UK 5 MHz band – Hams still transmitting out of band when using SSB

This appears to be a common problem, some UK Radio Amateurs are still transmitting out of band accidently not comprehending the 2.7 kHz wide bandwidth of their SSB (USB) signals.

At 0850z Tuesday 29th January 2013 I saw on my Flex-3000 SDR Panafall display a SSB (USB) signal with a carrier frequency of 5.380 MHz.

I tuned into the transmission and heard an M0I.. and an M0Z.. in QSO from the North East of England.

They had picked the centre frequency of the 5.378 – 5.382 MHz bandlet, presumably thinking that was OK. However because they were transmitting on a USB dial frequency of 5.380 Mhz their signal was occupying 5.380 – 5.3827 MHz. The highest USB dial frequency you can safely set for this bandlet is 5.379 MHz.

The problem is that is is difficult to comprehend in a text frequency listing form. The diagram below shows it visually.

5.380 MHz

You can see that with an USB dial frequency of 5.379 MHz that would take your SSB signal bandwidth right up to the top edge of this bandlet.

This problem isn’t confined to the 5 MHz band, yesterday there were overseas stations on the 20 metre band (14 MHz) transmitting on SSB (USB) on 14.350 MHz, whereas the highest dial frequency you should set on USB is 14.347 MHz to stay safely within the permitted allocation assuming a 3 kHz wide SSB signal.

Clearly the current training, best practice guidance, knowledge of operating procedures etc. are lacking for so many to make this fundamental error.

The easy solution is to remember to count down in 3’s (3 kHz) from the top of the bandlet edges when using SSB (USB) and that should be your highest USB dial frequency.

73 de Philip G0ISW

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