AM Radio IBOC - HD (Digital Radio on AM - (Bad!)

[vicmiller1]

AM Radio IBOC - HD (Digital Radio on AM - (Bad!) -
Causing Digital Interference and Raised Noise Floor in many parts of the AM Band ...
This blocks / disables / degrades AM-DX and reception of weaker stations ...
Also causes reduced Signal-to-Noise-Ratio (SNR) of (even strong) signals ...

Here is a reprint of a recent letter I've written to iBiquity and FCC:

What has really happened is that a (Bad !) trade was made which
has degraded the overall performance of Analog AM Broadcasting
in order to squeeze in HD (Digital) Radio on AM ... IBOC (In-Band On-Channel) ... (Bad !)
It's also on FM but it's not as bad since FM signals are wider band / wider separated ...

Note that the degradation is two fold:
1) spectral pollution and raised noise floor of
neighboring frequency space ...
2) Self (own station) Digital and Analog mixing (in the receiver side)
creating an accompanying 'hiss' which further limits the achievable SNR of received AM stations ...
There is a file called IBOC_Observations.mp3 that has audio clip samples of the resulting IBOC
interference ... It sounds like an additive "hiss" on the signal ...

So in a way it's like a self-fullfilling prophecy ... first, HD (Digital) radio degrades the Analog AM
performance (with its bad effects which limits detection range and achievable SNR), and then says
"I have a fix for you - it's digital radio " ... outrageous ...
HD Radio itself is causing AM band problems ...

The decision to allow HD (Digital) IBOC radio on AM effectively
forsakes / denies / ignores the great tradition, legacy, and real capability of
long distance radio transmission (can be over 1000 miles) of
clear strong AM broadcasting (AM-DX / BCB-DX).

Basically, the philosophy tries to turn the AM band into
another localized short distance "FM" band ... This is because even though the analog signal
is still strong to even 50 KW transmit,
But on the receive side, which would be / can be working deep
into the noise and can still work with only a modest 6 dB SNR on the receive side ...

But now with adjacent channel (Digital) interference from
(Digital) sidebands the noise floor is artifically raised and thereby denying the weak stations to
make it through and be heard ... So HD (Digital) signal components have crapped up
the AM band / raised the noise floor with its digital interference ...
Taking away the use / reception of the lower amplitude portion of the dynamic range of received signals ...

I also question the competency and impartiality of the IBOC decision ... It's almost as if this was quietly slipped in on the American public ... and furthermore, I don't like it ... I wonder if any FCC officials / decision makers on this IBOC issue had any vested interests / monetary interests in HD Radio on AM / IBOC ... and what influences iBiquity had in the decision making process ... Sounds like a "collaboration" based on monetary gain for special interests without including the American public ...
(The largest broadcasters and equipment manufacturers - both transmit and receivers) ... It also pushes out smaller stations and operators ...

Sombody should review the whole process for conflicts of interest and impartiality ...
There are many websites on this ... The FCC approval (the FCC Did Not do their homework and
Did Not Do Their Job ! ) ... Some of those FCC officials looked at it more as generating sales of new radios rather than any technical considerations at all ! (like Bad Interference on the bandwidth tight AM Band !) ...

FCC IBOC HD Radio decision (documentation) in the Year 2002) …
DIYmedia.net - FCC Commissioners Adopt IBOC-DAB

Something stinks here ... Oh Yeah ... It's IBOC - HD Radio on AM

Victor L. Miller - Electrical Engineer / Radio Engineer
E-Mail: vicmiller1@aol.com

 

[kb2vxa]

This is nothing new, IBOC has been a problem since its inception for reasons stated and a source of contention between Canada and US stations causing interference during nighttime propagation hours. One thing though, IBOC had no effect on what you claim to be a tradition and capability of AM long distance broadcast, that was forsaken long before IBOC. You have forgotten the FCC move to provide more local stations with no regard to sky wave including the once clear channel 50KW flame throwers. How many clear channels now, 3? Speaking of Clear Channel, one of a few companies providing satellite driven robots across the country and cookie cutter stations in every major market. No matter where you go it's all the same stations! It goes beyond broadcasting into concert venues, if you don't pay Clear Channel no concert.

Rant mode off, thwarted DXers continue.

 

[vicmiller1]

IBOC HD (Digital) Radio on AM (Bad !) - Follow-Up ...

Thanks for your comments ... Let me again repeat / support my claim that long range AM has been (further) degraded by IBOC HD (Digital) Radio on AM (Bad !) ... I am not only referring to "clear channel" operation ... but even without clear channel allocation ... many big, medium, and weaker stations can still really "reach-out" quite a long way ... and the fact that IBOC HD (Digital) Radio on AM notably raised the ambient noise floor across many portions of the AM Band and effects (raises) the noise floor in adjacent band positions means that weaker stations (even not clear channel stations) are covered up / not receivable at the lower / lowest end of the receive dynamic range - weak - near threshold signals ...

