WLS transmitter question.

[radiorob2.0]

...has the infamously lax maintainence of either WLS' or WMVP's transmitter sites improved at all in the last few years?

  Neither station is Lax in their transmitter maintenance, though the reception issue may leave you with that impression. The reception problem has to do with the increase in background noise from all the new microprocessor based appliances. The WLS and WMVP signal is the same strength, the background noise is just stronger these days.

The Part 15 monster is a giant reason as well.  But, let's not forget about all of those cell towers that have popped up over the last twenty years.  There's a factor that has done its share of damage to the AM band. 

[Brian Stevens]

So here we have a 50kw non-directional clear channel primary station toward the bottom of the dial that has signal problems which didn't used to exist!  What does that say about the over 4000 lesser signals out there?  Will the noise continue to get worse?  This sounds like an excellent argument for full digital HD on AM and the sooner the better!

How do you figure?  Isn't HD part of the problem with the hiss?  Or, are you thinking the total end of analog radio all together?  Can you pick up say Chicago's HD from tations that reach the Milwaukee area?

[semoochie]

Without an analog signal in the way, HD should be able to greatly expand its coverage area!  Apparently, it doesn't have to be done all at the same time.  Stations that are still successful could wait until it's feasible for them.  There's some question as to whether anyone will be in another 5 years or so.

[Philip J. Smith]

Full-power, exclusive HD Radio (the only signal true to the IBOC moniker) would have a coverage area more comparable to today's analog signals, because of the greater amount of power devoted to the digital-only signal.  The overall bandwidth for digital-only IBOC is narrower than the hybrid flavor, too, which would theoretically reduce adjacent-channel interference.

Don't bet on seeing HD-only AM stations anytime soon, if ever.  Even with so few overall listeners tuning into analog AM everyday, many cities still have AMs in their top 10.  I can't see any way, even in 5 years, for there to be enough HD Radio receivers on the market to make digital-only AM stations viable.  Every AM would vanish from the books, taking the entire band with it.

[Philip J. Smith]

In a follow-up to my post containing complete misinformation a few pages ago...  I apologize.     I don't know why I jotted down 860 WNOV as the "IBOC" station.  It was indeed WOKY 920.  I scribbled down that channels +/- 10 kHz were completely covered with noise, and "WAUR covered at IL/WI."  Obviously with WAUR being on 930, it makes sense that WOKY would be the noisy culprit, and the +/- frequencies where I heard hash would have been 910 and 930.

Again, my apologies...

As for its effect on WLS, it remains very possible that a receiver with wide IF stages could make listening to WLS far more difficult in the Milwaukee area than it once was.

[semoochie]

Most AMs have already vanished from the books!  It's the successful ones that only have 5 years or so left.

[w9wi]

The Part 15 monster is a giant reason as well.  But, let's not forget about all of those cell towers that have popped up over the last twenty years.  There's a factor that has done its share of damage to the AM band. 

I don't see where cell towers have damaged AM reception... 

with the possible exception of where a tower is very close to an AM transmitter and has distorted the AM station's pattern.  The FCC requires the cell company to fix such problems if the AM station was there first, but I wouldn't be surprised if there were cases where it didn't happen.

Cellular frequencies are MUCH higher than AM frequencies.  (heck, they're MUCH higher than *FM* frequencies)  In my experience with mobile ham gear (which should be even more susceptible to interference than AM broadcast receivers) the only time a cell tower is noisy is if the electric utility line feeding the site has a bad insulator...

(not to say there aren't plenty of electric utility lines that do just that)

[radiorob2.0]

Re Cell towers:

I'm talking about the structures in and of themselves. This is one factor that wasn't as prominent twenty years ago.  It has to have some kind of effect when most of these structures are two to three hundred feet tall, a good quarter wave height for a chunk of the AM dial.  You did bring up another demon of the AM dial, bad insulators.  Some engineers rode the rear end of the local utility to replace insulators; in those cities the AM dial is quiet.  However, many did not.  The situation where I live is beyond repair since it's cost prohibited to replace every insulator.  In other words, the utility said if you hold us to part 15 rules to replace every insulator we'll have to raise our rate and we will tell our customers why.       

[DavidEduardo]

Re Cell towers:

I'm talking about the structures in and of themselves. This is one factor that wasn't as prominent twenty years ago.  It has to have some kind of effect when most of these structures are two to three hundred feet tall, a good quarter wave height for a chunk of the AM dial. 

Most cellular towers are in the 60 or 70 foot range in urbanized areas to avoid interfereing with adjacent cells. Many, such as ones on commercial buildings and apartment houses are in the 40 foot range. And the increasingly popular "disguised like a tree" towers are about 50 feet. While a few are higher, due to irregular terrain, most are not.

At 890, a quarter wave vertical is about 276 feet high, and the optimum 5/8 wave tower used by most 1-A  clears is just under 700 feet.

[w9wi]

Re Cell towers:

I'm talking about the structures in and of themselves. This is one factor that wasn't as prominent twenty years ago.  It has to have some kind of effect when most of these structures are two to three hundred feet tall, a good quarter wave height for a chunk of the AM dial. 

I think David Eduardo is suggesting (and in my experience he's right) that those in cities are too short to have that effect.

Also, if the AM station was there first, the cellular company is required to detune their tower to ensure it doesn't affect the pattern of the AM station.  I know fybush.com has pictures of detuned cellular towers.  I'm sure there are towers out there that were *not* properly detuned, where the station didn't know to complain.