How Do 540 XEWA and CBK Co-Exist?

[Gregg]

On a separate thread, we were discussing Mexican stations that operate with more than 50,000 watts at night. One of them is 540 XEWA San Luis Potosi, powered at 150,000 watts day and night.

That leads me to wonder how XEWA co-exists with 540 CBK Watrous-Regina. Is 540 XEWA a Class I-A? If so, how does 540 CBK get to run 50,000 watts non-directional as well? Stations that share a frequency with a clear channel I-A have to use a directional antenna to protect them, even to this day. The only exception was 1070 KNX LA and CBA Moncton, which were on totally opposite ends of the continent. They were both 50,000 watt non-directional I-B stations. All other clear channel frequencies have only one non-directional full-power station.

XEWA and CBK aren't that far apart. San Luis Potosi is about 2200 miles from Regina, closer than Mexico City is. On other postings, I've read that CBK is audible day and night in Montana, the Dakotas and Minnesota, it's so powerful.

Then factor in how far stations so low on the dial travel. In the NYC area, 540 WLIE Long Island runs with 2500 watts by day. But even when it was around 500 watts it could be heard in the daytime as far south as Princeton NJ and as far north as Hartford CT. Can you imagine if a station at 540 has 50 kw or even 150 kw?


Gregg
[email protected]

 

[mimo]

540 is a clear for BOTH Mexico and Canada. Interestingly, XEWA comes in right where CBK fades at night. In Iowa where there is signal overlap, it's easy to separate the 2 signals as they come from different directions roughly 90 degrees from each other. One being northwest the other being southwest. It seemed to me that neither interferes with each other's general nightime service areas very much at all.

 

[davideduardo]

If so, how does 540 CBK get to run 50,000 watts non-directional as well? Stations that share a frequency with a clear channel I-A have to use a directional antenna to protect them, even to this day. The only exception was 1070 KNX LA and CBA Moncton, which were on totally opposite ends of the continent. They were both 50,000 watt non-directional I-B stations. All other clear channel frequencies have only one non-directional full-power station.

540 was a calculated exception, where Mexico got to share 540 with Canada in a post-NARBA politically laden addition in the 50's. Mexico had raised fairness issues about not getting enough clears, and they mentioned that Canada, with a lower population, got more.

But we have/had non-DAs in Mexico on 940 and 730, too.

And 150 kw XELO and 500 kw PJB existed, and the 100 kw Caracas station shared 750 with Atlanta. HRVW had 50 kw at San Pedro Sula, sharing with WSM. The difference is that Canada, the US and Mexico have a treaty, and the Netherlands Antilles, Honduras, Venezuela and the US have none.

 

[davideduardo]

Here is a fascinating news item from 1948 about how the clear channels worked to keep all interference off each frequency....

http://www.americanradiohistory.com/Archive-BC-IDX/46-OCR/1946-03-11-BC-0079.pdf#search="kfi"

This is about KFI objecting to Cuba's use of 640.

 

[Tim from Springfield IL]

540 is a clear for BOTH Mexico and Canada. Interestingly, XEWA comes in right where CBK fades at night. In Iowa where there is signal overlap, it's easy to separate the 2 signals as they come from different directions roughly 90 degrees from each other. One being northwest the other being southwest. It seemed to me that neither interferes with each other's general nightime service areas very much at all.

Alas, but the nighttime signal of KWMT-540 in Fort Dodge can in western and central Iowa (but KWMT is nulled to the north primarily to protect CBK):

http://radio-locator.com/cgi-bin/pat?call=KWMT&service=AM&status=L&hours=N

 

[davideduardo]

Alas, but the nighttime signal of KWMT-540 in Fort Dodge can in western and central Iowa (but KWMT is nulled to the north primarily to protect CBK):

http://radio-locator.com/cgi-bin/pat?call=KWMT&service=AM&status=L&hours=N

Unfortunately the radio-locator maps don't indicate what is called the night interference free contour. In the case of most newer night operations (with "new" meaning "post W.W. II) the area where interference from other stations may be objectionable is waaaay inside the inner red contour on radio-locator.

Using one I know, KTNQ in LA, the usable night coverage is nearly half-way inside the red contour at night; the rest of the area is outside the free-from-other-station-interference zone.

As has often been said, someone wants a night signal so badly they will settle for a very bad night signal.

 

[cyberdad]

Alas, but the nighttime signal of KWMT-540 in Fort Dodge can in western and central Iowa (but KWMT is nulled to the north primarily to protect CBK):

I'm in Des Moines tonight. A quick check of 540 yields a decent (but non-competitive) signal from KWMT, with CBK underneath. No XEWA, but my hotel room on the top floor of the West Des Moines Marriott is hardly an ideal location (although my room is pretty much noise free).

Agree 100% with David that the red lines on Radio-Locator do NOT always represent usable nighttime coverage area.

 

[Schroedingers Cat]

Inner contour on R-L is 2.5 mV/m. That was the defined NIF protection level of a Class III-A station back in the day. A III-B was protected to the 4 mV/m. The rules have changed for skywave computation and NIF computation, but few stations, even the former III-As, are as low as 2.5 mV/m. Many are above 25 mV/m. There's one station NIF that is around 100 mV/m, meaning a 5 mV/m signal interferes 10% of the time. In that case, it's probably one high power station that interferes.

