directional to the North. 3. WJR 760 50000 watts, Nondirectional. ... Here is a comparison of the 50% nighttime skywave fields from those stations in/near Mackinaw City, MI using FCC data and methodology: WWJ 2.1 mV/m WFDF 2...

... I was trying to find a strong Detroit station that I could hear in the FL Keys, but WJR had a competing signal from Tampa area and the other ones are all directional to the north. :( Yes, there isn't much of a chance for WJR to be heard south of ~Orlando, FL due to the co-channel interference p...

Probably this house was not located near the city center of Lockport, IL, which would put it ~3.5 miles from the WYLL nighttime array on its bearing of about 285°. WYLL radiates less than 100 watts toward that sector. WYLL has a nighttime field intensity of about 16 mV/m in the Lockport ZIP, where W...

RE: WXYT (AM) is quite weak everywhere south of its array near the I-275/I-75 interchange.

Below are plots showing the effective radiated power of WXYT based on their FCC pattern data.

The accurate measurement of radiated e-m field intensities requires a receive antenna with a known "Antenna Factor" for the physical conditions existing when using it to make the measurement. Below are a few comments about this from the National Institute of Standards and Technology in the U.S. http...

Below is a clip from VSoft showing some of the higher day/night AM broadcast field intensities at locations about 10 miles west of Pontiac, Michigan.

Nighttime skip in the Midwest has been abnormal recently. I've noticed that the Class As within 500-600 miles of my location in west central Illinois have been quite noisy — worse than the Class A signals arriving here from the east coast, at the same time.