ARCHIVE: Australian Ham Radio Discussion Forum ( AHRDF )

We learn from the vk7wi news that Peter VK7KPC says he may have made a major breakthrough on solving the mysterious appearances of AM aircraft band signals on VK7RAA.  You may recall we reported on this initially some months ago.

 The breakthrough on VK7RAA was traced to one particular Bombardier Q400 aircraft, a current iteration of the now classic deHavilland Dash 8.  The aircraft in question appeared to be VH QOJ, operated for QANTAS Link by Sunstate Airlines.

 Peter has been able to speak to the Sunstate Airlines maintenance team and discuss this issue. By happy coincidence, the aircraft was due in for routine maintenance at the time Peter made his enquiry. As a result, particular attention was paid to the radio installation during maintenance and a faulty antenna was detected.

 For good measure, the primary radio was removed, the secondary radio promoted to command status and a new secondary radio installed.  The old primary rig was then despatched to the service department for a closer inspection and testing.

 Needless to say, VK7RAA was and will continue to be closely monitored to see if any further errant transmissions occur.  It is also understood that staff of Air Services at Launceston will also be monitoring the aircraft for any strange radio emissions.

 Peter, well done on your efforts which seem to have produced the required fix.

From text edition for NOV 19  2017 - VK NATIONAL NEWS BROADCAST ON VK1WIA : http://www.wia.org.au/members/broadcast/wianews/

Also in MP3 edition of news available at: http://www.wia-files.com/podcast/wianews-2017-11-19.mp3

Possibly the same aircraft periodically heard on various 2M frequencies in SE Qld - and for quite a long time.

An update on this from last weeks VK7 news -

“While the secondary radio was connected in place of the original primary radio, the original primary radio was kept in service as the secondary radio, and not actually despatched for servicing, as reported. I may not have been clear in my explanation of what occurred at the maintenance base when giving my verbal report at the November general meeting.

In any event, we appear to have been premature in thinking we had found the fix, in light of another seemingly related issue which has been occurring over this last week, involving interference heard on 146.525 in the Don Heads area. Again the aircraft involved is

VH QOJ so it appears there is still a problem with the radio or radios on this particular aircraft. It has only been heard when VH-QOJ has been flying into Devonport and transmitting on 126.9 MHz. It does not seem to be occurring with other aircraft using this frequency.

Various other amateurs have also provided information and ideas relating to the issue and a lot of time has been spent investigating it, including by Greg VK7YAD who has been chasing this particular issue from at least mid-September, Joe VK7JG and now

Eric VK7EV, who has been monitoring and reporting on the latest interference after hearing it from Lillicoe.

At this time we are not sure if the interference occurs when the aircraft transmits when on an approach from the East of the airfield. If this is confirmed, I will be contacting Qantas Link Maintenance again to request more investigation.

73

Peter VK7KPC, Vice President NTARC Inc”

Thanks Peter for that correction and update. I may have misunderstood your earlier account of the maintenance steps taken by QANTAS Link or it may have been an assumption on my part that the high standards of maintenance required of airlines would have dictated that the radio be fully checked out on the bench. Given the subsequent appearance of interference on 146.525, such action would probably have been warranted. Be that as it may, thank you to all those amateurs that are spending time trying to solve this problem.