deer2me22002 wrote:
> Can i use a uni-
> directioal mike in a parabola? Can i build my own parabolic? How can
> it be done?
Yes a unidirectional mic will work in a parabolic. The biggest problem
with them is that usually the mic picks up from the end, so you have to
aim it at the dish, which means it sticks way out there. Such a dish is
unbalanced to the front and tiresome to aim. The small tie tac mics make
about the best inexpensive mic for a parabolic.
The hardest part of building a parabolic mic is coming up with a
suitable parabolic reflector. You need one at least 20-24" in diameter,
but not too big or heavy to carry, plastic ones are a bit better than
aluminum as they ring less if hit.
You can buy a Telinga dish as a spare part from Doug if you can't find
anything else. The Telinga dish has the added advantage that it can be
rolled up, though not tightly.
As far as the rest of it, here's a drawing of one way, I picked this off
the net and modified it so it would be a bit more durable:
http://frog_recordist.home.mindspring.com/naturerecordists/pipes-2.gif
I went by home depot yesterday and picked up the fittings so I could
build a example. There I found some rug castors that are plastic disks
with rug on one side, Ideal for clamping the dish where I show rubber or
foam. I'll put up a page on this as soon as I have time to get it made.
I've got a spare dish for my Telinga and a Sony ECM-T140 mic I can use.
I got parts so I could make it out of 1/2" or 3/4" pipe, I'm sure the
mic support will be ok in 1/2", not sure on the handle. Be sure and find
the focus of the reflector before cutting the pipe to length. You
probably want to plug the threaded fitting with foam as well to keep
sounds from coming in up the pipe.
There are lots of variations, a parabolic mic is really fairly simple.
If you bought the Telinga dish and the sony tie tac mic new, you should
still be able to put it together for about $150 US. Most of that is in
the dish and mic. So finding those cheaper can save lots.
I've heard of folks making small parabolic dishes by heating a sheet of
thermoplastic held by it's edges until it sags to shape. Doing that with
a circle big enough to do a 2' reflector would be a bit of a
undertaking. It has to be heated evenly.
Walt
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