Can The AM Band Be Saved?

[K6JHU]

Assuming that the band doesn't die completely in about 10 years I would predict the 50kw power houses will still be there with sports, talk and maybe news. The 5-10kw stations will be brokered or ethnic, and the graveyards will be NPR/college.

[KeithE4]

Assuming that the band doesn't die completely in about 10 years I would predict the 50kw power houses will still be there with sports, talk and maybe news. The 5-10kw stations will be brokered or ethnic, and the graveyards will be NPR/college.

Why would any educational institution or other secular, non-comm broadcaster bother with AM anymore?  That dog died in the 1930s, with only a few exceptions.  They'd be better off just streaming if no FM frequency is available.

[DavidEduardo]

Actually, the NRSC curve is about a +10db boost starting flat at 1 Khz and running up to 9.6 Khz.  I think you have to be down something like 40 db by 10Khz.  So there's a minor boost in highs, the idea being that it would help make it sound a little brighter on typical, rolled-off radios.

Maybe this is my misinterpretation, but I thought that the NRSC-3 standard added recommendations for receivers that included the HF boost, while the NRSC-1 followed more thoroughly by NRSC-2 determined the cut-off at 10 kHz, and the attenuation from 10 to 20 kHz and above 20 kHz, among other things (like the low frequency rolloff, also). I did not understand that there was a 10 db boost in transmission... and have never observed it in receivers made pre-NRSC that have greater bandwidth than the 10 kHz NRSC mask.  

[TheBigA]

Why would any educational institution or other secular, non-comm broadcaster bother with AM anymore? 

Yep...The Ohio State University just sold WOSU-AM to concentrate on FM-only facilities.  The costs are outweighing the benefits.

[KeithE4]

Why would any educational institution or other secular, non-comm broadcaster bother with AM anymore? 

Yep...The Ohio State University just sold WOSU-AM to concentrate on FM-only facilities.  The costs are outweighing the benefits.

It wouldn't surprise me, although I haven't heard anything, that the other Big Ten schools with AMs (Illinois, Iowa, Michigan State, Minnesota, Purdue, Wisconsin) dump them in the next few years.  I think they're the last major universities that still operate AM stations, along with a few small colleges.

[johnbasalla]

The most important point is that The Ohio State University SOLD their AM station.  In other words, somebody wanted it.  Now if they couldn't find a buyer and just shut it down, that would be more compelling proof of the demise of AM radio.

[PTBoardOp94]

Sort of.  WOSU AM was purchased by a Catholic non-profit for a modest $2 million and is running religion.  Ohio State paid $6.5 million for the class B1 FM signal that succeeds WOSU AM.

[w9wi]

It wouldn't surprise me, although I haven't heard anything, that the other Big Ten schools with AMs (Illinois, Iowa, Michigan State, Minnesota, Purdue, Wisconsin) dump them in the next few years.  I think they're the last major universities that still operate AM stations, along with a few small colleges.

Wisconsin's station in Madison is the justification for a translator, so I think it will probably stick around for awhile.  (it's also a point of pride, claiming to be the first broadcast station in the U.S. and having a pretty decent claim as #2.)  I'm a bit surprised they haven't shut down the other station, but I haven't run the FM coverage up there, it's possible there are still significant gaps. 

Minnesota's station is also the justification for some translators.  I suppose they might think about closing it if they can get reliable access to someone's HD2. 

I would see MIchigan State as the one most likely to go away.

[NightAire]

David,

Unless this is just a suggested specification, check out page 10 of this pdf file for the pre-emphasis, and page 12 for the de-emphasis:
http://www.nrscstandards.org/SG/NRSC-1-A.pdf

I remember an engineering friend who told me after NRSC came in, he could no longer stand to listen to the AM radio in his ('55? '65?) pickup...  everything was too bright.   

(I'd gotten the impression some stations had been boosting their highs a LOT more than 10db, so this was a bit of a compromise at the time!)

I find most AM stations sound a little better in wideband on the Superradio III with the treble dialed back a little, but it's not horrible.

EDIT:  re-reading your response, I think we may be talking about nearly the same thing.  The cutoff is basically 10 Khz (9.6, close enough) and drops like a rock below that.

A little more research has shown, though, that the NRSC mask IS a requirement for all U.S.A. AM radio stations:

NRSC-1, published in July 1998... A modified 75 u/sec preemphasis/deemphasis curve was recommended, much like the long used system used in FM exciter and receiver designs. In addition, the standard recommended limiting audio bandwidth to 10 Khz (-30db @ 10.5 Khz., -40db @ 11.0 Khz., -50db @ 15. Khz.). This "audio masking" scheme reduced percentage of modulation at 15 Khz. down to as little as .32 percent...  NRSC-1 was a voluntary standard.

NRSC-2, published in June 1998, further described the reduction of AM broadcast spectrum bandwidth as a product of limiting audio frequency bandwidth. This original voluntary standard is referred to today as the AM "audio mask".

NRSC-3, introduced in June 1990, established audio bandwidth and distortion standards for AM receivers.

All of these standards have now been accepted by the FCC as mandatory for licensed AM broadcast stations.

from http://part15.us/node/703

[kenglish]

.................In a decade or so the AM band will probably another ham radio band.

Lotta good that'll do us, with all the noise on it    /