Class "A" AM Channels (including Nashville's Class "A's")

[scottwmro]

I know this doesn't necessary have anything to do with Nashville Radio Directly, but I think somebody had told me that Class "A" AM stations were limited down to a 650 mile protected range or 50% RMS. Is this true?

Of course this would effect WSM as a Class "A", non-directional operation, but one person on here doesn't understand that even though WLAC is a "Class A", they are directional at night, protecting (I think) WWZN out of Boston at night, which is liecnsed as a Class "B" station.

WLAC has a deep null towards Gallatin at night, and that's why Mr. Juilan hears the fading on WLAC at night, due to they are protetecting the station in the northeast that is co-channel with them. Even in the days of the late night R-n-B on WLAC and Randy's Record Shop Ads here in Gallatin on 1510, the directional pattern was there to protect WWZN.

Can somebody fill in the holes here?

 

[K4WRF]

Now the WLAC story is a long, interesting and convoluted one and can't be explained in one line so here is my summary!

Class “A” AM stations today are protected to their 0.5 millivolt per meter 50% coverage contour this is expressed 0.5 mv/m, 50%. 50% denoting probability. That comes out to about 750 miles in many cases, a little less the further north the station is.

WLAC was known as a Class 1-B until about 25 years ago when they made them all class “A”. WLAC moved to 1510Kc in early 1941 as part of NARBA treaty. They were on 1470kc before that. The Spokane null is very deep, the Boston null 59 degrees is not as deep but broad, about 2kw goes toward Boston, right across Gallatin. The reason WLAC protects Boston is because of a political situation at the time that involved the owner of WMEX. WLAC had to limit radiation towards WMEX to protect their 2.5mv/m ground wave preserving their original signal before the shift in 1941. As a result, WMEX did not protect WLAC’s 0.5 mv/m sky-wave but more like the 2.0mv, a unique “grandfathered” situation. The first application that WLAC proposed for 1510kc consisted of a two-tower directional array just north of the old County hospital area that produced a null towards KGA in Spokane, best described as a cardioid pattern.

The WLAC directional antenna produces a very deep null over several degrees towards KGA about 50 watts, a minor null towards Boston about 2000 watts and a coincidental null toward the south about 40kw. The lobe to the southwest is 180kw, southeast 120kw and due north about 60kw. These would be “effective radiated” power levels. The RMS you speak of is a statistical measure and the azimuth quadratic mean or the whole signal or about 2500mv/m, enough about that.

In 1980, the Boston station filed an application to relocate their transmitter and increase power to 50kw at night. This was just fine with WLAC because as a condition, WMEX would have to now further protect the 0.5 contour observing the current rules, grandfather status was lost.

The selective fading heard is a function of the frequency of the station and the antenna configuration, producing a high take-off angle component that causes the selective fades you hear. Every station has this, it is just more pronounced on some less on others. Simplistically, one ray leaves the antenna and passes across the earth to a receiver at point X. Another takes a longer path via sky-wave, arriving at the point X receiver at another time. Not arriving at the same time or in phase depending on the time, produces a partial, all the way up to full null or cancellation, it’s all a matter of geometry or vector addition. This has ALWAYS been there and was magnitudes worse before the move to the Old Hickory Blvd location when a flat-top antenna was used. This was according to Charles Dorris and Miller Watkins who worked at WLAC from day one.

As far as someone having reception issues with WLAC at a distance of thirty-miles in daylight hours, I would tend to question the receiver sensitivity.

w/

 

[Tom Wells]

In 1965, WLAC was as strong and clear as WSM at the southern tip of Lake Michigan.

Now, they sound like any graveyard station. No null in my direction, I'm less than one degree different in angle, and only 40 miles further, but
there's a world of difference.

 

[radionekkid]

In 1965, WLAC was as strong and clear as WSM at the southern tip of Lake Michigan.

Now, they sound like any graveyard station. No null in my direction, I'm less than one degree different in angle, and only 40 miles further, but
there's a world of difference. 

Lot of chatter on Wlac now some daytimers stay on air after sunset.

 

[scottwmro]

Now the WLAC story is a long, interesting and convoluted one and can't be explained in one line so here is my summary!

