Discussion in 'Amplitude Modulation' started by NA5B, Nov 25, 2019.
1) FWIW, this is NOT an Amateur Radio Service issue but since we're into AM technology in this forum it is an interesting topic nonetheless.
2) This is a Voluntary plan and analog AM broadcast stations will not be forced into accepting a system that may decrease their listener base. AM broadcast stations will have a choice to either upgrade to the all-digital system or remain analog.
3) Suggestion: If you intend to make comments to the FCC please educate yourself on this topic by reading
4) Comments of late to the FCC has shown that some people are not aware of what the FCC is actually proposing. Again, it is a Voluntary plan and analog AM broadcast stations will not be forced into accepting a system that may decrease their listener base.
Now back to our regularly scheduled program.
Look at the comments to any proceeding in the ECFS website, you will see that a large number of commenters haven't a clue what the FCC is proposing nor what they are commenting on.
I have never hid from the fact that I work for Xperi, so biased yes, but facts are facts, and when facts are either misrepresented or ignored I take issue with this. Everything you laid out technically is correct. As far as chips are concerned: my question is why would a chip maker/ receiver maker install a system that is not used where the cars are sold? You put in open source DRM code, but what signal would it receive? The ship has sailed on the DRM argument as far as a standard in the US. Chips are indeed capable of either DRM or HD, but most do not have the memory to do both. however with the advances being made, and processing power becoming better at a lower price point, you will start to see a proliferation of multi baseband processes possible.
Also, working for Ibiquity/Xperi for 12 years now, I have had a lot more insight into how a receiver is manufactured and the how and why's as well. How long do you think it take a car maker from proof of concept to assembly line to produce a radio? The answer would probably surprise you. Also, do you know how much money it takes a car manufacturer to install and keep an AM radio in the car, a lot more than you think. This is why some car makers are REMOVING AM from the car. It costs far more to implement AM, than it does FM, especially with Electric cars. Also the electronics from other devices within the car make it harder and harder to justify AM's existence in the center stack.
i think the biggest thing that bothers me are the naysayers who will on one side of their mouth, we need less government to run our lives, while out of the other, we need more government mandates to enforce Part 15 and clean up the noise sources and switching supplies, and open up the analog bandwidth. The ship has sailed there as well. people like their gadgets, plain and simple. many can say"we''l I don't buy this or that, and I run a car that's 20 years old, etc....". That is simply not the vast majority of americans or even many users worldwide. My 2 pennies. The last I will comment on the subject.
The FCC asked for comments and I think it is a good idea to debate the issue and to present facts.
It is clear from the FCC's documents that much engineering and performance data needs to be clarified before implementation, hence the FCC's need for clarification.
I would not classify myself as a naysayer because I actually submitted an engineering suggestion to the FCC as to how to measure the output power of this digital waveform, since I do not believe it can currently be measured properly with typical Field Engineer's equipment due to the 64-QAM average-to-peak power ratio (PAR).
I have had a lot more insight into how a receiver is manufactured and the how and why's as well. How long do you think it take a car maker from proof of concept to assembly line to produce a radio?
I counted and have documentation on at least 4 different chip makers that include DRM decoding. Do you realize that in order to turn on these features a simple I^2C programming data stream is all that is needed? In fact in order to turn-on any of the many internal decoding features it simply requires I^2C programming. So I say development time would not be as long as you might think.
As far as cost is concerned, DRM is open-sourced whereas IBOC requires a cost associated with the license.
Here is a major question for you and the industry: Why was the DRM system never tested?
Here is another suggestion: Why not simply upgrade the C-QUAM system since the technology already exists and since most transmitters since about 1978 can accomodate C-QUAM?
I never did see a response to this exchange:
W2ZE: Also, Xperi is waiving the licensing fee for stations converting to MA3. So that barrier has been removed.
If this is true, Xperi has not publicly stated the waving of licensing Fees.
According to https://docs.fcc.gov/public/attachments/DOC-360519A1.pdf ,
Footnote 20 Page 4 NRSC-5-D Standard at 14, n.3. We note that NRSC-5 does not include specifications for audio source coding and compression (i.e., the means by which the audio data to be transmitted on a radio wave is encoded or compressed prior to transmission). In the iBiquity system, audio source coding and compression are handled by iBiquity’s HD codec (encoding software). iBiquity has committed to license all patents necessary to implement NRSC-5, either with or without the HD codec. It is also possible within the NRSC-5 standard to use audio source coding and compression schemes other than iBiquity’s HD codec. See Letter from Michael Petricone (Consumer Electronics Association) and Valerie Schulte (NAB) to Marlene Dortch, Secretary, FCC, dated May 18, 2005, in MM Docket No. 99-325.
There is a difference between licensing all patents and waving those license fees for those patents.
I also think Field and Consulting engineer's and station owners of all sizes and formats should weigh-in and let the FCC know how their customer base views this proposed system in terms of economics and possible listener loss.
