• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

Do stations use the sunrise/set times shown on FCC AM Query? the whole month?

1

1L6E6VHF

I've been using the FCC's AM Query to find the sunrise and sunset times for an aid in AM BCB DXing. Both in terms of targeting stations around sunrise and sunset (especially at the beginning of the month now, and, probably, the end of the month in the fall) and in trying to use the pattern change time as an indication of that unidentified station I may have heard.

I find, to my surprise, that the sunset/sunrise times heard do not always match the published times (and I'm not talking about stations with PSRA/PSSA).

On Thursday, WWJ seemed to change from daytime to nighttime at 5:00 EST - an hour early. A few days earlier, I was listening to CKLW at 6:00, expecting to hear a pattern change, and did not hear one (CKLW seems to be so strong to the Southwest all night, that I wonder if they are now DA1 on day pattern).

WCAR 1090, spent much of this past fall running their night pattern as a DA1. They have since fixed this problem, but, this morning, there was no change at the posted time 7:30 AM EST, allowing me to listen to WBAL on the East Side of Detroit instead. WCAR did change, popping in loud and clear, but at 7:59:10 instead. (WCAR's power to the East is vastly greater by day, because they protect Class A WBAL at night).

Could that have been some kind of "critical half hour" not shown in the database?
 
I looked up WWJ and WCAR. Both of these stations should make the switch at sunrise and sunset as detailed in their station license. The change over would be on the quarter hour. :00 :15 :30 :45 depending on what is in their license. There is nothing special about their licenses as for critical half hour or similar. I did not check CKLW as I'm not sure of Canadian rules but I suspect they are similar to the FCC.

The FCC averages the sunrise and sunset times for each month to the nearest quarter hour based on the sunrise and sunset time on the 15th of that month.

A station may be late changing due to some kind of technical issue. An example would be if there were tower maintenance personnel on a tower. Don't think you would have that problem with WCAR. You would not want to exceed the FCC mandated safety regs. Equipment failure might delay the change over as well.

A lot of stations have their changes done by automation and if the automation is not properly configured, then the station may be early or late in switching.

My guess is either someone was asleeep at the wheel or the stations in question have a lamptimer problem.
 
The timers that stations use to switch from day to night are usually based on a "clock" in the hardware. Many of those run fast or slow, depending on the hardware. It takes some tweaking of the software to make it stay in sync with actual time. Sometimes power interruptions at the transmitter site can make the automated controller forget the time. Usually there is a battery back up on these devices, but sometimes the back up fails also. Most automated controllers make a phone call to the human operator to tell it that it needs to reset the clock.

I don't know of any station that uses a human anymore to make the switch.
 
When I was a CKLW listener in Western Ohio in their top 40 era, we lost them (sharply reduced signal) at sunset. Once in a while someone at The Big 8 would forget to throw the switch and we'd be very happy...it would at least hold it's own with PJB Bonaire. On the other hand sometimes they wouldn't go back day pattern - in one case they were on DA-N (or possibly low power ND) for a week.
 
When CKLW moved from 1030 to 800 in 1941, they were 5000 watts nondirectional full-time. When they went to 50000 watts, the day and night patterns were designed to protect those directions that needed to be protected to the 5000 watt level to not overlap. This resulted in some areas being nulled to somewhere around the equivalent of 3000 watts, so it did not "clip" the protected contours in off azimuth directions. But 3000 watt nulls are not deep. The maximum in the daytime toward Ohio is somewhere in the same range as a 50000 watt Class I-A nondirectional station inverse field and as I recall, slightly more. I'll look it up.
 
CKLW 230 degree day radial standard pattern IDF=3376 mV/m @ 1 km
CKLW 230 degree night radial standard pattern IDF=497 mV/m @ 1 km
WJR 230 degree (and every azimuth) nondirectional theoretical IDF=2845 mV/m @ 1 km

At one time the FCC had a table of cities which were used to determine the sunrise and sunset times. You can probably find these in some publication available on David's site. All stations in a city used the same sunrise and sunset times. Now, stations as close as a few miles apart in the same city have some months that differ by 15 minutes, including WWJ and WXYT. The new times are determined by the exact coordinates of the transmitter site. With two site operations, I think it is the night site that determines the sunrise and sunset times.

