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'[OT] Re: purchase an axe for karaoke'
1998\12\20@184833 by James Cameron

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Vadim Jakunin wrote:
> [paraphrased: what can be done electronically to disturb a karaoke
> site eight to ten metres away?]

Not a lot.  I won't give any advice to help, since I might then be an
accomplice to an illegal activity.

However, to protect yourself against this sort of attack tends to be
simple; a good balanced microphone, cable, and amplifier.  If they use
two conductor jack connectors, chances are it ain't balanced.  If they
use three pin cannon connectors, it is most likely balanced.

--
James Cameron                                      (spam_OUTcameronTakeThisOuTspamstl.dec.com)

OpenVMS, Linux, Firewalls, Software Engineering, CGI, HTTP, X, C, FORTH,
COBOL, BASIC, DCL, csh, bash, ksh, sh, Electronics, Microcontrollers,
Disability Engineering, Netrek, Bicycles, Pedant, Farming, Home Control,
Remote Area Power, Greek Scholar, Tenor Vocalist, Church Sound, Husband.

"Specialisation is for insects." -- Robert Heinlein.

1998\12\21@120739 by Peter L. Peres

picon face
Nothing is as good as an old oil furnace ignitor unit mounted in a small
box (insulated) with a power cord, plugged into an outlet on the same
circuit as the amps (long wires preferred), with its own spark gap in the
box (adjust for long sparks) imho. Hehehe. I think it's even legal. Let
them find the circuit.

Peter

1998\12\21@140408 by lilel

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> Nothing is as good as an old oil furnace ignitor unit mounted in a
> small box (insulated) with a power cord, plugged into an outlet on
> the same circuit as the amps (long wires preferred), with its own
> spark gap in the box (adjust for long sparks) imho. Hehehe. I think
> it's even legal. Let them find the circuit.
>
> Peter

I use one of those in my Rube-Goldberg-Frankenstein Brownout and
Noise generator.  My boss makes me hook PICs up to it to see if
regular noise will make them puke.  It's also got:

    SCR lamp dimmers
    DC motors
    Universal motors
    Chattering relays

Won't stop a PIC with a brownout circuit at all!


-- Lawrence Lile

"Nyquist was an optimist."

=> Median Filter Source Code
=> AutoCad blocks for electrical drafting

at:  http://home1.gte.net/llile/index.htm

1998\12\21@141449 by dave vanhorn

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There was a time that I was laid up after a car accident.
I discovered that my upstairs neighbor liked to practice his gitaur music,
which he certainly needed to do.
I also discovered that when I talked on the local repeater using my 2 meter
rig and 160W amplifier, he would, for some reason, stop practicing rather
abruptly, with a loud thumping noise.



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1998\12\21@154418 by paulb

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Peter L. Peres wrote:

> Nothing is as good as an old oil furnace ignitor unit mounted in a
> small box (insulated) with a power cord, plugged into an outlet on the
> same circuit as the amps (long wires preferred), with its own spark
> gap in the box (adjust for long sparks) imho.

 Memory tells me you're really "hot" on that furnace igniter!
--
 Cheers,
       Paul B.

1998\12\22@163026 by Peter L. Peres

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Hello Paul,

>   Memory tells me you're really "hot" on that furnace igniter!

 Why would that be ? When I was in need of HV for sick experiments I used
2 cascaded HOT transformers w. separate secondary and a few cascades. I
think I reached 90kV a few times ? ;)

bye,

       Peter

1998\12\22@190453 by Mark A Moss

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I beleive spark gap telegraphy was banned internationally around 1938.
If you aren't using it to communicate though...

Mark Moss
Amateur Radio Operator, Technician, and General Tinkerer


On Mon, 21 Dec 1998 19:06:00 +0000 "Peter L. Peres" <.....plpKILLspamspam@spam@ACTCOM.CO.IL>
writes:
{Quote hidden}

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1998\12\22@192409 by Peter L. Peres

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On Tue, 22 Dec 1998, Mark A Moss wrote:

> I beleive spark gap telegraphy was banned internationally around 1938.
> If you aren't using it to communicate though...

If it was not then, then the current FCC RFI rules buried it, but oil
furnaces use it all the time...

BTW, am I the only one to notice that the *first* demonstrations of radio
wireless communication used a spark gap transmitter AND receiver, worked
somewhere in VHF (probably around our FM bands of today, or higher,
judging from the dipole sizes), and used NO semiconductors, let alone
valves ? (H. Hertz). That much for advanced technology.

Peter

1998\12\23@054400 by g.daniel.invent.design

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Peter L. Peres wrote:
> BTW, am I the only one to notice that the *first* demonstrations of radio
> wireless communication used a spark gap transmitter AND receiver, worked
> somewhere in VHF (probably around our FM bands of today, or higher,
> judging from the dipole sizes), and used NO semiconductors, let alone
> valves ? (H. Hertz). That much for advanced technology.
> Peter

And Tesla invented radio control and flourescent lights and free
broadcast power for a society he thought was altruistic etc.

Strange that Edison appears to be so popular in the USA still.

--
Steam engines may be out of fashion, but when you consider that an
internal combustion engine would require recovery of waste heat by
transfer just before top dead centre then fashion becomes rather
redundant, USE STRATIFIED HEAT EXCHANGERS ! and external combustion.

