AM and USB on 40 and 80 meters

"We have been receiving a lot of positive feedback to the new draft 40m band plan", WIA Director Glenn Dunstan VK4DU said. "One idea that has been put forward is the creation of specific segments for AM and Upper Side Band modes on 40 and 80 meters." "Some amateurs are purchasing older ex commercial HF transceivers, which only operate on Upper Side Band. As we all know, it is standard amateur practice to operate in Lower Side Band mode on bands below 10 MHz", Glenn said. Whilst Upper Side Band can be used on 40 and 80 meters, widespread use would create significant disruption.

"Accordingly, any USB operation needs to be confined to a specific segment, preferably at or near the upper band edge", Glenn said. "This is a simple matter on 40m with its 300 kHz of spectrum; however 80 meters presents a challenge."

"One alternative is to assign a single USB channel on the bottom edge of the DX window at 3776 kHz; however this could cause interference to DX operations. So, realistically, the only other suitable area for USB operation would be around the top end of the main 80 meter band".

"It is therefore suggested that a single USB channel be established at 3696 kHz. This assignment would ensure that emissions do not extend beyond the band edge, and minimise interference to the automated Morse broadcast from VK2WI at 3699 kHz."

On 40, it is suggested that USB operation be confined to the segment above 7280 kHz. The requirement to maintain emissions within the band edge means that the highest carrier frequency for a USB signal is 7297 kHz. "An AM segment on 40 is relatively simple to assign", Glenn said. "The most logical spot is around 7146 kHz, the frequency used by AR NSW for their Sunday AM broadcasts. Assignment of an AM channel at 7146 kHz would allow AM users to call back after the broadcast".

AM operation on 80 meters could be difficult, given the high levels of use by SSB stations. It was suggested that the AR NSW AM broadcast channel 3595 kHz could be used, however this is right in the middle of the busiest segment. The only suitable channel is around 3690 kHz.

Feedback to these proposed segments is more than welcome. Please send your thoughts via email to vk4du@hf.ro

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