New Digital Petition at the FCC -- RM-11831

Discussion in 'Ham Radio Discussions' started by K0IDT, Mar 31, 2019.

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  1. KA9Q

    KA9Q Ham Member QRZ Page

    Are they? I didn't see how they were doing that. I'd like the League to promote technology and education in general and ham radio in particular as an excellent way to do it.

    I don't have any special interest in either Winlink or Pactor. I'm here (and filing FCC comments) because Winlink/Pactor4 is only the latest target of a perennial backlash against technological progress on the ham bands. I'm especially concerned about any attempt to change the longstanding rule that only a specific intention to obscure an amateur communication counts as a prohibited code or cipher. This is crucial because anything one might do to use the spectrum more efficiently invariably makes a communication harder to monitor.
     
  2. KB9MWR

    KB9MWR Ham Member QRZ Page

    Well some years back it sure seemed like they were behind the Winlink/Pactor ARES push. If that wasn't there doing then I am not sure where it came from.

    I am in the same boat, I really don't have an interest in Winlink or Pactor. But I do understand peoples concern. However, I won't go so far as to agree with Rappaport. I think you are right and modulation gets more complex, its inherently harder to monitor. But at the same time, without a way to monitor, that makes it hard to self police (a lot of peoples concern), but even more importantly to me is the learning angle. So I do think encouraging folks to support open source and write white papers on things is good. How to balance that with the commercial ham market, and how to not hamper folks with playing with things that today only exist in a closed chip form are the areas that need to be worked out.

    I'd like to see a pretty major overhaul of the rules, not just addressing the bandwidth stuff.

    That standards for certification of Power Amplifiers rules that where designed around preventing unlawful amplifiers in the Citizens Band is hampering people from pairing the low drive HackRF boards etc with amps. And I can't see the CB concern as valid anymore. Does CB still exist?

    I'd like to see all modes on equal ground. I still see the rules for Spread Spectrum as very restricted. I don't feel that 70 cm Amateur TV being able to occupy 6 MHz, but data modes cannot is right... etc.

    There are mess load of others.
     
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  3. KA9Q

    KA9Q Ham Member QRZ Page

    Well, that's probably because it worked well for ARES. I've heard talks by local ARES and Red Cross people saying how much they love Pactor. It gives them what they want -- record communications, ie., email -- and it "just works". There are few higher compliments to an engineer than to say his stuff "just works", i.e., reliably without lots of configuration, troubleshooting hassles, etc.
    I've been careful to distinguish what I'd like to see in an ideal world with the way the world actually is, and I'm very concerned about the negative unintended consequences of trying to get my ideal world through legal force. I think the best way to answer proprietary technology on the ham bands is to beat it at its own game by developing and releasing as open source stuff that works better. It won't necessarily be compatible with the proprietary stuff (in fact it probably won't be) but it'll function even better. The classic example so far is VK5DGR's CODEC2 as an alternative to the proprietary AMBE. Unfortunately the radios with AMBE are mass-produced in China...
    I think it does, but yeah, this is a good example of an unintended consequence. The major technology development since those rules were passed is the rise of good, broadband solid state RF power amps. What do the rules say? You'd have to go out of your way to block 27 MHz on them. Just remove the filters...
    Agreed, I also want to see more spread spectrum, especially in multiple-access networks where it can actually be much more efficient than narrowband stuff. But automatic transmit power control is essential to make this work. I'd be happy to see more of that in the ham bands, even for narrowband modes.

    At the risk of really stirring up some hornets, I've been thinking of experimenting with frequency hopped spread spectrum (Hedy Lamar's famous invention) on HF. Obviously I'll need an STA, and I'll also have to do my homework to avoid angry hams with pitchforks and torches coming to my door. One good application might be a QRPp transmitter on a balloon far out over the ocean.

    Yup!
     
    Last edited: Jun 17, 2019
  4. SM0AOM

    SM0AOM Ham Member QRZ Page

    @KA9Q

    It would be interesting to know what the reasons behind the FCC:s micromanagement of amateur radio really are. Compared to regulations in other parts of the world, the regulations are "byzantine".

    From an outsider's view, they seem like a "patch-work" that is perpetually growing with each addition, which seems to address some specific condition without taking account of the consequences in other areas. One of the rules which is most difficult to understand from an outside perspective is the arbitrary 300 baud HF symbol rate restriction.

    It appears that it was conceived to prevent any use of medium-modulation rate wide-shift FEK on HF channels such as Bell 202, perhaps as an enhancement of 300 bps HF packet.
    With such simple schemes, the occupied bandwidth becomes directly proportional to modulation rate.

    Already in 1980, it was very well known in HF data communications circles that such modulation schemes do not work reliably in the HF dispersive channel.
    So why did the FCC place a "wet blanket" over amateur radio use in the US
    of improved modulation schemes for HF digital communications?

