On 27 July, 16:30, "William Sommerwerck"
wrote:

I suspect the transmitter is shutting down after 30 seconds of no input.
Without a carrier to quiet the receiver, you then hear the noise in the
receiver's circuits.

If this is correct, it's downright odd, as there would be no good reason to
shut off the transmitter -- which I assume is /not/ battery powered.

Thanks for the reply.
The transmitter is mains powered through a transformer.

I did a bit more investigating
I usually play Quick-time files in Media Player Classic. This brings
on the effect soonest.
It also happens when I play the same files in Windows Media Player,
though the period of quiet lasts much longer, perhaps 2 or 3 minutes.
If I play an *.avi file in Media Player Classic, I get the same, much
longer period of quiet before the noise starts.
It also happens when I use Winamp but again, after the much longer
quiet period.

So Quick-time files in Media Player Classic is the worst combination.
Also the most desirable combination.
Although the software has an effect I don't know if it can be adjusted
through software.
--
Regards,
Geoff Mills