From Central Coast Aero Club News August 2013:
Radio Blues
For some time now, VH-AFZ has had an intermittent radio fault which causes a high pitched whining sound to start up randomly after the radio warms up.
It is highly annoying, and believe us when we say that it is even more so for the instructors who have to deal with it all day (not an hour at a time!)
We have been endeavouring to solve the problem since June last year, and have had 4 return trips to Bankstown as well as two new (faulty) radios installed.
The supplier of the radios has been very slow to respond to our warranty claims and keeps supplying radios which are faulty.
In the meantime we have to persevere and hope that a solution is arrived at in the near future.
We thank you for your patience.
Magneto issues? Bad earth?