One night someone called Jack Stockton on WCFL and said they were listening to WCFL in California. Jack didn't believe him. I asked the late Charlie Gustafson, once an engineer at the transmitter site in Downers Grove, whether this ever happened to his knowledge. He said that when he was there, the pattern was always changed. The term that he used was that the pattern change was effected "religiously". The older and newer day patterns might allow listeners to hear WCFL in California late at night, but I doubt that it could be heard with any but the most unusual conditions before pattern change in Chicago, or with the night pattern.
 
Last edited:
Schroedingers Cat said:
When CKLW moved from 1030 to 800 in 1941, they were 5000 watts nondirectional full-time. When they went to 50000 watts, the day and night patterns were designed to protect those directions that needed to be protected to the 5000 watt level to not overlap. This resulted in some areas being nulled to somewhere around the equivalent of 3000 watts, so it did not "clip" the protected contours in off azimuth directions. But 3000 watt nulls are not deep. The maximum in the daytime toward Ohio is somewhere in the same range as a 50000 watt Class I-A nondirectional station inverse field and as I recall, slightly more. I'll look it up.
Click to expand...

CK's day pattern has major lobes near dead north, the east-southeast (like towards Cleveland) and to the southwest (towards Toledo), the nulls were shallow and broad, to the northeast, the south-southeast, and the west-northwest. The WNW null did not seem to protect any particular station in that WSGW was not in that null. The station in Rockford, MI on 810 fit into that null long after CKLW took that pattern.

The night pattern has deeper nulls, protecting CBQ in Port Arthur (that station went to FM and that city is now part of Thunder Bay), and a string of 800's in Canada along the 401/Autoroute 20 corridor (also silent keys now). In the night pattern, that lobe to the southwest is gone (or, at least, is supposed to be), to protect XEROK. Thus, they are/were weaker in Toledo at night than during the day (Kahn actually had someone tape CKLW in Toledo at night to demonstrate platform motion in a tape handed out to radio stations).

Growing up near Cadieux and Harper on Detroit's East Side, CKLW was super strong day and night, stronger than WJR.
 
We were about 175 miles from Windsor southwest of Lima. The Big 8 was a blaster on day pattern, much weaker but not gone on night pattern. Add PJB to the mix and at night it was usually a strong PJB, with CKLW well underneath it, and the occasional XEROK
 
"It's Chinatown, Jake."

That about sums up the state of Canadian compliance with day/night parameters these days. What appears on paper and what happens in the field are two very distinct things. Since there are almost no Canadian AMs that still have protection to other Canadian AMs, Industry Canada really doesn't seem to much care what happens after dark (or before.) There's been speculation that IC's lack of concern may be a quiet reaction to the interference generated by US-based IBOC. I wouldn't know.

As for US licensees, do note that the times given on AM Query are in standard time year-round. With respect to WWJ, it may well be that whoever programmed the antenna controller didn't bother accounting for the two days of November that are in EDT, and simply set up November for 5:00.

And I can testify to one station that still uses a human to make the switch: the antenna controller for WXXI 1370 here in Rochester is controlled by the fully-staffed master control at WXXI-TV, where real live MCR operators push the buttons twice a day.
 
CKLW's night pattern was changed several years ago to keep more signal in Canada and send less to the US. Of course 800 is more or less a graveyard mess. While driving toward Sandusky one fall evening, I could barely make out CKLW in Bucyrus, Ohio. In the old top 40 days it would have been listenable.
 
Do you have any information on whether this was an actual pattern change? The way I heard it, it was a rebuild. Usually, the combined requirements of adjacents and cochannels don't allow that much change, particularly considering WSGW blocks much change to the NW. Normally these are in the US Database when they affect US stations, since it is the Region II Database that is used. FM is a different matter, though accuracy is necessary in short spaced border areas. Call letters are hopelessly out of date for sure.
 
