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HD Radio Self-Noise
- Thread starter k6sti
- Start date
When was this published, 1997? Come to find out, HD radio interference for modern receivers never was a thing.HD Radio Self-Noise
ham-radio.com
Sure, you use some capacitance sliderule tuner from the 60's might hear the sidebands, but that's likely the time one needs to evaluate the vintage of their hardware, especially when .001% of the radio listening public might suffer an issue.
Excellent work k6sti on this and on other projects you've been kind enough to share.
I like the axial ratio measurements report. Being on the edge of that hill facing the station you are measuring is good. Might be interesting to try the measurements at a lower elevation on the valley floor.
What if you put the antenna and meter on a cart and moved it in a radial line from the transmitter a few wavelengths, noting if and how moving the cart changes H-Pol and V-Pol signal?
Do you think if you measured phase difference between H-Pol and V-Pol elements of a crossed dipole, this could provide interesting information?
In the azimuth to your test location, do you think the radio station transmitting antenna could have different H-Pol and V-Pol ERP?
The digital radio time alignment article is excellent.
I like the axial ratio measurements report. Being on the edge of that hill facing the station you are measuring is good. Might be interesting to try the measurements at a lower elevation on the valley floor.
What if you put the antenna and meter on a cart and moved it in a radial line from the transmitter a few wavelengths, noting if and how moving the cart changes H-Pol and V-Pol signal?
Do you think if you measured phase difference between H-Pol and V-Pol elements of a crossed dipole, this could provide interesting information?
In the azimuth to your test location, do you think the radio station transmitting antenna could have different H-Pol and V-Pol ERP?
The digital radio time alignment article is excellent.
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There are so many other reasons besides self-noise that would impair an analog FM signal for an audiophile's ears, starting with the 75-microsecond preemphasis.
Anyone that concerned about audio quality on a "local live concert" (and who broadcasts those anymore?) would do well to just get an HD tuner and enjoy the lack of pre-emphasis, wider dynamic range, additional stereo separation, and so on. Probably won't need that "rooftop antenna" for a clean signal lock, either.
By the way, when those local symphony concerts WERE being broadcast, they were at the mercy of the local telco and however good or bad the 15 kHz copper lines were.
Look, I get it - I used to read Stereo Review and High Fidelity back in the day, too. But my charge as an engineer in 2023 is to make sure my stations are serving the listeners of 2023, not 1983. And the listeners of 2023, predominantly in cars, aren't getting this kind of self noise in the real world. What they do get is multipath and a noisy RF floor, real-world problems for which HD is a solution, not a problem.
Anyone that concerned about audio quality on a "local live concert" (and who broadcasts those anymore?) would do well to just get an HD tuner and enjoy the lack of pre-emphasis, wider dynamic range, additional stereo separation, and so on. Probably won't need that "rooftop antenna" for a clean signal lock, either.
By the way, when those local symphony concerts WERE being broadcast, they were at the mercy of the local telco and however good or bad the 15 kHz copper lines were.
Look, I get it - I used to read Stereo Review and High Fidelity back in the day, too. But my charge as an engineer in 2023 is to make sure my stations are serving the listeners of 2023, not 1983. And the listeners of 2023, predominantly in cars, aren't getting this kind of self noise in the real world. What they do get is multipath and a noisy RF floor, real-world problems for which HD is a solution, not a problem.
And one more thing - those "audiophile" radio broadcasts 50-plus years ago came out of studios that were way less advanced than what we have today. All that analog gear had to be perfectly installed and constantly maintained to come anywhere close to "audiophile" quality. Tape heads and turntable cartridges deteriorated quickly. Consoles and wiring could get noisy. Studio-transmitter links were primitive.
My digital studio has a noise floor lower than you'll ever hear on broadcast radio. There's never going to be a ground loop or crosstalk between channels. Everything stays perfectly in phase. If my source material is clean, it stays precisely clean all the way through the system and arrives at the transmitter precisely as it left the studio. And that transmitter is going to be a lot cleaner than the old Collins or Gates from 1970, too. No aging tubes to create AM noise.
