Jim
No form was needed. Using cardboard from a shipping
box that contained some furniture I ordered, I cut out
12 sections as described on the web page and hot glued
them together.
The mounting ring keeps the parabola quite stiff.
After construcion I gave it two coats of shellac and
then spray painted it(not shown in pictures).
I used a cassette recorder at the time (cheap) and a
microphone made from a Radio Shack capsule as
explained in:
http://ourworld.compuserve.com/homepages/G_Kunkel/microphone.htm
I had glued a 2inch celluoid cone to the capsule to
capture more of the focus "sphere".
The difficulty was with the size. I had constructed it
to record some Great Horned Owls that were calling at
night in February. I could not close to them because
they were 200 feet below my house, in a steep gully,
and they called late at night. It there was any wind
the parabola was unmanageable. I had designed the
mount so that I could adjust the vertical angle
easily, but the direction was a matter of picking it
up and setting it down it what I assumed was the right
direction. Doing this in the dead of night when the
temperature was -10F cured me of the quest.
Later testing showed that the parabola with its 12
inch focal length was like trying to use a 50 x
spotting scope to see a warbler flying around in a
tree. Luck is too much a factor. If the owls would
call more often it would be easier. I subsequently had
more luck with the 18 inch parabola. If the size were
scaled down, or a better method of training the dish
were implemented it would become a powerful tool.
Greg Kunkel
--- Jim Morgan <> wrote:
> Greg,
>
> From the pictures on your website
>
http://ourworld.compuserve.com/homepages/G_Kunkel/cardboard/cardboard.htm
> you have done an excellent job of putting together a
> nice looking 52 inch
> parabola.
>
> I was wondering how you did such clean job of
> assembly. Did you use a form
> of some sort. Is there any problem with rigidity of
> the dish?
>
> I would expect that you are getting improved low
> frequency gain with a dish
> this large. Ever try it out on Mourning Doves?
>
> What do you use for a mic and recorder?
>
> I for one would be interested in knowing more about
> your experiences and
> results with this large dish.
>
> Thanks for sharing,
>
> Jim Morgan
>
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