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Re: Snow on telly, help needed !
Tesla List wrote:
>
> Original Poster: "R.E.Burnett" <R.E.Burnett-at-newcastle.ac.uk>
>
> 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.)
It sounds like you might be generating large quantities of RFI from the
coil itself. The reason I say this is that with your coil running at 2kw
and it emmitting around 3ft arcs, you may be loosing alot of power
somewhwere resulting in the interference.
For instance, my coil runs at 1.08kw and produces almost 3ft arcs(~34").
I have to run my coil a good 20-30ft away from my house to stop the
static on my tv. I personally haven't had any complaints from others
with tv interference. If I were you I would double check to make sure
your coil is in perfect tune and maybe step up your grounding system to
say 2-3 8ft copper pipes or ground poles and space them 8ft apart.
One other thing that may or may not pertain to it, is the spark gap its
self. I personally beleive that almost all of the RFI comes from the
gap. I have noticed that running lets say a single static gap will give
off way more RFI than a muti section gap. Depending on your gap type and
your gap spacing alot of the RFI could possibly be coming from the gap.
If any of these states are proven to be false please let me know.
Chris