If the audiophiles back in the day with their oxygen-free cables and 300-pound turntable mounts could have seen the crappy radio studios of the day with lamp wire and plywood holding things together at the far end of the audio chain...
My digital studio has a noise floor lower than you'll ever hear on broadcast radio. There's never going to be a ground loop or crosstalk between channels. Everything stays perfectly in phase. If my source material is clean, it stays precisely clean all the way through the system and arrives at the transmitter precisely as it left the studio. And that transmitter is going to be a lot cleaner than the old Collins or Gates from 1970, too. No aging tubes to create AM noise.
If the audiophiles back in the day with their oxygen-free cables and 300-pound turntable mounts could have seen the crappy radio studios of the day with lamp wire and plywood holding things together at the far end of the audio chain...
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The price you may pay comes in the form of digital artifacts, especially if a station is running multiple HD channels.
A theory I have (and it is mine) is that people vary considerably in their sensitivity to digital artifacts. I can tolerate quite a bit of compression and start hearing it only at a 128 kbps mp3/64 kbps aac bitrate rate. Others are far more sensitive, like my husband. I think part of that is that he has perfect pitch (and I don't). He pretty much can't stand digital anything other than uncompressed formats. He is also a big-time classical listener, though I had to call his attention to KVOD - which, by the way, is digital only on KCFR-HD2 and not on its main analog signal.
While none of this has anything to do with "self noise", it does speak to the acceptability of compressed digital formats for at least some people.
HD does a great job of solving multipath issues, no doubt about it. But there's a trade-off: noise for analog, toilet-swirl sounds for digital...for some people, at least.
My personal opinion, based on A/B comparisons with a high-quality tuner from 1990, an NAD 4300, which has been re-capped, and the Sangean HDT-1X tuner is that the 4300 has a punchier sound with better stereo separation than the HD reception on the Sangean. There may be more noise on the NAD but there are no digital artifacts that are added as a result of HD encoding and decoding. Certainly there could be multiple factors, including the individual components used in each tuner. But there are times when I go, "eh, whatever".
The main issue I have with HD carriers is that they tend to "fool" the automatic tuning systems of recent DSP-based radios made in China into thinking that there's a station on a frequency adjacent to the frequency that a station actually is on. Tecsun radios tend to have this problem quite a bit.
As for "self noise" - yeah, I've never heard it myself. There were discussions about it several years ago on the FMTuners mailing list but I haven't seen any recently.
When I get a little more information, and have a little more time when I'm not traveling so much, I'm planning to post something to the DX and Reception forum about my experiences with FM reception in a relatively flat area of Denver. The results have been somewhat surprising, with simple, stupid stuff sometimes getting better, cleaner reception than fancier antennas. Good FM reception is still an art, I'm concluding.
Seems to me there are 2 options for improving FM stereo sound quality in cars:
This ~41 year old Carver tech and
Diversity antenna systems
IMHO, the Carver tech could probably be improved with 40+ more years of psychoacoustic information and it could be boiled down to an analog IC or some DSP code and used in the FM sections of new car radios (this would be the simplest option since it wouldn't require more than 1 antenna on the car).
Kirk Bayne
No average consumers have claimed the industry needed to improve analog FM quality in cars. There's simply no call for it.
Vehicle electronics manufacturers have done some form of diversity reception before, including Lexus/Toyota. Some still do.
That's how they moved away from unsightly vertical antennas and went to shark fin, in-window, or a combination of both running diversity.
I support ongoing activity by broadcasters and the FCC, such as digital radio.
Reading the tremendous, detailed and impressive amount of work done by Xperi, NAB, NPR, and many others, comments in the proceedings, and observing the methodical and careful FCC process, I think we (and our audience) will be fine.
