Fastest and Slowest Pattern Changes

[mimo]

I remember Calgary's AM 106's pattern change in the 80's. If you lived in Vancouver and were listening before the pattern change, you'd just hear a slight click and that was it. It was already in clearly and the pattern change only cut out the southeast direction of the pattern to protect KYW. They were/are non directional days. If you were listening in Medicine Hat, Alberta, 3 hours away, you'd hear the station slowly go from listenable to clear as the sunset approached, then it sounded like someone just turned the station off. Pattern change was always lightning fast.

CIWW 1310 here in Ottawa seems to go off for as long as 5 seconds during their change. It's really bad when it happens during a traffic report, as you lose some valuable info. CJAD 800 has a fast one, and when it happens right before the news in the morning you'll hear "stand by as we go to full power".

 

[FreddyE1977]

Some of these posts remind me of a couple of others.

WWVA 1170, night pattern steered STRONGLY away from Tulsa. A pretty easy catch over most of the
eastern half of Ohio during the day, I have been as close to their towers as I-70 between Zanesville and Cambridge
(maybe a one hour drive at most) when the pattern changed and ....poof.....totally disappeared.

WMNY 1360, McKeesport, PA - Strong daytime signal over most of Greater Pittsburgh during the day,
at night they have to shift to a second tower much farther south of the city and power down to 1kW.
They absolutely disappear in my part of town, and reception is VERY spotty in most other parts of Pittsburgh
(until you get down far enough to the southeast to be approaching McKeesport itself). Back when they were
doing local talk as WPTT the 3-6 afternoon host used to joke about the "Low Power Hour" in the winter and
would say things like "for any of you who are still listening after five o'clock..."

 

[317C50KW]

I worked at a 1KW 3 tower DA-2 in the 1970s. The transmitter was a newer Collins 831 and the station engineer mounted the control panel for the Collins right about the turntables (transmitter was in the next room). But the phaser control....it was on the opposite side of the room.
You had to power down the Collins, walk around the console horseshoe, hit the phaser button, walk back around and bring Collins back up.
Then it was a trip back to where the phaser was to check the Potomac antenna monitor and write down the readings. There was usually 15 seconds or so of dead air and obviously it was always done during a record. Today that station is DA-1, thankfully!

i remember hearing a aircheck of KHJ in its prime also playing a "pattern change" announcement.

I'm aware of 4 pattern changes in Dallas currently. KRLD is almost instantaneous, they still run their IBOC too. KTCK is about 2 seconds long, there's a power increase/decrease that goes along with their pattern change. KSKY is also in the 2 second range. KFXR has two sites at different powers and occasionally 1 transmitter won't drop carrier when the other comes on, that can be fun to listen to for a few seconds with the carriers beating against one another!

 

[KR4BD]

Back in the mid-1960's, I lived in Warren, Ohio about 40-50 miles South of Ashtabula's WREO-970 (It's now WFUN). At sunset, they went from 5 KW to 1 KW and also changed patterns. When the change was made, they made this announcement: WREO now pauses for a moment to allow the competition to catch up... In Warren, even with the reduced power, the signal remained somewhat strong as the night pattern favored a N/S direction from Ashtabula. It took a few seconds for the change to be completed as I recall.

 

[ChuckTiller]

1070 KNTH in Houston has 11 towers. 10KW day/5KW night, DA-2. I timed the change at 3 seconds. When you're sitting there on the air, it sounds like an eternity.

 

[swfl]

Back in the mid-1960's, I lived in Warren, Ohio about 40-50 miles South of Ashtabula's WREO-970 (It's now WFUN). At sunset, they went from 5 KW to 1 KW and also changed patterns. When the change was made, they made this announcement: WREO now pauses for a moment to allow the competition to catch up... In Warren, even with the reduced power, the signal remained somewhat strong as the night pattern favored a N/S direction from Ashtabula. It took a few seconds for the change to be completed as I recall.

I remember WREO well. I grew up in Lake County just to the west of Ashtabula County. WREO's day pattern is somewhat oval in shape leaning more east/west as compared to their night pattern which was north/south not to mention the reduced power. During the day WREO was like a solid local in Lake County but come sunset if you were anywhere west of Painesville or so...POOF..GONE.

