"Ca****cher"

Had a similar problem with a dish network box about 2-3 years ago. The
CFL was in a floor lamp line-of-sight about eight feet in front of the
box. Pressing a key on the remote would yield unexpected results. After
several days we correlated the problems with the light (which wasn't used
all the time). I suspect the CFL emitted significant IR which confused
the receiver in the box.


** Ordinary incandescent lamps emit lots of infra-red energy and have no
such effect - cos the IR is not modulated like the light coming from the
LED in a remote.

So, what is different about CFLs ?

Well, the internal inverter circuit operates at around 40kHz, so that must
be the culprit.

But I see no way a CFL can generate MODULATED infra-red light - certainly
the tiny filaments will not do it and the phosphors have little IR output
and enough persistence to eliminate light modulation at such a high
frequency.

However, the high voltage, high frequency drive to the fluoro tubes IS
radiated for several metres and can be picked up by sensitive electronic
devices. Just wave a scope probe near one and you will see what I mean.

The photodiode amplifier circuit in an IR receiver is very sensitive,
operating down to the microvolt level, so it must be possible for a CFL
radiating the same operating frequency to interfere with them.



..... Phil