Fastest and Slowest Pattern Changes

[Schroedingers Cat]

Cyberdad just posted about hearing station IDs during station pattern changes. Over the years, these have become less manual, faster and more automated. Does anyone recall any particularly slow or fast pattern changes? It would seem that the longer in between day and night patterns, the more likely it is to hear distant station IDs. CHYR/CHIR/CHYR-7 710/730 was certainly the slowest I can remember, having to change pattern and frequency and power. Stations like WFDF at the old site that were DA-1 that had no carrier interruption when they reduced power from 5 kW to 1 kW except in nulls and outlying areas where the S/N ratio would change more. It was not that noticeable at all locally. When they went back from 1 kW to 5 kW, the AGC response was much more noticeable. Even the DA-2 pattern change between 50 and 25 kW is very quick and sometimes still easy to miss. You have to listen for it still even as DA-2.


I seem to remember CKLW 50 kW U DA-2 pattern change as being quite noisy, and the old WCFL 50 kW U DA-2 as less noisy but Charlie Gustafson said that was because they turned the modulation off completely for a significant amount of time during the change.

Anyone remember some of the mechanics and electronic sequences of the pattern changes and why they were noticeably fast or slow, quiet or noisy? I seem to remember from the NAB Engineering Handbook that in the early days of DAs the phaser had to manually manipulated without RF present to accomplish some changes.

 

[cd637299]

Hmm, I never gave this much thought. The AM stations in south FL *all* seem to take about 3 seconds between patterns or power changes.

Is there audio anywhere for me to hear, of CHYR/CHIR, or the WNZK frequency-swap deal?

cd

 

[Schroedingers Cat]

I probably have a CHYR/CHIR/CHYR-7 pattern change somewhere in my unlabeled, unscoped archives. I don't know what kind of shape these would be in.

 

[cd637299]

I probably have a CHYR/CHIR/CHYR-7 pattern change somewhere in my unlabeled, unscoped archives. I don't know what kind of shape these would be in.

Don't lose sleep looking for it!

cd

 

[K4WRF]

Over the years have seen and built some extensive Rube Goldberg antenna change-over systems to allow some simplicity, speed and "one-button" remote operation. Some of these involved more relays that a pin-ball machine and were about as complicated. I saw one that was written up in Broadcast Engineering years ago that used a motor driven cam-wheel that engaged several micro switches as it passed, each one of them initiated a function in the progression. Plate off> night pattern> tx power selection> plate on. A couple places I worked at required it to be coordinated with the studio so that it wouldn't happen during a spot, ID, news or music. We had one where the newsman would place an intentional pause in his speech to accommodate pattern change and the reading of the common point or antenna current w/o modulation. Another where there was a pause in the station ID. We had to work to get it under three seconds as that was just not acceptable with the PD's in those very competitive years. I was once told that the RCA BTA50F models were not very graceful in accomplishing this by simply muting the rf drive w/o killing the audio. The modulator was still working and a loud arc would result as there was plenty audio but no RF to modulate. One station I worked at still used early 40's antenna relays until the 80's, no carrier interlocks... At 50kw, if it didn't all go well it could get rather noisy when the transmitter would try to come back on into a BAD load. Conti 317C carrier tube to the right side of the cabinet flash... BANG!!!

 

[gar hi]

Wow, this thread reminds me of when I was growing up and had discovered AM DXing only a year earlier and was still learning the basics.

Even though it was a local station, I liked to hear the old 990 WIBG make the pattern switch at dusk.

It not only changed directions but the power was reduced from 50 kw to 10 kw and even being that close to Philadelphia, the signal difference between day and night was very noticeable a few miles across the river.

The song 'Diamond Girl' by Seals and Crofts will always remind me of when I first heard them switch patterns. During the switch, they were off the air maybe two to three seconds.

But that first time I heard this, I didn't know why they went off for a couple seconds and then became much weaker. My older brother explained it to me and showed me his handbook that had the lists of stations, their powers, and signal directions, like the online one we use now.

 

[1L6E6VHF]

Hmm, I never gave this much thought. The AM stations in south FL *all* seem to take about 3 seconds between patterns or power changes.

Is there audio anywhere for me to hear, of CHYR/CHIR, or the WNZK frequency-swap deal?

cd

I now feel so bad that I never thought to tape it - today, it would have been thought as something of a "classic"

At least in the morning 730->710 switch, they made a production out of it. A recording started out something like this: "CHYR pattern and frequency shift...Technology allows us to bring you the sound of "cheer" radio 24 hours day and night. Please tune your radio to AM 710. You will be on 710 when you hear the sound" - at which point the station broadcast what could be described as a "cartoon machinery sound", on 730, which briefly continued after they had shifted to 710.

And they REALLY got out on 710. They used to have a break that went "CHYR, Radio 7, Canada. In the air, everywhere, including ******" (which would be any of several alternating cities in SE Michigan, SW Ontario, or Northern Ohio)

I guess I better take my digital camera with me tomorrow to record WNZK's frequency shift (which is not anywhere near as artistic).

