[sci.electronics] audio jamming

terryb.bbs@shark.cs.fau.edu (terry bohning) (02/13/91)

Let us suppose you have an interest in interfering with a neighboring
apartment's sound system.  So when it's the FM, it's easy to hook an old
Heathkit vacuum tube signal generator to an old car antenna and capture 
the receiver on that frequency (altho' more power on the 10.7 MHz IF would 
alleviate tuning the generator).

But what about when it's a CD, tape, or album?  Which would be better
(easier, cheaper, more effective): inducing transients on the power line 
or radiating AF hash into space?  

Transients on the power line have to get thru the power supply filtering. 
Anyway, that runs the risk of damaging equipment, which is not the 
objective.

Radiating AF hash seems like it may be better, but what is a good way to 
generate it? Would an old auto ignition coil hooked to a non-resistive 
spark 
plug and suitably triggered work well?  Or is there an easier way?

Technical responses only, please.

terryb.bbs@shark.cs.fau.edu (terry bohning) (02/14/91)

terryb.bbs@shark.cs.fau.edu (terry bohning) writes:

> 
> Technical responses only, please.

For those who have trouble with euphemisms and have sent me their 
opinions, let me rephrase the last line:
"IF you have absolutely no knowledge of the situation, then keep 
your opinions to yourself".

For those who have sent sympathetic messages and requested any 
useful technical info I might receive, I will happily comply.

dana@locus.com (Dana H. Myers) (02/14/91)

In article <FqBaX1w163w@shark.cs.fau.edu> terryb.bbs@shark.cs.fau.edu (terry bohning) writes:
>Let us suppose you have an interest in interfering with a neighboring
>apartment's sound system.  So when it's the FM, it's easy to hook an old
>Heathkit vacuum tube signal generator to an old car antenna and capture 
>the receiver on that frequency (altho' more power on the 10.7 MHz IF would 
>alleviate tuning the generator).

  Though Part 15 rules may allow the broadcast of a low power signal in
the AM and FM broadcast bands, I'm fairly certain emitting RF to
intentionally interfere with other radio services is ALWAYS illegal. So,
technically, this is illegal. Emitting a powerful signal on 10.7 Mhz is
*especially* illegal.

>But what about when it's a CD, tape, or album?  Which would be better
>(easier, cheaper, more effective): inducing transients on the power line 
>or radiating AF hash into space?  
>
>Transients on the power line have to get thru the power supply filtering. 
>Anyway, that runs the risk of damaging equipment, which is not the 
>objective.
>
>Radiating AF hash seems like it may be better, but what is a good way to 
>generate it? Would an old auto ignition coil hooked to a non-resistive 
>spark 
>plug and suitably triggered work well?  Or is there an easier way?

   Hooking up a spark gap to an antenna does not just radiate audio
frequency energy; it generates fairly broadband RF noise. In fact, some
microwave sources are essentially a spark gap inside a tuned cavity.

>Technical responses only, please.

  Technically? What you are discussing will generally interfere with much
more than just an audio system. One sure fire approach is to generate a
large amount of RF in close proximity to the system. In general, with
few exceptions, doing this will technically be inconsiderate and
illegal.

  The last time someone asked about this, we ended up in flame war.

  Just try to be an adult.

-- 
 * Dana H. Myers KK6JQ 		| Views expressed here are	*
 * (213) 337-5136 		| mine and do not necessarily	*
 * dana@locus.com		| reflect those of my employer	*

richi@hpopd.pwd.hp.com (Richard Jennings) (02/14/91)

I suppose knocking on the door and politely asking the occupants to
reduce the volume is out of the question?  :-)

richi.
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -
 Richard Jennings, Software Development Engineer
 Pinewood Information Systems Division,           the home of HP's Advanced
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                       AdvanceLink, OpenMail and Multi-media communications
 Hewlett-Packard
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robf@mcs213k.cs.umr.edu (Rob Fugina) (02/15/91)

In article <1991Feb13.224108.2823432@locus.com> dana@locus.com (Dana H. Myers) writes:
>technically, this is illegal. Emitting a powerful signal on 10.7 Mhz is
>*especially* illegal.
>

You've made me curious...why do you say *especially* illegal?  Of what
significance is that frequency?

