[CQ-Contest] band plan definition - LSB vs USB

Steve London n2icarrl at gmail.com
Wed Oct 3 16:24:02 EDT 2012

Corrected to 14247 to 14347. No need to make 20 meters any smaller than it 
already is !

The following applies to amateur radio operators in the United States, quoted
directly from the FCC regulations:

97.307(b) Emissions resulting from modulation must be confined to the band or
segment available to the control operator. Emissions outside the necessary
bandwidth must not cause splatter or keyclick interference to operations on
adjacent frequencies.

97.307(d) For transmitters installed after January 1, 2003, the mean power of
any spurious emission from a station transmitter or external RF amplifier
transmitting on a frequency below 30 MHz must be at least 43 dB below the mean
power of the fundamental emission.

Now, my interpretations, using the upper band limit of 20 meter SSB as an example:

- If my station is operating on USB, with a typical 3 dB transmit bandwidth of
2.7 kHz, then virtually all of the power of my fundamental emission is above my
suppressed carrier frequency, and extends from my suppressed carrier frequency
to at least 2.7 kHz above my suppressed carrier frequency.

- Therefore, if I am transmitting on a suppressed carrier frequency above
14347.3, there can be absolutely no doubt that I am violating my country's
regulations. My country's regulations supersede anything stated in an IARU band
plan. (For those who might consider this too technical, the suppressed carrier
frequency is the frequency shown on your radio's digital display.)

- When you consider the shape factor of typical transmit filtering, and the 3rd
order IMD characteristics of SSB transmitters, the situation is actually much
worse than I have stated. Your suppressed carrier frequency would need to be
significantly below 14347.3 for all of your emissions to be at least 43 dB down
from the mean power of your fundamental emission.

And, on a more personal level, if you are running on any frequency above 14347
(or 21447), you simply will not work me. I sincerely hope that other USA
stations abide by the FCC rules, too.

Steve, N2IC

On 10/03/2012 07:22 AM, Tõnno Vähk wrote:
> There is one thing has been bothering me for a while and I am sure there are
> some knowledgable people here who can explain this.
> ITU R1 band plan says:
> * - Lowest dial setting for LSB Voice mode: 1843, 3603 and 7053 kHz*
> But it does not mention the highest dial setting for USB on 20-10 meters.
> So is it allowed to work USB on 14349 what concerns the band plan?
> IARU Region 1 and Region 2 band plans both also say:
> *Transmitting frequencies: The announced frequencies in the band plan are
> understood as “transmitted frequencies” and not those of the suppressed
> carrier!*
> What does it mean? Does it mean that furthermore, it is stressed that 14349
> is OK as it is the transmitted frequency?
> 73 Tonno ES5TV _______________________________________________ CQ-Contest
> mailing list CQ-Contest at contesting.com
> http://lists.contesting.com/mailman/listinfo/cq-contest

More information about the CQ-Contest mailing list