On Thu, 19 Jan 2012 21:22:26 +0100, Ben / SM0KBW wrote:

The stability is one of things I want to study - and you're probably
right in that long term stabilty will be a problem. I've done some
calculation and used 45% efficiency and the result was around 30 dB.

I don't think it will be too horrible as long as the antenna parts and
pieces can be adjusted for optimum performance. At 1.2Ghz, that
shouldn't be much of a problem. If you were building at 10GHz, I
would be seriously worried.

Yes I've thought about single curved parabolic reflectors as you
describe, but it would give polarization in one plane only and the
standard is circular polarization for EME at 23cm.

Nope. As long as the width of the antenna is 1/2 wave or larger, it
will work with CP. I don't think that there's any way such a
reflector can convert circular polarization into elliptical (but I'm
not sure).

I will certainly consider inflatable antennas, funny idea!

Not funny. I've tried to build an inflatable tower for Field Day for
the last few years. Each year, something goes wrong, usually by
running out of time. With the proper materials and design, inflatable
antennas are fairly simple to construct out of vinyl and glue.

Incidentally, China has a storage space problem. So, for the annual
parades and events, all the decorations and props are inflatable. When
not in use, they're fairly small. Something like these arches:
http://www.china-inflatable.com/products/inflatable_arches_1.htm
Bosch Aerospace used to build inflatable towers for the military. It's
now LTA Projects. The videos are fun to watch:
http://ltaprojects.com
Yes, they have a ham version:
http://ltaprojects.com/ham.html

Galvanized Chicken net is easier to obtain, cheaper and as you wrote,
it was what people used in earlier designs.

WELDED galvanized wire mesh, not ordinary chicken wire. Most chicken
wire is not welded.
http://www.wirefenceonline.com/welded/gaw



--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

On Tue, 17 Jan 2012 07:56:44 +0100, Ben / SM0KBW wrote:

Hello!

I'm planning to build a parabolic reflector using aluminium net.

The kind of net i found is just a weave of aluminium threads, no
connnection between the threads. Is this going to reduce the performance
of the reflector?

The net is built of 0.4 mm thread and the hole size is 1.5 * 1.5 mm. I'm
planning to use the reflector on the 23 cm band.


73
Ben / SM0KBW

If these work at 2.5 GHz, I think you'll be able to use about anything as
long as the parabola is correct. http://www.qsl.net/n9zia/wireless/
page04.html

On Thu, 19 Jan 2012 07:46:40 -0600, dave wrote:

On Tue, 17 Jan 2012 07:56:44 +0100, Ben / SM0KBW wrote:

Hello!

I'm planning to build a parabolic reflector using aluminium net.

The kind of net i found is just a weave of aluminium threads, no
connnection between the threads. Is this going to reduce the
performance of the reflector?

The net is built of 0.4 mm thread and the hole size is 1.5 * 1.5 mm.
I'm planning to use the reflector on the 23 cm band.


73
Ben / SM0KBW

If these work at 2.5 GHz, I think you'll be able to use about anything
as long as the parabola is correct. http://www.qsl.net/n9zia/wireless/
page04.html

http://www.qsl.net/n9zia/wireless/pi...4dB_dish-1.jpg