Excerpt from the FCC August 1st 2023 release:
"...We reiterate that the Commission initiated the process of authorizing digital broadcast operations in 1999 with the eventual goal of moving terrestrial broadcasting from an all-analog to an all-digital world. Although we have stated repeatedly that there is no timetable for this eventual change to all-digital broadcast radio—and do not alter that stance in any way today—our objective remains to advance the progress of digital radio without causing harmful interference or disruption to existing analog operations. This is especially true given the record evidence of increased digital FM receiver penetration, even though we recognize that such receivers are far from ubiquitous, and that the record is less complete with regard to non-automotive digital FM receiver penetration. It is this desire to encourage continued adoption of digital FM broadcast technology that informs our tentative conclusions and proposals in this NPRM...."
Here's a thought- when thinking about this, substitute something else and see if and how it changes your view.
For example, the restaurant business instead of radio, and food quality instead of audio quality.
Reading the tremendous, detailed and impressive amount of work done by Xperi, NAB, NPR, and many others, comments in the proceedings, and observing the methodical and careful FCC process, I think we (and our audience) will be fine.
Excerpt from the FCC August 1st 2023 release:
"...We reiterate that the Commission initiated the process of authorizing digital broadcast operations in 1999 with the eventual goal of moving terrestrial broadcasting from an all-analog to an all-digital world. Although we have stated repeatedly that there is no timetable for this eventual change to all-digital broadcast radio—and do not alter that stance in any way today—our objective remains to advance the progress of digital radio without causing harmful interference or disruption to existing analog operations. This is especially true given the record evidence of increased digital FM receiver penetration, even though we recognize that such receivers are far from ubiquitous, and that the record is less complete with regard to non-automotive digital FM receiver penetration. It is this desire to encourage continued adoption of digital FM broadcast technology that informs our tentative conclusions and proposals in this NPRM...."
Here's a thought- when thinking about this, substitute something else and see if and how it changes your view.
For example, the restaurant business instead of radio, and food quality instead of audio quality.
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Great info k6sti. It's too bad that an FM analog signal has to suffer because of its HD counterpart(s), but I think 98% of audiophiles that considered FM analog a high quality audio source have moved on to Hi-Res streaming now (like Tidal, Qobuz, Apple, Amazon, etc.). Almost all audiophiles have finally accepted digital as a high quality audio source. Hopefully the few remaining die-hard FM listening audiophiles are also switching off all of their LED lighting, solid state dimmers, noisy switching power supplies, fluorescent lighting, etc., etc., at home, along with making sure that yagi is pointed directly at the transmitting antenna (with no obstructions in its path), before engaging in some serious FM analog listening, otherwise the FM analog noise floor has already been compromised. I love my Yamaha T-85 tuner, but I switch it on *maybe* once a year. From an audio standpoint, I no longer listen critically to FM. Thankfully in my case most of my favorite radio stations (KCSM, WQXR, WFMT, WCRB, to name a few) supply their listeners with a decent streaming signal, and that's now where most of my listening takes place. Radio audio quality just doesn't get any better than BBC Radio 3's streaming audio. I still listen to analog FM (and AM) while driving, but with that noisy environment, who cares about S/NR or stereo separation.
The over-the-air broadcast has a large audience, and I think over-the-air will remain important for years to come.
As we speak, broadcasters are allocating resources and taking action to improving the streaming audience experience.
This is a great time for audio. Over-the-air analog broadcasting can and does have better audio quality than ever, we have digital radio, and streaming. Streaming audio quality will improve as "higher speed" Internet becomes more available.
As we speak, broadcasters are allocating resources and taking action to improving the streaming audience experience.
This is a great time for audio. Over-the-air analog broadcasting can and does have better audio quality than ever, we have digital radio, and streaming. Streaming audio quality will improve as "higher speed" Internet becomes more available.
Brian, by noisy environment do you mean road noise or noise in the reception?
My view is a "correct" listening environment cannot exist for a driver. The space is too small, and orientation of the loudspeakers for stereo is not possible, unless you mean a very near field monitor. Years ago I solved this problem by wearing headphones when driving, and received a ticket from a police officer in Miami on the 836 just west of the bay. I was quite put out by this.
