AM HD TURNOFF PACE ACCELERATES

[Savage]

I believe the correct term is "RMS field" in referring to the main lobe in directional systems. It's cited in the station's license.

I like your idea of letting stations increase power to overcome incoming HD interference, but where do I go to get reimbursement for the rebuild of the 4-tower directional system and phasors, new TX line, bigger transmitter, all the engineering plus the vastly higher monthly electric bill?? From personal and professional experience I can tell you, the power required would be massive in many installations (including WYSL.)

I do appreciate the sentiment, but I think it would be far preferable to just turn off the HD noise. Battling RF with RF will probably not improve the listenintg experience.

 

[Savage]

Or:

How about "the contract is up, this thing has been a disastrously expensive boondoggle, it's run up the maintenance budget in a down market, it blew up 14 power modules on the main Tx, the licensing fee is confiscatory, listeners (or other stations) are complaining about lousy quality, interference and reception, budgets have been cut, and in the interest of job security I have no interest in going to the GM and arguing that we should continue something that costs a ton, makes my job difficult and produces no listenership" ??

Maybe something like that??

 

[TheBigA]

Maybe something like that??

Sounds like trying to prove the negative again.

 

[Savage]

On the contrary. I see it as "sanity," an interesting concept, combined with the good ol' human trait, self-preservation. I'm sure you'll argue otherwise for the sake of doing so, but it is beyond dispute at this point that HD Radio is intensely disliked by local radio management, where the expense and operational headaches have been imposed by corporate dummies. Any CE who foolishly persists in glugging the Kool-Aid of this embarassing train-wreck and sincerely lobbies for pounding more money down the IBOC rathole, could do so at the peril of losing his job - unless you happen to work for CBS or Crawford or the two or three other stubborn believers (read: "HD investors," usually with money and career capital.)

 

[davideduardo]

I think the point here is, it's indisputable that HD has not helped AM.

When AM is declining for so many reasons, it is convenient to grasp for straws. AM HD is pretty much valueless, but every time it looks like common sense will prevail, something else comes up to prolong the life of AM HD. The latest is the NAB inquiry into AM and the rapid increase of car manufacturers that are putting HD on the dashboard.

Some of us know that AM HD will not make any difference no matter what. But hope is a hard quality to kill.

Blaming the continuation of HD on the meager investments some of the radio companies made to keep the digital initiative alive is not the reason, though.

Managers believe in and practice the elements of marketing and promotion, not qualities necessarily useful for an engineer. Engineers may want to cut off AM HD now, as it seems impractical... while management tries to perpetuate the hope and the hype. There is no conspiracy and no black helicopters.

When you hear hoofbeats, look for horses, not zebras. If you're interested in likely correct conclusions, that is.

Thanks for the lesson in Ocam's Razor.

 

[Savage]

Yes, Occam's Razor is amazingly predictive, isn't it?

Listen, All Ye To Whom This May Apply: I sincerely wish you well as you insistently cling to the rail of the steeply slanting deck on the Titanic's sister ship the RMS Ibiquity, screaming: "It's unsinkable! The NRSC mask says so!!"

But here in the warm, secure world of the motor launch we speed away from the unfolding disaster scene of IBOC (where we appreciate, for starters, the realities of what people want to listen to on the radio and where we know, like "there is no crying in baseball," there is no "ERP" in AM broadcasting.) Please don't think I'm rude if I roll up the window because, as much as I want to hear you yelling in the widening distance, there's a cold North Altantic wind that's making the cabin chilly and I really have to get to the happy hour going on aft. Godspeed! Make mine a double Dewar's, lads!

(Historical footnote: the RMS Ibiquity lends special significance to the term "triple screw steamer."

 

[Chuck]

Here's a simple test that anyone here should be able to do:

It's been documented in this group that certain stations are turning their HD on and off in somewhat predictable patterns. Do those stations exhibit any increase or loss in ERP or ratings as a result of HD?