Me  robf@cs.umr.edu

terryb.bbs@shark.cs.fau.edu (terry bohning) (02/15/91)

robf@mcs213k.cs.umr.edu (Rob Fugina) writes:

> In article <1991Feb13.224108.2823432@locus.com> dana@locus.com (Dana H. Myers
> >technically, this is illegal. Emitting a powerful signal on 10.7 Mhz is
> >*especially* illegal.
> >
> 
> You've made me curious...why do you say *especially* illegal?  Of what
> significance is that frequency?
> 

The significance is that this is the Intermediate Frequency of virtually
every consumer broadcast band superheterodyne FM receiver in existence,
If you broadcast on 10.7 MHz with enough power to hit the IF amps in the
receiver, you will capture it no matter which station it's tuned to.

I seriously doubt that it is any more illegal according to written law
to xmit on 10.7 MHz than 1 MHz, but the fact is it create a lot more
interference.  The IF freq for consumer AM receivers (if anyone still 
cares) is 455 kHz.

lairdkb@mentor.cc.purdue.edu (Kyler Laird) (02/15/91)

In article <37340001@hpopd.pwd.hp.com> richi@hpopd.pwd.hp.com (Richard Jennings) writes:
>I suppose knocking on the door and politely asking the occupants to
>reduce the volume is out of the question?  :-)

Oh, c'mon!  Part of being a computer nerd/EE geek is being advanced enough to
avoid human contact by sending electronic messengers.

How about a robot that seeks out loud noises and carries a big stick? 
	...or...
Pick up one of the little noise alerts from Radio Shack (on sale now for only
~$5.00!!) - make a phone interface with your neighbor's phone number programmed
for constant redial as long as the noise persists.
	...or...
Sneak into his apartment and put a BSR-X10 wall outlet in where he plugs his
stereo in.  (I did this once in a dorm - fun for a bit.)


(Don't make me do smileys...)

--kyler

dkazdan@cwsys3.cwru.edu (David Kazdan) (02/15/91)

I've always wondered how these became the standard IF frequencies,
along with 50 KHz for the third IF in the older triple-conversion
short wave rigs.  Any history known here?

--David, AD8Y

elmquist@nachos.SSESCO.com (Chris Elmquist) (02/15/91)

In article <37340001@hpopd.pwd.hp.com> richi@hpopd.pwd.hp.com (Richard Jennings) writes:
>I suppose knocking on the door and politely asking the occupants to
>reduce the volume is out of the question?  :-)

In my case it is--  since I've already done it at least a dozen times...
and so have the police.  I've written letters to the landlord of the
adjacent condominium unit, complaining about the noise.  The letters
go unanswered.  These people  are intentionally obnoxious.  The rest
of the residents in this condominium building are as frusterated as
I am and now I'm going to do something about it.  If their TV and
radio are unusable-- the hope is that they will move away.

-- 
Chris Elmquist, N0JCF
Internet: elmquist@SSESCO.com
   AMPRN: N0JCF@WB0GDB.MN.USA.NA
 BellNet: (612) 785-3516

smithj@hpsad.HP.COM (Jim Smith) (02/16/91)

I think the solution to your problem already exists in previous posts to
sci.electronics:

Just build the nuclear weapon which was outlined recently, and, in order to
get away before it explodes, use the cheep one-time-only delay circuit which
was also discussed recently.

The resultant electromagnetic pulse oughta knock out the guy's stereo just
fine.    :-)

Seriously, though, you say that if we don't know the particualar situation's
details, we shouldn't comment.

