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How to build a rifle mike
NOTICE: TO ALL CONCERNED Certain text files and messages contained on this site deal with activities and devices which would be in violation of various Federal, State, and local laws if actually carried out or constructed. The webmasters of this site do not advocate the breaking of any law. Our text files and message bases are for informational purposes only. We recommend that you contact your local law enforcement officials before undertaking any project based upon any information obtained from this or any other web site. We do not guarantee that any of the information contained on this system is correct, workable, or factual. We are not responsible for, nor do we assume any liability for, damages resulting from the use of any information on this site.
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%% RIFLE MICROPHONE %%
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%% Another file from: %%
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%% Omnipotent, Incorporated %%
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This is a most unusual project; we are going to mount a sensitive
microphone behind a series of acoustic wave guides and hope for the
best. Actually, our wave guides are aluminum tubes cut to resonate at
frequencies near the human voice range. This arrangement also serves
to make the unit highly directional as sound other than that arriving
at the mouth of the tubes arrives at the mic in an out-of-phase
condition and cancels itself out.
With this easily constructed device it is possible (under ideal
conditions) to pick up conversations several HUNDRED feet away, in
fact, reports of recording conversations up to 30 yards away THROUGH A
CLOSED WINDOW have been made...
The device is quite easy to construct: First get together the
following materials:
[1] 56' of 3/8" outside diameter
aluminum tubing (hardware stores)
[2] 1 sensitive amplifier with
operating paraphenalia
[3] 1 sensitive microphone element -
use either a good condenser or a
crystal, as their outputs tend to
be a bit higher than their dynamic
counterparts.
[4] 1 funnel
[5] Assorted small hardware
Cut the tubing into 37 pieces ranging from 1" through 36" in one
inch divisions. Now bundle them together symmetrically with one end
flush (as shown). As you assemble them, blue them together in several
places to assure they remain in the state you have put them in (were
it only so easy with people...).
OOO
OOOOO
OOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOOOOO
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OOOOO
OOO
Flush ends of tubes
Take the funnel and fit it around the flush end of the tube
bundle. Being astute enough to read this, I am sure you will notice
the tubes do not exactly fit into the funnel. At this realization,
take a small hammer and beatt the funnel to nearly as possible. Now
fill the remaining spaces with a good rubber based caulking compound.
The microphone element is placed in the neck of the funnel (with
a rubber grommet if it is small enough to fit up into the neck -
otherwise set it into the other end of the neck before caulking the
tubing in place). Glue the mic into place and caulk any air space
around it.
Run the microphone wires out the neck of the funnel, glue in
place, and also caulk to give it a closed, fairly air invincible seal
around the entire unti. If you really feel up to it, fiberglass resin
can be used instead of caulking compound.
M ###\
I ### \
C ### \
### \_________# wire
E ### #______
L => ### funnel #
E ### _________#
M ### / ^
E ### / grommet
N ### /
T ###/
Run the output wires to your amplifier and place the entire unit
on some sort of support, a camera tripod being ideal. (Need I remind
you to check matching impedances?). The unit should be aimed at the
subject and then panned about for maximum volume (sound does not
travel in a straight line, but may vary with wind, etc).
If wind noise overrides your target noise you can place a piece
of cheesecloth across the end of the unit. If a particularly
difficult noise interferes with your pick-up you can often plug up the
tube(s) carrying this noise with a cork.
Good hunting, avoid paranoid people who may feel your rifle mic
more than resembles the real thing...
Coming soon from Omnipotent:
=-=-=-=-=-=-=-=-=-=-=-=-=-=
THE BLITZ BOX!
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