 

[Schroedingers Cat]

I think a carrier gap in DA-1 stations indicated that they were switching transmitters. Almost all old 5 kW stations had previously been 1 kW and the 5 kW might have had a 1 kW power reduction feature, but they almost always kept the 1 kW transmitter for auxiliary use. Those Sunday night power reductions that had a carrier gap on a DA-1 station may have indicated that work on the 5 kW transmitter would soon begin. There was often a noticeable difference in the audio quality and spectrum of the backup transmitter, and that also depended on how well the transmitter was being maintained. Some stations even had an old, old 250 watt transmitter to use in extreme emergencies. When both the main and auxiliary were down, that 250 watter often had noticeable audio distortion.

 

[charlestondxman]

In our area, we have WTMA going from 5kw to 1kw. They just flick a switch and poof, the change occurs. Since I am only a few miles from the transmitter, there is no noticeable difference.

 

[cyberdad]

Some stations even had an old, old 250 watt transmitter to use in extreme emergencies. When both the main and auxiliary were down, that 250 watter often had noticeable audio distortion.

I worked at a 5kw fulltime station in the '70s that had one of those emergency 250-watt transmitters....complete with it's own "emergency stick"....a former TV tower next to the building that housed our studio and offices. (Both the radio and TV operations had long since moved to remote locations). Anyway, when that backup transmitter needed to be used, I don't know what was worse....the lousy signal or the lousy audio that was on it!

 

[1L6E6VHF]

<snip>
I'm aware of 4 pattern changes in Dallas currently. KRLD is almost instantaneous, they still run their IBOC too. KTCK is about 2 seconds long, there's a power increase/decrease that goes along with their pattern change. KSKY is also in the 2 second range. KFXR has two sites at different powers and occasionally 1 transmitter won't drop carrier when the other comes on, that can be fun to listen to for a few seconds with the carriers beating against one another!

When WWJ built their Newport TL in 1998, they would sometimes test the Newport TL with programming during the day. For several days, sometimes for hours on end, they would be running both the Newport and Oak Park sites simultaneously. The Newport site also had a slight audio delay relative to Oak Park. It was a real mess!

 

[Cincinnati Kid]

I remember when WCKY 1530-AM used to switch to a night-time directional pattern in the period of 1965-1968. It seemed to take place about 8:30 P.M. Cincinnati time, but it may have differed depending on sunset elsewhere in the country. I recall this in those years because WCKY was airing the Cincinnati Royals basketball games. The home games used to begin shortly past 8:00 P.M. and somewhere in the first or second quarter, play-by-play announcer Ed Kennedy would say, "This is WCKY, Cincinnati. We now pause five seconds for antenna switch". Of course, I never noticed any difference in the signal here, but in certain parts of the station's large coverage area, listeners may have noticed something or may have lost the signal altogether.

 

[Schroedingers Cat]

Anybody remember WCKY having a 3 tower dogleg array? I believe that now they have a four tower parallelogram. They go directional at sunset in Sacramento.

 

[RadioFan2J3]

I think a carrier gap in DA-1 stations indicated that they were switching transmitters. Almost all old 5 kW stations had previously been 1 kW and the 5 kW might have had a 1 kW power reduction feature, but they almost always kept the 1 kW transmitter for auxiliary use.

The carrier gap could very well be due to shifting from one transmitter to another, and from a power consumption standpoint with tube type transmitters, it might make sense to run a smaller transmitter.

But even if it is a 5kW TX with a 1kW power cutback, especially in the days of tube transmitters, most of these power changes come from either placing series resistors in the PA plate voltage circuit or possibly changing taps on the plate power transformer, both would (normally) require a shut-down of the high voltage to prevent arcing at the switching points.

The newer solid state transmitters should be able to make a power transition without any interruption of the carrier, if there are no antenna changes. If there are any antenna changes, I’d think you would want carrier off to eliminate arcing in the antenna switching networks, unless the power levels are low enough that arcing isn’t a major concern.

Well designed antenna switching systems would have interlock and position feedback switches on the RF switches to prevent the transmitter from going on the air if all the switches are not in their proper positions for the pattern desired.

 

[schmave]

Some of these posts remind me of a couple of others.

WWVA 1170, night pattern steered STRONGLY away from Tulsa. A pretty easy catch over most of the eastern half of Ohio during the day, I have been as close to their towers as I-70 between Zanesville and Cambridge (maybe a one hour drive at most) when the pattern changed and ....poof.....totally disappeared.

I've never heard WWVA right at the pattern change, but they're gone at night here. I've heard people farther west saying they've heard it at night, but here about 95 miles west of the tower, I've never heard a trace of them after nightfall. Daytime signal is decent.

 

[Cincinnati Kid]

I recall being in Eaton, Ohio in late December in the mid-1990's. Eaton radio station WCTM at 1130 kc signed off at sunset and KWKH from Shreveport, Louisiana came roaring in. Then an hour or so later, KWKH altered its signal pattern and WNEW from New York City could be heard.

