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Thread: USB or LSB?

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  1. #1

    Default USB or LSB?

    My grandson was over yesterday and he ask about USB or LSB and how do we know which to use. He also asked, "Where in the rules does it say which sideband to use on which band?"

    I love that little brat, but he gives me a headache.

    OK, so where is the rule found? It's not in the band plan (that I could see).

    Conner is right where I want him to be so that he will ask the big question, "Can I become a Ham Grandpa?" Unfortunately Grandpa is a dummy.

    Thanks for any help you can give an ODL (Old Dummy Load)
    [CENTER][B][I][COLOR="Red"]Romans 5:8 But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us.[/COLOR][/I][/B][/CENTER]

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  2. #2

    Default

    It's not a rule, just a guideline.

    <10 mHz use LSB, >10 mHz use USB.

    The reasoning for it was the common use of 9 mHz filters for filtering out the sidebands, back in "the day."

    Hope that helps.
    Last edited by K2KLI; 07-21-2009 at 01:23 PM.

  3. #3
    Join Date
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    Default

    The standard operating practice for SSB is, as 'KLI says, to use LSB below 10 MHz, and USB above 10 MHz. This is not a regulation, nothing forbids you from using the "other" sideband, but then who would you talk to?

    The convention is, so I've heard, largely historical, based on the design of an early SSB rig. The IF was 9 MHz, which is 5 MHz below the bottom of 20 meters and 5 MHz above the top of 80 meters. When mixed with a 5-5.5 MHz VFO, the sum frequency was at 14.0-14.5 MHz, which covered 20 meters, and the difference frequency was at 4.0-3.5 MHz, which covered 80 meters.

    I wrote the 80 meter frequency range backward to indicate that with this approach the higher the VFO frequency, the lower the mixer output frequency. This also meant that if you started with an upper sideband signal on 9 MHz, you still had a USB signal on 20, but an LSB signal on 80, and thus the convention was born.

    Now, with the digital modes, all bets are off. I've heard old RTTY ops say that RTTY is LSB everywhere, and new PSK ops say that PSK is USB everywhere, and that if things don't work to just use the software "invert" switch. I'll leave it to someone else to enlighten us on that part.

    73,
    Dale, AB1GA

  4. #4

    Default TNX

    Thanks for the great feedback!
    [CENTER][B][I][COLOR="Red"]Romans 5:8 But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us.[/COLOR][/I][/B][/CENTER]

    [COLOR="Lime"][B][I][CENTER]QSL for Century Club Nets via cc net Bureaus
    All direct QSLs w/ sase answered asap
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  5. #5
    Join Date
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    Default

    Quote Originally Posted by K2KLI View Post
    It's not a rule, just a guideline.

    <10 mHz use LSB, >10 mHz use USB.

    The reasoning for it was the common use of 9 mHz filters for filtering out the sidebands, back in "the day."

    Hope that helps.
    Yip...the "standard" was actually all Swan's fault. They made the first multiband SSB transmitter uisng the heterodyne method, and everyone followed suit.

    eric
    "The more you know, the less you don't know."

  6. #6

    Default

    [QUOTE=AB1GA;1643310]
    I wrote the 80 meter frequency range backward to indicate that with this approach the higher the VFO frequency, the lower the mixer output frequency. This also meant that if you started with an upper sideband signal on 9 MHz, you still had a USB signal on 20, but an LSB signal on 80, and thus the convention was born.
    [QUOTE]

    Please, not again.
    This is an "urban legend" that has no engineering relevance.

    It can easily be shown that subtracting the VFO from the IF (IF higher than the VFO) still provides USB output from USB input.

    It is only when the VFO frequency is higher than the SSB IF frequency that
    sideband inversion occurs.

    The practice that sideband sense should change at 10 MHz actually comes
    from early (1940's/50's) commercial point-to-point ISB usage, and was formalized in the CCIR 249 Recommendation. This was derived from the mixing schemes used in the earliest SSB/ISB exciters.

    Today, almost all of the commercial and military SSB users employ USB emissions regardless of frequency. This is mandated in the ITU Radio Regulations and in the ICAO rules for maritime and aeronautical SSB.

    The amateur radio usage of LSB below 10 MHz and USB above can be considered as an anachronistic remnant.

    73/

    Karl-Arne
    SM0AOM

  7. #7
    Join Date
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    Default

    The 10 Mhz. convention has become blurred recently, anyway with the inclusion of the 5 Mhz. band, which is USB, only.

    I know that my father had an early SSB rig, which was centered on the 'Silver Sentry' mechanical filter, circa 1950, and as I recall it was designed to operate 20 meters and 75 meters using the single filter. I thought the IF was 9 Mhz. because he used a modified Command Set as a VFO and I believe it was a 5 Mhz. Command set. But, if we reverse that, with the IF at 5 Mhz. and the VFO at 9, the old story works. Perhaps, though, they shifted the 9 Mhz. IF carrier so that the lower sideband was selected for use on 75. I thought his exciter only had a single crystal, but my memories from 50 years ago are rather dim. I do think it's unlikely that they would have used a 9 Mhz. VFO, as VFO stability above 5 Mhz. was not great.
    EchoLink, IRLP, Allstar and DSTAR linking - adding interest to repeaters worldwide 24X7

  8. #8
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    Default

    Quote Originally Posted by SM0AOM View Post
    ...
    Please, not again.
    This is an "urban legend" that has no engineering relevance.

    It can easily be shown that subtracting the VFO from the IF (IF higher than the VFO) still provides USB output from USB input.

    It is only when the VFO frequency is higher than the SSB IF frequency that
    sideband inversion occurs.
    ...
    73/

    Karl-Arne
    SM0AOM
    My apologies to all for my erroneous post, and thanks to Karl-Arne for the correction.
    Dale, AB1GA

  9. #9
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    Default

    Would someone be considered a LID if they did use USB on 75 or 40m, or LSB on 20, 17, 15, 12, 10? Or is it merely frowned upon because of tradition?

  10. #10
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    Default

    Quote Originally Posted by AB1GA View Post
    This is not a regulation, nothing forbids you from using the "other" sideband, but then who would you talk to?
    You might be surprised at how many people you would find to talk to
    All of them telling you "YOU'RE DOING IT WRONG!"

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