I think in a vehicle it is more about the overall "feel" of the sound, which is probably how most civilians hear audio.
As you know, most audio professionals listen to their work in a multitude of environments- nearly technically correct acoustical environment, earbuds, smartphone, smart speaker, laptop, grocery store. I recall reading someone recalling they regularly found Bones Howe in the studio late at night after everybody had left, listening to his mixes on a tiny speaker to see how they held up.
Today, it is interesting listening to contemporary music on AM radio, and noticing how some mixes sound great and others fall apart.
Some mixes sound good on/in nearly every sound system and environment.
My view is a "correct" listening environment cannot exist for a driver. The space is too small, and orientation of the loudspeakers for stereo is not possible, unless you mean a very near field monitor. Years ago I solved this problem by wearing headphones when driving, and received a ticket from a police officer in Miami on the 836 just west of the bay. I was quite put out by this.
I think in a vehicle it is more about the overall "feel" of the sound, which is probably how most civilians hear audio.
As you know, most audio professionals listen to their work in a multitude of environments- nearly technically correct acoustical environment, earbuds, smartphone, smart speaker, laptop, grocery store. I recall reading someone recalling they regularly found Bones Howe in the studio late at night after everybody had left, listening to his mixes on a tiny speaker to see how they held up.
Today, it is interesting listening to contemporary music on AM radio, and noticing how some mixes sound great and others fall apart.
Some mixes sound good on/in nearly every sound system and environment.
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That may be true, but those PUR (People Using Radio) numbers keep shrinking every year. Plus, people under 30 supposedly never use radio. OTA radio may eventually simply age out. AM, except for the flamethrowers in big cities, is pretty much dead already.
I'll agree with that. Transmitters, STL's and consoles have probably never been better when it comes to audio specs. However, if HD is playing havoc with its analog counterpart, where's the FM analog audio quality benefit?
That day is already here for most of us.
Road noise.
Brian, I agree with your comments.
Part of this is the individual experience across the US. I live in the urbanized area of a top 50 market and have a phone and plan that would not be considered cheap. Traveling about in the car, most of the time I can stream audio on the phone just fine.
It is stunning how good it can sound, but...
My major gripe is not being able to button push between content streams instantly. I hear pre-roll commercials, buffering, and endure pop-ups and nagging messages. One streaming content gateway "pops up" with audio and a pitch for programming even when their website is not open in the browser. Some of this may be by design, remember radio stations that gave away radios that would receive only their station?
Despite what some may say, streaming media might not offer more audience choice, if the content creators intentionally try to restrict audience choice.
Thus, for me streaming is a poor listening experience when compared to pure linear over the air broadcast.
There are places where streaming and the Internet in general slow down and become useless, the smartphone becomes a brick. These locations are astounding because they are not in the woods or a place where you might expect it to happen.
Other places, mobile Internet is solid. It can pinpoint location with great accuracy. As you may know, the FCC is seeking greater location accuracy for phones, with ability to pinpoint elevation in addition to ground position. The idea is to permit first responders to locate an emergency in a multi story building. This can be a life saver. It is another example of the good things the FCC does.
Once again, I will mention that those who may be concerned with privacy can choose to hear audio content over the air with a receiver, in complete privacy.
What happens in your radio, stays in your radio.
Part of this is the individual experience across the US. I live in the urbanized area of a top 50 market and have a phone and plan that would not be considered cheap. Traveling about in the car, most of the time I can stream audio on the phone just fine.
It is stunning how good it can sound, but...
My major gripe is not being able to button push between content streams instantly. I hear pre-roll commercials, buffering, and endure pop-ups and nagging messages. One streaming content gateway "pops up" with audio and a pitch for programming even when their website is not open in the browser. Some of this may be by design, remember radio stations that gave away radios that would receive only their station?
Despite what some may say, streaming media might not offer more audience choice, if the content creators intentionally try to restrict audience choice.