(Side Note: it is amazing how the human hearing can filter and process receivable signals right at noise levels - with a very small (probably 0 - 2 dB) signal-to-noise ratio (SNR). zero (0) dB is Not the same (of course) as no signal ... 0 dB is signal power equal to noise power ... )

So every dB of raised noise floor steals away long range receive distance !

Many Thanks,
Victor L. Miller - Electrical Engineer / Radio Engineer
E-Mail: vicmiller1@aol.com

 

[vicmiller1]

More on IBOC HD (Digital) Radio on AM (Bad !)

Let me also add / point out ... that the FCC "doubled-down" and further pushed IBOC by approving an increase of IBOC from 1% modulation to 4% modulation (unbelievable and bad) ... this increase only creates even more raised noise floor and also increases (self) mixing between the analog and digital portions (of the same signal) ... and this is even more noticable on strong signals ... so it's not just about affecting the weak reception ... the (self) mixing on receive does create more additive noise - for Strong Signals ! with it's analog and IBOC digital components - both strong in the detector !
This has the effect of producing / creating a self-limiting achievable signal-to-noise SNR ...

The signal-to-noise ratio (SNR) can be thought of as a measure of "clean-ness" in the final received signal at the end-user output ... A large Signal-to-Noise means what you're hearing is predominantly "signal" with no degrading additive noise ... so a large / maximized SNR is important (of course !) ... Lower SNR means the signal is not fully "swamping out" the additive noise ...

SNR applies not only to audio ... but the concept of SNR also applies to Video / Video signals as well ...
A large video SNR means the original picture is reproduced faithfully and is much stronger than the additive noise - which in the case of video ... the noise is what people would commonly call "snow" so high video SNR means all picture with minimal degrading "snow" ...

Many Thanks,
Victor L. Miller - Electrical Engineer / Radio Engineer
E-Mail: vicmiller1@aol.com

 

[vicmiller1]

Continuation on IBOC, SNR and BER - Bit Error Rate

Let me also continue ... for digital signals ... instead of using signal-to-noise ratio (SNR) as a measure of goodness in the overall link (faithful reproduction of the original source material) ... for digital signals a different, more meaningful measure of goodness / success is used ...

That measure / criteria is the Bit Error Rate - BER ... the Bit Error Rate ... tells you out of a million (or many millions) of sent symbols how many were not properly detected as the right state (a 1 or a 0) ...
The Bit Error Rate depends on how strong the signal is compared to the disruptive noise which also accompanies the signal ... When the signal is way stronger than the noise the receiver will usually / easily determine properly whether the sent symbol is a 1 or a 0 ... but as the signal gets weaker / closer to the noise level the additive noise can add or subtract to the signal enough to make the receiver determine the wrong bit state and make an error ! ...

It can be theoretically predicted (for a given signal-to-noise), and can also be measured ... the measurement is straightforward ... a generator makes millions of random bits 1's and 0's ... and they get sent through the link ... the received bits are "compared" to the sent bits and they should match perfectly ... the generator keeps score of how may errors occured per million bits sent ... That's the measured Bit-Error-Rate ! ...

So we see Bit-Error-Rate is sort of an equivalent measure of link goodness for digtial links as SNR is for analog links !

Victor L. Miller - Electrical Engineer / Radio Engineer
E-Mail: vicmiller1@aol.com

 

[kb2vxa]

" ... but the concept of SNR also applies to Video / Video signals as well ..."

Unless I'm mistaken video S/N ration (snow) became a moot point with the advent of DTV.

 

[Thayne]

" ... but the concept of SNR also applies to Video / Video signals as well ..."

Unless I'm mistaken video S/N ration (snow) became a moot point with the advent of DTV.

You are right about DTV--If you think about anything to do with TV it is amazing how the quality (of the equipment) has stayed affordable yet the programming really sucks. (Don't need any stinkin flyback transformers anymore)

Nobody has any reason to listen to AM much anyway, unless you live on a farm and want to hear about local news & hog prices. I always liked to prowl AM when I was a kid, but those days are over--nobody cares any more and from what I see iBiquity has not caused anyone to listen to better fidelity on AM.
There are too many options like satellites, mp3's so that FM is even stagnant or dying.
Besides the Gubment doesn't care if we cant hear KOA or KRLD tell us when the barbarians are coming--

 

[KC4RAF]

Yeah, but I still like to listen to

W.o.l.d!

 

[w2xq]

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Want an example, Warren? WPHT-1210 ( tx in Moorestown ) sidebands' garbage spreads out +/- 20 as seen on an SDR display in the Philly area. Boy do I miss those Monday morning silent periods. TA and TP DXing is gone.

 

[w2xq]

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Thayne, I for one would miss the AM radio which I listen to almost all the time when in the car. Some talk shows are not on satellite. The long range reception of AM stations driving from Denver to Yellowstone was a pleasure as we got into the foothills of the Rockies. Cell coverage in WY is sorely lacking in the central and western wide open spaces, so things like iHeartradio are out. And, IMHO, for fun you can't beat the local programming of the myriads of graveyarders scattered through WV, KY and TN.

