On Sat, 07 Jan 2012 14:51:23 -0800, Jeff Liebermann
wrote:

On Sat, 07 Jan 2012 14:39:02 -0700, wrote:

One thing that strikes me about this is the random (erratic?) nature
of this interference, varying both in time and duration. To me, that
rules out many devices - common home appliances, factory equipment,
radio transmitters, etc. One thing that does operate on a similar
pattern is a telephone. Is it possibly a cordless telephone operating
on an oddball frequency?

Think about something run by a thermostat, low control switch, or
motion detector. They tend to cycle erratically. Things like a
furnace, electric heater, water pressure boost pump, pool heater,
demand water heater, sump pump, etc. There are also some uncommon
devices that cycle. Negative ion generator, parking lot light
controller, external HDD or NAS boxes, motion detector operated
devices, iPhone background sync, etc.

However, I've been fooled before with this pattern. I was looking for
such things, only to discover that the interference was coming from a
microwave oven at a local eatery. During lunch, the microwave ovens
were in use almost constantly. At other times, a minute or so at a
time. Kinda sounds like the original description.

Dumb story: Many years ago, I had a very difficult time trying to
find the source of short bursts of RFI. I tried for days and failed.
Oddly, the interference seemed wide spread and appeared almost
everywhere that I was sniffing. Eventually, the gears that drive my
brain engaged and I discovered that the Motorola Bravo pager that I
was carrying at the time, was the source. Argh.

Let's look at your list:
Think about something run by a thermostat, low control switch, or
motion detector. They tend to cycle erratically.

A thermostat - refrigerator, freezer, or heating / cooling tends to
cycle at a fairly constant rate, at least for the majority of the time
(an exception would be when a large amount of food is added to a
refrigerator, or a freezer, or when the set temerature of a thermostat
is changed). A motion detector would operate at erratic times, but
not for only 10 seconds.

Things like a
furnace, electric heater, water pressure boost pump, pool heater,
demand water heater, sump pump, etc.

Again, these would tend to operate on a regular cycle except for an
'on demand' water heater. However, the 'on demand' heater fails the
'on for one hour ' parameter.

There are also some uncommon
devices that cycle. Negative ion generator, parking lot light
controller, external HDD or NAS boxes, motion detector operated
devices, iPhone background sync, etc.

Again, these devices fail either the '10 second' or 'one hour'
parameter.

PlainBill