HD radios no longer available

[StephanieNYC]

Clearly it isn't a technical issue, since you won't say whether you have first hand knowledge of FM co-or adjacent channel interference, so what it it?  I

If you're on Long Island, a lot of New York City stations get trashed because of other adjacent channels in Connecticut running IBOC.  Same applies for some Connecticut stations vs. New York City.-- prime example: 101.1 out of NYC vs. 101.3 out of New Haven. 

Another one that can cause a mess is here on Long Island: 92.3 out of New York, vs.s 91.9 out of Lake Ronkonkoma.

[Tom Wells]

Kelly, I wold be willing to bet that Savage is concerned for the radio success of others, and knows that somewhere, each
"technically compliant" but extra wide iboc signal intrudes on someone's formerly useful coverage area, AM or FM.

This is called empathy, I think.  It's an old fashioned concept, like not throwing trash out the car window or passing people
real fast on the right because it's such things are selfish and thoughtless.

Even if littering and passing on the right were legalized, many of us could not lower ourselves to that standard.

Now about the SCA-like noise I hear in stereo decode.....  It's small, but exists.  Will you address this concern?
Why is this imposed equivalent of multipath noise for all now a good thing?


Then there's the sidebands being too much to achieve stereo decode at all, on a Sansui TU-7700 seven miles from WLUP.
No amount of attenuation, amps, rotors, and Winegard fringe FM-only yagi in the attic will bring in WLUP  97.9 in stereo
anymore.  Can I bill ibiquity for the cost of buying another tuner, or modifications to permit me to use this tuner fully?
Please address why the loss of stereo in FM analog is an acceptable tradeoff.

How much worse will FM iboc increases make it?  Will no FM stations decode in stereo without new IF filters or something to deal with
the sideband intrusion? 

If I were in Maryland, I'd go over to ibiquity's offices and wash their windows for free one night as a favor.
I'd use a heavy-grit scotchbrite (copyright Minnesota Mining and Mfg Corg) pad and kitchen cleanser.
Then they could visually enjoy the same thing they do to radio.

As they same in many other countries,  "same-same".

[Kelly]

First of all, thanks for the reply and rational discussion Tom.  So far Stephanie, and you are the only ones that mention real examples, and you siting equipment models.

Let me begin a response by saying that I've been involved with a few FM/IBOC installations, and have not heard one listener complaint  about either not receiving stereo anymore, or noise.  Even the Chrysler car radios from the 90's that have a "noise detector" which when seeing subcarriers, rolls off high end and operates in mono-blend, don't seem to have problems with the IBOC carriers.

Like anything else I suppose there are poor installations, or poor maintenance practice that don't operate within the mask.  The requirements for FM out of band emission remain =>-80dB past 198.4kHz  Obviously stations should be operating within the mask, which can easily be verified using a good spectrum analyzer.  Because the IBOC sidebands are modulated RMS, and unaffected by the analog carrier, one can quickly identify whether the station is operating in compliance.

Regarding your Sansui 7700 series FM tuner, it's been a while since I've laid hands eyes on one, but I believe that receiver was sold in the mid 70's?  Something like 1974-1977?  As I recall it also uses capacitive tuning?  Again it's been a while, so pardon my lapse in memory.  What I do remember, is that Sansui was using an IF strip designed to operate with either European or US standards.  Unfortunately some of the Japanese capacitive-tuned FM radios of the day also drifted slightly as they warmed and cooled, so if a station was running SCA, you could hear a whistle after extended use.  I had the aforementioned problem with a Pioneer tuner of a similar vintage.  What I found which helped was to shotgun replace all the tantalum caps in the IF section.  Tuning gets a little sloppy as those caps age.  Of course that won't fix the wider than normal IF section, but it helps a great deal.  Ultimately I believe you won't find the same problem with a modern "processor-tuned" receiver.

Okay next my response to your question: "How much worse will FM IBOC increases make it?"  It would be helpful if I knew a few more specifics of your concern.  I assume you're talking about stereo decoding of analog on an older tuner?  Or are you referring to any tuner, old or new? 

Like with DTV, assuming you stay within the mask, there should be no problems with interference to the analog carrier or adjacent channels.  In fact, DTV with very high power levels deviating 6Mhz wide, it's common to combine multiple DTV and analog carriers in the same transmission line, and antenna with no adverse effects.  As a matter of fact, a few monts ago I tuned up a combiner for a channel 51 NTSC, and a 50 DTV.  Both running into the same antenna.  The TPO from the channel 51 was combined 100kW, (TPO not ERP), and the DTV-50 was 5kW TPO.  There were no problems with proofing both stations, and the DTV was just inside of the mask.

The same should be the case with FM IBOC.  The one difference is that DTV stations typically use "brute-force" bandpass filters at the transmitter output in an effort to insure spectral mask compliance.  As you know, the physics are pretty simple really.  With FM anyway, it's all about occupied bandwidth/deviation.  Power density or field strength does not effect the deviation, unless of course the amplifier is presented with a bad load, over-driving an amplification stage, or other problems that starts generating harmonics from clipping, ect.  A good steep band pass filter could reduce the chances of that problem occuring, but like DTV, adds group delay to the transmission system.  Chances are good with the relatively narrow sideband carriers for IBOC, it shouldn't matter.       

[Tom Wells]

I think few modern PLL FMs will have much problem with stereo decode, but it is amazing how wide the stereo decode "bandwidth"
as seen by the user on the Sansui for a non-iboc station like WFMT, to razor-thin for most ibocs, then not at all for some like WLUP.


