Understanding the 60 meter band channels (Part 1)

Allowing amateur operators use of the 60-meter band was fiercely opposed by the National Telecommunications and Information Administration (NTIA). The ARRL argued that the 60m band could bridge a much-needed gap for use by amateur radio operators involved in emergency communications, when 80m is too short and 40m is too long. The FCC went to the mat for the amateur radio community and fought the NTIA until they agreed to share 5 lightly used areas of spectrum with the amateur radio community. The NTIA considered each of these 5 portions of spectrum as channels. But the agreement required the amateur operators not to exceed 2.8 kHz of transmit bandwidth. So, when we modify an older radio to operate on the 60m band, we must be mindful of our TX bandwidth.
I will attempt to clear up the confusion concerning the 60-meter band. Channel 1 of 60 meters has a center frequency of 5332 kHz, or 5.332 MHz. That means that our 2.8 kHz of TX bandwidth must fall within +/- 1.4 kHz of bandwidth. For example, our transmit audio on Channel 1 USB must not extend beyond 5.3334 MHz. If we transmit using upper sideband modulation, on the center frequency of the channel, 5.332 MHz, with a 2.8 kHz TX bandwidth, we will be 1.4 kHz beyond our channel slot. Above and below our 2.8 kHz of allowed bandwidth are portions of the spectrum that are allocated for government use. We cannot, and must not, transmit in these portions of the 5 MHz band.
If this still seems confusing, let’s consider one of the questions on the amateur radio exams. On the 20-meter band, the maximum frequency we can set our VFO to is 14.347 MHz, when using USB. The VFO display is indicating where our suppressed carrier will be centered. Furthermore, the lower sideband will be suppressed. When we transmit, our 2.8 kHz wide upper sideband modulation won’t extend beyond 14.350 MHz. Though your radio might be able to transmit with a bandwidth of 3 kHz, setting the TX bandwidth to 2.8 kHz helps ensure that your modulated signal doesn’t extend beyond the band edge. Many radios from the past shipped with a default TX bandwidth of 2.8 kHz. That is a reasonable bandwidth that yields good quality TX audio.
Now let’s apply all of this background to 60 meters. The official center frequency of channel 1 is 5.332 MHz (5332 kHz). Now, assume that you have an older radio and you have performed the MARS modification to the radio, so you can transmit on 5 MHz. As a bonus, you’re going to assign the ten 60-meter channels to memory positions in your older radio, to mimic how newer radios include pre-programmed 60-meter channels. In order for your 2.8 kHz wide upper sideband modulation not to extend beyond 5.3334 MHz, you must set your suppressed carrier frequency 1.4 kHz below the designated center frequency of the channel. But alas, you actually set the suppressed carrier frequency, as displayed on your radio, to 1.5 kHz below the center of the channel. I know it seems confusing, because we are told that the entire channel must be only 2.8 kHz wide, not 3 kHz. But the FCC appears to be allotting us 3 kHz of bandwidth. We should still keep our TX bandwidth at 2.8 kHz to ensure that we don’t inadvertently exceed our limits on the 60-meter channels.
I hope this video helps clear some of the confusion associated with the 60-meter band.
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