Extra Class question of the day: stay in band

When using a transceiver that displays the carrier frequency of phone signals, the highest frequency at which a properly adjusted USB emission will be totally within the band is 3 kHz below the upper band edge. (E1A01) So, with your transceiver displaying the carrier frequency of phone signals, you hear a DX station’s CQ on 14.349 MHz USB. Is it legal to return the call using upper sideband on the same frequency? No, the sidebands will extend beyond the band edge. (E1A03)

The reason for this is that the USB signal extends from the carrier frequency, which is the frequency that the transceiver is displaying, up 3 kHz. When you set the transceiver to 14.349 kHz, the upper sideband will extend up to 14.352 MHz, and because the amateur radio band stops at 14.350 MHz, some of the transmission will fall outside the band.

A similar thing happens, but in reverse, when you operate lower sideband, or LSB. When using a transceiver that displays the carrier frequency of phone signals,the lowest frequency at which a properly adjusted LSB emission will be totally within the band is 3 kHz above the lower band edge. (E1A02) With your transceiver displaying the carrier frequency of phone signals, you hear a DX station calling CQ on 3.601 MHz LSB. Is it legal to return the call using lower sideband on the same frequency? No, my sidebands will extend beyond the edge of the phone band segment. (E1A04)

The lower sideband will extend down 3 kHz from the carrier frequency. So, when your transceiver is set to 3.601 Mhz, your signal will extend down to 3.598 MHz, which is outside the phone band.

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