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IBOC rules published in Federal Register

The Federal Register (in the reference in the post above) says (in part):

• Authorizes AM nighttime
operations and FM dual antenna
configurations;

Sounds pretty convincing for a Sept. 14 date.
 
GOOD! Let's jam the band out of existance - then the spectrum can be auctioned for other services. I also like that we are jamming Mexican and Cuban stations - they have been putting their trash over our borders for years, its time for us to return the favor.
 
I guess we'll know by the end of September just how bad it will be for nighttime AM.

But I thought this quote from contract engineer Kevin Berlen was interesting:

“The biggest problem I have with the technology is the total disregard for the NRSC curve that we have been operating under for many years now...The NRSC system implemented to help reduce AM interference is not perfect but it mitigated a great number of the interference issues.

“AM IBOC totally blows this foundation away,” Berlen said. “It is astonishing to me that AM stereo was implemented over two decades ago and with minimal impact on adjacents. With today’s technology, we should have been able to do better.”

Another station manager said that "AM IBOC will be the “death knell” for small to medium markets."

http://www.rwonline.com/pages/s.0049/t.7843.html

So we'll just have to wait and see what happens.

db
 
And what isn't stated is that the HD signal COMPLETELY FITS under the existing NRSC mask (the NRSC curve is an audio equalization standard). HD does not ignore the mask. As a matter of fact, there is an NRSC-4 mask for HD which is MORE stringent than the present NRSC mask - and the HD signal fits under it.

From testing I've participated in, my prediction is the sky won't be falling any time soon.

Tom Ray
WOR
 
Tom Ray said:
From testing I've participated in, my prediction is the sky won't be falling any time soon.

Tom Ray
WOR
Click to expand...

That's why I think it's important to reserve judgement until IBOC for AM is fully implimented. IBOC seems like a technology that will have to have full real-world use before we can arrive at a final answer as to whether it causes wholesale interference or not...or whether the interference it does cause is acceptable.

Of course, the number of AM stations that have converted to HD Radio is relatively small at this point, so it may be a while before we see the full impact of it. I would be very interested to see what kind of impact it has (if any) on small and medium market stations.
db
 
Tom Ray said:
And what isn't stated is that the HD signal COMPLETELY FITS under the existing NRSC mask (the NRSC curve is an audio equalization standard).  HD does not ignore the mask.  As a matter of fact, there is an NRSC-4 mask for HD which is MORE stringent than the present NRSC mask - and the HD signal fits under it. 

From testing I've participated in, my prediction is the sky won't be falling any time soon.

Tom Ray
WOR
Click to expand...

Of course the sky won't fall in. Everyone knows that the AM band has no interference issues whatsoever. There's plenty of room for what would otherwise be unlicensed stations programming fully modulated white noise and garden sprinkler sounds on adjacent frequencies.

So what's a tiny amount of noise? I betcha nobody will notice. If anyone complains, it'll be troublemakers making things up.

Don't be surprised to see long lines of radio listeners outside Radio Shack stores demanding to buy an HD radio at any price.

HD radio will save the AM band you know.

Now Coast-To-Coast AM will finally sound the way it always should have sounded on all analog radios - audio with a sort of UFO noisemaker effect.
 
The problem with the NRSC restrictions and HD is that the HD sidebands are 1:1 peak to average ratio and were not designed to handle the type of audio growth created by the sidebands.

This type of modulation was not even considered when the rules were passed in the early 1990's.
 
Tom Ray said:
And what isn't stated is that the HD signal COMPLETELY FITS under the existing NRSC mask (the NRSC curve is an audio equalization standard). HD does not ignore the mask. As a matter of fact, there is an NRSC-4 mask for HD which is MORE stringent than the present NRSC mask - and the HD signal fits under it.
Click to expand...

Tom, as you're well aware, NRSC mask compliance measurements are made with the spectrum analyzer in "peak-hold" mode for at least ten minutes. This amount of time is specified in the FCC rule (73.44) because it takes a while for analog sideband peaks to "accumulate", because they are of short duration and have a low average power.

Try changing the analyzer from peak-hold to averaging mode, then compare the occupied bandwidth of an NRSC-compliant analog-only station with one running HD. I would expect a big increase in energy on the first-adjacent channels and beyond, because the digital sidebands are continuous.

Shouldn't the averaging method do a better job of representing "real world" interference than the peak-hold method?
 
Tom Ray said:
And what isn't stated is that the HD signal COMPLETELY FITS under the existing NRSC mask (the NRSC curve is an audio equalization standard). HD does not ignore the mask. As a matter of fact, there is an NRSC-4 mask for HD which is MORE stringent than the present NRSC mask - and the HD signal fits under it.
Click to expand...

The problem is the duty cycle. The NRSC mask was designed for accomodating intermittent high-frequency material of short duration - cymbal crashes, the crack of a baseball bat, gunshots, stuff like that. The designers never anticipated outer areas of the mask being filled by material with a 100% duty cycle.

I guess we'll all find out in a month.
 
vsa said:
Of course the sky won't fall in.
Click to expand...