Well, I wouldn't want to assist someone in committing an act of criminal
aggression without at least an explanation.
	(I've been watching CNN too much!   :-) )
I think what you're trying to do is impractical anyway.  If you really want
to take out the guy's stereo, put 440V on his power line for a while.  :-)

elmquist@SSESCO.com (Chris Elmquist) (02/17/91)

Thanks to all who responded with both the legal and moral issues surrounding
this discussion.  I guess my posting reflected a fit of emotional disfunction
when I implied that I intended to jam my neighbors radio and TV reception.
It's a most frusterating situation and when several postings suggested
knocking on the door (something that has been exhaustively attempted) my
fuse blew.

I do not condone illegally transmitting on frequencies for which you are
not authorized. I would stand to loose my amateur license as well
as possibly going to jail.  It's not worth that much to me just to
get even with these jerky neighbors.

As many e-mail responses indicated, there are plenty of other ways to
approach this problem.  I like the idea of a sound absorbing barrier
against the offending wall--  I'm going to pursue this approach rather
than the RF one.

End of "re: audio jamming" for me...

Chris

terryb.bbs@shark.cs.fau.edu (terry bohning) (02/17/91)

Summary of possible ECM against offensive audio sources:

This summary is for informational purposes only.  
Intentionally interfering with licensed broadcasts or broadcasting
at all without the appropriate FCC license is illegal.

For FM and TV broadcasts, a signal generator or other 
RF source which is tuned to the appropriate frequency and suitably coupled 
to space (ordinarily via an antenna) may be used.  
If adequate power is available, broadcasting on
an IF frequency would alleviate the need for manually tracking the 
receiver frequency.  Broadcast band FM receivers ordinarily use an 
IF of 10.7 MHz, TV receivers use a picture IF of 45.75 MHz and a 
sound IF which is 4.5 MHz below that, at 41.25 MHz.  TV receivers built
before 1950 or so use a picture IF of 25.75 MHz.  Broadcast AM receivers
use 455 kHz as the IF freq.

Direct audio sources (tapes, CD, albums) are tougher.  Because of equipment
complexity, size, and power levels, it's difficult to get an audio 
wavelength 
propagating.  In any event, the offensive source has nothing 
to act as an antenna except perhaps a long run
of speaker wire.  This would *really* require a lot of power.  

A possibility appears to be a CB radio.  Consider a common emitter
transistor stage in an audio amp which has a lightly bypassed or 
unbypassed emitter resistor.  Then the base-emitter junction (diode)
and the emitter resistor in conjunction with the bypass cap 
(or the capacitance to ground of the subsequent stage)
form a classical AM detector circuit.  There are of course 
many other potential AM detectors in an audio amplifier chain, 
including IC's and FETs.  If this method is effective, it can of course 
also be used against RF sources, since these are ultimately converted
to baseband (audio).

CB radios are cheap and widely
available.  Experimentation with power levels may be required.  In the
mid to late 1970s, linear amplifiers were available from many 
CB shops.  These usually consisted of Horizontal Output Tubes from 
television receivers of the day connected in a grounded grid configuration. 
 
For each tube in the unit, about 50 to 75 W of power was obtained.  A lot 
of
older 10 meter amateur gear has been converted to run on 11 meters 
(CB band = 27 MHz).  Many of the aforementioned linears were designed to 
run
on 10 meters, but came with instructions telling which components
*not* to change to allow the unit to run on 11 meters.  
Conveniently, a small bag of said components was also supplied.  Some 
higher power linears (500W up) simply had straps across several turns of 
the 
air-core coils in the unit.  Cutting these straps retuned it to 11 meters
by increasing inductance in the tank circuits.

Lower modulation freqs may work best so they
don't get bypassed to ground.  CB channels have a 6 kHz bandwidth, so the
transmitters limit the highest modulating freq to less than 3 kHz anyway, 
usually with a fairly obvious filter.
If the modulation freq were 60 Hz, even a knowledgeable listener might
believe it to be an equipment malfunction and perhaps remove the offensive
unit for a trip to the repair shop.  Voice modulation is ordinarily
inadvisable.  Lastly, note that very little, if any, 
CB gear is rated for continuous duty.  

