Re: [IRCA] The Increase of AM Noise

[LEE FRESHWATER <amlogbook@xxxxxxxxx>]

Bravo !!!!   well said !!!
  
  Lee Freshwater
  Ocala FL
  

Rene Tetro <rtetro@xxxxxxxxx> wrote:  Fellow Hams and DXers,

The  following is the text of a message that I sent to our company's  engineering email list concerning the increase of electrical noise on  the AM band. I thought you might find it interesting. We hams and dxers  are not the only ones who are concerned about the trend of increased  electrical noise. Broadcasters are, as well, and have a lot at stake in  doing something to see the situation is improved.

73,
Rene'
W2FIL,
Lansdale, PA

---------------------------------------


There's  been a lot of discussion recently on various engineering sites and  publications, and among radio dxers, about the deteriorating state of  AM coverage. I would obviously concur with this (who couldn't?). The  situation is evident to anyone who listens to AM radio, and it seems to  be getting worse as time goes by.

Laying IBOC and BPL aside for  a moment, which have their own set of interfering dynamics, there are  other issues that are becoming more predominant on the AM band. Most  notably there has been a dramatic increase in electrical noise on the  band in recent years. This is getting worse and is having the effect of  dramatically reducing coverage in many cases. All of the latest  electronic gadgetry seems to be the major cause of "dirty power lines"  and other noise. Among the devices that seem to be most culpable are  medical devices, computers, light dimmers, and - one of the biggest  offenders - newly designed electronic, SCR controlled, traffic signals.  There are so many other devices, they become too numerous to mention.

What  concerns me as an engineer is the effect this is having on  listenership, as well as the practicality of continuing to use the 0.5  mV/m contour as an indication of normal daytime coverage. From  listening to our stations and many others, it appears that a more  realistic figure would be 2.0 mV/m or even higher in extremely bad  situations - as much as 5 or more millivolts. 

I have had  discussions with our general manager and many others over the past few  years, including sales people, listeners, and others concerning this  phenomenon. I get calls regularly from listeners who complain that they  have great difficulty in hearing the stations because of "static." Be  they managers, sales people, listeners, or others, they all say the  same thing: "The station's coverage just isn't what it use to be!" And  I have to agree with them. WNTP, for instance, does not have nearly the  daytime coverage it had when I worked here in the early 80s...even with  one less tower and an loosened directional pattern.

As far  management and sales are concerned, and therefore from the standpoint  of those who are largely non-technical, the first thing to come under  suspicion is a change in the transmission system (either transmitter,  or antenna, or both). When one performs a quickie proof on the antenna  system, and checks the power/impedance/etc, all is found to be normal.  On WNTP, for instance, our Inverse Distance Fields on all radials are  pretty much exactly what they were in 1986 when the system was built;  but, electrical noise has reduced usable coverage by at least 1/3. 

I  know that we are not the only stations who are experiencing such  problems. And it is not just broadcasters. The problem also exists for  hams and other users of the radio spectrum. It is evident across the  nation. In a large market such as Philadelphia, the electrical noise  can be incredible. For instance, attempting to listen anywhere near the  electrified 25,000 Volt, 25 Hz powered commuter rail lines is next to  impossible. This is especially evident on the Amtrak Pennsylvania main  line near Downingtown and Thorndale, along which Business Route 30 runs  for several miles. When such lines extend for great distances along  heavily used roads, it becomes a major issue. Another example is a  traffic light located about a mile from both our transmitter site and  the site of KYW. Since new circuitry was installed a while ago, it is  impossible to listen to either WNTP or KYW (both of which are 50kw) or  WFIL (which is 5kw). The buzz from the light circuit creates a loud
 hum  !
 that overpowers the audio of these and other stations.  "Buzzes" from other traffic lights are just as bad.

I  fear that all of this does not bode well for the future of AM radio.  Electrical noise is reaching a point of being such a concern that IBOC  and BPL, as issues, pale by comparison.

I say all of this to ask  a simple question: is there some way broadcasters can combat the  encroachment of noise on AM? I the answer to that question. We, as a  society, are too dependent on these new technologies to expect a  turn-about. Will greater regulation on electrical devices solve the  problem? Perhaps as a long-term solution; but in the short term I only  see the situation getting worse. It seems to me that broadcasters,  either through the NAB, SBE, or other organizations, (perhaps in  cooperation with ARRL and other interested parties) need to band  together to put a stop to the construction and deployment of electrical  devices that pollute the airwaves. The FCC and other regulatory  agencies must place more stringent requirements on devices so as to  greatly reduce or eliminate unwanted electrical noise. If something is  not done soon, we will have reached the point of no return, and  broadcast AM will become a medium whose practical applications are  forever
 relegat!
 ed to history. Likewise, amateur radio and other  users of the LW-MW-HF spectrums face a similar fate. For broadcasters,  there is too much at stake from a business perspective to allow that to  happen. As AM broadcasters, it is our duty not to go down without a  fight. 

Rene'

Rene F. Tetro
Chief Engineer
Salem Communications - Philadelphia
WNTP-AM / WFIL-AM
117 Ridge Pike
Lafayette Hill, PA  19444
Phone:  610- 828-6965  Extension 41
Fax:  610-828-6725
Email:  rtetro@xxxxxxxxx

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