650 WSM question

[radiojay1]

Here is an excerpt below from www.wsmonline.com about the history of WSM. I had asked before about if kilocycles were any different then kilohertz and about if the propogation of the low frequency. Now I am curious about something else. I know they are a clear-channel broadaster, but what does Class 1-A mean?

By late 1932, WSM had joined a small, elite group of maximum-power, Class 1-A, clear-channel broadcasters. The stations new 50,000 watt status, coupled with the low 650 kilocycle frequency, made WSM a nation-spanning giant. (Clear-channel status meant it was the only station in the entire U.S. permitted to broadcast on the 650 frequency.) At the heart of this expansion was a diamond-shaped, vertical antenna which was 878 feet high, the tallest tower in North America at the time.

 

[jcolletta275]

Class 1-A is the official name for true clear-channel status. As the text points out, "Clear-channel status meant it was the only station in the entire U.S. permitted to broadcast on the 650 frequency." That's the basic definition of Class 1-A.

 

[lfuss]

Class 1-A is the official name for true clear-channel status. As the text points out, "Clear-channel status meant it was the only station in the entire U.S. permitted to broadcast on the 650 frequency." That's the basic definition of Class 1-A.

Not quite true. Clear channel stations are protected more so than non-clears, but they're not the only ones on the channel. Many 1A's have other occupants on the channel. For example, 650 also has fulltimers in Minnesota, Wyoming, Utah, California, Washington and Massachusetts. Further south of Nashville, WSB shares 750 with a similar number of stations, including a 50 kw station in Portland (and another in Anchorage). WGN in Chicago shares 720 with a 50 kw station in Las Vegas. No clear channel station in the U.S. has exclusive use of their channel, not a one!

 

[semoochie]

Not anymore! The word used was "meant", past tense. The last of the clears coverage was greatly reduced about 25 years ago, 20 years after several of them were taken down a step. Before the 1960s though, clear channels reigned supreme! Even in the 1970s, they were quite a force!

 

[jcolletta275]

That was my point... I should have made that clear. 1-A's technically no longer exist, and that makes WSM (and all other former class 1-A's) exempt from protection across the country. Sorry for the confusion.

 

[radionekkid]

That was my point... I should have made that clear. 1-A's technically no longer exist, and that makes WSM (and all other former class 1-A's) exempt from protection across the country. Sorry for the confusion.

Thats not right. Old class 1a radio station now known as class a station and still protected out to about 750 miles raduis and not exempt from protection.

 

[jcolletta275]

That's not how I understood it... do you have any reference I could take a look at?

 

[Doctor_Technical]

Mark Durenberger has an excellent multipart series on just this subject. From the National Radio Club site:

http://www.nrcdxas.org/articles/clear01.html
http://www.nrcdxas.org/articles/clear02.html
http://www.nrcdxas.org/articles/clear03.html
http://www.nrcdxas.org/articles/clear04.html
http://www.nrcdxas.org/articles/clear05.html
http://www.nrcdxas.org/articles/clear06.html

 

[K4WRF]

Mark Durenberger’s series on the long term clear channel battle was excellent. The current FCC rule pertaining to this question is specified in 47 CFR, Part 73.182. In summary, the rule states that Class “A” stations receive co-channel nighttime sky wave protection to their 0.5mv 50% sky wave contour. The interfering signal is limited to 26db below 0.5 mv (0.025mv). That’s about 750 miles in most cases.

Watt Hairston

 

[jcolletta275]

Okay, my mistake... we're actually in agreement here (I misread what radionekkid had written, and he/she'd misunderstood what I was trying to say). I realize the current incarnation of 1-A's (now called Class A) doesn't carry nationwide protection from interference. I'm saying that previously, when the class was called 1-A and before the rules were re-written, they did have nationwide protection.

Am I correct?

 

[CW]

That was my point... I should have made that clear. 1-A's technically no longer exist, and that makes WSM (and all other former class 1-A's) exempt from protection across the country. Sorry for the confusion.

Thats not right. Old class 1a radio station now known as class a station and still protected out to about 750 miles raduis and not exempt from protection.

Exactly which is why 650 KIKK Houston is a daytimer only...(and only 250watts day..but gets out like crazy!)

 

[semoochie]

I believe the clears were protected on their own channel out to 0.1mv/m with significant adjacent protection as well.

 

[PTBoardOp94]

Originally, pre WWII, the clears were the only station on their frequency in the country.

I'm not sure about adjacent protections. WLS and WBBM in chicago are only 40khz apart, and both are clears.

 

[semoochie]

40Khz is adequate and very common separation for stations covering the same locality. 30 is pushing it in that neither station can overlap the other's city grade contour but 40 is fine. The last time I checked, WBBM was still on 780 with WLS on 890. Perhaps, you're thinking of 2 other stations that are 40Khz apart.

 

[al_atl]

I'm sure there are other examples, but off the top of my head I thought of 1010-WINS and 1050-(can't remember the calls) in NYC. Though not clears, WGST-640 and WCNN-680 in Atlanta both run 50-KW during the day. In Toronto there are 50-KW stations on 640 & 680 and 1010 & 1050.

 

[jcolletta275]

Originally, pre WWII, the clears were the only station on their frequency in the country.

That's what I was thinking. Thanks for the confirmation.

I'm not sure about adjacent protections. WLS and WBBM in chicago are only 40khz apart, and both are clears.

40? I'm counting 110 (890-780=110).

 

[Tom Wells]

Originally, pre WWII, the clears were the only station on their frequency in the country.

That's what I was thinking. Thanks for the confirmation.

I'm not sure about adjacent protections. WLS and WBBM in chicago are only 40khz apart, and both are clears.

40? I'm counting 110 (890-780=110).

What IS an issue in Chicago is that 670 WSCR, 720 WGN, and 780 WBBM are all 50kw, and all Xmit sites are within a 5 mile circle.
Consider the possible intermodulation problems...and yet all manage to exist without spurs and such.
What is awful is the IBOC hash in this circle, and 50 miles out, wiping all other signals out.
Poor WNDZ in Portage Indiana, squished in at 750, can barely be found amidst all the hissing....
30 khz would have been just fine in analog days, but 40khz is necessary with IBOC.

 

[BobOnTheJob]

Stupid IBOC...WGN used to be nice and clear southeast of Indianapolis. WLW's IBOC puts a very irritating noise behind WGN now. Wheoever designed this crap -- AM AND FM -- ought to be banned from radio engineering.

 

[davideduardo]

40Khz is adequate and very common separation for stations covering the same locality. 30 is pushing it in that neither station can overlap the other's city grade contour but 40 is fine. The last time I checked, WBBM was still on 780 with WLS on 890. Perhaps, you're thinking of 2 other stations that are 40Khz apart.

20 kHz is adequate, too. In many places in the world, this is the standard in same market separation.