🚀 go-pugleaf

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.