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Re: [TCML] Treating RF feedback
Hi Alton,
I'm pretty sure I get what you're describing. It would be difficult, but I
'might' be able to sink a few shorter rods around the coil. However, after
hearing what Jim had to say and a bit of meditation, I think it might be
best to rely on the counterpoise (as much as I loathe the thing) and
eliminate the supposed interference in the AC lines. The only places I can
really place the rods are a bit too close for comfort (two to five feet) to
buried wiring and conduit leading up to control panels. That, and it would
be a real pita to get a few rods even three feet deep.
Good suggestion, but I think a real RF ground to earth is out of the
question, unfortunately.
Thanks,
Brandon H.
On Sun, Mar 17, 2013 at 6:01 PM, w5als <w5als@xxxxxxxxx> wrote:
> hi
> RF is RF it make no difference weather I am on 125.210 running a 1000
> watts or
> on 40 meter 7.210 running a 1000 watt or a tesla coil. The idea is to get
> rid of the RF and if you
> are trying to ground and you can not get the rod deep enough you use more
> than one
> rod, this is simple physic's put the RF in the ground. This is only
> grounding the bottom
> of the secondary coil nothing else. I am not talking about your electrical
> plug at all.
> The closer the ground rods are to your coil the better it is. The ground
> rod have to
> be far enough apart that they don't effect each other. Brandon if you
> don't understand
> what I mean email me direct and can talk on the phone and I can explain it
> better
> thanks
> alton
> w5als@xxxxxxxxx
>
>
>
>
>
> On 3/17/2013 5:54 PM, Jim Lux wrote:
>
>> On 3/17/13 3:01 PM, w5als wrote:
>>
>>> HI Brandon Being a ham operator and tesla coil, I will tell you what
>>> I would do.
>>>
>>
>> Bear in mind that what's effective at 2-30 MHz (HF radio) and 100kHz or
>> 100 MHz might be quite different.
>>
>> If you can get at lease 4ft in the ground that will work
>>
>>> but do 2 ground rods at lease 4 ft apart. you have to be the length
>>> of the ground rod apart from each other min. More the 4 ft. would be
>>> better. Done not run one wire and go from one to another. Run 2
>>> separate wire's to each one, with them coming to a common spot. I
>>> mounted a wall outlet in my shop with nothing hook to it but the
>>> ground wire's only. Than when I use my Tesla coil I plug my ground in
>>> that outlet only. If you use 3 short ground rod's use 3 separate
>>> wire's. But the deeper the ground rod the better. alton w5als
>>>
>>
>> Are you saying that the bottom of the secondary coil is connected to the
>> "greenwire" ground pin at that receptacle, which is then connected to your
>> three rods?
>>
>> Or do you have 3 rods driven surrounding your TC, you have wires from the
>> rods to the TC location, and then hook that to the bottom of the secondary
>> coil.
>>
>> And have a dedicated outlet for the TC power.
>>
>> I'm not sure there's any good physics behind this suggestion. Not that it
>> doesn't work, but I suspect that if it does work, it's because of factors
>> other than the ground rods, per se.
>>
>> WIthout knowing more about how your house is wired and where your TC is
>> relative to those ground rods (and more important the wires going to them)
>> it's hard to say whether this is an effective strategy. Or, more to the
>> point, measuring the RF current in those ground wires.
>>
>>
>> For EMI/EMC and tesla coils, there's two factors to bear in mind..
>>
>> there's the 100-300 kHz frequency from the coil itself.. but that doesn't
>> propagate very well, and the "antenna" (e.g. the coil) is a very tiny
>> fraction of a wavelength. So all the 100kHz fields tend to be close to the
>> coil, and you don't have to get very far away before they are "small". (if
>> you're 10 coil heights away.. e.g. 30 feet from a 3 foot high coil) I'll
>> bet they're almost negligible.