Getting back to on-frequency pattern shifts. I'll never forget how I found out they even existed. I was 9 years old and was listening to WWJ on a crystal set, to a mystery radio program that must have been among the very last scripted story radio programs in US radio, when I suddenly, completely, lost the program. I had thought something came loose on the radio, but found that the radio was fine (CKLW and WJLB still booming in). Now, I had a book with a list of station power levels, and it said WWJ was 5000 day and night. I figured this must be a misprint, and called WWJ the next morning to find out what their nighttime power was.

An engineer told me it was 5000 watts, and I refused to believe him. I thank the engineer of long ago for how patient he was in explaining the "second tower" and the directional signal (note that back then, WWJ's Detroit city of license was entirely in their null at night!)

 

[pianoplayer88key]

I have a few pattern change recordings of local stations up on YouTube.



#1 - KCBQ - Day 50kW DA -> Night 2.9kW DA(2) - https://www.youtube.com/watch?v=7eQql8niXLE

For this one I'm actually tuned to the adjacent channel (1160) during most of the change. I wanted to see how much 1170's signal being there vs not there affected reception of 1160. (This was at a time when KCBQ was off for several seconds during its change. More details are in the video description box.


#2 - KFMB - Day 5kW ND -> Night 50kW DA - https://www.youtube.com/watch?v=ICaOz_Nvxeo

There are several clips in this one. I'm hoping to somehow ID what station is there when KFMB is briefly absent, but so far haven't had any luck. More details in description box.


#3 - KCBQ - Night 2.9kW DA(2) -> Day 50kW DA - https://www.youtube.com/watch?v=XoH4ftOjG7M

Due to the somewhat strong signal, audio is a bit tough to hear on this one, except when I tune to the 2nd harmonic near the end of the clip. Pattern change can be heard, though, by the background noise coming up. More info in description.


Regarding the KCBQ pattern change, the night/day change went as follows:
Step 1 - Off Air for several seconds
Step 2 - back on Night mode for several seconds. (In Video #3 I notice it doesn't come immediately on, but something seems to make a couple steps with about a 1-second interval. Any idea what that is?)
Step 3 - Quickly off Night mode then back on Day mode, so fast that it could practically be done between syllables in a spoken word and you'd hardly miss anything.
The day/night change was the reverse of this - first the quick switch to night, then several seconds later the transmitter was off for several seconds, then back on at night mode.

For a while, now, KCBQ has eliminated the long off-air period, and now only has the quick switch.


When using just the built-in ferrite antennas on my Tecsun PL-398mp in my back yard, indicate signal strengths are approximately:
760 KFMB - 71 dBµ daytime, 81 dBµ nighttime
1170 KCBQ - 80 dBµ daytime, 67 dBµ nighttime

 

[Schroedingers Cat]

I guess the shortest gap in programming would be when there are two sites and both the day and the night sites are both on at once (hopefully for a very short time)!

One engineer explained to me that there would have to be a carrier gap even with DA-1 stations, but another engineer explained a method where there would be no gap in the carrier. The only noise I heard on some DA-1 stations was the receiver AGC response. On a good old fashioned signal strength indicator with a d'Arsonval movement meter, the pin just moved up or down. On power up it would get loud and then settle back to the same volume level.

 

[Schroedingers Cat]

As for WWJ, where I have lived, it was and is always STRONGER at night when they changed patterns. Even now, I live close enough to the azimuth pattern maximum that it gets stronger when the major lobe narrows and squeezes more inverse field in my direction. It is enough of a change to be audibly more S/N, D/U after pattern change at night. With 5 kW, I could get WWJ 950 at night even on a Remco Caravelle about 45 miles away, especially after WFDF 910 signed off at 12:30 AM until around 1980 when it went 24 hours. WCFL 1000 was strong enough at night to be heard with 910 on the air. WLS 890, you had to wait until 12:30 AM to get it on the Remco Caravelle.

WWJ's old night pattern exceeded the Class B minimum for 1000 watts in all directions. In later years I was told that the nulls were measurably deeper and could not be maintained at a shallow enough level to get a good signal into some areas.

 

[K4WRF]

I have a few pattern change recordings of local stations up on YouTube.


Step 2 - back on Night mode for several seconds. (In Video #3 I notice it doesn't come immediately on, but something seems to make a couple steps with about a 1-second interval. Any idea what that is?)

All 50kw transmitters employ a ramp-up or in the case of the Harris DX50 a step-start turn-on. DX50 steps on low then high in about a second to limit current inrush. Nautel and Harris 3DX50 ramp up in about 100 ms or so IIRC.

 

[FreddyE1977]

I probably have a CHYR/CHIR/CHYR-7 pattern change somewhere in my unlabeled, unscoped archives. I don't know what kind of shape these would be in.

Did that change include some sort of announcement to retune your dial to 730, or did they just presume their
listeners knew this?

