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G0TEZ > TECH 01.09.08 00:31l 38 Lines 1341 Bytes #999 (0) @ WW
BID : 320070G0TEZ
Read: GUEST
Subj: Cheapo Gun Mic
Path: IZ3LSV<IK2XDE<ON4HU<ON0BEL<GB7FCR
Sent: 080831/2202Z @:GB7FCR.#16.GBR.EU #:12704 [Blackpool] FBB-7.03a $:320070G0
From: G0TEZ@GB7FCR.#16.GBR.EU
To : TECH@WW
Here's a cheap, useful 'gun mic' which I made a few of in the '80s.
I took a squeezy washing up liquid bottle and cut the bottom off.
I inserted two moving coil loud speakers to act as microphones, set far
enough apart so that they reinforced each other when in phase and gave it
a directional ability.
The whole thing was wrapped in foam as in John's diagram.
The amp was any old AF amp but I found the best was obtained from scrap CB
radios of the time. Like ham radio, they had the human voice speech range.
In fact most of the bits came from CB as I was a 'Rig Doctor' at that
time.
In practice, I found that, if the mic was put outside my landing window
and aimed at the end of the garden path, about 30', it picked up the
voices of visitors who were talking about me before they came and knocked.
Often they talked about pleading poverty because I was an 'easy touch'.
Forewarned is forarmed, as they say. I could hear them in my shack and be
down at the door ready to open it instantly when they knocked, usually
catching a bit more of the conversation in the process.
None of them seemed to notice this.
Idle, useful and virtually free; I used them a lot for several years.
73 - Ian, G0TEZ @ GB7FCR
Message timed: 17:50 on 2008-Aug-31
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