Class “A” AM stations today are protected to their 0.5 millivolt per meter 50% coverage contour this is expressed 0.5 mv/m, 50%. 50% denoting probability. That comes out to about 750 miles in many cases, a little less the further north the station is.

WLAC was known as a Class 1-B until about 25 years ago when they made them all class “A”. WLAC moved to 1510Kc in early 1941 as part of NARBA treaty. They were on 1470kc before that. The Spokane null is very deep, the Boston null 59 degrees is not as deep but broad, about 2kw goes toward Boston, right across Gallatin. The reason WLAC protects Boston is because of a political situation at the time that involved the owner of WMEX. WLAC had to limit radiation towards WMEX to protect their 2.5mv/m ground wave preserving their original signal before the shift in 1941. As a result, WMEX did not protect WLAC’s 0.5 mv/m sky-wave but more like the 2.0mv, a unique “grandfathered” situation. The first application that WLAC proposed for 1510kc consisted of a two-tower directional array just north of the old County hospital area that produced a null towards KGA in Spokane, best described as a cardioid pattern.

The WLAC directional antenna produces a very deep null over several degrees towards KGA about 50 watts, a minor null towards Boston about 2000 watts and a coincidental null toward the south about 40kw. The lobe to the southwest is 180kw, southeast 120kw and due north about 60kw. These would be “effective radiated” power levels. The RMS you speak of is a statistical measure and the azimuth quadratic mean or the whole signal or about 2500mv/m, enough about that.

In 1980, the Boston station filed an application to relocate their transmitter and increase power to 50kw at night. This was just fine with WLAC because as a condition, WMEX would have to now further protect the 0.5 contour observing the current rules, grandfather status was lost.

The selective fading heard is a function of the frequency of the station and the antenna configuration, producing a high take-off angle component that causes the selective fades you hear. Every station has this, it is just more pronounced on some less on others. Simplistically, one ray leaves the antenna and passes across the earth to a receiver at point X. Another takes a longer path via sky-wave, arriving at the point X receiver at another time. Not arriving at the same time or in phase depending on the time, produces a partial, all the way up to full null or cancellation, it’s all a matter of geometry or vector addition. This has ALWAYS been there and was magnitudes worse before the move to the Old Hickory Blvd location when a flat-top antenna was used. This was according to Charles Dorris and Miller Watkins who worked at WLAC from day one.

As far as someone having reception issues with WLAC at a distance of thirty-miles in daylight hours, I would tend to question the receiver sensitivity.

w/

Thanks Watt,

I think it was Dave Hultsman that told me that Class A’s were cut down to 650 miles. I think he indented to say 750 miles.
I knew that when WLAC signed on, I guessed it was 1926 to 1941, that it was on 1470, and used two Self Supporting towers with a vertical wire strung between the two, using that Western Electric Air cooled box at 5 KW.
I read in my RCA Antenna Handbook, published in the late 40’s/early 50’s, that at the time WLAC’s antenna system was built, off of Murfreesboro Road, technology had not advanced along enough about exciting a vertical half wave tower with a full ground plane for returning currents, improving the ground wave signal. I didn’t realize that the two tower, wire deal, was called a flat top antenna, I guess used mostly for shortwave now. I question, the reason to relocate WMEX antenna & why did they not put up a fight to keep their grandfather status.

**Watt, while I have you on the line, got 2 questions:
1. WLAC left the 1470 allocation to go to 1510 in 1941, as we know WSOK (now WVOL) went on in 1951, but on by Cal Young and Bill Barry. What Changed in the 9 years or so that WSOK was classified as Daytime only and in 58, why such a weird directional pattern, when WLAC didn’t have that hanging over their heads in 1940?

2. A slant wire antenna feed. I know that 1490 in Lebanon is using one, but if tuned up correctly, is it just as efficient as a 3 wire unipole? I know the FCC really doesn’t allow them anymore, but it just seemed apparent to me that the slant wire made the upper part of the tower structure hot and but gain.

 

[deltas69]

Mr. Juilan hears the fading on WLAC at night, again..and i am repeating myself..i'm NOT listening to any radio at night..i'm speaking of 1510 in the middle of the day..11 am til 3 pm..

