Bonnie, Where did the "technology jail" go that you have touted so many times when discussing current regulations?
Secondly, how do you deal with the need to declare your proposal as a "standard" so that manufacturers will begin to produce equipment? Something this complicated will require a standard definition like the 802.11 wi-fi definition or perhaps the DRM standard. Will the FCC or ARRL need to make it a "standard"? Once this standard is declared, and amateurs invest in it, how does the next standard get rolled out. Do hams need to start an equipment depreciation expense account so they can roll over their hardware in five years? Will declaring a standard foster experimentation? Jim WA0LYK --- In digitalradio@yahoogroups.com, "expeditionradio" <[EMAIL PROTECTED]> wrote: > > Recently, there has been a flurry of concern over whether USA will > follow the rest of the world's lead using bandwidth based spectrum > management in the Amateur Radio Service. Presently, FCC's rules do > not seem to limit a digital signal's bandwidth on the HF bands. > > The absence of HF digital finite bandwidth limits in USA's Amateur > Radio Service rules has been widely misunderstood, leading to > much superstition, myth, and angst among operators who want clear > guidelines for transmissions... > > Some have pointed to an obscure FCC rule sentence, to argue that there > is a bandwidth limit on digital signals equal to an AM phone signal... > but the rules do not say that at all. Here is what the rule > actually does says: "§97.307(f)(2)No non-phone emission shall > exceed the bandwidth of a communications quality phone emission > of the same modulation type..." > > This begs the question: > What is a "Communications Quality Phone Emission of the Same > Modulation Type..." ? > > "Communications Quality" is a relative term without a clear definition > in the Amateur Radio Service FCC rules. It has been widely > interpreted that a voice audio response of 300Hz to 3000Hz is > adequate for conveying telephony speech, and this might apply to > "a communications quality speech circuit". But, this is not etched > in stone for the Amateur Radio Service, and many hams consider > a wider audio response is necessary for them. > > A simple audio frequency response is not really enough to describe a > "communications quality" telephony speech circuit, and an adequate > end-to-end signal-to-noise ratio is also needed for the listener to > comfortably understand speech, so some level of signal to noise > ratio is needed to maintain a "normal" end-to-end "communications > quality" circuit. 20dB SNR is adequate for most people. > > OFDM Digital Voice has become a popular "Phone Emission" recently. > FCC says that OFDM Digital Voice is "Phone", in this FCC rule > §97.3 (c)(5) definition: > "Phone. Speech and other sound emissions having designators with A, C, > D, F, G, H, J or R as the first symbol; 1, 2 or 3 as the second > symbol; E as the third symbol." > > Here is an example of one possible OFDM Digital Voice Phone Emission: > 1. Emission Type = D1E or D2E > 2. RF Emission Occupied Bandwidth = 25kHz > 3. Communications Quality = Normal > 4. Audio frequency response = 300Hz to 3kHz > 5. RF Signal Noise Ratio Threshold = 0dB > 6. Symbols per second = 300 baud > 7. End-to-End Signal Noise Ratio = 20dB > > As you can see in the above example, this fits a reasonable definition > like a glove, for FCC purposes in the Amateur Radio Service for > a state-of-the-art "Communications Quality Phone Emission". > > Now we arrive at the final part of the FCC bandwidth limitation for > non-phone signals, that must be complied with for digital signals: > "...of the same modulation type" > > That final clause appears to limit non-phone emissions, like data or > image to the bandwidth of a same modulation type phone signal. > > Therefore, we can demonstrate compliance by first transmitting the > 25kHz bandwidth OFDM Digital Voice signal in the example above, in > USA's HF "Phone" SubBands, and then use exactly the same 25kHz > bandwidth OFDM signal for transmitting text or data in USA's HF > "Data" SubBands. > > Is there an FCC Bandwidth Limit for Digital on HF? > Perhaps the finite band-width limit is exactly the width of > the Amateur Band or SubBand. > > Bonnie KQ6XA > > . >
