Peter wrote:
> ... A line filter
> is the inline 'box' type of RLC filter used to remove EMI from mains wiring.
> E.g. from Corcom etc.
That wouldn't be too hard or expensive to do, I'll have to order a 
couple of filters with my next order to Mouser, Jameco, etc.

>  The effect you are seeing is likely caused by the wire
> going out acting as an antenna and coupling common mode current into the GFI.
>   
That's the sort of thing I was thinking was happening, but that being 
out of my normal turf, I didn't know the words to use. :)

> There is a reason for which mains hauling switchgear is more intelligent than a
> GFI and makes several 'self repair' attempts in such a fault case, before giving
> up. Typically after a nearby lightning strike the breakers restart after 60
> seconds, and try it again three times, waiting successively longer times. If
> there is a short or repeated trips within that amount of time they stay off and
> operator intervention is needed.
We are on a rural electric cooperative power utility, and their 
switchgear tries 3 time within about 10 seconds to reset before giving 
up. If a tree branch or Squirrel (small mammal) briefly causes a short, 
all is fine, otherwise a crew is dispatched to fix the problem. Recently 
a crew was replacing a 3 phase pole, and instead of going to the 
substation, and opening the breaker, I think the took a hot stick with a 
ground conductor and brought the circuit down, because we got the 3 
resets before it went down for the duration of their work. Now I am on 
their call list before they take us down for maintenance.  The house 
main has a whole house surge suppressor, and I am generous with 
suppressors around the house at equipment. Last thing I lost was a 2 
years ago, a dialup modem, but that came in the phone line, which now 
has a suppressor on it also. Glad it wasn't an internal modem!

>  I don't think that you want to copy this
> behavior. The line filters will likely reduce the sensitivity of your coherer
> receiver to reasonable levels. They should have no impact on the normal GFI
> functionality. I don't know what your code says about outdoor electrical
> installations but I am fairly sure that this type of thing (30 meters of mains
> to an outside building just like that) is totally illegal in most places when
> not installed and checked by an authorized electrician. I don't even want to
> think about what permits would be needed to use such an electrical installation
> anywhere near a producing gas well, even if it would not be next to a house.
>   
Actually electric power at a gas well is common. The production wells 
that produce oil also have a "pump jack" (typical equipment seen at an 
oil well, big counterweighted shaft going around maybe 4 RPM, pulling a 
rod going down the well bore. It's a piston pump pulling the oil up in 
many stages.) Usually there is an electric motor maybe 5 or 10 HP. As 
for the electric near the natural gas, that's not an issue, unless there 
is a defect in the well casing or piping, which is not wanted to loose 
the gas there is no hazard. State regulations require 200' to a 
building, but once the well is in, maybe you could build much closer. In 
cities we see once in a while a well being plugged in city neighborhoods 
with small lots(maybe 50' x 140') . In some instances the conduit might 
want to be explosion proof, but I'm not sure that is required in this 
case. Electrical inspection in our area is lax to non-existant. With the 
blind flange off the top of the well, if ignited, the flame would be a 
modest maybe 4' high, and a nice hand warmer for the well driller. The 
driller used a cable tool rig to drill the well, and when the bit was 
going up and down in the well, the driller would light the gas, and keep 
his hands warm. :)
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