 

[romer979fm]

Mr. Juilan hears the fading on WLAC at night, again..and i am repeating myself..i'm NOT listening to any radio at night..i'm speaking of 1510 in the middle of the day..11 am til 3 pm..

"was it over when the Germans bombed Pearl Harbor? Hell No!"

("but the...")

"never mind...he's on a roll"

 

[scottwmro]

Mr. Juilan hears the fading on WLAC at night, again..and i am repeating myself..i'm NOT listening to any radio at night..i'm speaking of 1510 in the middle of the day..11 am til 3 pm..

Pat,
Read Watt's comments, sounds like you have a receiver problem. WLAC is non-directional during the day. I know in some of these newer cars, AM radio stinks, as they have reduced the bandwidth down to almost 2KC on the high end, making it sound like land line audio to me. They should never go below 7 KC on the high end.
Last I heard, WLAC was at 5 KC, but that could have changed, due to adjustments to the IBOC digital exciter. My favorite radio is a C. Crane, which is costly, but worth it. Any AM radio from Wal-Mart and some from Radio Shack are crap!

 

[radionekkid]

Every station moved that night except for wsm and wlw and others on low end of dial 550 in st loius didn't move. wlac moved to 1510 some other station moved to 1470 that same night. 1470 became class 3 allocation, kdka was on 980 up until then 980 is wisx or what ever it is now. wlac moved to dickerson rd in 1942 had trouble getting parts to finish job due to war. I think mr dorris and watkins must be dead now had forgot about them,

 

[w9wi]

I'm not Watt, but...

**Watt, while I have you on the line, got 2 questions:
1. WLAC left the 1470 allocation to go to 1510 in 1941, as we know WSOK (now WVOL) went on in 1951, but on by Cal Young and Bill Barry. What Changed in the 9 years or so that WSOK was classified as Daytime only and in 58, why such a weird directional pattern, when WLAC didn’t have that hanging over their heads in 1940?

AM frequencies were moved lock, stock, and barrel in early 1941. Pretty much every station operating above 730kHz changed frequency one night. With a few exceptions, every station on a given frequency moved by the same amount - everyone on 780 moved to 790; everyone on 940 moved to 970; everyone on 1460 moved to 1500. The purpose was to bring the U.S. into compliance with a new international treaty that opened clear channels for Canadian, Mexican, and Cuban use. Before the treaty, the U.S. pretty much kept all the clear channels for itself. The treaty also opened up the 1510-1600kHz band, which had previously been used only for experiments.

The channel designations moved with the stations. Before the move, 1470 was a "clear channel" - after the move it was regional. (and the new 1510 channel was "clear") Before the move, 1200 was a "local channel" - after the move it was "clear". (and all the Class IV - now Class C - stations that were on 1200 were now on 1230)

There were only five radio stations in Middle Tennessee at the time:
WSM-650 (50,000 watts)
WSIX-1210 (250 watts)
WTJS-1310 (250 watts; Jackson.)
WHUB-1370 (250 watts; Cookeville)
WLAC-1470 (5,000 watts)

(WSIX, like many other stations, moved to a regional channel - in their case 980 - with a directional antenna, after World War II. WSIX's move opened up 1240 for a new station, with what I think most of us know as WKDA taking the channel over in 1947. Likewise with WTJS which ended up on 1390.)

If WVOL had existed in 1940, it would have been on 1440kHz. It would have had to protect the same stations it's protecting now. (I'm guessing Peoria, Ill. and Rome, Ga. among others) It would have had the same directional pattern. It's just that the whole thing would have moved up 30kHz that night.

(luckily there were a LOT fewer directional antennas back then. Something like that would be nearly impossible to repeat today because of the massive amount of work that would be necessary to retune that many DAs for the new frequencies!)

http://en.wikipedia.org/wiki/North_American_Radio_Broadcasting_Agreement

 

[deltas69]

well i don't understand any of the technical stuff..don't need to as all i care about is the music whether 10 or 10 million are listening..but theres no one playing what i care to listen to..but i digress..i suppose all of the above explains why i can't get wls at night..tried the other night waiting outside for my wife..use to blow the knobs off my 64 GTO back in 1970...i've tried to pick up wlac in four different vehicles on that stretch..no difference..but i do understand the pi$$ poor am recievers that car makers put in cars..they figure who listens to AM anymore..