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Discussion in 'Amplitude Modulation' started by K4KYV, May 25, 2019.

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  1. K4KYV

    K4KYV Subscriber QRZ Page

    Before starting up ER, while AMP/X was still going strong, Barry called me on the phone to let me in on his plans. I had no objections, and Roger's role with AMP/X was already beginning to ease out. The main problem with ER, like the mainstream publications, has always been lead time, so it isn't a good vehicle for getting breaking news out to the AM or amateur community. Back in the Docket-a-Month era, NPRMs would sometimes (I suspect intentionally) be released with only a 30-day comment period to follow, which would likely be closed before QST even reached members, let alone their having time to compose and submit comments.

    With AMP/X, whenever there was an FCC or ARRL bombshell or a new anti-AM petition, we were able to get the information in the mail in a matter of days, even if it meant not having time to do the complete issue as originally planned. I recall a couple of special mailings that only included some bit of urgent news. We usually got the news from W1AW bulletins or from the other ham radio newsletters, or indirect clues from those sources that something was about to happen. Occasionally we received phone calls from people who had inside access to the information, and a few times information was even gleaned from something overheard from over-the-air discussions. In the general ham radio newsletters like ARRL Letter, HR Reports and W5YI Report, which also began to appear about that time because of the increasing lead time for QST and other mainstream rags, such news sometimes was dispensed timely but without any mention of the effect it would have on AM, or else it would be buried in the other content so that few readers would have noticed it.
     
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  2. N2EY

    N2EY Premium Subscriber QRZ Page

    Agreed! The RBB proposal was a textbook example of something that could have been worked into a good idea, but was totally destroyed by bad presentation.

    The fundamental concept of RBB wasn't a bad one: Put modes of similar bandwidth together, to maximize the use of available bandwidth. Narrow and wide do NOT coexist well!

    BUT

    The way it should have been done would be to present the reasons for it to the amateur community, showing the pros and cons and draft versions of the proposal. See what folks think, work out compromises, revise and rewrite, etc. Make the terms and realities clear (many folks thought that if RBB were enacted, everyone would need expensive test gear so they could measure the actual bandwidth of their signals!).

    Then revise and rework and discuss until a workable plan emerged.

    But that was not done - and the result was overwhelming opposition, not just from AM folks. There were LOTS of SSB users who cried "NO DATA MODES IN THE PHONE BANDS!" and such.

    Shot themselves in the foot, really.

    (Some may remember the failed "Communications Think Tank" proposal, which was opposed even more strongly....)
     
  3. K4KYV

    K4KYV Subscriber QRZ Page

    The key word is "Necessary bandwidth" vs "Occupied bandwidth". The FCC has always steered clear of specific limits to occupied bandwidth, leaving the standard as "good engineering and amateur practice".
    That was a fatal flaw with Docket 20777; it proposed strict limits on occupied bandwidth, plus it was intentionally designed to "deregulate" AM out of existence. Look up the definitions of the terms occupied vs necessary bandwidth. Any regulation-by-bandwidth would have to be by necessary, not occupied bandwidth. Necessary bandwidth defines the class of mode, not the maximum bandwidth a station is allowed to transmit.
     
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  4. K5UJ

    K5UJ Ham Member QRZ Page

    My memory may not be completely accurate about this now, but I recall that the original bandwidth petition was started by two or three angry slopbucketeers, who had a hate-on for ESSB. By the early 2000s, some ESSB ops (full disclosure: I had some gear that allowed this and I tried it out for a time) had modified Kenwood rigs to put out SSB up to 5 or 6 kc on the high end and the space shuttle audio crowd were beside themselves. The whole "ham radio is communications and that means communications grade audio" line was everywhere. The petition was calculated to ban ESSB but AM got caught up in it (I may be only remembering the ARRL petition now) because it specified an AM occupied bandwidth of 6 kc at minus 20 something dB. That pretty much meant any AM with more than around 2 kc of audio would be illegal. Once everyone began to figure out the ramifications, (no vintage 1930s rigs, broadcash rigs, with any kind of decent audio, let alone a full range high fidelity sound) the battle was on. Credit also should go to the Communications Think Tank for their strategically timed and excellent petition.
     
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  5. W1BR

    W1BR Ham Member QRZ Page

    That would assume that AMers would not come up with a SSB system with carrier. That would allow the proposed 6-kHz BW with pretty decent fidelity. It would have made the old boat anchor heavy metal modulation system obsolete.... by many AM guys these days are using fairly modern solid state gear and are pretty resourceful.
     
  6. N2EY

    N2EY Premium Subscriber QRZ Page

    I know the definitions, Don. That's not the point I was trying to make; apologies for not being clear.

    The Big Mistake was that the RBB petition/proposal was formulated and sent to the FCC without FIRST getting widespread support in the Amateur Radio community. Getting such support would have undoubtedly resulted in major changes to the proposal, such as changing to "necessary bandwidth" - and other changes. RBB would have allowed wide data modes to coexist with 'phone modes, and that idea was widely opposed by 'phone ops - most of them SSB users!

    This bypassing-the-process is what causes so many proposals to go nowhere with FCC. We see it time after time, including such classics as NCVEC's "Communicator class" nonsense, and the "Communications Think Tank" fiasco. Neither had a snowball's chance due to widespread opposition in the comments.

    It used to be that FCC was actively involved in Amateur Radio regulation and policy, and would support lengthy discussion, multiple proposals, etc. Just look at the 1963-1967 era when "incentive licensing" generated about a dozen (!) proposals and two different responses from FCC (1965 and 1967). FCC got over 6000 comments in those pre-internet, pre-copy machine days!