 

[jd]

There's one station NIF that is around 100 mV/m, meaning a 5 mV/m signal interferes 10% of the time. In that case, it's probably one high power station that interferes.

You might remember that WADK 1540 Newport RI had an application to add night service a few years ago with 5kW (originally proposed with an incredible 20kW). Their calculated NIF was 95.3mV/m, with the sole contributor being WDCD Albany. Despite that, and the fact that the station would cover only around 80% of Newport, the FCC actually approved the application. But WADK is still a daytimer; the CP expired back in 2007.

 

[pianoplayer88key]

I'm in Des Moines tonight. A quick check of 540 yields a decent (but non-competitive) signal from KWMT, with CBK underneath. No XEWA, but my hotel room on the top floor of the West Des Moines Marriott is hardly an ideal location (although my room is pretty much noise free).

Agree 100% with David that the red lines on Radio-Locator do NOT always represent usable nighttime coverage area.

Nor, in my opinion, do the blue lines indicate the limit of daytime coverage. I've been able, in low noise areas (and/or far enough in frequency from local transmitters), to hear stations well outside the blue line in the daytime using only a portable's built-in ferrite antenna.

 

[cyberdad]

Nor, in my opinion, do the blue lines indicate the limit of daytime coverage. I've been able, in low noise areas (and/or far enough in frequency from local transmitters), to hear stations well outside the blue line in the daytime using only a portable's built-in ferrite antenna.

Also agree. Absolutely.

 

[Schroedingers Cat]

There's one station NIF that is around 100 mV/m, meaning a 5 mV/m signal interferes 10% of the time. In that case, it's probably one high power station that interferes.

You might remember that WADK 1540 Newport RI had an application to add night service a few years ago with 5kW (originally proposed with an incredible 20kW). Their calculated NIF was 95.3mV/m, with the sole contributor being WDCD Albany. Despite that, and the fact that the station would cover only around 80% of Newport, the FCC actually approved the application. But WADK is still a daytimer; the CP expired back in 2007.

I couldn't remember what station it was. There have been a few like that. More than likely, it required quite a number of towers to protect WDCD (WPTR to us oldtimers), KXEL, and CHIN. 80% is all that is needed, but there are plenty of applications that require a city of license change because they can't get the 80% coverage.

Somtimes a single contributor is more annoying than multiple contributors like Class Cs/Class IVs, because you can hear the interfering signal audio clearly in the background.

 

[jd]

As complex as it might have appeared they proposed using just three towers. You're right about KXEL, which had to be addressed with a curative amendment. And yes, I know about the 80% portion of the rules, but the wording wasn't right. Instead, I probably should have emphasized that WADK would have struggled to ensure that amount of population coverage. Then again, we'll never know how it might have worked out (or not).

 

[Schroedingers Cat]

Usually, to get an interfering signal of 5 mV/m 10% skywave, you need a 50 kW directional station with a maximum nearly in that direction. The former Class I-As are almost all nondirectional, and use half wave plus towers that cut down the skywave close in at high elevation angles where the maximum skywave naturally occurs. Most of the former I-Bs are directional, as are the former Class II-Bs and the new powerful former Class IIIs.

 

[cyberdad]

A little update from the road trip I've been on this week, which included a big chunk of I-35. I spent nights in each of the following....

Des Moines: KWMT dominant on 540, but CBK audible.

Kansas City: CBK dominant, but other unidentifiable stuff in the background.

Dallas: I thought I had XEWA, but it turned out to be a semi-local 540 broadcasting in Spanish.

Austin: Hotel not good for DXing. I'm hearing something in Spanish, but very weak due to the steel/concrete structure

Tonight I'm in Houston. What I assume is XEWA is on top. Talk show in Spanish with female host. Other Spanish underneath.

 

[radioman148]

Thanks for your report Cyberdad. I'm always interested in hearing about what you're hearing on the road.

 

[boiseengineer]

Little ol' KNAK Delta UT is just audible daytime in Boise.

 

[cyberdad]

Thanks for your report Cyberdad. I'm always interested in hearing about what you're hearing on the road.

Thanks, Radioman. I'm scheduled to go to Columbia, SC the week after T-Day. There is, however, a possibility that I'll get out of it. Obviously, if I go I'll post anything of interest.

One thing you and the other Chicago area guys might find interesting... Monday morning just after sunrise in Kansas City. Roughly 7:30-8am. WMVP was roaring in with a monster signal. Obviously on day pattern, but I've never heard them that strong that far west. In fact, I don't have any memory of having heard them in Kansas City at all....and I've been going there on a fairly regular basis off and on for about 30 years.

 

[Schroedingers Cat]

WMVP has a dogleg three tower array now, withdifferent parameters. The day pattern is two towers, but those parameters may be different also. They have also been operating STA at times from the WLS tower when they worked on the new WMVP array, but I don't know if it is operating that way now. I can't remember whether they have an auxiliary at the WLS site.

 

[rbrucecarter5]

Very strong patterns to the South in Houston tonight. I doubt CBK makes it in here very often, but definitely not tonight. I can't even get WBAP or WSB the pattern is so strong South! Spanish language obliterating WBAP was a shock.

In other news, Algeria is underneath Havana on 530/531. But in Houston the two are the same direction so it is impossible to null one to get the other. Very strong 1 kHz heterodyne as well.