All things being equal, every situation is different. 
My car radios are FM mono, and the tuning "capture and AFC" seems a bit weird as a I tune for best signal on the old
'66 or '72.  I should really test the '84 Blaupunkt to see what it thnks of all this. It hasn't been on since the late 90's.
But I hear no added noise in mono decode.

I' hanven't had the top off that Sansui in 20 years, so I believe you're right.  And it probably has numerous caps
"not spec" in many ways.  It might even be OK with just a proper alignment.  Where the heck is my RF osc these days?

The noise I mention is truly very, very tiny, and I could only detect it in the briefest of the few moments modern FM
gives to modulation less than 10%.  You'd hear it on a classical station, which is why WFMT hasn't yet, but they may do it yet.
People actually complained a lot when they added SCA, and WFMT yanked it....or am I thinking of WNIB?

I suffer nothing from loss of weak signals as the Chicago market is full up.
But I think many rimshot/commute and otherwise power-challenged FMs are gritting their teeth when
listeners give up listening to a borderline weak local signal for a stronger signal.

I will leave this fight for those with real experience in the FM situation.
I guess I'd give the FM a thumbs up, and the AM a thumbs down.  Cut losses, get real, get to work. Part of this system works.

I can't add anything other than to say that at least 100 mhz behaves better for such an application, and FM certainly does a much
better job of being deaf to the dig. sidebands.

Please forgive any missing h's.  This dang keyboard.
Is a crumb or something in the keyboard making the h "funny" an analog or a digital problem?
I  see several arguments for both sides. But I think it is eventually an analog problem, though digits are involved.

[Kelly]

Based on the feedback from adjacent or co-channel problems like Savage has experienced, I agree with your take that perhaps they need to go back to the drawing board on Hybrid IBOC AM.  I also agree that FM IBOC seems to work as designed, depending on the vintage and condition of the demodulating device.

Since you are one of the few, and I might add rational, people critcal of IBOC on this board that seem to be technically inclined, allow me to ask you a hypothetical question regarding digital for Medium Wave broadcast band use..

Based on tests done in the field with stations, and by Ibquity, (http://www.nrscstandards.org/DRB/Non-NRSC%20reports/AM_All_Digital_Report.pdf),  it appears the challenges with AM-IBOC come when operating in "Hybrid" mode, that being with the reduced bandwidth analog carrier, flanked by Primary and Secondary digital carriers.  The occupied bandwidth certainly pushes the limits, combined with the possibility of extended sideband interference caused during analog carrier shift.  As one can see in "Figure 2" of the Ibquity report titled "AM All Digital IBOC Spectrum, the amount of occupied bandwidth is reduced considerably, and the carrier shift factor is removed entirely. 

About five years ago, I wrote a letter to the NAB and the FCC concerned about the use of Hybrid mode, and that doing so would not be a good test in proving the viability of digital modulation in the Medium Wave band.  I suggested that the commission allow existing licensee's to apply for a channel in the AM Expanded band, (1605-1705kHz), for their market, allowing stations to construct a 1kW ND, All-Digital IBOC transmission system, that would retransmit the analog station programming.  Obviously this limits the amount of stations to those who can afford to construct and operate a second transmission system, but slides any potential interference to the end of the MW broadcast band where few stations generally exist anyway.  Besides, the whole AM stereo requrement never got off the ground on that end of the dial, so why not continue using it for experimentation?

Unfortunately, one would need to use the Ibquity modulation scheme for consistency with receivers, but in theory, operation at a low power and reduced occupied bandwidth shouldn't effect the analog portion of the band.

Okay now just watch, Savage is going to rip me again because his station in Northern NY is operating in the Expanded Band!  Wouldn't ya know it??   

[Tom Wells]

I didn't read the report at this time, but do recall from an earlier read just how much better the all digital signal was for bandwidth.
Wasn't it a single sideband reduced carrier?
It would probably not be nearly as loud to tune past on an analog radio as the carrier is only strong enough as need be for reference.

As an engineering solution I like it, but unless some standard exists for a radio to know where to go for freq x's digital signal.
Could  maybe small-frequency shift the AM to report the offset +/-  in a very-slow data packet....

There's enough room in the expanded band for testing, but when shown to work well there, we'll need to come up with spectrum for everybody.   I like fixed offset shifting, every digital signal a certain amount above or below in frequency, but for every new
signal (when they are similar or near),  new intermod products occur, so we might need to put the digitals for the MW AMs in HF anyway.


I don't think there be any interference to the AM band at large if the digital testing stayed in the expanded band.

But it will work well enough that with major acceptance, the intermod problem would arise.

If we go lower than the .530 mhz for the digitals, we've got beacons and even less resolution for the data.

If we go above  1.6 we quickly get to skip territory, so it's hard to guess which would work better.
Then there's the all the other allocations to avoid as we go up in frequency.
There is no free lunch in bandwidth, and to move equal amounts of information will use effectively the same amount
of bandwidth regardless of mode.   It was proven to us in school and I should be able to cite someones name to this dictum.
Which of course is why hybrid must add about 10khz of data on each side of an AM analog to move same info in another mode.
Coulda been done in one sideband, but we won't go into that, will we  .

Regarding WLUP, it must be my location has an unfavorable cancellation as the other FM ibocs have the same strength, but then
no problem with mpx.   Today no mpx from WLUP. (not that I'd be listening, but once upon a time in the late 70's)

[Savage]

So, Kelly, are you enjoying the "conversation" you're "having" with me - where you supply both sides of the dialogue?

If you're interested in actually knowing what my objections are to HD-FM, they're set forth in great detail in the thread "FM IBOC Power Increase Sought," back up on the HD Radio board.  You know, the place where you've been tossed, edited and sent to TIO for being insulting and profane on sundry occasions.