One suggestion has been to induce transients on the AC line by 
interrupting a large inductive motor with an SCR.  Obviously, if the 
transients are sufficiently large and/or fast, 
expensive equipment may be destroyed.  
Furthermore, such transients would be totally indiscriminate in whose
equipment and which equipment would be affected.  In addition, 
it is unclear whether these transients could be coupled through the pole
transformer and beyond or not.  Also, turning
a piece of equipment off does not necessarily protect it from line
transients, so the consequences could be very far-reaching.  
Implementing this action would violate more than 
FCC regulations, and would leave the implementor open to criminal 
prosecution and legal action.

gil@limbic.ssdl.com (Gil Kloepfer Jr.) (02/21/91)

In article <332@nachos.SSESCO.com> elmquist@SSESCO.com (Chris Elmquist) writes:
>I guess my posting reflected a fit of emotional disfunction
>when I implied that I intended to jam my neighbors radio and TV reception.

I wouldn't agree with this.  Although I don't think it's necessarily
a good idea, I can see where one can easily be driven to this extreme.

>As many e-mail responses indicated, there are plenty of other ways to
>approach this problem.  I like the idea of a sound absorbing barrier
>against the offending wall--  I'm going to pursue this approach rather
>than the RF one.

I have two problems with this idea:  will the barrier absorb the
thump-thump-thump that dingbats of the genre described generally
emit by cranking the bass as well as the volume, and who is going
to pay for this sound barrier?  I find it hard to swallow that
there isn't more that can be done with inconsiderate folks like
this.  I know, life isn't fair...but everyone has certain
buttons.

I'm not condoning the practice of RF pollution to get even with
the neighbors, but question how to cost-effectively deal with the
*noise* pollution eminating from the neighbor's place.

I realize this discussion does fall outside the realm of electronics,
but perhaps that there's an electronic solution (or catalyst) that
could help solve the problem.
-- 
Gil Kloepfer, Jr.              gil@limbic.ssdl.com   ...!ames!limbic!gil 
Southwest Systems Development Labs (Div of ICUS)   Houston, Texas
"There are beautiful people I wish would have never opened their mouths,
because such ugliness oozes out."  Philosophy Prof. at NYIT

limey@cs.mcgill.ca (Mark ORCHARD-WEBB) (02/21/91)

    This little debate has brought back the memory of a most enjoyable
solution I found to a similar problem.  The method I used to retrain
a loud neighbour was to install a pizoelectric transducer in his 
ceiling (he was directly below me, it often seemed he kept his LS
lying on their backs as in the Beethoven's 5th torture scene in
Clockwork Orange)  These transducers can be capable of 100dB SPL at 
high frequencies.  The transducer was hooked upto an amplified
oscillator at around 17KHz.  When the offending music becomes intolerable
turn it on.  The beauty of it is that due to the already high SPL
in the guy's apt he does not appreciate it as a foriegn sound but rather
as pain (I find the sensation somewhat of a creeping pressure on the
scull).  I having 6 inches of wood flooring was reasonably isolated
from the high frequency but he was only 1 inch of plaster away from it
so it was quite effective.  Better yet he seemed to think that it was 
his sound system at fault since I saw him hauling various parts out
on different occasions after the retraining began.  Eventually I hooked 
the thing up to respond linearly to the SPL in my apt while I was away.
Sure enough after a few months, as with the little white rat, my
neighbour learned that socially deviant behavior was related to pain
and his behavior was modified.
    A few notes:  The frequency of the oscillator should be just above
             the range where it is an identifable sound just a sensation.
                  Please do not do this around animals I am sure that this
             will cause them much more distress than the original noise.

Mark, (sometimes refered to by fellow physists as pscho.)