Speaking of 730, WPIT here in Pittsburgh seems to be one of the longer changes. At sundown they drop down
from 5000 all the way to 24 watts. There is generally a loud pop, followed by a few seconds of dead air. Then
they pop back on at much lower volume with a whole lot more noise (though still listenable, which is impressive
running on less than half a light bulb)

 

[schmave]

Here in Columbus, the pattern changes I've heard for WTVN (610), WVSG (ex-WOSU on 820) and WBNS (1460) each consist of a very brief drop of the carrier, then the signal change. While all of those stations have very effective directional patterns, WTVN and WBNS still can be heard in their nulls for a bit after the change just because the skywave hasn't taken over yet. I heard WTVN very weakly an hour or so after the pattern change in Zanesville, about 50 miles east of the tower. Later at night, it's completely gone.
In the heart of WVSG's null toward WBAP, the signal disappears within 3-4 miles. It is extremely effective.

 

[tomservo]

The only big gap I remember hearing as a kid was WAPI in Birmingham, which would go off for 2-3 seconds. The night pattern did a good job of covering the city so there wasn't too much more noise if you were in the city, it was just a few moments off the air.

I can vaguely recall hearing other stations during that switchover but back then I never though about trying to DX the gap. Being on 1070, I bet WIBC in Indy or WDIA in Memphis were there and I just never noticed!

 

[The King Bee]

For many years, WAKY-AM (790 kHZ, 5kw ND-D, 1kw DA-N) from Louisville played a message immediately before and after a power & pattern change with a brief explanation of what was happening and why.

At sunset, it let their many suburban/fringe listeners know that they were about to lose the WAKY signal, thanked them for listening, and invited them back at sunrise. Right after sunrise, they welcomed the audience back with a "hello...here we are!" cart. WAKY had a huge footprint for a 5kw station (as does its successor, WKRD), with ratings book presence in Terre Haute, Bloomington (IN), Lexington (KY) and even Cincinnati (OH) as a Top 40...they were one of the best 10 stations in any format nationally.

Their transmission system made ultra-smooth, glitch-free power and pattern transitions in less than 3 seconds.

 

[Icangelp]

For many years, WAKY-AM (790 kHZ, 5kw ND-D, 1kw DA-N) from Louisville played a message immediately before and after a power & pattern change with a brief explanation of what was happening and why.

At sunset, it let their many suburban/fringe listeners know that they were about to lose the WAKY signal, thanked them for listening, and invited them back at sunrise. Right after sunrise, they welcomed the audience back with a "hello...here we are!" cart. WAKY had a huge footprint for a 5kw station (as does its successor, WKRD), with ratings book presence in Terre Haute, Bloomington (IN), Lexington (KY) and even Cincinnati (OH) as a Top 40...they were one of the best 10 stations in any format nationally.

Their transmission system made ultra-smooth, glitch-free power and pattern transitions in less than 3 seconds.

Interesting thread.

Now, I'll sidetrack it a bit.

I don't know whether it was the fact that WAKY didn't reach northern Indianapolis, or we just weren't aware of it, but when I was growing up in the late 50's and 60's, I don't recall ever listening to WAKY. Neither did any of my friends. Over the years, I've heard many WAKY air checks, and know I missed a great station. WKLO wasn't so bad either.

 

[Icangelp]

It is still odd experience for me to be listening at sunset when a station suddenly changes patterns and disappears completely.

 

[davideduardo]

...as a Top 40...they were one of the best 10 stations in any format nationally.

One of Gordon McLendon's creations, of course. KLIF, KELP, KEEL, KELP, KILT, KTSA... all great Top 40's in their prime.

 

[schmave]

It is still odd experience for me to be listening at sunset when a station suddenly changes patterns and disappears completely.

WKNR is the first I ever heard disappear completely. I remember driving back from Cleveland with a few buddies listening to something on there - this was 2-3 years ago - and telling them we'd lose the signal completely within a few minutes. We were south of Mansfield at the time, and come 5 p.m. it was gone.
Most of the pattern changes I've heard, I've been somewhere where the signal still comes in to some extent - if not better - at the change. In Toledo, WTVN actually gets stronger at sundown. Neat to hear.

 

[cyberdad]

Where I grew up about 40 miles northwest of Chicago (Wauconda), the one that sticks out in my memory was WOKY/920 from Milwaukee....about 55 miles to my northeast. At 5kw daytime, I was in the null. At night even on 1kw, more signal went to the southwest. The result was that the signal popped when they went to night pattern, even though the power was reduced. The opposite happened when they powered up at sunrise.

The result was a station that suddenly nearly disappeared when it went to higher power as the sun came up.

Meanwhile the effect of the Chicago stations with night patterns.....WIND and WCFL...was negligible. Where I live now, about 12 miles west of where I grew up, WIND's pattern change on 560 is still unnoticeable. WMVP (ex-WCFL) on 1000 shift to night pattern is apparent, but not to the point where listenability is significantly impacted.

Its been a while since I've caught any of these at the time of the pattern changes, so I can't say which is now fast or slow. "Back in the day", WIND and WOKY were fairly swift. WCFL was slower, which is how I managed to catch a couple of KTOK TOH IDs.