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Snow on telly, help needed !
I was operating my 2kW Tesla coil a couple of weeks ago, when someone
in my street complained about snow on their television screen. The
person who complained lives 5 houses along from me, and said that it
was affecting all of the televisions in the street ! My coil produces
2 to 3 foot arcs and works great otherwise.
I have Searched the Tesla List Archives and have tried many things
but the problem still persists. This annoys me since I have read
posts from people who claim to operate their coils in rooms next to
TV's without any interference.
My coil is operated in a garage that is around 20 feet from my house,
and is fed by two-core cable from the house (LIVE & NEUTRAL). When
powered up, several horizontal lines of white dots appear on my TV
in the house. They are not really bright but enough to be a problem.
I thought that this must be due to noise being conducted from the TC
back through the LIVE and NEUTRAL wires into the house, so I took the
following precautions:-
1. I have installed a two-stage RFI filter at the TC end of the mains
cable. This filter is run in reverse and has its earth (CASE)
terminal connected directly to the RF ground rods. I have also
fitted a VARISTOR from LIVE to NEUTRAL. The filter is connected
"back-to-front".
2. I have installed a single-stage RFI filter at the power socket end
of the mains cable (in the house.) The Earth terminal of this is
connected to the earth pin of the plug. The filter is connected
"back-to-front".
3. I have changed my RF ground from one 2 foot copper pipe, to three
2 foot copper pipes connected together by 10mm˛ earthing cable.
Seperate earth cables run from the secondary, the transformer and
the filter, back to the group of ground rods.
Wall FILTER 1 FILTER 2 HV
socket ----- ----- TRANSFMR
E--------!E ! Supply cable ! ! ----
! ! ! ! ! !
L N------!N N!--------/ /-------!N N!-----! !--> To RQ-gap
! ! ! 20ft of 2 core ! ! ! ! and rest
----------!L L!-------/ /--------!L E L!-----! !--> of the TC.
----- ----- ----
! !
! ! (-T-)
! ! #
! ! #
! ! # TC
! ! # sec.
! ! #
! ! #
! ! !--
------------! ! !
! --------------------! !
! ! ---------------------------!
\ ! /
\ ! /
\!/ Common RF ground
------- 3x 2ft copper pipes
! ! ! in watered soil.
! ! !
! ! !
! ! !
! ! !
! ! !
My thinking behind the 3 seperate earhing cables was that the heavy RF
current from the TC-sec would be carried directly to the ground rods.
The transformer and filter earths would then both use seperate cables
to avoid picking up the RF from the secondary ground.
The only thing I could not try was a full Faraday cage because the
garage is full of shelves and things. It is not practical.
None of these measures have been successful, and since the TC is
clearly audible outside, I cannot operate it at all without complaints.
I have some questions:-
1. Can I realistically hope to run a 2kW RQ-gap TC in a domestic garage
without causing ANY snow on neighbours televisions ?
2. If so, what am I doing wrong ?
3. Is my ground sufficient and wired correctly.
3. Is some filtering on the HV side of the transformer likely to help ?
Please help me ! I am a qualified electrical engineer with a working
knowledge of RFI and EMC, but I am confused by this. Computers etc.
operating in the house are not affected, although TV's in houses 150ft
away have snow. If this cannot be solved I have no other option but
to pack up.
Cheers,
Richard Burnett.
(Making some TVI in sunny Newcastle.)