You heard it first from: Graham Daniel, managing director of Electronic
Product Enhancements.
Phone NZ 04 387 4347, Fax NZ 04 3874348, Cellular NZ 021 954 196.

1998\12\28@090911 by paulb

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Hello Peter.

>  When I was in need of HV for sick experiments I used 2 cascaded HOT
> transformers w. separate secondary and a few cascades.  I think I
> reached 90kV a few times ? ;)

 How did you measure it?  I've noticed the amateur HV sites on the web.
You could have a lot of fun with a recycled X-ray machine!
--
 Cheers,
       Paul B.

1998\12\28@133656 by Peter L. Peres

picon face
On Sun, 27 Dec 1998, Paul B. Webster VK2BZC wrote:

> Hello Peter.
>
> >  When I was in need of HV for sick experiments I used 2 cascaded HOT
> > transformers w. separate secondary and a few cascades.  I think I
> > reached 90kV a few times ? ;)
>
>   How did you measure it?  I've noticed the amateur HV sites on the web.
> You could have a lot of fun with a recycled X-ray machine!

TV service HV probe, slightly modified (2 probes in series, one shunt R).
This goes to 60 kV give or take. The monster pegged the meter connected to
this (300V)  quite solidly, and I deduce from this that it went there. You
know that gut feeling you get with analog meters about how far the needle
would go if it wouldn't be stopped mechanically ? The reading was WAY over
60kV in any case.

Such a probe can be had for very little money, used, from a TV shop going
out of business.

Re: X rays: I have digged some more and found out that certain early makes
of DY86 (EHT rectifier valve for TV service) were responsible for most of
the X rays sprayed onto onlookers by early TV sets. They radiate most when
polarized BACKWARDS or driven with RF (microwave oven ?) w/o heating.
Apparently the electrons emitted by spontaneous emission in the CATHODE
hit the Thorium coated Anode hard enough to do this given enough
voltage ;).

OTOH the only reasonably accurate way to measure EHT without loading it is
a differential electrometer (chopped capacitive divider type). Lacking
this, a scope 'bare' tube w. psu will do a fine electrometer (remember the
B/E field deflection experiment in school ? - the electrodes need not be
INSIDE the tube as long as the Aquadag is far enough off ;).

Electrometer tubes can be gotten hold of, too, but a heptode will oblige
if only for low voltages. The 5th (?) grid is very well insulated and can
work wonders in cathode repeater configuration... but noval sockets will
arc violently at ~1.5kV or so.

Last let's not forget the BF245 electrometer ;) The venerable FET can be
used together with a 9V battery and a LED like in this URL:

<there should be an URL here but i lost it. plse use a web search engine
with the words 'inexpensive' 'homemade' 'electrometer' 'LED'>

Just in case you did not know, simple differential electrometers need to
be chopped to be useful, but the sky is the limit for what voltage you can
measure (literally). A simple chopper is an Al camping dish with 2 90
degrees sectors removed (or mug-bottom circles cut out - but that's
harder), stuck on the axis of a servo turning fairly slowly. It obscures a
coin that acts as sense electrode. Behind the coin there is the conductive
wall of a grounded box which is also shielding everything, and holds the
servo. The coin is installed on a piece of styrofoam about 1/2 as thick as
the distance between the box bottom and the rotating dish. This is a
fairly portable unit that can measure <g> very high voltages, including
that of clouds before a storm f.ex.. Of course the calibration depends on
the distance to the target, as well as on the potential difference.

As a sugar cube to replace the lost URL, here is my description of what it
did, and a magnetometer URL you can build on a weekend:

The FET electrometer: Take a 9V battery clip, a BF245(C) FET, and a red
LED (5mm) and a 1Meg resistor. Wire +Battery to Drain, LED Anode to
Source, LED Cathode to -Battery and leave the gate sticking up in the air.
Solder a short (2-4 in) piece of rigid straight wire to the resistor, and
the other side of it to the Gate, and use a clamp or similar device to
temporarily contact the tin body of the battery with the -Battery (this is
a handle - the battery, that is;).  Stick a battery into the thing and you
are ready to go.

All the usual cat fur, Bakelite experiments etc will work. There is one
caveat: This is a unipolar instrument. Because of the FET junction that
conducts the other way around, the thing has different sensitivity for
positive and negative charges. It needs to be nulled from time to time
(touch the probe with another finger). Alternately, charge probe
negatively (light goes out), and measure opposite charges.

This may look like a toy, and is advertised as such, BUT if you use it in
the differential way with a calibration box it can measure any potential
fairly accurately. The 5Vgs0 of the BF254 is ridiculously small vs. most
HV sources and the null position can be determined very accurately.

I suppose that a VFET can be substituted with success (ex: BSS175 ?) but a
resistor is required for the LED and the gate protection diodes may come
in the way.

More interesting reading:

Phil's Magnetometer and prospection page
http://members.aol.com/phil770/page1.html

Two DIY Magnetometers:
http://www.uksmg.org/magnet.htm

Prof Pico's Picoamp site:
http://www.cantech.net.au/~pico/

There is MUCH more. At least these guys are not Quacks, there is a lot to
learn from what they did, and their recipes yield useable instruments.
Don't miss the experiment with the reverse biased diode leakage on Pico's
page, it speaks volumes about everyday problems.

Peter

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