138 lines
4.0 KiB
Plaintext
138 lines
4.0 KiB
Plaintext
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%% %%
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%% ================ %%
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%% RIFLE MICROPHONE %%
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%% ================ %%
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%% %%
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%% Another file from: %%
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%% %%
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%% ------------------------ %%
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%% Omnipotent, Incorporated %%
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%% ------------------------ %%
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%% %%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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This is a most unusual project; we
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are going to mount a sensitive
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microphone behind a series of acoustic
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wave guides and hope for the best.
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Actually, our wave guides are aluminum
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tubes cut to resonate at frequencies
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near the human voice range. This
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arrangement also serves to make the
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unit highly directional as sound other
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than that arriving at the mouth of the
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tubes arrives at the mic in an
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out-of-phase condition and cancels
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itself out.
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With this easily constructed
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device it is possible (under ideal
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conditions) to pick up conversations
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several HUNDRED feet away, in fact,
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reports of recording conversations up
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to 30 yards away THROUGH A CLOSED
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WINDOW have been made...
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The device is quite easy to
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construct: First get together the
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following materials:
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[1] 56' of 3/8" outside diameter
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aluminum tubing (hardware stores)
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[2] 1 sensitive amplifier with
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operating paraphenalia
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[3] 1 sensitive microphone element -
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use either a good condenser or a
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crystal, as their outputs tend to
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be a bit higher than their dynamic
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counterparts.
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[4] 1 funnel
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[5] Assorted small hardware
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Cut the tubing into 37 pieces
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ranging from 1" through 36" in one inch
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divisions. Now bundle them together
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symmetrically with one end flush (as
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shown). As you assemble them, blue
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them together in several places to
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assure they remain in the state you
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have put them in (were it only so easy
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with people...).
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>
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> OOO
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> OOOOO
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> OOOOOOO
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> OOOOOOOOO
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> OOOOOOOOO
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> OOOOOOOOO
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> OOOOOOO
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> OOOOO
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> OOO
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>
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> Flush ends of tubes
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Take the funnel and fit it around
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the flush end of the tube bundle.
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Being astute enough to read this, I am
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sure you will notice the tubes do not
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exactly fit into the funnel. At this
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realization, take a small hammer and
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beatt the funnel to nearly as possible.
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Now fill the remaining spaces with a
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good rubber based caulking compound.
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The microphone element is placed
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in the neck of the funnel (with a
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rubber grommet if it is small enough to
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fit up into the neck - otherwise set it
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into the other end of the neck before
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caulking the tubing in place). Glue
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the mic into place and caulk any air
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space around it.
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Run the microphone wires out the
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neck of the funnel, glue in place, and
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also caulk to give it a closed, fairly
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air invincible seal around the entire
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unti. If you really feel up to it,
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fiberglass resin can be used instead of
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caulking compound.
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> m ###\
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> i ### \
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> c ### \
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> ### \_________# wire
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> e ### #______
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> l => ### funnel #
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> e ### _________#
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> m ### / ^
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> e ### / grommet
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> n ### /
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> t ###/
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>
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Run the output wires to your
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amplifier and place the entire unit on
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some sort of support, a camera tripod
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being ideal. (Need I remind you to
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check matching impedances?). The unit
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should be aimed at the subject and then
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panned about for maximum volume (sound
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does not travel in a straight line, but
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may vary with wind, etc).
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If wind noise overrides your
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target noise you can place a piece of
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cheesecloth across the end of the unit.
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If a particularly difficult noise
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interferes with your pick-up you can
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often plug up the tube(s) carrying this
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noise with a cork.
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Good hunting, avoid paranoid
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people who may feel your rifle mic more
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than resembles the real thing...
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