 

[vicmiller1]

AM Still OK for Me ... Still Some Good Local AM Stations

I still enjoy AM Radio here ... I have a bunch of antique radio consoles that I've restored and enjoy using them especially on weekends ... I don't like anybody including iBiquity and FCC messing with the good old AM Band ... Still can reach out well over 1000 miles at night ...
Stop IBOC Now !!!

Victor L. Miller
vicmiller1@aol.com

 

[vicmiller1]

Continuation: For Digital TV (DTV) The video is a bitstream and Bit Error Rate applies as a measure of overall transmission / link success ... by the way even Bit Error Rate primarily still depends upon the achieved Signal to Noise Ratio - SNR ... so even for a digital transmission , ultimately the signal dominance over noise is still the key ... of course error correction (which uses some of the available bandwidth / capacity) does improve the effective Bit Error Rate

Victor L. Miller
vicmiller1@aol.com

 

[Thayne]

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Thayne, I for one would miss the AM radio which I listen to almost all the time when in the car. Some talk shows are not on satellite. The long range reception of AM stations driving from Denver to Yellowstone was a pleasure as we got into the foothills of the Rockies. Cell coverage in WY is sorely lacking in the central and western wide open spaces, so things like iHeartradio are out. And, IMHO, for fun you can't beat the local programming of the myriads of graveyarders scattered through WV, KY and TN.

I understand what you are saying; I miss a lot of things from my younger days. When I was about 15 I got to go to the old KOA transmitter at Tower road & Colfax which at one time was cooled by a fountain outside the building. That whole 4 legged tower was sitting on 4 big porcelain insulators & the whole tower was THE antenna. The tubes were magnificent to me as was all the associated transformers, etc.

Now if you look at at the new stuff like digital TV transmitters all you see from the front side is many racks of modules-all looking about the same. The only thing that really amazed me was the combiners and the "coax" that looks like copper/brass pipe about 8" in diameter that must have cost a fortune that goes all the way from the Transmitter room to the antennas on the tower thru a tunnel.
Impressive, but not nostalgic at all.

 

[vicmiller1]

Yes ... The big antennas standing on the large porcelain insulator ...
In NY Metro WABC is the BIG station on 770 AM
It's big tower is a diamond shape ... so it comes to a unified "point" - not really a point ,
at the bottom ... It is insulated from ground with a big porcelain insulator ... and that
porcelain insulator supports the full weight of the whole antenna tower ...
The single, bottom-loaded, omnidirectional tower height is 648 ft - big ...

Here's a picture of it
http://hawkins.pair.com/wabcnow/wabcn21.jpg

http://hawkins.pair.com/wabcnow/wabcn3.jpg

Victor L. Miller
vicmiller1@aol.com

 

[n2nov]

W.o.l.d!

I sure miss my friend Harry Chapin. I met him in 1978.

 

[kb2vxa]

Oh forget Hairy Clothespin and WOLD when there's George Carlin and Wonderful WINO. (;->)

"Yes ... The big antennas standing on the large porcelain insulator ...
In NY Metro WABC is the BIG station on 770 AM
It's big tower is a diamond shape..."

You describe a Blaw-Knox tower, the photos clearly show otherwise. The only NYC station to use a Blaw-Knox was WADO at its site in East Rutherford, NJ, being on 1280 it was short and unimpressive. When they raised power from 5 to 50KW daytime the tower came down and was replaced by a 3 tower self supporting array.

 

[vicmiller1]

OK ... I just meant the tower came to one leg / spot at the bottom ... one load bearing point ...

Victor L. Miller
vicmiller1@aol.com

 

[ab3a]

Look at the market. IBOC digital broadcasts are going nowhere. Few are buying these radios. They're not showing up in cars. Nobody seems to be advertising these features.

I don't think you'll have to say much to the FCC. This thing is going the way of AM Stereo and music broadcasts on MW.

There just isn't enough interest...

 

[vicmiller1]

Yes, Agreed, It's Going Nowhere - AM IBOC HD (Digital) Radio on AM - Bad ! ...

Yes, Agreed, It's Going Nowhere - AM IBOC HD (Digital) Radio on AM - Bad ! ...

Yes, definitely no public interest, and I hope it (IBOC HD Radio on AM Band) Self-Destructs very soon ...

With satellite radio, internet radio, self-contained mp3 players, etc HD Radio is a loser ... (Not to mention all the technical negatives I've already covered in earlier posts on this very thread) ...

So Yes, I find your comments to be a confirmation of the hope for it to Soon-to-Disappear !
IBOC HD Radio on AM (and maybe FM too, - but HD Radio on FM is not as serious a drawback) ...

My comments to the FCC were driven by the idea that IBOC HD Radio on AM Band has already had a
more than 10 years of real-world operation yielding a full public "trial" that clearly rejected it ...
So rather than keep it going, I was verbalizing the idea of actually stopping it ... take it off the air ... and
at least remove the degraded effects and let traditional AM Band Broadcasting perform to it's best ... !

Many Thanks !

Victor L. Miller - WA2RCC
E-Mail: vicmiller1@aol.com