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AM Frequency of the Week: 900

cyberdad said:
Re: XEW. My money would be on 60.
Click to expand...
Texted a friend in Mexico City and he is quite sure that they re-licensed for 100 kw so as to not leave rural areas unserved, but are running 60 kw only.

Mexico has certain requirements when a service is abandoned that don't allow denial of service to rural areas. That is why 540 in SLP is still on, as going FM only prevents a lot of little rural areas to lose their only service.
 
radioman148 said:
I'm trying to figure out why XEW is virtually non existent in the Chicago area even in the winter. It was a pretty easy catch years ago. I wouldn't think it's just the lower power. Is it the transmitter location?
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I have a theory about that. It used to be there were no stations operating in the US at Night on 900 and other Mexico I-A Channels. Now there are numerous stations operating nondirectionally on the channels, like a Class IV channel. This causes a general increase in the amount of interfence on the channel. This blots out the weak signals from what remains of the superpower I-A signals in most openings.
 
Schroedingers Cat said:
Here is the description of the old WFRO 900 facility. 500 watts Day, 287 watts Night. Blanket Nighttime authorization automatically made it Class B because it was over 250 watts. The Cavell Mertz site shows the tower placement diagram and pattern.


FCCInfo Results

FCC Info is a Radio and Television Station Search Engine provided by Cavell, Mertz & Associates, Inc.
fccinfo.com
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Very interesting. I had forgotten about their night authorization.
 
Schroedingers Cat said:
I have a theory about that. It used to be there were no stations operating in the US at Night on 900 and other Mexico I-A Channels. Now there are numerous stations operating nondirectionally on the channels, like a Class IV channel. This causes a general increase in the amount of interfence on the channel. This blots out the weak signals from what remains of the superpower I-A signals in most opening
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A very likely explanation.
 
The only exemptions for stations to operate at Night on the Mexico I-As ended up on WHN 1050 50 kW DA, and WGAR 1220 50 kW DA. If you read the footnotes on the NAB Engineering Handbook sites, there were further restrictions on both the Canadian and Mexican Clear Channels. Near the border, within a certain radius, Daytime stations were normally only allowed 1000 watts. Since the next level up was 5000 watts, the Agreement negotiators had to approve that, even if the 5 uV/m contour didn't cross the border. There used to be a 1 1/2 Hour Morning and Evening hour Critical Hours restriction on the Canadian Clear Channels, not sure about Mexico. I haven't seen any applications that had that exhibit recently, so I'm not sure if it still exists.

See pages 1-9 to 1-12 for the treaties as they stood in 1960, when a lot of stations were being authorized.

 
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All of the US stations on the Mexico Class I-A Channels are still generally limited to 500 watts Night. There were negotiations to increase the limit to 1000 watts Night, but some kerfuffle about NAFTA back in the 1980s put the brakes on that, and it really hasn't changed. I think they have to have some indefinite lengthy negotiations to do it in certain cases.
 
kevtronics said:
Is there any other 50 kW station with as crazy of a nighttime skywave pattern as CHML?


And were the lobes specifically aimed at NYC & Philly, Pittsburgh, and Minneapolis, or was that just happenstance? It looks like even Bermuda may get good nighttime reception of CHML.
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Probably not many, but the skywaves are not properly displayed on fccdata.org and similar software. It is not properly displayed due to software limitations. That appears to be because there are large arcs where there is NO siginifcant skywave, and it just "connects the dots" to arc to the next lobe, making it appear very strange. As I said in other posts, CHML has the about longest span of directional antennas of any station. According to the late great John Kraus, the gain of a widely spaced by wavelength broadside array is greater than a smaller array. But the horizontal RMS of a broadside array is reduced, because a larger amount of power goes above the horizontal. This produces very large IDFs for a very narrow beam width, which the CHML patterns demonstrate.
 
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DavidEduardo said:
Texted a friend in Mexico City and he is quite sure that they re-licensed for 100 kw so as to not leave rural areas unserved, but are running 60 kw only.

Mexico has certain requirements when a service is abandoned that don't allow denial of service to rural areas. That is why 540 in SLP is still on, as going FM only prevents a lot of little rural areas to lose their only service.
Click to expand...
Given that XEW is auidible in states bordering Mexico, I'd guess that 60kw is more than adequate for meeting the Mexican government's riural coverage mandate.

I don't know what the rules are in Canada, but my guess is that the same thinking regarding serving rural areas is what's behind blowtorches like CBK and CBW not migrating to FM. Saskatchewan arguably has Canada's biggest percentage of rural populaton living distantly from cities. So one station with a vast province-wide coverage area is the most efficient and cost-effective way to distribute CBC programmin. More populous provinces, such as Ontario and Quebec, have larger rural populations in terms of raw numbers. But not on a perecentqge basis. And also in closer proximity to larger towns and cities, where local translators and rebroadcasters arw a better solution for province-wide local CBC coverage.
 
kevtronics said:
Is there any other 50 kW station with as crazy of a nighttime skywave pattern as CHML?


And were the lobes specifically aimed at NYC & Philly, Pittsburgh, and Minneapolis, or was that just happenstance? It looks like even Bermuda may get good nighttime reception of CHML.
Click to expand...
I'm not going to try to answer your question, because I don't really know the answer. I will, however, confess that for quite a few years, I was under the impression that CHML was actually running 50kw. I presumed that basked on the strong signal I was repeatedly hearing from CHML on visits to the the Minnesota and Wisconsin north woods.
 
cyberdad said:
Given that XEW is auidible in states bordering Mexico, I'd guess that 60kw is more than adequate for meeting the Mexican government's riural coverage mandate.
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Mexico has certain groundwave day and night contour requirements for AM that are very localized. The concept is to provide service to rural areas that are not near metro areas. So it took a lot of effort for the PRISA / Televisa alliance to get powers on 730, 900 and 940 reduced because of regions, mostly to the south of Mexico City, that are "underserved".
 
cyberdad said:
I'm not going to try to answer your question, because I don't really know the answer. I will, however, confess that for quite a few years, I was under the impression that CHML was actually running 50kw. I presumed that basked on the strong signal I was repeatedly hearing from CHML on visits to the the Minnesota and Wisconsin north woods.
Click to expand...
CHML is 50 kW full-time. They upgraded from 5 kW in 1978:

CHML-AM | History of Canadian Broadcasting

www.broadcasting-history.ca www.broadcasting-history.ca
 
XEW had a good signal in central Indiana in the early 1970's . You could listen to it on pocket transistor radios.
 
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Now that I think about it, I do remember hearing XEW when CHML was off. I also heard XEOY 1000 during WCFL silent periods. I would tune in in the middle of the Night Monday Mornings.
 
Here are some pictures of XEW in 1963, including the three 250 kw transmitters that alternated every 2 hours, every day.


(That's me as a 17-year-old inside one of the transmitters)
 
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