I just looked at the Canadian station histories. They did replace the five towers around 2004. The 800 stations in Canada (Thunder Bay and Belleville) that have possibly left the air would not have to be protected. Perhaps the nulls were made more shallow, but they could not increase overlap to US stations that would result if they reduced the daytime array to two or three towers from the Harrow location. I have not noticed any night skywave increase toward Thunder Bay in my travels.

I just looked. CJBQ is still operating on 800 in Belleville.
 
Last edited:
Good Question

I think they do follow the sunrise/sunset times, as dictated by the FCC. In my area, we have three daytime only stations: WNDZ (Portage, IN) 750 AM, WAIT? 850 AM, and WWHN 1510 AM. WNDZ 750 AM signs off precisely at sunset and signs on precisely at sunrise. The other two stations follow general times set by the FCC, and power down during critical hours.
 
In Ottawa after dark you can hear CKLW, CJBQ and CJAD all at once. CJBQ and CKLW both come from the same southwest direction while CJAD is more of an east or east south east direction depending on your location in the metro area. It seems to me that the Canadian stations don't change at the same time all month like in the U.S....instead the pattern changes seem to change every week to be as close as possible to sunset. There can be a HUGE difference between sunset in the beginning of October versus the end. As much as an hour difference.
 
I don't believe these were the same events. I've seen a before and after map of CKLW's night pattern; basically it just didn't jog south in the US as much..more of a straight east pattern. The tower rebuild came later and was unrelated. During the rebuild CKLW ran 5kW non directional day and night from what I understand
 
R. Fry and I noticed that there was an apparent change in the CKLW pattern way back, and that possibly the pattern changed then, based on some really old coverage maps from when they were first 50 kW. But that was many years before the towers were rebuilt. People have said they don't think the pattern is anywhere near what it was in the 1960s to the Northwest, but that is a longstanding observation and not anything recent, and may have to do with development. If the radiation to the north is a lot less, it would seem that it would be more apparent. But if I can get a chance, I'll download the Baserad databases and check to see if it has changed in the Canadian database.
 
Schroedingers Cat said:
R. Fry and I noticed that there was an apparent change in the CKLW pattern way back, and that possibly the pattern changed then, based on some really old coverage maps from when they were first 50 kW. ...
Click to expand...

What I noticed is that the "0.5 mV/m" coverage pattern shown on CKLW's QSL card from the 1970s (in the link below) was suspiciously large toward/near Grand Rapids for their daytime pattern.

WJR (also shown in the link) radiates considerably more power toward Grand Rapids than CKLW, yet CKLW shows their 0.5 mV/m contour to exceed WJR's 0.5 mV/m contour in that sector -- even though WJR's propagation path to G. R. is a little shorter.

Also CKLW's daytime RMS at 1 km is 1888 mV/m compared to 2848 mV/m for WJR.

My guess is that CKLW showed their 0.1 mV/m contour on their QSL card and mistakenly identified it as their 0.5 mV/m contour -- and that their radiation pattern hasn't changed since they first went to 50 kW.

http://s20.postimg.org/n55d73enh/CKLW_WJR_Coverage_Compare.gif
 
Last edited:
Schroedingers Cat said:
... Remember that Windsor is pretty much straight north from Harrow, and the WSGW 0.5 mV/m goes into areas straight north also, and even a little East of North still in the US.
Click to expand...

Could someone please explain the relevance of the daytime ERPs radiated by the CKLW DA located "pretty much straight north from Harrow" on its WNW bearings toward Grand Rapids, MI with the daytime ERPs radiated by WSGW toward its N and NNE bearings ?
 
I said that Windsor is pretty much straight North from Harrow, where CKLW's transmitter is located. It was stated that CKLW had changed patterns. I implied that if they filled the nulls toward vacated Canadian frequencies, it would be right toward WSGW and increase the overlap. Under the treaty, the 0.5 mV/m of CKLW is not supposed to overlap the 0.5 mV/m of WSGW. Subsequent changes are supposed to maintain or improve the overlap situation, not make it worse. It appears that the 5 kW to 50 kW increase of CKLW in 1949 was done without considering WSGW, which came on the air in 1950, but likely it was a situation where both applications were out there simultaneously without knowing what the other was doing, and perhaps they later negotiated to lessen but obviously not eliminate overlap.
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom