WJR vs WTOR Groundwave Signals

[rfry]

...And of course the new WTOR "Toronto" on 770. That overlaps WJR in Canada and over the water.

No doubt about the groundwave interference in Ontario caused by the sidebands of WTOR (770 kHz) to WJR (760 kHz), and vice-versa.

Comparing the groundwave fields of the two in London, ON (about 116 miles from each transmitter site) and assuming 15 mS/m paths for both stations, WJR has about 3 mV/m and WTOR has about 1.5 mV/m.

London, ON is on the 263 degree radial from the WTOR transmitter, and at that bearing their IDF at 1 km is about 1420 mV/m.

WJR has an IDF at 1 km of about 2845 mV/m toward all azimuth bearings.

The fields in London, ON were generated using the FCC groundwave propagation charts for those IDFs, frequencies, and ground conductivity.

The fields from the two in London, and the difference in the IDFs on those bearings both show that WJR radiates about four times as much power toward London as WTOR.

Comparing the groundwave fields of WJR and WTOR in Erie, PA shows 0.64 mV/m for WJR for a 162 mile path, and 0.27 mV/m for WTOR for a 95 mile path. Conductivity assumed to be 8 mS/m in both cases.

Of interest, WJR has about twice the groundwave field in Erie, PA as KDKA, even though KDKA uses a Franklin type antenna, and the KDKA-Erie path length is around 109 miles (about 33% shorter than WJR-Erie).

RF

 

[spunker88]

There is quite a bit of water in the ground path from Detroit to Erie, PA. I know from my local AM dial Lake Ontario certainly helps Toronto stations come in stronger via groundwave.

 

[rfry]

There is quite a bit of water in the ground path from Detroit to Erie, PA. I know from my local AM dial Lake Ontario certainly helps Toronto stations come in stronger via groundwave.

According to the FCC M3 map of ground conductivity in the US, the Great Lakes all have a conductivity of 8 mS/m, which is the value I used in my analysis.

Most of NY state has an M3 conductivity of 4 mS/m, so stations received in Watertown, NY from Toronto would have better groundwave propagation conditions than for those received over most groundwave paths entirely in NY state.

 

[Schroedingers Cat]

However, if you look at the Canadian conductivity map, or an application done for a US station in the FCC database, you will see that Canada considers the conductivity of the Great Lakes on their side of the border to be 10 mS/m.

And here's a study that shows the conductivity of Little Portage Lake that, once you convert uS/m to mS/m, comes out to about 50 mS/m on average.

www.mlswa.org/.../Little Portage 97-05 WQ report.doc

I will continue to look for actual measurements of Great Lakes water.

If that link is not working, try this one from a Petoskey based water quality organization.

http://www.watershedcouncil.org/learn/water terminology/

According to these, the typical conductivity of fresh water inland lakes is 40 mS/m.

 

[Schroedingers Cat]

Actually, their measurements are in uS/cm, not uS/m. I used the correct conversion in my post. One link said sea water was 50000 uS/cm, so just divide by ten to get the more familiar form.

I would like to see what the FCC did to adjust for the fact that water has a dielectric constant of 78 and the groundwave curves are for a dielectric constant of 15.

 

[Schroedingers Cat]

http://ohioseagrant.osu.edu/_documents/publications/CTR/CTR-082.pdf

On Page 26 of the above document, it shows Lake Erie conductivity averaged about 40 mS/m.

 

[rfry]

According to these (links omitted), the typical conductivity of fresh water inland lakes is 40 mS/m.

Just to note that if the Great Lakes had conductivities approaching 40 mS/m, then the measured field intensities from WJR in northeast Ohio would show a pronounced improvement over their field intensities in central Michigan. But this is not shown in the link below.

The WJR field contours in northeast Ohio after crossing Lake Erie are located at about the same distances from the WJR transmitter as those in central Michigan -- which have all-terrain paths.

The paths from WJR toward central Michigan are shown on the FCC M3 map to have a conductivity of 8 mS/m, so it seems reasonable to conclude that the conductivity of paths across Lake Erie must be close to that value as well.

http://i62.photobucket.com/albums/h85/rfry-100/WJRGroundwaveMeasuredCoverage.jpg

RF

 

[Schroedingers Cat]

I wonder where exactly the conductivities are being measured. If it is near the shore, a river, other tributary, or drainage near the shore might explain a near shore increase. Once dispersed, or far enough from shore, the concentration of ions perhaps decreases along with conductivty.

 

[Schroedingers Cat]

http://planning.westchestergov.com/water-stresses/conductivity

Inorganic compounds increase conductivity, organic compounds decrease conductivity.

 

[Schroedingers Cat]

The Lake Erie measurements were made near the shore where there is a nuclear power plant, east of Toledo and north of Oak Harbor. They are close to the other studies done on smaller lakes. I would suspect that all were done close to the shore, where runoff and tributaries may contribute to higher conductivity. Think of it like a beaker of water, and pouring some salt into it. When measuring the conductivity of the water at the top of the glass beaker, there would be an initial spike, and then it would fall off to a value consistent with complete mixing in the whole volume of water. Might explain the WIND signal along the Lake Michigan shoreline, getting a constant source of ionic runoff.