 

[TedAlexander]

At WKNR we switch between a DX50 @ 50kw for days, and a DX10 @ 5kw for nights. All the switching is done through an antenna controller that has 4 different modes we could use as needed, one button push. It allows 50kw days into 4 towers in a "distorted parallelogram" configuration. At night we use 4 towers (2 in common with the day pattern) @ 5kw into a symetrical parallelogram. Because of the calculations and parameters, even though the license states 4.7kw nights, we actually feed 5.4kw into the common point, and days we feed 52.5kw into the common point. There are also two non-directional modes for maintenance and emergency use which allows two of the towers to be used that way. We can also feed the night pattern @ 5kw from the DX50 or run the DX10 @ 10kw into the day pattern. The DX50 can also run 12.5kw into either of the two non-DA towers. The DX10 can run 10kw into either of the non-DA towers.

The night pattern is so tight to the west, to protect KOA, that you can look at the towers from about 5 miles away, and hear KOA clearly underneath. That 5kw pattern was installed in the early 1940's and has been unmodified since then.

Pattern change time from day to night or night to day takes about 3 seconds, changing patterns and transmitters.

Ted Alexander W8IXY

 

[KR4BD]

Some of these posts remind me of a couple of others.

WWVA 1170, night pattern steered STRONGLY away from Tulsa. A pretty easy catch over most of the eastern half of Ohio during the day, I have been as close to their towers as I-70 between Zanesville and Cambridge (maybe a one hour drive at most) when the pattern changed and ....poof.....totally disappeared.

I've never heard WWVA right at the pattern change, but they're gone at night here. I've heard people farther west saying they've heard it at night, but here about 95 miles west of the tower, I've never heard a trace of them after nightfall. Daytime signal is decent.

Funny, you never hear WWVA at night less than 100 miles west of the towers. In Lexington, KY, I can always hear them at night, although they are usually quite weak, but still dominate on 1170. Shortly before OUR KY sunrise, they have a KILLER signal here as they probably go ND 30 or 45 minues before OUR Local Sunrise in Lexington where it still will be dark.

 

[davideduardo]

Well designed antenna switching systems would have interlock and position feedback switches on the RF switches to prevent the transmitter from going on the air if all the switches are not in their proper positions for the pattern desired.

This thread reminds me of the transmitter switching I saw in 1963...

http://www.americanradiohistory.com/Archive-1963-Radio-Photos/Mexico-Radio-Photos.htm

Scroll down to the third row of pictures labeled "antenna switch."

Two engineers were required for the transmitter switching, which was done every two hours to rotate between the three "main" transmitters to give each equal airtime.

One engineer would kill carrier on the on-air transmitter, and yell "cambo" ("switch") while the other engineer would pull out one knife switch and push in the other, one with each hand, and then yell "cambio" in return at which point the first engineer would apply plate voltage to the transmitter that was going on duty.

The procedure was done in a pause between the distinctive station chime and the ID as "X-E-W La Voz de la América Latina desde México". The switch was not noticeable on the air. It was done so fast that there would be an RF arc over the disengaging switch.

All three transmitters were 250,000 watts each. They could use verbal commands because the transmitter room was very very quiet as cooling was done by water, using outdoor cooling towers and pumps rather than indoor fans.

 

[Schroedingers Cat]

Freddy may remember WFNT, which was formerly WKMF 1470 5 kW day, 1 kW night, DA-2. It is a 3 tower in line with quarter wave spacing, about a half mile down the road from WTRX. The night pattern appears to not have changed since the original incarnation, WWOK, signed on in 1947 as 1 kW DA-1. The 5 kW day pattern dates to 1959, with little change except augmentations. One night in the 1970s I called when the signal indicator on my radio was more consistent with the day facility than the night. I called and to my surprise, my neighborhood ham friend Chris answered the phone. He was CE at one local station but worked another as an assistant engineer. He had figured out who I was first, which gave me a bit more credibility. He said he had changed to night facilities, but said that some phaser components sometimes got stuck, and he rocked a couple switches back and forth until it all changed.

 

[Cincinnati Kid]

With regards to WWVA; I have never received it very well in the Cincinnati area at night or during the day. That was the case even long before there was a station in this area on 1160 kc. I tend to think their signal (particularly at night) is more north and south which would make it better up and down the east coast. Back in the 1970's WWVA featured an all-night program hosted by Buddy Ray that was aimed at over-the-road truckers.