Anyone else have trouble with HF - tripping GFCI in my garage when keying
the mike.

On Fri, 12 Nov 2004 04:55:12 GMT, "Joel" wrote:

Anyone else have trouble with HF - tripping GFCI in my garage when keying
the mike.

I don't have trouble with HF tripping the GFCI in YOUR garage, but I sure as
hell have a similar problem here in my shack.

Cheap shots aside, the GFCI usually contains a toroidal core which has the
active and neutral (return) lines pass through it, and a secondary winding which
sees the difference between the active and neutral currents i.e. the current
passing through another route (ground assumed). The secondary feeds an
amplifier which drives the trip circuit.

In an endeavour to obtain decent sensitivity AND fast reponse, there appears to
be a general lack of RF immunity in these devices.

If I use a VHF handheld within a metre or so of appliances connected via the
GFCI, no problem. However if I use the same device sitting in its mains-powered
charger base - on or off charge - the interrupter trips. I also have a 25W
transceiver on 80 MHz (commercial) which caused frequent tripping on Tx until I
took remedial measures.

presumption mode Enough RF is conducted along the power lead to result in RF
in the toroid's secondary which the amplifier rectifies/detects. /presumption
mode

In the case of the 80 MHz set, I slipped a toroid over the DC power lead. (RF
choke). DC power is derived from a mains PSU. Antenna is not earthed to this
system. Problem gone.

In your instance, it may be RF entering by direct radiation from the antenna
into the GFCI or power cables passing through same, OR it may be RF getting
conducted back up the supply of the HF set. Trial and error should determine
which - does it trip when you run the Tx into a dummy load? Can you try a
toroid around the supply cable?

I have had this problem with some GFCIs in my home (bathrooms, kitchens). I
determined that it was one particular brand (don't remember which one) and
replaced them with another manufacturer's and the problem went away.
--
-larry
K8UT
"Joel" wrote in message
...
Anyone else have trouble with HF - tripping GFCI in my garage when keying
the mike.

This would be a good article for QST -- a review of ground-fault
interrupters for those with adequate RFI protection.

"Joel" wrote in message
...
Anyone else have trouble with HF - tripping GFCI in my garage when keying
the mike.

Anyone else have trouble with HF - tripping GFCI in my garage when
keying
the mike.

An interesting tale of GFCI and RFI. Square D was/is a manufacturer of those
little devils. In manufacturing they had a test table where they took
representative samples of the weeks manufacture and ran them under load for
some period of time. These would operate satisfactorily for some extended
period and then the first of the week they would find a large failure rate.
At times, as much as 50 percent of the run had "failed".

Eventually, they found that the plant closed for the weekend, and the guard
in making his rounds would check in on his walkie talkie at a reporting
station located adjacent to the test table. The miniscule amount of RF would
trip those suckers and caused Square D to incorporate some RFI protection.

I have tripped mine causing the street lamp to fail (among other circuits)
but only when running high power on 2 meters. (KW level) If you're failing
yours, it's most likely quite old, either manufactured before they
recognized the problems, or having failed whatever protection that was built
into the module. Would suggest that replacement with a new one from your
local electric supply house will cure the problem.

W4ZCB

Its interesting this topic came up this week. At work (NASA's Johnson Space
Center) I've been working an issue related to a GFCI circuit on the
International Space Station. Seems ESA (European Space Agency) has built a
GFCI circuit into their UOP (Utility Outlet Panel) which, just like all
other GFCI's, monitors the safety wire for excess current in order to
protect the crew, etc.

Unlike your residential GFCI circuits, the UOPs are for DC, not AC. It
turns out that with some of the EMI filters we put on our loads, you could
get enough significant ringing off the L-C filters to trip the UOP. Yet
another problem that you can run into with GFCI, only in the DC world.

Just thought I'd throw that one out there.

Jason
KB5URQ
(Electrical Power Distribution & Control, NASA-JSC)

"Joel" wrote in message
...
Anyone else have trouble with HF - tripping GFCI in my garage when keying
the mike.

FOLLOW-UP

My 40meter dipole, which I just put up, hangs over a corner of my garage.
About 5ft above the roof. I suppose that's close enough to trip GFCI's. And
it's only about 15ft above ground. But it works great!
Someday I might have to put up some sort of vertical.
My old 20meter dipole, which is a little more out of the way, works fine.
Doesn't trip any of the GFCI's.
I put a homemade air balun on the 40M yesterday. Didn't seem to make any
diff.
Tripping GFCI's in the garage is mostly just a nusiance. I can put up with
it. Although I have a 24hr timer on one circuit. But I wonder if it affects
the neighbors' GFCI's. I don't think I'll ask them.