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AM Daytime And CH NW Straits Area Of Michigan

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Rich F.
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Re: AM Daytime And CH NW Straits Area Of Michigan

Post by Rich F. » Fri Oct 23, 2020 4:48 am

Below are some observations based on the latest posts in this thread by others ...
  • The 0.5 mV/m contour on the "Neilsen" map I posted appears to be drawn there by a source other than the the Chief Engineer of WJR. But I doubt that the Neilsen data shown there is incorrect for that time period.
  • The WJR coverage map from the Radio Locator website shows three field contours, described on their website this way: The "local", "distant" and "fringe" lines on the AM maps correspond to the predicted 2.0, 0.5, and 0.15 mV/m contours respectively (of the groundwave propagation signal).
  • The Straits area of Michigan is located about 260 miles away from the transmit site of WJR (Great Circle path). The old M3 conductivity map of the FCC shows 8 mS/m for the entire path length from the WJR antenna to the Straits area.
  • Following is the output data from an old Fortran program I was involved with before I retired, which used a digitized set of the FCC MW propagation field curves vs. path length and soil conductivity. I believe those curves are ~ the same as those used by the FCC to this day. This output data is shown in a primitive way, but with high accuracy.
    Image
  • The Radio Locator map shows about 0.15 mV/m near the Straits, the Fortran output shows about 0.1 mV/m there.
  • There isn't much practical difference between the present-day Radio Locator calculation and that based on the FCC groundwave propagation charts for WJR for a ~260 mile path along 8 mS/m soil conductivity.



    CK-722
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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Fri Oct 23, 2020 8:25 am

    One of Art Vuolo's very first WJR Radioguides, distributed at Big Boy Restaurants statewide circa 1975, had a WJR Coverage Map from a few years later. It is similar to the one Rich posted, but doesn't have the bulge toward the Straits Area with Grayling in the wrong place. I'll see if I can find it online.


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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Fri Oct 23, 2020 8:31 am

    Here's a similar map to the Radioguide map, which was basically monochrome.


    Image
    Last edited by CK-722 on Fri Oct 23, 2020 8:33 am, edited 1 time in total.


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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Fri Oct 23, 2020 8:40 am

    Haven't seen this WCFL Skywave Map before, which came up in my search.

    Image


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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Fri Oct 23, 2020 10:25 am

    Here is a very similar coverage map for WGN.

    Image


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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Fri Oct 23, 2020 10:31 am

    To test the hypothesis that Lake Michigan conductivity exceeds M-3, some engineers with trusty calibrated Potomac AM BC field strength meters, who take care of Grand Traverse Region stations, should go out to Lake Michigan near the Mason Manistee County line and actually measure it where the WGN Map shows the extent of their 0.5 mV/m. Then go up the coast of Lake Michigan and take readings at several points further North and see where the 0.5 mV/m really is.


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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by Turkeytop » Fri Oct 23, 2020 12:18 pm

    CK-722 wrote:
    Fri Oct 23, 2020 10:25 am
    Here is a very similar coverage map for WGN.

    Image

    WGN has a strong signal at night in Florida.


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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Fri Oct 23, 2020 5:13 pm

    WGN 50% Skywave using new skywave model. The predicted 0.5 mV/m 50% Skywave does not go out as far as the old model, where it was assumed to go out about 750 miles. It's also based on a geomagnetic midpoint latitude, which makes a nondirectional signal go better to the South than to the North.

    https://www.fccdata.org/?lang=en&facid=72114
    Last edited by CK-722 on Fri Oct 23, 2020 5:45 pm, edited 1 time in total.


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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by Rich F. » Fri Oct 23, 2020 5:36 pm

    I saw a daytime GW contour map for WGN at that link; is there also a nighttime skywave map there (that I missed)?



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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Fri Oct 23, 2020 5:49 pm

    Rich F. wrote:
    Fri Oct 23, 2020 5:36 pm
    I saw a daytime GW contour map for WGN at that link; is there also a nighttime skywave map there (that I missed)?
    Not that I could find. If we have maps like that in our possession, we should scan them, give ourselves credit like the ARSA site for station music playlist surveys does, and share the scan with David at americanradiohistory.com to archive.

    I did approach Gary Pfeifer, the biggest contributor of music surveys on the ARSA site, about a section for coverage maps. He was going to ask the site manager, but I never heard back.


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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Sat Oct 24, 2020 12:49 am

    WOWO Daytime Coverage Map.

    Image


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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Sat Oct 24, 2020 1:02 am

    Found this looking for other classic Coverage Maps.

    Image


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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Sat Oct 24, 2020 1:14 am

    Image


    Is THAT where they got the idea for the 486-SX?

    Same (x, y, z), different (t)

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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Sat Oct 24, 2020 1:17 am

    WLAC Nashville 50% Skywave.

    Image


    Is THAT where they got the idea for the 486-SX?

    Same (x, y, z), different (t)

    Your bullet missed my trial balloon.

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    Re: AM Daytime And CH NW Straits Area Of Michigan

    Post by CK-722 » Sat Oct 24, 2020 1:20 am

    WGN Groundwave.

    Image


    Is THAT where they got the idea for the 486-SX?

    Same (x, y, z), different (t)

    Your bullet missed my trial balloon.

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