If some people get improved reception, then nothing will happen as far as they are concerned. In fact, they may be very happy. The people who get worse reception will simply not listen to AM radio. There are plenty of other choices. Since the word on the street is that nobody listens to AM more than a few miles away from the transmitter site, I guess the stations owners won't care, and the people who never tune in AM with any regularity will never notice.

I will hazard a guess that the size of the group who never tunes in AM may increase for the foreseeable future, at least, until every car comes standard with a nice new HD radio. That may be a while. Some broadcasters can probably wait that out. Others may not be so lucky.


But he sky will not fall. We’ll just do something else.
 
Tom Ray said:
And what isn't stated is that the HD signal COMPLETELY FITS under the existing NRSC mask (the NRSC curve is an audio equalization standard). HD does not ignore the mask. As a matter of fact, there is an NRSC-4 mask for HD which is MORE stringent than the present NRSC mask - and the HD signal fits under it.

From testing I've participated in, my prediction is the sky won't be falling any time soon.

Tom Ray
WOR
Click to expand...

We will see how your nighttime audience more than 10 miles away from the towers enjoys IBOC hash from WLW and WGN mixing with your analog audio. Because WLW and WGN analog signals will make digital decode very difficult except in the central part of the city. Have fun - I don't envy your future problems after September 15th.

In our market - fans of Cowboy 1190 can kiss their station goodbye at night as WOAI 1200 - only 280 miles away - wipes out their station. The daytime situation has been bad enough as residual skywave from WOAI puts hash on the station. When they go down to 5kW on a wierd 12 tower pattern at night, they are going to get clobbered.
 
vsa said:
Now Coast-To-Coast AM will finally sound the way it always should have sounded on all analog radios - audio with a sort of UFO noisemaker effect.
Click to expand...

Except in Portland where Coast-to-Coast is on 1190 KEX, broadcasting in HD...
 
Tom Ray said:
Tom Ray
WOR
Click to expand...

You might be interested in 710 monitored in the Dallas market. Daytime 710 is a particularly fascinating situation here. 50 kW KEEL Shreveport, only 200 miles away, mixes almost equally with KGNC Amarillo 360 miles away - and it is only 10 kW! Any distance to the Northwest, and KGNC eclipses KEEL. This is a splendid example of the effect of ground conductivity at the transmitter site being a big factor in coverage. KGNC is a MONSTER because the ground conductivity is good.

I am sorry to report I have never been able to receive even a trace of WOR in the Dallas area. Before newer stations came on the air, WABC and WCBS were regular and easy catches here. Dallas has had a legacy 660 for decades that precluded any attempt at receiving WFAN (the old WNBC).
 
rbrucecarter5 said:
We will see how your nighttime audience more than 10 miles away from the towers enjoys IBOC hash from WLW and WGN mixing with your analog audio. Because WLW and WGN analog signals will make digital decode very difficult except in the central part of the city. Have fun - I don't envy your future problems after September 15th.

In our market - fans of Cowboy 1190 can kiss their station goodbye at night as WOAI 1200 - only 280 miles away - wipes out their station. The daytime situation has been bad enough as residual skywave from WOAI puts hash on the station. When they go down to 5kW on a wierd 12 tower pattern at night, they are going to get clobbered.
Click to expand...
Are we going to get FCC policies tested in the courts? There are two seemingly contradictory policies. First is that a station is supposed to be free of "objectionable" interference inside its protected contour. Second is that a station is allowed to run modulation that falls within the NRSC mask. What happens if a station is running something that supposedly fits in the mask, yet still causes objectionable interference inside the protected contours of other stations? I think the band is so overloaded with stations that this type of interference is going to be widespread in less than 30 days.
 
rbrucecarter5 said:
GOOD! Let's jam the band out of existance - then the spectrum can be auctioned for other services. I also like that we are jamming Mexican and Cuban stations - they have been putting their trash over our borders for years, its time for us to return the favor.
Click to expand...

I just do not believe the sky is going to fall when nighttime IBOC is authorized. We as DXers will notice a higher noise floor, but the general public won't care. That being said, I don't believe nighttime IBOC will be very effective. I think the digital signal will fail even for the high powered stations. I own 2 HD radios and was initially supportive of AM IBOC, but now believe it works well only on FM. I think an all-digital scheme would work on AM, but I don't see how we would get there? As time goes on, more amd more FM stations will adopt IBOC, while at the same time, many AM station will turn it off. WSAI (1360) left their IBOC on "accidentially" at night and the range of the digital signal was restricted about the 50mv/m contour due to the analog signals coming in on 1350 and 1370.
 
Again the problem with the IBOC rules is that the new "protected," "interference-free", "city grade contour", and such are mentioned in the IBOC rules and by iBquity but NO actual mv/m values are given in ANY official or unofficial publications. SO you end up with no actual mv/m field values that may or may not be interfered with in protests. It is a cute trick that they have gotten away with so far, these undefined terms. No matter what mv/m is actually measured it is always "not the correct protection" mv/m reading. The past standard contours of protection are meaningless with these new IBOC rules.
 
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