Jeff Layman wrote:

** Really ?
What makes you sure it is a DC motor ?

See under "Energy efficiency" on page 3 he
http://www.fantasiaceilingfans.com/c...chure-2014.pdf

** So my original hunch was correct.

Some modern ceiling fans use low voltage( ie 24V) BLDC motors operating from a SMPS - all crammed into the same housing.

Why one would run in the wrong direction before correcting itself is a tad mysterious.





No. The 999kHz local radio transmitter (1kW) is about 15 km away..

** So the available signal is weak.

Fairly so, but reception is quite acceptable when the fan is off.


** You have missed the point.


The fan is in a new metal-framed conservatory.

** So the signal inside is very weak.

Indeed, even with a loop aerial connected.


** Assuming the fan has not developed a fault since you installed it, the RFI you are hearing may well be within legal limits for such appliances.

The AM and HF (short wave) bands do not enjoy the same regulatory protection as FM and TV reception does - so things like SMPSs and motor drives are permitted interfere somewhat with AM receivers in the same premises.

Having only weak signals available in the vicinity makes it so much worse.

Is the fan motor in a plastic enclosure ?

A grounded, metal one would be far better at supressing AM band noise.


..... Phil






--

Jeff