    73/
    Karl-Arne
    SM0AOM
     
  5. KA9Q

    KA9Q Ham Member QRZ Page

    You were commenting on my definition of "efficient use of the radio spectrum". In short, it's "maximizing the information I transfer to my intended receiver while minimizing the interference I cause to everybody else". I don't think anybody can argue that this isn't a good idea.

    Do you see why this fundamentally conflicts with "making my signal easy to monitor"?

    I have no way to know that you want to monitor my signal unless you tell me, and then you become one of my intended receivers. Otherwise you're just one of the many unintended receivers I'm trying to protect by sending as little signal energy as possible. I'll do that with as many of these things as possible:

    1. Pointing a directional antenna at my intended receiver;
    2. Choosing a modulation and coding method that minimizes the required energy per user data bit (the "per bit SNR" or Eb/No);
    3. Using just enough transmitter power to meet the Eb/No threshold at my intended receiver;
    4. Multiple access protocols to avoid stepping on active receivers (not transmitters) sharing the channel;
    5. Minimizing my occupied bandwidth to reduce the chances of landing in an unintended receiver's passband;
    6. Taking advantage of what the receiver already knows (including what I've already sent him) so each new bit I actually send will convey as much information as possible (to him).

    You may recognize #6 as data compression. #3 is always a good idea, even if few people do it. #1 is not always physically practical, especially at lower frequencies.

    There's a fundamental conflict between #2 and #5, because schemes with lower Eb/No thresholds require more occupied bandwidth relative to the user data rate. The famous Eb/No = -1.6 dB Shannon limit applies only when you have infinite bandwidth. When your bandwidth is limited to your data rate, the Shannon limit is 0 dB. This is a complex tradeoff that also implicates #4, since "listen before transmit" isn't foolproof -- you may hear a quiet channel because of a skip zone. We hams have a procedure for that: "Is the frequency in use?" or "didit dit" on CW.

    Methods #1, #3 and #6 will obviously impair your ability to monitor my signal if I don't know you're listening. But even #4 can do it, because the real goal is to defer to an active receiver, not an active transmitter, and this means transmitting on top of another signal if I know that I won't interfere with its intended receiver. But I might step on top of your receiver if I didn't know (because you didn't tell anybody) that you're trying to monitor that other signal on the channel.

    Whole textbooks have been written on all the tradeoffs here because the radio spectrum is such an incredibly valuable shared resource. But you should see by now what I've been trying to say, and why giving priority to ease of monitoring will vastly reduce our ability to use our limited spectrum in ways that minimize unintended interference to others.
     
    Last edited: Jun 17, 2019
  6. KA9Q

    KA9Q Ham Member QRZ Page

    I think it's very simple -- the hams keep asking them to do it. The present case is a perfect example.

    Compared to the 1970s, today's US ham rules are actually much less onerous in some ways. Back then you needed special FCC licenses to put up a VHF/UHF repeater, which needed a special call signs (e.g., WR2AJI). You needed to file paperwork much like that required in the commercial services, e.g., maps showing the repeater site with a height above average terrain (HAAT) calculation. All this over-regulation went away with the retirement of the FCC's Prose Walker.

    There also used to be much tighter regulation of language and content, with ongoing wars between FCC enforcement and, e.g., the infamous "Mount Wilson animal house" repeater on 147.435 MHz in Los Angeles. I think this eventually ended when a court ruled that the hams were within their First Amendment (free speech) rights. Interestingly, this has actually worked out well for everybody. The 435 repeater is still on the air (I'm monitoring it right now) and its denizens (or their logical descendants) are as crazy as ever. But by leaving them alone in their own sanctuary, the crazies leave everybody else alone. Win-win. I don't particularly like the idea of non-hams seeing 435 as the face of ham radio, but it's actually quite mild in comparison with modern online social media.
    Never attribute to malice that which can be explained by stupidity...or simple ignorance. In those days, when it came to new amateur digital rules the FCC largely listened to the ARRL, which in turn listened mainly to its Digital Systems Committee -- of which I was a member in the mid 1980s. And to be honest I don't think we understood nearly as much about the physics and math as we do now. In my defense, I was then a "protocol guy"; I didn't really learn about modems (especially for fading dispersive channels) until I went to work for Qualcomm in the 1990s.
    Not sure I understand. Strictly speaking, by limiting baud rate rather than bit rate or bandwidth, the FCC created a loophole for OFDM that could be much wider than 300 Hz (though I wouldn't want to try to exploit that loophole). The one thing it does constrain is the use of single carriers at high symbol rates with adaptive receive equalization, a la Pactor 4. While that was known technology in the early 1980s, it was clearly well outside amateur capabilities. Not now, of course.

    At the expense of stirring up another hornet's nest, if it were up to me I'd just get rid of all FCC-mandated amateur band plans and bandwidth limits (assuming you stay in the band) in exchange for use of automatic transmitter power control, cooperative multiple-access protocols and other good-faith methods to limit interference. I don't know how well (or even if) all this could work, but that's the best argument for letting us try it out. We're supposed to experiment, you know...
     
