Do stations use the sunrise/set times shown on FCC AM Query? the whole month?

[gr8oldies]

Remember any coverage map drawn by a sales department is going to be a little over-generous. We used to vacation north of Grand Rapids when I was a kid in the late 60s/early 70s and we lost CKLW well before Grand Rapids and they were barely a whisper in Fremont. CK's night pattern did however, blast in

 

[Schroedingers Cat]

I've seen many coverage maps that were done by consulting engineers. They were accurate based on M-3. I've seen some based on proof of performance data. I've seen ones done by sales departments, and those are pretty obvious-circles, ellipses, etc. The one R. Fry linked is a QSL card signed by Ed Buterbaugh. So I'm surprised if it isn't accurate or mislabeled.

The five tower configuration of CKLW looks like something Carl Smith would have come up with. It's a parallelogram with a fifth tower in the middle.

Within 250 miles or so, the skywave pattern is much different than the groundwave pattern. What you get in Western Michigan is high angle radiation. The lobe to the near north shifts substantially counterclockwise in the night pattern also.

 

[rfry]

I've seen many coverage maps that were done by consulting engineers. ... The one R. Fry linked is a QSL card signed by Ed Buterbaugh. So I'm surprised if it isn't accurate or mislabeled.

Yes, that is surprising. But here is some analysis to support what I wrote about the 0.5 mV/m contour shown on CKLW's card more reasonably applying to their 0.1 mV/m contour. At any rate CKLW's field in/near Grand Rapids could not equal that of WJR.

The length of the path from CKLW's array to the center of metro Grand Rapids is about 148 miles, on a bearing of 295[SUP]o[/SUP]. According to their daytime pattern plot on the FCC website they radiate a field of 811 mV/m at 1 km on that bearing. For 8 mS/m, d.c. 15 earth conductivity (to keep it simple), that field would fall to 0.094 mV/m at the metro center of Grand Rapids.

The length of WJR's path to the center of metro Grand Rapids is about 134 miles, on a bearing of 293[SUP]o[/SUP]. WJR's field at 1 km is 2,848 mV/m (all bearings). For the same earth conductivity, WJR's field would fall to 0.497 mV/m at the metro center of Grand Rapids.

It was interesting to see the ERP it takes on those radials for those fields to be generated ...

WJR: 92,670 watts
CKLW: 7,565 watts

 

[rfry]

Exploring the comparison of CKLW with WJR on their radials toward Grand Rapids, for the parameters shown earlier in this thread...

The 0.5 mV/m field of CKLW would be present about 80.3 miles downrange on their 295[SUP]o[/SUP] radial, which is located about 3 miles SSE of Mason, MI in Ingham county. That location is about 68 miles short of the metro center of Grand Rapids.

The field from WJR at that same point 3 miles SSE of Mason is 3.45 mV/m.