Interference case #175 (FM) - Second adjacent degrades noise floor by 10 db

[audiophile.]

For second adjacent channel interference, the required RF D/U ratio to maintain reference audio noise must increase by 9.6-dB (from –27.5-dB to –17.9-dB) to maintain the same reference noise when IBOC is added to the analog interferer. This value of degradation may be significant depending on the distance and height relationship of the desired and undesired stations.

http://www.nrscstandards.org/DRB/Non-NRSC reports/Npriaais1.pdf

 

[audiophile.]

quote author=IBOCRocks link=topic=48042.msg332183#msg332183 date=1158766887]

"When did this happen? iBiquity did the research, it was peer-reviewed, tested, and accepted. The NRSC committee and the FCC looked at it and approved it for testing. How did iBiquity write their own rules? I'lll concede that IBOC on AM is an issue, but I 100% disagree that FM is a problem. I've travelled all over, and have not had any reception issues, nor have we heard of any widespread interference complaints. Again, the coverage isn't poor - there are lots of people who pull out "predicted" coverage maps, but in the middle of the country, a 50Kw FM running IBOC can easily cover 30+ miles in HD/HD2. Receiver design is the key...you don't need to use "brute force" to get a clean signal...you need just enough to decode."

Becasue the FCC did not even consider alternative working technologies, as DRM, which doesn't have the serious issues, as with IBOC. There are many testimonials to IBOC FM interference.

There are many testimonials, most of which are anecdotal at the moment. Until there is some solid proof, and some rulings to back it up, it's a "he said, she said" proposition.

The FCC is free to consider or not consider anything. At the time IBOC appeared to them to be the superior technology. Who knows, they may still feel that way.
[/quote]

Here you go IBOCRocks...

 

[IBOCRocks]

quote author=IBOCRocks link=topic=48042.msg332183#msg332183 date=1158766887]

"When did this happen? iBiquity did the research, it was peer-reviewed, tested, and accepted. The NRSC committee and the FCC looked at it and approved it for testing. How did iBiquity write their own rules? I'lll concede that IBOC on AM is an issue, but I 100% disagree that FM is a problem. I've travelled all over, and have not had any reception issues, nor have we heard of any widespread interference complaints. Again, the coverage isn't poor - there are lots of people who pull out "predicted" coverage maps, but in the middle of the country, a 50Kw FM running IBOC can easily cover 30+ miles in HD/HD2. Receiver design is the key...you don't need to use "brute force" to get a clean signal...you need just enough to decode."

Becasue the FCC did not even consider alternative working technologies, as DRM, which doesn't have the serious issues, as with IBOC. There are many testimonials to IBOC FM interference.

There are many testimonials, most of which are anecdotal at the moment. Until there is some solid proof, and some rulings to back it up, it's a "he said, she said" proposition.

The FCC is free to consider or not consider anything. At the time IBOC appeared to them to be the superior technology. Who knows, they may still feel that way.

Here you go IBOCRocks...
[/quote]

To be clear, this is measuring the effect on SCA's. Moreso, from the executive summary:

"On average, the added IBOC-interference effect, based on population, was projected at
2.6%. This figure varied considerably, from as low as 0.3% in markets with relatively flat terrain
and high transmitter power and antenna height to 8.5% in the Los Angeles market on station
KPCC."

This looks like a situation that may be easily mitigated. Or not.

While I don't discount the results, I don't believe that it's a deal-breaker. You could come to a few different conclusions here.

 

[audiophile.]

I have no problem with what you said.

If 67 kHz is affected, we could also expect some increase on the stereo noise measurements. Probably 3-7 dB.

 

[IBOCRocks]

I have no problem with what you said.

If 67 kHz is affected, we could also expect some increase on the stereo noise measurements. Probably 3-7 dB.

Good point. I don't think I've actually measured separation before and after an HD install. I should, just to see what I come up with.