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 )