Don't know about that, but some NCE's, especially in the crowded Northeast, complained that IBOC interference from adjacent or second adjacent channel stations reduced their coverage in areas they had previously served. No coverage translated into fewer pledges when it came time to do their semi-annual pledge drives. That translates to lower income for the station. If that is true (and I think it is), I say damage has been done.

 

[TheBigA]

If that is true (and I think it is), I say damage has been done.

Let's see the documentation.

Also, if you're talking NCEs, that means FM. This thread is about AM.

 

[iyiyi]

Here are some realistic numbers. A class B FM, 50kw ERP, 150 meter HAAT. Figure a 20kw FM transmitter. Plan on losing about 8.4kw shoving it up the pipe. You got around 11.6kw that finally makes it to the antenna. The antenna gain concentrates this 11.6kw into a directional signal focused on the horizon. The transmitted signal will then provide 50kw voltage levels in a suitable, properly located FIM. This is known as ERP. You have a 20kw xmtr that loses 8.4kw to heat in the coax providing 11.6kw at the antenna. This set up is "effectively" radiating the same power as pumping 50kw into a dipole.

A 5kw AM with an antenna resistance of 102 ohms would have a base current of about 7 amps. AM power is measured by multiplying the antenna base current squared times the antenna resistance. 7 X 7 = 49 X 102 = 4.998kw. Unlike the FM, AM power is directly calculated. If that 5kw AM has 5 towers, then the total power emitted from the entire array will still be 5kw. A good example is 1190 Dallas, TX. Night power is 5kw into a 12 tower array. The main lobe sends about 2,700mV/km signal toward Ft. Worth. A non directional 50kw AM would be expected to deliver about 2,700mv/km. Although the "ERP" of the main lobe is 50kw, the total power output from all twelve towers combined is still only 5kw.

-

 

[TheBigA]

Although the "ERP" of the main lobe is 50kw, the total power output from all twelve towers combined is still only 5kw.

Great. Now is any of that affected by adding HD to the signal in any way?

 

[iyiyi]

Assuming that the broadcast plant is "HD-able"? No adverse effect. But there are 89 pages of testimony in this thread full of "broadcasting experts" telling me that I'm talking through my hat.

 

[Tom Wells]

Of course the radiated power is still what it is.

What all of us are trying to get through is that every part of the the modulation of an AM
subtracts/reduces some of the unmodulated carrier's total power.

At full modulation by a single pure tone, all the power is in the sidebands, and it would be "as loud as possible".

If some of the power is being used to create wideband hiss from 5 khz to 30 khz, then that power is not
available for modulation that is useful to humans. Instead part of the power is being used to create wideband
hissing that humans can also hear, unfortunately it is "in the way" of the sound we'd trying to hear.

If someone wishes to see this as not adverse, I suppose it is their choice.

Some people do not consider a "full diaper" an adverse thing either, I suppose, but anyone with normal operating
senses does, and would prefer the extraneous "data" not be there.

In the case of the diaper, the "modulation" tells us that something is full of feces.

In the case of wideband hiss being introduced into a station's own audio, the modulation tells us something is full of.....

Let the radio be for those with ears to hear.

Those who cannot hear might be wise to find employment where the product is something other than sound.

 

[TheBigA]

What all of us are trying to get through is that every part of the the modulation of an AM
subtracts/reduces some of the unmodulated carrier's total power.

Fine...just give me something scientific. Quantitative. That's what I'm saying.

 

[Tom Wells]

What all of us are trying to get through is that every part of the the modulation of an AM
subtracts/reduces some of the unmodulated carrier's total power.

Fine...just give me something scientific. Quantitative. That's what I'm saying.

Do you think I have a degree in some kind of witch doctoring?

Do you suppose my professors of electronics and radio engineering were teaching something not based in science?

I am not a radio amatuer, and I AM a scientist.