For those interested in this very interesting technology please see the PDF.
I don't have a dog in this fight, since I don't have a receiver at home or in the car that is DRM or HD capable, and my analogue FM works fine. I rarely listen to AMBC, more because of the sorry content of what is broadcast than for technical reasons, although the power line noise is a factor. Power lines usually run alongside roads, so almost anywhere you drive, you have a strong noise source only tens of feet from the receiving antenna. At any given time, there is an overwhelming likelihood that at least one poorly maintained power line will be acting up within RFI distance from the receiver.
I have not researched the issue, so I cannot speculate which is technically superior, DRM or HD 100% digital, or if they are about the same. What concerns me is the apparent conflict of interest with the FCC mandating a proprietary system that the broadcaster must pay a recurring licence fee to use, in addition to the initial inflated cost of the equipment.
We need a world-wide standard. With analogue radio, no matter where in the world one travels, AM and FM radios work the same. With some countries now adopting DRM and others HD and who knows what other digital standards, we can no longer travel with our radios with the assurance they will operate wherever we go. Even Canada may adopt a different standard from USA, so our radios may not work after we cross over and drive a few miles from the border. Right now, I can pick up CJBC, Toronto here in TN, entertainment quality, using my 160m beverage.
I can see the advantage of digital AM if the fidelity and noise rejection are indeed superior to analogue and coverage is close to identical, but I see no advantage with digital FM except maybe for the sub-carrier channels. OTOH, from occasionally listening to the AMBC I hear a lot of adjacent channel interference from stations running i-Buzz. I read a lot of complaints in the BC rags about IBOC not having the coverage range of analogue FM, and of the loss of quality when the radio transitions from analogue to digital with variations of the signal. Would all-digital HD have the same coverage range as analogue FM?
I totally agree on that point. I hear the same thing all the time on a wide variety of issues besides the FCC. We need sensible gov't regulations. We operate as a mixed economy, not a freewheeling market economy nor a government operated top-down centrally planned economy as some on both sides the aisle would wish, nor would we want either. Much of the current political debate is over the proper balance of each in our mixed economy.
But a majority liking their i-Gadgets doesn't give the industry the green light to pollute the public airwaves. The FCC has dismally failed in enforcing Part 15 and Part 18 regulations, allowing the unimpeded importation of RFI-spewing consumer junk, and anaemic enforcement against harmful interference emanating from electric power utilities. Yes, people like their i-Gadgets, but let them pay a few pennies more per item to assure that they are clean and don't pollute the radio spectrum. If the EPA can get away with serious gov't over-reach like the recent prohibition of paint remover that actually works (methyl chloride) because 3 people over a period of a decade got hurt from not following conspicuously posted warnings and instructions, and prohibiting gas cans that have a vent allowing them to actually pour without spilling gas when re-fuelling the lawn mower or chainsaw, because a few gas fumes might escape if the owner forgets to replace the vent cap, why can't the FCC equally "over-reach" by prohibiting the importation of garbage with blank holes in the circuit board where RFI suppressor components should have gone?
Thanks for posting Mike.
Roadblocks to better technology are also holding back television from migrating to ATSC 3.0
One large problem is manufacture of capable receivers.
Your point about government mandates verses so called free market is an excellent one.
In the distant past FCC had required all new televisions to include a UHF tuner.
If it were not for that mandate, UHF would have not been anywhere near as successful as it was/is.
Later mandates such as television sets marketed as receivers needed to work on digital television after a certain cutoff date were met with widespread non-compliance.
There are plenty of instances where someone has taken a financial shellacking when government steps in to mandate newer standards.
This is certainly a part of the current proposal to keep this decision voluntary.
Remember how many 23 channel CB sets were heavily discounted when the calendar was about to flip over to 1978 or whenever the new 40 channel models were mandated?
The current AM proposal, being non-backwards complaint and seemingly way past due does not remind me of Blue skies.
What does this have to do with AM on Amateur radio one might ask?
The answer is surplus availability and participants with an interest in the broadcast business.
Actually you have 16 amplitude states and 4 phase states which gives you a possible 64 total states.
This is explained in my full class notes:
Digital (i.e., HD Radio) on the FM bands does have one big advantage: multipath resistance. The FM channel is often wider than the coherence bandwidth, meaning that selective fading often takes out part of the signal but not all of it. This is why analog broadcast FM can sound extremely distorted even when the signal remains strong. It's also why FM is rarely used on HF.
This is what OFDM is all about. By adding error correction and spreading everything across a whole bunch of narrow channels, even the complete loss of one (or a few) of those narrow channels to selective fading can often be filled in by the remaining channels. This is even more effective when you can use part of the neighboring channels, as in the US IBOC schemes.
It depends on the exact shape of the constellation, as there's more than one way to lay out the 64 channel states. Not every combination of phase and amplitude may be valid. About all you can say is that there will be 64 of them.