OFDM on HF

[Jeff King]

Hmmm... I'm a member of the HSMM and I don't feel this way. I don't think there should be any legal restriction on the bandwidths amateurs can use on the amateur bands, other then good amateur practice. Amateur radio had a long history of self policing, and for the life of me I cannot understand why the ARRL keeps wanting more and more regulations. We should strive for less and less regulations and try and make amateur radio more relevant to society.

Now, I can be pragmatic within the group, but I have spent some amount of time doing fire control for the HSMM on premature blanket statements such as this. 



On Thu, 20 Jan 2005 13:42:58 -0600, dubose at texas.net wrote:
>
>For those interested in OFDM type modualtion (MT63?) on HF, here is
>how the ARRL HSMM feels about the subject.  The following is
>submitted by John Stevenson, KD6OZH, an HSMM WG member and Project
>Leader for the RMAN-UHF project.
>
>Walt/K5YFW
>
>==========================
>
>"OFDM Modem
>
>The 70 cm band is ideal for HSMM and, using the following
>interpretation of FCC regulations, we should be able to use OFDM
>modems with an occupied bandwidth up to 9 MHz (at least) on the 70
>cm band. HSMM would be classified as an image emission type. This
>interpretation also allows 6 kHz (or more) bandwidth OFDM modems on
>the MF and HF amateur bands.
>
>In 47 CFR 97.315 the emission type "image" is defined as including
>"emissions having B as the first symbol; 7, 8 or 9 as the second
>symbol; W as the third symbol".
>
>In 47 CFR 2.201 (c) (2) a first symbol of B defines the type of
>modulation of the main carrier as an "emission in which the main
>carrier is amplitude-modulated (including cases where sub-carriers
>are angle-modulated) with independent sidebands". The OFDM modem
>fits this description as it has a central carrier with multiple
>subcarriers in the upper and lower sidebands that are angle (phase)
>modulated. In 47 CFR 2.201 (d) (5) a second symbol of 7 indicates
>that the nature of the signals modulating the main carrier are "two
>or more channels containing quantitized or digital information". 47
>CFR 2..201 (d)(2) and (3) indicate that time-division multiplex is
>excluded for a single channel so the time division multiplex
>inherent in HSMM communications creates two or more channels.  In 47
>CFR 2.201 (e) (8) a third symbol of W indicates that the type of
>information to be transmitted is "a combination of the above" and
>that includes (4) "facsimile", (5) "data transmission, telemetry and
>telecommand", (6) "telephony" and (7) "television". HSMM fits this
>definition as it includes data, speech and image components.
>
>In 47 CFR 97.305 "a station may transmit the following emission
>types on the frequencies indicated, as authorized to the control
>operator, subject to the standards specified in 97.307(f) of this
>part". The following table includes the "image" type for all bands
>and references 47 CFR 97.307 (f) (2) for the 160 m through 1.25 m
>bands but does not reference it for the 70 cm through 1 mm bands.
>
>This is the only restriction on the image emission type and states
>that "the total bandwidth of an independent sideband emission
>(having B as the first symbol), or a multiplexed image and phone
>emission, shall not exceed that of a communications quality A3E
>emission". I can't find a definition for "communications quality"
>but it seems to be taken as 3 kHz on the MF and HF bands.
>
>Thus OFDM modems using 6 kHz or less should be authorized on 225 MHz
>and below and OFDM modems with no bandwidth restriction on 420 MHz
>and above. If the emission must fit within the bandwidth used by
>existing analog image communication devices, that bandwidth would be
>9 MHz for DSM AM ATV with a 4.5 MHz sound subcarrier.
>
>The HSMM Working Group specifically requests that the ARRL legal
>counsel, Chris Imlay, review this plan.
>
>Submitted by John Stevensen, KD6OZH, HSMM WG, and RMAN-UHF Project
>Leader.."
>
>========================
>
>
>
>
>
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