[BC] AM Allocation research

[Jeff Glass]

Hello,

Anyone here know how long the channel allocation rules have been around for class C AM stations?

I have done the calculations for existing class C AM stations, and two out of the two pairs of existing stations come up short spaced.

I used the FCC web Java script as well as a couple of Great Circle programs suggested by the membership here. I'm therefore confident that the distances are OK. I also deliberately picked two stations to study that have the same ground conductivity as per FCC map in 73.190, so I don't have to mess around with an Equivalent Distance calculation since the ground conductivity is the same as per the map.

I used actual antenna RMS for the two stations and when that came up close spaced, I used the minimum acceptable RMS of 241 mv/m @ 1 km as per the FCC rules. I then followed 73.37(b) and assumed both stations putting out 250 watts (120.5 mv/m effective field) and still ended up with a short spaced situation.

The geographical spacing comes out to 132 km. The required cochannel spacing is the radius of the .025 mv/m contour plus the radius of the .5 mv/m which comes to 154 km required spacing.

I don't recall there ever being a short-spaced situation with AM class C, do you? My understanding is that these rules are pretty old.

I'm probably making some silly mistake somewhere :-) BTW, the station spacing I'm studying is WGEZ from WZOE on 1490, if you want to follow along.

Thanks,

Jeff Glass
Northern Illinois University