I'm enough an authority to know my statements are based in science and fundamentals,
any call for such proofs either is a call from truthful ignorance or decided obstructionism.
What I can't speak with authority about a subject or an aspect of a subject, I say nothing authoritative at all.
I may offer opinions and even apologize for my ignorance in a particular matter.

A, if you'd like to share a little more about your background, I might be able to see how and why you see things
the way you do. It would seem that you live in a fulltime business-capital-investments-etc aspect of "the industry".
If you have never done any radio engineering work or play then I can understand why the distinctions
we argue about here are of no consideration or understanding to you.
Repeating that there is no interference does not magically make it stop.

Many people hear the hiss, but few have the background to know who is doing it and why it exists.
I have always had to assist others technologically, since I was a boy, so this is as easy as breathing.
Do you suppose I dig ditches for a living and then just made a patentable electronic invention then wrote a utility patent
just so I could put that on a tagline and then make crazy statements here? That's way out there..

Seriously, why would I be blowing you smoke and why would you be so predisposed to think so?

 

[TheBigA]

I'm enough an authority to know my statements are based in science and fundamentals,
any call for such proofs either is a call from truthful ignorance or decided obstructionism.

So believe what I say because I say it, or you're an obstructionist? What a crock.

My (advanced) degree is in science too, and if I said that in college, I'd have been hooted down.

You're making generalizations about people. And I don't think your degree is in psychology.

If people are hearing hiss and it is affecting their behavior, how many is it affecting? And since you're dealing in psychoacoustics, are they able to distinguish HD hiss from all the other noise? I'm not asking you for proof, but simple quantitative numbers. Because I'm not seeing it in the ratings.

 

[iyiyi]

Well... It looks like there really is a "Truth in Every Toke"! Yes? AM radio needs a carrier that can stand and deliver. A good xmtr will keep a rock solid carrier that will not budge whether modulation is zero or 135% (positive peaks). Negative carrier shift will at best make your station sound like shit. At worst it will produce a NAL. Wimpy carriers, like other wimpy things, ain't able to deliver the load.

 

[Tom Wells]

I'm not trying to prove ANY kind of numeric statement regarding ratings or money.
Nor would I try.

When an AM is fully (100% minus/whatever it can do positive) modulated the "carrier" is GONE.

Negative carrier shift does sound awful.

As far as believing what anyone says, you would demand numeric prooof if someone told you
hemoglobin exchanges carbon dioxide with oxygen?

 

[TheBigA]

As far as believing what anyone says, you would demand numeric prooof if someone told you
hemoglobin exchanges carbon dioxide with oxygen?

That's not the issue here. You're making claims about the behavior of people, and it's clearly outside of your expertise.

 

[richllewis]

Since my last post I got an Insignia radio for FM IBOC and on FM it sounds good. I tried it out on one of the Mississippi Public Broadcasting FM stations on Mississippi. I wish that more stations in Mississippi would go the FM IBOC route. Here in Mississippi there wasn't a station here that went the AM IBOC route. Not even Clear Channel in Jackson had their AM stations doing IBOC on AM. I am also glad that WWL-AM in New Orleans did not go the AM IBOC route either.

I do have a question about Memphis. Why is WREC still IBOC and WDIA is no longer IBOC? They are both Clear Channel stations but WREC is Talk and WDIA is urban.

 

[Tom Wells]

As far as believing what anyone says, you would demand numeric prooof if someone told you
hemoglobin exchanges carbon dioxide with oxygen?

That's not the issue here. You're making claims about the behavior of people, and it's clearly outside of your expertise.

The issue seems to be maturity, ignoring facts does not change the manner in which AM modulation works.

I'm sorry that somethng makes it so hard to accept facts from others.

In a situation where humans want to make progress, it's first helpful to find points of agreement.

Insistent refusal to work toward progress is either a decidely closed mind or willful antagonism.

Those with enough money to buy their way through life's problems don't need to acknowledge facts or science.

If F E Terman himself were to come back from the grave and explain modulation products you would reject that, too.