From: "Levon Louis" <>
>
> So who makes the best-budget parabolic mic or dish to make myself one?
> Sorry if I am coming in on the end of this.
>
> Levon
I don't recommend any of the inexpensive made up parabolics. They are
generally designed around picking up voice frequencies. Their mics are
usually quite noisy. And very often they are way too small a diameter.
You can easily build something better for the same money.
As far as I'm concerned the best full up parabolic for nature recording
is the Telinga. It is, however, not a low budget item.
One can distinguish between parabolic dishes and dishes near the right
shape, which are much more common. If possible stick with parabolic.
Cheapest is obviously a found one off somebody's junk pile. Takes lots
of looking sometimes. Usually it will be a small satellite tv dish,
which is designed with off axis focus, making building it up interesting.
The dish from the Telinga is available as a spare. It has several things
going for it. For one it's focus is inside the front plane of the dish,
which can make for less of the noises off to the side reaching the mic,
and makes it much easier to wind protect. It's also clear, which some
find useful in aiming it. Clear does have the advantage of creating less
of a visual signature to scare things as well. It is a very light dish,
and can be rolled for travel if necessary. Note that the rolled dish
takes a little time to regain shape, so more for airline travel than for
something like walking to your record area. Finally, if you get deeply
into nature recording with a dish you will lust after a Telinga until
you finally get one. Then the dish from your homemade becomes a spare
for the Telinga. Note that the Telinga itself consists of a whole system
designed to work together. It's not easier to do better, even starting
with the same dish.
Edmund Scientific sells some polished aluminum parabolic dishes,
designed for solar cookers. The largest size is ok for a dish. Note that
a parabolic dish can be a solar cooker, and it does not take polished
aluminum. Always use care with a parabolic as far as pointing it at the
sun, you can get your mic a bit too warm. Note also that metal
parabolics tend to "ring" more than plastic ones.
The only other one I knew of was available from one of the places that
supplies science fair and "spy" products. But they have discontinued it.
Similar places can be looked at.
As far as making a dish from scratch, it can be done. Make a carefully
shaped mold for a fiberglass one, for instance. A template cut to a
parabola and rotated over plaster can form the shape, for instance. It's
a large amount of work for just one dish, more like something for a
group. And unless you are very good with carbon fiber or kevlar, it's
probably going to be heavier than the above dishes. But the plus side is
you can make any variation you want.
You can short circuit the hand made process a bit if you have access to
a dish already that the owner is willing for you to make a mold from.
The mold is the hard part.
Note you want a dish at least 20" in diameter. The smaller the dish the
less gain you will get at low frequencies, and 20" is about as small as
you want to go for that reason. Unless, of course, you are specializing
in something that only calls in high frequencies.
Walt
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