    Last edited: Jun 17, 2019
  7. SM0AOM

    SM0AOM Ham Member QRZ Page

    Compared to this, it appears that we are "blessed" with an Administration that currently just says "No" to any proposals from radio amateurs...

    Regarding the symbol rate, I might have expressed myself somewhat unclear.

    What I meant is that simple FSK or FEK using modulation rates much higher than about 300 bps do not "make it" through dispersive channels without applying adaptive equalisers.

    Those were in their infancy in 1980, and were at the "edge" of realisability even with professional resources.

    A clever implementation of channel estimation and equalisation using the inverse impulse response was used in the 600 bps Glenayre/Canadian Marconi HF modem that saw limited use in Arctic point-to-point circuits, and it also was considered
    in an early air/ground HF datalink proposal.

    When studying different coding and modulation schemes for the proposed HF datalink in the ICAO and AEEC, a report compiled in 1982 by my "future boss" SM7EXE about the error-rate performance of HF FSK and MSK modulation surfaced.

    It showed that by using adaptive modulation-rate management which uses the "good" parts of the channel time for higher-rate transmission, 600 bps and above, it was possible to transfer data with reasonable latencies, but the average data throughput became severely limited anyway compared to those obtainable using QPSK and QAM modems using constant modulation rates and adaptive equalisers.

    Regarding the HF frequency hopping spread-spectrum, I am searching the archives for the 1985 paper "Frequency-Hopping Radio for HF: An Experimental System" by Lindblad et al which describes the fundamentals of a quite simple system that even was realisable with early 80s technology.

    SDR would make such a system very much within reach today in countries that actually permit expanding the amateur radio state-of-the-art.

    73/
    Karl-Arne
    SM0AOM
     
  8. KA9Q

    KA9Q Ham Member QRZ Page

    Whether that's good or bad would depend on the specific proposal, no?
    Right.
    What is the problem? Is it the difficulty of equalizing a channel that's constantly changing? ATSC (the North American digital TV standard) has the same problem since it uses 8-ary AM at a high symbol rate (our channels are still 6 MHz wide). Receive equalizers are mandatory, and at least the early ones didn't work well in mobile environments.

    So I'm still skeptical that you can adequately equalize a ham HF channel for a high symbol rate, but I suppose it's possible if conditions are reasonably stable. Otherwise I'd think OFDM would work better, though it does have a high peak-to-average power ratio. I keep thinking about ways to handle that particular problem, such as having a separate RF power amplifier for each OFDM carrier that runs at saturation and combining their outputs at high level. Another is to increase linear amplifier efficiency by running the final stage in saturated mode and applying the envelope at high level with collector or drain modulation. I'm not enough of an RF guy to know which of these (if any) are really practical.
    Let me know if you find it.
    Yes. My thinking is M-ary FSK (like one of the JT modes) with a frequency hop on each symbol.

    You going to be at Friedrichshafen? I will be there for the first time. It's this weekend.
     
  9. SM0AOM

    SM0AOM Ham Member QRZ Page

    Family commitments keeps me in Sweden this weekend.

    It would certainly have been nice to discuss topics of mutual interest over a beer. :)

    73/
    Karl-Arne
    SM0AOM
     
  10. KX4Z

    KX4Z Ham Member QRZ Page

    Wow! I can learn a lot just by looking up the terms you guys are using. You are way beyond me and I hope you succeed

    Florida is much better organizing its volunteer emergency comms response after the lessons learned in the category four (or five ?) hurricane last year ; HF surprisingly is going to play an even larger role. The VHF systems simply don’t cover enough of the state to be politically supportable by the government. I just finished teaching one of the new revamped EC 01 courses , 21 hours, of which at least 10 were hands-on ; we did a ton of educating... bringing people up to speed on loads of technologies

    JS8 appears to me to offer a new opportunity for very low speed automated relaying of critical information out of disaster areas So we are now investigating it locally...

    On another forum we have gotten lots of loud statements from government types about their vast communication systems, but it looks like basically what they used them for was real time video ; Some of this is tightlipped so I can’t get much more knowledge

    One of the shelters still went day after day with a public health crisis on their hands..... and there was plenty of honest blame to spread around for why that happened, despite best efforts by many people ...... Better training, would likely have solved that particular crisis much more quickly

    I just shake my head when people say there is no documented need for volunteer emergency communications, they just don’t know what goes on

    I believe I heard we had 22,000 people in shelters. When you’ve got that level of risk of pandemic (if they are poorly managed) it gets attention. And at least one notable shelter was very poorly handled. One official at least lost their position related in someway to this

    Whether justified or not I can’t really say I don’t know the details, but huge efforts are being made to improve the volunteer response at least. State assets with Vhf/uhf repeater capabilities are now moving towards adding HF capabilities so they are not so isolated. Some of the stories are pretty funny.

    Reality is sometimes much more interesting than fantasy

    It would be interesting to know which group wanted to send a lawyer to the ARL discussion. Lawyers can be good & bad. It would be interesting to know why they wanted one


    Gordon
     
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