After having replaced a faulty actuator and updating to the latest firmware (Version 3.29) I noticed an occasional 'MOTOR FAIL' error when attempting to tune to 6,600kHz. The short story is that this error can be provoked depending upon how the actuator is driven into its lower electrical limit.
Using the Test/Debug feature by pressing and holding the '/' key for 3 seconds, and starting by driving the antenna well away from its lower electrical limit, if the antenna is then driven into its limit at high speed by pressing and holding the '3' key, when the motor stops and the resonant frequency measured it is 6,547kHz. If the antenna is again positioned well away from its limit, and now driven at medium speed by pressing and holding the '2' key, the resonant frequency when the motor stops is now 6,588kHz, and if this is repeated but at slow speed with the '1' key the frequency is only 6,593kHz.
This latter frequency is very close to the lower limit of 6,600kHz, and if the electrical limit is reached during a fine tune operation, then a 'MOTOR FAIL' message will be triggered.
Repeating this experiment at the upper electrical limit gives 30,319kHz at high speed, 30,199kHz at medium speed, and 30,189kHz at slow speed. This shows that the setting is much less critical at the upper end of the tuning range as these frequencies are well removed from the upper limit of 29,800kHz.
The obvious cure for this is to drive the actuator into its electrical limit using 24V, but now alter the gap of the plates to compensate for the overrun, and I suggest 14mm instead of 15mm. I will shortly be re-locating my antenna, and I will experiment and see if I can determine the optimum spacing. Adrian Ryan, 5B4AIY