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Discussion in 'Becoming a Ham - Q&A' started by KD5PIV, Jul 21, 2009.

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  1. KD5PIV

    KD5PIV Guest

    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.:eek:

    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):eek:
  2. K2KLI

    K2KLI Banned QRZ Page

    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: Jul 21, 2009
  3. AB1GA

    AB1GA Ham Member QRZ Page

    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.

    IU4FLP likes this.
  4. KD5PIV

    KD5PIV Guest


    Thanks for the great feedback!
  5. KL7AJ

    KL7AJ Ham Member QRZ Page

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

  6. SM0AOM

    SM0AOM Ham Member QRZ Page

    N2EY likes this.
  7. K0RGR

    K0RGR Premium Subscriber QRZ Page

    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.
  8. AB1GA

    AB1GA Ham Member QRZ Page

    My apologies to all for my erroneous post, and thanks to Karl-Arne for the correction.
  9. NN4RH

    NN4RH Premium Subscriber QRZ Page

    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. AC0GR

    AC0GR Ham Member QRZ Page

    You might be surprised at how many people you would find to talk to
    All of them telling you "YOU'RE DOING IT WRONG!" :D

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