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WBBM AM to diplex with WSCR

Technically, would it have been possible for WBBM to diplex with nearby WGN and maintain its 50 kW power?
 
Kemosabe said:
No doubt. I was curious whether it would be possible technically for 720 and 780 to share the same tower.
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Schroedinger's Cat can answer this better than I, but that looks like a situation where such extreme High Q pass and rejection circuits would have to be used that both station's bandwidth would be compromised.

There is a much greater ability today to use software design techniques for tuning networks, so this is a good question.
 
100 kHz is about the practical limit for diplexing. Stations like WGN and WBBM have long been decent sounding stations, and 60 kHz diplexing, though theoretically possible, would result in stations sounding as muddy as you can imagine on a low budget small town station. You'd otherwise have circuits as complex and as comparatively expensive as a McIntosh Tuner, and those even have audio quality issues apparent in narrow mode. You'd also have receiver induced intermodulation products interfereing with other stations, in this case, at 660 kHz and 840 kHz, interfering with WSCR and WAIT.
 
One thing I forgot is that since WBBM and WGN were closer together, x,y,z AND 1/t (f or Greek nu), wavelength and hence antenna height, they would be able to be closer to 50 kW if not 50 kW, than from the WSCR site, which is further away. But the overwhelming diplexing problems would remain for 720 and 780. At one point, WABC 770, WCBS 880, and WNBC 660 were going to TRIPLEX! Can you imagine all the intermod problems with that as well as tight frequency rejection requirements at 110 kHz OR even 220 kHz? That's a topic history for Scott Fybush to report on.
 
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WBBM has filed a license to cover application with FCC for the construction permit which will move their transmitter to the Bloomingdale, Illinois site. As part of the application WBBM also requests a program test authority. At the same time WSCR has filed an application for direct measurement

According to the application WBBM has to vacate their current Itasca site by August 2019, so they are asking FCC to expedite the process.

It looks like the WBBM move to Bloomingdale will be happening very soon.
 
For close to a year, I've noticed a degraded WBBM daytime signal in western lower Michigan (not sure of the nighttime signal). WGN and WSCR have been noticeably stronger than WBBM over this period. In fact, WBBM's daytime signal near Grand Rapids is perhaps no stronger these days than that of the recently relocated 640 WMFN.

I assumed WBBM was already testing from the new site or broadcasting from its longtime site at reduced power via STA. Instead, perhaps the signal degradation is the simply attributable to deferred maintenance.
 
MarkW said:
For close to a year, I've noticed a degraded WBBM daytime signal in western lower Michigan (not sure of the nighttime signal). WGN and WSCR have been noticeably stronger than WBBM over this period. In fact, WBBM's daytime signal near Grand Rapids is perhaps no stronger these days than that of the recently relocated 640 WMFN.

I assumed WBBM was already testing from the new site or broadcasting from its longtime site at reduced power via STA. Instead, perhaps the signal degradation is the simply attributable to deferred maintenance.
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This past winter WBBM's skywave was just as strong as always as they could be regularly heard on SDR's in Hawaii and Europe. Based on your description I'm guessing that perhaps there has already been some construction around their tower degrading the groundwave signal.
 
Mark, it’s further away from us now, too. We’re on the very edge of sensitivity in SE MI. If you go to the Western parts of Flint, Livingston County, or Ann Arbor, the Chicago Five Class As are very noticeably better. I used to listen to WCFL in the Daytime along I-75 West of Flint on the Delco back in the Day. By the time you got to Lansing, WAIT and WIND were received.
 
All I know is 780 during the day for the past year has sounded weaker than ever in the Grand Rapids area. Always used to be on par with WSCR and WGN strength wise. For the past year, it's been no stronger or barely stronger than WLS, WMVP (WCFL) and WMFN.
 
MarkW said:
All I know is 780 during the day for the past year has sounded weaker than ever in the Grand Rapids area. Always used to be on par with WSCR and WGN strength wise. For the past year, it's been no stronger or barely stronger than WLS, WMVP (WCFL) and WMFN.
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Be interesting to find out if it gets better when they move to the WSCR tower.
 
radioman148 said:
Be interesting to find out if it gets better when they move to the WSCR tower.
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MarkW and radioman148, if you look at the contours on the application or both on the fccdata.com site, the contours (2 mV/m is shown on fccdata) pull in quite signifcantly to the NE, due to matching the contours to the South. I don't see how WBBM can be as strong in Michigan as before, unless there was a maintenance issue at the WBBM site.

https://www.fccdata.org/?lang=en&facid=9631
 
I just did some calculations as to the overall situation for WBBM, considering both decreased power and increased radiation efficiency. Its basically like they decreased to 40000 watts Day and moved a few more miles away from the Lakeshore of Chicago, the resort areas of influential Chicago Politicians and Businessmen on the Eastern Shore of Lake Michigan, essentially the de facto Chicago Radio Market, where the Fata Morgana even allows you to view the Chicago Skyline occasionally (WOOD-TV Grand Rapids Meteorologist and Valpo Professor Ellen Bacca did a story with a lot of pictures of this phenomenon, an impressive but almost spooky and surreal depiction of Physics), and the rest of the DXers in Michigan. I don't know if WCFS 105.9 makes up for that completely.

https://twitter.com/ellenbacca/status/988631104839135232

So the truly provable Trump Obstruction is the Trump Tower obstructing Marina City!
 
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The thing that bothers me from a Radio Hobbyist/Radio Historian perspective is that the Day facility with 35 kW falls short of the efficiency of a 50 kW Class I-A/A facility, being 1581 mV/m inverse field at one mile, vs. the Historical Class I-A minimum inverse field efficiency of 1591 mV/m at one mile. The Night 42 kW pretty closely matches most Class I-A/A inverse field.
 
MarkW said:
All I know is 780 during the day for the past year has sounded weaker than ever in the Grand Rapids area. Always used to be on par with WSCR and WGN strength wise. For the past year, it's been no stronger or barely stronger than WLS, WMVP (WCFL) and WMFN.
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WBBM sounds "weaker" than WGN in Chicago, even when you're within visual distance from both TX sites. It's an audio processing issue, not field strength.
 
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