Operating on 60m can be challenging for operators in the UK because the 60m allocation is divided into several narrow, non-contiguous channels, each with its own bandwidth limits and regulatory nuances. As a result, UK amateurs must pay close attention to which channel they are operating on, what emission modes are allowed, and the maximum occupied bandwidth permitted for each specific frequency segment. This fragmentation makes it harder to use wider digital or voice modes consistently, and it adds an extra layer of operational complexity when switching between channels.
We face a similar situation in the US, where 60 m operation is also channelized rather than assigned as a continuous band. However, all U.S. channels share a uniform bandwidth limit of 2.8–2.9 kHz, which at least provides some standardization across the available frequencies. Because of that ceiling, we must use a much smaller transmit filter—typically rolling off at around 2850 Hz—to ensure that our occupied bandwidth stays within the FCC rules for all channels. Even though the channelization is restrictive, the consistency makes station configuration and compliance somewhat easier compared to navigating multiple channel classes with different bandwidth limits.
This article will explain why you are getting an out-of-band error when operating on the channelized 60m band.
I'll use the 11th channel, 5403.5 to 5406.5, which is only 3 kHz wide and the most problematic, as an example.
In most cases, if you are transmitting out of band on the 11th UK 60m channel (5403.5 to 5406.5 kHz), it is because the TX filter bandwidth is too wide since the 5403.5 channel is only 3000 Hz wide.
If you have the radio set for USB mode and the Slice frequency is set to 5403.5 kHz, all of your RF emissions must be contained INSIDE the channel bandwidth. Having RF emissions beyond 5406.5 kHz is transmitting out of band.
The transmit filter (not the RX filter) bandwidth you have configured in the radio determines the passband of your transmitted RF emissions. This is an important factor.
If the slice is in USB mode and the 11th 60m channel frequency is set to 5403.5, and your TX filter bandwidth is set from 0.1 to 3.0 kHz (100-3000 Hz), you take the slice frequency and add the TX filter upper limit.
For this example, all values are in kHz; the math is simply 5403.5 + 3.0 = 5406.5, and from the channel chart, the upper-frequency limit for channel 11 is 5406.5, so your RF emissions are within the channel limits, and the radio will transmit. You can do this test yourself.
Now, if your slice frequency was not 5403.5, but let's say it was 5404.5 and your TX filter was set from 0.1 to 3.0 kHz, then the math is: 5404.5 + 3.0 = 5407.5. Since the upper limit of your RF emission is at 5407.5 kHz, the resulting RF emission is 1 kHz outside the channel bandwidth, the radio will not allow you to transmit.
Where most people run into problems is operating digital modes. Some digital modes do not have the designated sub-band frequency at the lower frequency of a channel. In these cases, you have to prevent the digital moe application from changing the frequency of the slice receiver -AND- you have to configure the TX bandwidth so that all your emissions are inside the channel bandwidth.