>>
>>
>> For EMI, I think a bigger problem is the transients from the actual
>> sparks, and those radiated from the wires going to the spark gap. The
>> latter typically radiates at VHF sorts of frequencies (think of the wires
>> going to the spark gap as a dipole radiator, with the spark gap at the
>> center). Several coilers have measured substantial radiated fields from
>> this source, and since VHF receivers are pretty sensitive, it's easy to jam
>> them. Whether it could "false trigger" is another story..
>>
>> Then there's the wide band transients from when the spark "fires". You
>> have a very high di/dt, so you get a fairly big magnetic field radiated
>> from a loop that's fairly large (ground, secondary coil, topload, spark,
>> wherever the spark hits, conductor from spark end to ground). This is why
>> you *don't* want to run a coil indoors with a 50 foot wire to the ground
>> outside. You're making the transient transmitter more effective by making
>> the antenna bigger.
>>
>> some analysis from a few years ago is here
>> http://home.earthlink.net/~**jimlux/hv/tcemi.htm<http://home.earthlink.net/~jimlux/hv/tcemi.htm>
>>
>> The problem with things like garage door openers is that they have
>> unshielded wires going to the photosensors and limit switches, so you could
>> easily get a pretty big receiver loop (with "capacitive coupling" being
>> part of the loop). In my garage case, the opener is about 10 ft from the
>> door, and there's a wire that goes down to each side of the door where the
>> photosensors are, and then a ground through the plug in the ceiling for the
>> opener. So there's this huge 8 footx15foot rectangular loop to pick up
>> signals (the wire from the photosensor runs along side the metal track of
>> the door, and has significant capacitance to "earth ground" since that
>> track is connected at the slab with an anchor bolt. It's kind of like it
>> was designed for poor emi performance.
>>
>> Sprinkler systems are worse. They are very cost sensitive, so the output
>> is typically a bunch of triacs connected right to the microprocessor
>> switching the 24VAC to the valves, and there's a common ground wire for all
>> valves. It's easy to get a big loop between "valve hot" and "common ground"
>> depending on how it's wired. And if there's much induced voltage on the
>> control wires, then the triac will switch on (or, simply that the triac is
>> a 50V part, and it just avalanches when there's a spike). Your TC is
>> emitting pulses synchronized with the power line, so it's optimally timed
>> to trigger the triacs with an induced gate pulse.
>>
>> Since people want to save money, the valve wiring is often sort of a
>> point to point daisy chain, rather than a single twisted pair to each valve
>> (the latter would be ideal for EMI), and the wires are buried and often
>> have some conductitivty to the surrounding soil. I had terrible trouble
>> with EMI on my first sprinkler timer.
>>
>>>
>>>
>>>
>>>
>>> On 3/17/2013 3:45 PM, Brandon Hendershot wrote:
>>>
>>>> Hi All,
>>>>
>>>> With the renovation of my coil nearly complete, I'll need to
>>>> address the old issue of electrical appliances going haywire
>>>> whenever I run my coil. At the time I didn't have a proper RF
>>>> ground, only a counterpoise. On separate occasions, I'd have the
>>>> jacuzzi tub turning on or the sprinkler system switching the
>>>> sprinkler heads like pinball paddles. My hunch was RF interference
>>>> which the list seemed to support. I'm currently attempting to
>>>> install a 10' ground rod but that's proving difficult with my dry
>>>> rocky soil. Since my deadline is fast approaching I may need to
>>>> rely on the counterpoise once again and I want to make sure I don't
>>>> go fizzling all the fancy electronics we've acquired in the past
>>>> years since I retired my coil.
>>>>
>>>> On a separate topic, any bright ideas on getting a 3/4" copper pipe
>>>> backed with city water pressure through a boulder?
>>>>
>>>> Thanks, Brandon H. ______________________________**_________________
>>>> Tesla mailing list Tesla@xxxxxxxxxx
>>>> http://www.pupman.com/mailman/**listinfo/tesla<http://www.pupman.com/mailman/listinfo/tesla>
>>>>
>>>
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>>>
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