Thus, for me streaming is a poor listening experience when compared to pure linear over the air broadcast.
There are places where streaming and the Internet in general slow down and become useless, the smartphone becomes a brick. These locations are astounding because they are not in the woods or a place where you might expect it to happen.
Other places, mobile Internet is solid. It can pinpoint location with great accuracy. As you may know, the FCC is seeking greater location accuracy for phones, with ability to pinpoint elevation in addition to ground position. The idea is to permit first responders to locate an emergency in a multi story building. This can be a life saver. It is another example of the good things the FCC does.
Once again, I will mention that those who may be concerned with privacy can choose to hear audio content over the air with a receiver, in complete privacy.
What happens in your radio, stays in your radio.
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There's a discussion over on the National Radio side that claims that even though using streaming via smartphones, something like 46% of AppleCarplay/Android users are listening to traditional radio content. That brings up the question of whether radio or TV transmission facilities will even be needed in the future. In other words; if consumers consume radio programming via their ubiquitous smartphones which is the way they run their lives anyway, why should radio or TV bother with traditional transmission gear, tower/land leases, and all the utilities and maintenance plus licensing required to keep it all running?
I don't think anyone is saying it is. The concern is a nothing burger. A weak red herring. A solution in search of a problem.
Responding to the technical point- the concern is existing and increased interference at the fringe coverage of closely spaced stations in a first-adjacent channel relationship. In some areas, formerly listenable stations have been subjectively obliterated by digital radio signals.
Some are concerned the protected contour of all radio stations will soon be the 60 dBu contour.
Spectral power distribution of the digital radio signal is significantly close to the center frequency of first adjacent channel stations.
The engineers will provide information and analysis, stakeholders and the FCC will decide, and the engineers will make it happen.
The first point- consumers will do what consumers do. Things go and things come back. The mainframe came back as the cloud.
Some are concerned the protected contour of all radio stations will soon be the 60 dBu contour.
Spectral power distribution of the digital radio signal is significantly close to the center frequency of first adjacent channel stations.
The engineers will provide information and analysis, stakeholders and the FCC will decide, and the engineers will make it happen.
The first point- consumers will do what consumers do. Things go and things come back. The mainframe came back as the cloud.
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It's still a nothing burger Greg. How much outrage or concern have you heard about this issue from flummoxed consumer groups?
Answer: zero. Who is this 'some'? One Ham and a couple old timer radio nerds who still want to listen to the Metropolitan Opera with an old McIntosh tuner? That kind of complaint is the definition of a first-world problem. Chances are the station broadcasting the Met is already does so in HD. A simple trip to Amazon for an HD tuner would solve the problem by eliminating terrestrial noise and improving overall quality.
I get it, change is hard for some. Just look at the old-timers that for years claim there's nothing wrong with the quality of AM broadcasting. It may be fine for them, but someday they'll be gone. What's left behind for the next generation? Nothing but the refusal of innovation by the previous generation.
Make what happen? This isn't an actual real world problem.
It's the same human need or desire in a different package, for a new generation, or demographic.
There is not one generation or demographic.
i.e. who's real world?
For example one generation may feel electric vehicles are the only way forward. Yet...
I used the make it happen sentence to illustrate that many people are career service employees, such the FCC staff, consulting engineers, programmers, attorneys, etc. They have personal views, but do their jobs in a neutral way, to serve their employer.
Specialists in many professions get into the details not of concern to the general population. This is normal, and sometimes it saves lives. Like nuances of metal fatigue in aircraft.
There is not one generation or demographic.
i.e. who's real world?
For example one generation may feel electric vehicles are the only way forward. Yet...
I used the make it happen sentence to illustrate that many people are career service employees, such the FCC staff, consulting engineers, programmers, attorneys, etc. They have personal views, but do their jobs in a neutral way, to serve their employer.
Specialists in many professions get into the details not of concern to the general population. This is normal, and sometimes it saves lives. Like nuances of metal fatigue in aircraft.
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