Re: Snow on telly - Results :-(
to: RE Burnett
Try placing a 100 watt, 10 to 50 Ohm resistor in series with your sec
ground strike rod (between the ground ball and the actual ground). This
will kill some of the Q of the arc and reduce overall radiation. The exact
resistor value is not critical. And --- never run your coil without the
sec load as the super high Q will damage your caps or xmfr.
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Snow on telly - Results :-(
> Date: Wednesday, January 13, 1999 9:27 PM
> Original Poster: "R.E.Burnett" <R.E.Burnett-at-newcastle.ac.uk>
> Snow on telly - Results of testing :-(
> Last Monday, I took the day of work to investigate and resolve the
> television interference that my neighbours were experiencing. There
> was nobody at home, so it gave me an ideal chance to try the many
> things that were suggested to me by LIST MEMBERS. I also got a few
> photographs and a bit of video of the coil running.
> For those who like to "cut-to-the-chase", I was unable to solve the
> TVI problem. However, if you are interested, here is a summary of my
> actions and (lack of) results:-
> 1. Tried removing the entire secondary winding and toroid assembly,
> then running the TC and checking for TV interference.
> RESULT: The TV interference was much brighter on my TV and one
> several houses away. This made me think that noise
> generated in the spark-gap and primary circuit is the
> cause of the problem.
> 2. Tried listening on an AM radio (not tuned in to anything,) and had
> a mate walk down the road with the radio to investigate the extent
> of the radiated interference. My friend walked about 150 yards
> away from the coil.
> RESULT: He said that he could hear the raspy crackling sound
> of the TC anywhere on the AM band at 150 yards away.
> He turned around and walked back because it had not
> begun to fade away !
> ( Since I am an electrical engineer by profession I
> was greatly disturbed by this and decided to limit
> individual run times to around 1 second until the
> problem could be rectified.)
> 3. Carefully checked for optimum tuning by adjusting the primary tap
> clockwise and anti-clockwise by a half turn to confirm equal
> degradation in tuning and performance.
> RESULT: Tuning was spot on !
> 4. Tried increasing grounding to 4 copper tubes, each 4 ft into watered
> soil. These were tied together with copper stip, and connected to
> TC parts by individual heavy-duty cables as described in my first
> post on this subject.
> RESULT: No noticeable difference to interference or spark length
> at my power of 2kW.
> 5. Tried an RC snubber across the RQ spark gap and then across the
> primary winding. Snubber consisted of a rolled poly 600pF cap and
> a bunch of parallel Carbon Film resistors (R = 150R.) This should
> reduce the Q of spurious UHF resonances in the primary arrangement
> by absorbing the high frequency energy.
> RESULT: No noticeable difference. The Resistors did get warm
> though, so some power was being absorbed when it was
> connected across the spark gap.
> 6. Tried an RC filter at the HV transformer bushings. Two resistors of
> 1K 50W at each bushing and a 600pF cap across the transformer HV.
> RESULT: No noticeable difference. The power resistors did get
> hot quickly as expected.
> 7. Tried shielding the spark gap and fans in an grounded Al foil
> covered box.
> RESULT: No noticeable change to interference.
> 8. Replaced my power transformers and balasting with a 600W neon, and
> retuned at lower power. Also I checked the LIVE and NEUTAL lines
> in the house with a scope.
> RESULT: No decrease in TV or Radio interference. Live and
> Neutral did have very small glitches when the TC was
> running, despite 2 common-mode filters and one
> differential mode filter.
> By now I was beginning to realise that I was fighting a loosing battle
> and decided to take a few photographs and a bit of video before people
> came home from work. The coil would then be dismantled.
> Several hours after packing up, I had a visit from a local telephone
> company engineer who said he was investigating a fault he had
> discovered on several lines in our area.
> It is clear to me that continuing to operate my "low-powered" TC in
> a residential area is not an option. And I was shocked at the extent
> of interference that I saw, and surprised by the limited effect that
> any standard engineering practices had on stopping it.
> I am not beaten by many challanges, but I am definitely beat by this !
> But its not all bad news, the pictures and video turned out great,
> and a local University is interested in buying some of the TC parts.
> I would like to thank anyone who gave me guidance in this "black art"
> of interference suppresion. I will keep on the list and will be
> interested to read peoples responses.
> PS. TERRY F, Sorry for such a long post.
> Richard (Richie) Burnett.
> - Wishing I had a Mu-metal garage
> ( in Newcastle )