An Urban Legend Disproved

Discussion in 'Ham Radio Discussions' started by N2EY, Jan 1, 2015.

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  1. KO6WB

    KO6WB Premium Subscriber QRZ Page

    There's some references to ITU/CCIR Recommendation 249 as one contributor to the sideband inversion and which sideband will be used.
    The component count is a good one to use since amateurs usually use the least to get the most.
    I've had a WRL Duo-Bander 84 which was SSB on 80 and 40 meters. It had a 5MHz region IF with a VFO in the 1.5 to 2.0MHz range.
    Both the additive and subtractive method were used. Subtract and you had 80 meters and add, you had 40 meters. Both bands were LSB.

    Have fun
    73
    Gary
     
  2. WA8FOZ

    WA8FOZ Premium Subscriber QRZ Page

    No requirements here, but if you pick the wrong sideband, you won't have as many people to talk to:).

    Certain people have been said to record an SSB transmission with their receivers in AM mode; and then transmitting the recording in SSB mode on the opposite sideband....
     
  3. W1GUH

    W1GUH Ham Member QRZ Page

    One of the tricks me and friends would do when QRM encroached on our conversation would be to switch to the other sideband if it was clear. It usually was and we'd carry on the conversation unbothered.
     
  4. N2EY

    N2EY XML Subscriber QRZ Page

    In most cases, an SSB rig intended for amateur use displays the suppressed-carrier frequency. So when you switch sidebands, you're also changing frequency.
     
  5. N2EY

    N2EY XML Subscriber QRZ Page

    With one exception, US amateur regulations have never specified which sideband to use. The whole LSB/USB thing has always (with one exception) been completely voluntary under FCC/FRC rules for amateurs.

    The one and only exception is/was the channels on 60 meters. There, USB was required, so that the primary users could understand and ID any amateurs using the channels. But that's the single exception which proves the rule.

    I don't really think so.

    First, the tradition is very old, dating back to when only 75 and 20 were available to US hams for 'phone between 2.5 and 25 MHz. More to the point, if you look at the design of most SSB ham rigs for the past 60+ years, complying with the tradition meant more components, not less. Example: All the Heath SB series, plus the HW-100/101/104, plus all the S-line, plus all the Drake line separates, could have a component-count reduction if we all used the same sideband on all bands. I suspect most other rigs could as well.

    It is true that some low-cost rigs managed to save components and meet the tradition by ingenious choice of heterodyne scheme. But they were designed AFTER the tradition was in place - they didn't create it!

    Most of all, the point of this thread was to debunk a common urban legend in amateur radio about the origin of a tradition.
     
  6. W1GUH

    W1GUH Ham Member QRZ Page

    So what? Except, of course for band edges?
     
  7. N2EY

    N2EY XML Subscriber QRZ Page

    Just that there's no magic in one sideband or the other.

    The band-edge thing has caught the unsuspecting, btw.
     
  8. W1GUH

    W1GUH Ham Member QRZ Page

    OK....

    But one needs to ask what is the frequency of a SSB signal, anyway? Technically it's not just one frequency but a band of frequencies. But VFO's only display one frequency. So, one could argue that the "frequency" of a SSB signal is what the VFO says (assuming, of course, proper calibration) while specifying which sideband. In that case, switching sidebands in a radio where the (untransmitted, or at least suppressed) carrier remains the same doesn't "change the frequency." The VFO reads exactly the same.

    "The band-edge thing has caught the unsuspecting, btw."

    Sure has, but we're discussing the "frequency" of an RF signal, not rules compliance.
     
  9. N2EY

    N2EY XML Subscriber QRZ Page

    Yes, but the part of the band occupied by the signal changes completely.

    In commercial practice, the "frequency" of an SSB signal is often specified as the center of the channel rather than the frequency of the suppressed carrier.
     
  10. SM0AOM

    SM0AOM Ham Member QRZ Page

    Not only in "commercial practice", but in the ITU Radio Regulations is the concept of "assigned frequency" or "centre frequency" used.
    The concept of "suppressed carrier" or "reference" frequency is carried along for legacy reasons, but the use of assigned frequency takes precedence
    in frequency tables.

    The main point with using the assigned frequency concept is that interference calculations become more unambiguous and simplified, because there is only one assigned frequency regardless if the emission is LSB or USB. Today, this has minor impact on radio amateurs except at the band edges, but it may turn out important if or when we end up with channelised HF bands.

    73/
    Karl-Arne
    SM0AOM
     
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