    But that was half a century ago, long before deregulation and "legacy radio services".

    What FCC wants from hams NOW is proposals that are complete, concise, don't cost FCC more resources, and have the overwhelming support of the Amateur Radio community BEFORE FCC ever gets them. Otherwise, FCC just gets annoyed at having their limited resources wasted.

    FCC knows about the internet, about forums like this one, about email reflectors, websites, etc. They even know hams can get on the air and talk to each other! So they EXPECT us to reach some sort of consensus BEFORE bothering them. "Mom doesn't want to settle arguments. Mom wants QUIET."

    Heck, look at what happened in the 2000s with code testing. In the 1999 restructuring R&O (98-143?), FCC made it crystal clear that the ONLY reason they kept the 5 wpm code test was because of the ITU-R treaty. All other code testing was GONE. In April 2000, the changes became effective.

    In July 2003, the ITU-R treaty changed. There was some debate as to whether Congress had to formally ratify the treaty before FCC could drop code testing completely, and the question of whether they would just issue an executive order of some sort saying, in effect, "we debated all this several years ago and resolved that the treaty was the only reason to keep 5 wpm testing. Now the treaty has gone, so we're dropping the 5 wpm test. Have fun!"

    But FCC didn't do that, and it became clear that they'd need a formal proposal.

    The smart thing to have done would have been for the no-code-test folks to have written a simple, solid proposal, with lots of support, and submit that ONE proposal to FCC. But...they didn't - FCC got a raft of proposals, many of which were nearly identical in their effect. Heck, NCVEC submitted two proposals! All of them got RM-numbers, comments, reply comments, etc. - and the whole mess took more than 3.5 YEARS to complete. And all they did was drop 5 wpm!

    IOW, if you want FCC to do something, you have to make it easy for them to say yes. Otherwise they either say no or take years to do anything at all. But hams keep making the same mistake over and over and over.

    73 de Jim, N2EY
     
    K4KYV likes this.
  7. K4KYV

    K4KYV Subscriber QRZ Page

    You were clear enough and I did not intend to contradict what you stated. I was merely pointing out a fundamental distinction in terms, that might even allow some form of regulation-by-bandwidth to be a viable alternative. Many if not most hams are unaware of the difference. Regulation by (necessary) bandwidth is not the same thing as imposing specific, legal, enumerated limits on occupied bandwidth.
    SSB with carrier is not AM; it's SSB with poor carrier suppression, and works poorly with a conventional envelope type detector. The reason for this lies in the fundamentals of modulation/demodulation; a phenomenon called quadrature distortion is inevitable when SSB + carrier is received with a conventional AM detector. What you are proposing is ESSB with carrier. You wouldn't need the full carrier, since a full carrier would not properly demodulate the signal in the first place; a "pilot" carrier reduced by 20 dB or so would be sufficient. The receiver would have to include a synchronous detector, which is a BFO that locks onto the pilot carrier to insert a full carrier with zero frequency and phase error, sometimes referred to as "exalted carrier". The ESSB boys have missed the boat by insisting on fully suppressing their carrier and manually tuning in the signal on the receiver.

    Considering the dwindling of all modes of activity on HF in recent years, the bands are no longer congested as they were in previous decades, when the obsession with "bandwidth" was felt justified by many.
     
  8. WN1MB

    WN1MB Ham Member QRZ Page

    If memory serves, the ARRL Letter was started up to address the "breaking new/lead time" conundrum. Perhaps W9BRD can shed some light on this...
     
  9. W9BRD

    W9BRD Ham Member QRZ Page

    The ARRL Letter predates predates my second stint at ARRL HQ (1985-1996). Although I was its editor and paste-up artist for a short time, I can't state the basis for its existence for sure. A likely strong driver was ARRL Officialdom consistently being scooped by The HR Report and The W5YI Report, in which first-to-mindshare race QST's multimonth lead time would certainly have been a factor.

    Best best regardses, Dave
    amateur radio W9BRD
     
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  10. W9BRD

    W9BRD Ham Member QRZ Page

    AM Equivalent (AME). It works well enough for CHU, for which and for similar stations, avoiding spectral regrowth (partial regeneration of the missing sideband) in the transmitter is quite the linear-amplification challenge. If you're receiving AM with envelope detection, quadrature distortion due to the missing sideband during non-fading reception is a drop in the bucket compared to the distortion that occurs on carrier troughs with selective fading of full-carrier, double-sideband signals received with envelope detection. (And yet, truth be told, I find that distortion quite romantic, and almost miss it when I'm using a local carrier for demodulation, phase-locked or not... Ah, the muscular multihop sound of Radio Australia on 9580 -- good times, good times.)

    My fave ham-institutional misinformational factoid is the "the carrier doesn't carry anything" misconception about full-carrier AM when that mode is considered as part of an end-to-end communications system that includes the receiver and its cost, reproducibility, and ease of operation. Assuming that the receiver uses diode/envelope detection and carrier-operated AGC, the carrier (a) provides the 0-Hz frequency and phase referent for the sideband(s); (b) provides the full-quiet (zero modulation) reference for AGC; and (c) provides, at the correct level relative to the sideband(s) the energy necessary to do the work of heterodyning the sideband(s) back to baseband. End-to-end, an information-communication system that leverages the carrier in all three of these ways is actually quite elegant.

    The reason AM had to go for general ham use was the defensible concept of the redundancy and spectrum inefficiency of the second sideband for pure comms purposes, but also, as By Goodman once told me in describing how the phone bands sounded in the 1930s, because heterodyne interference "back then" was murder.
     
    Last edited: Jul 4, 2019
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