We've had a LOT of fun (& publicity )here in New Zealand over DIY
antenna brewed up for 2.4GHz USB WiFi.See = www.usbwifi.orcon.net.nz
The parabolic Chinese cookware used gave ~15dB gain at 2.4GHz, but of
course any radiation will be concentrated at a parabola's focal point.
Aha - could suit "log cabin in the woods " cell phone boosting ?
Indeed it does, & 900/1800MHz GSM cell phone reception improvement has
also been verified when the phone is cradled at the FP.
Naturally you'll find it hard to speak at this position,unless perhaps
a Bluetooth headset used, but at least inward calls/text messages can
now be received. See = http://www.usbwifi.orcon.net.nz/cellbear.jpg
& http://www.usbwifi.orcon.net.nz/wokaxim.jpg

This sure beats constructing Yagis,& 12" woks here in NZ are just
~US$5! Stan ( ZL2AJZ )

We've had a LOT of fun (& publicity )here in New Zealand over DIY
antenna brewed up for 2.4GHz USB WiFi.See = www.usbwifi.orcon.net.nz
The parabolic Chinese cookware used gave ~15dB gain at 2.4GHz, but of
course any radiation will be concentrated at a parabola's focal point.
Aha - could suit "log cabin in the woods " cell phone boosting ?
Indeed it does, & 900/1800MHz GSM cell phone reception improvement has
also been verified when the phone is cradled at the FP.
Naturally you'll find it hard to speak at this position,unless perhaps
a Bluetooth headset used, but at least inward calls/text messages can
now be received. See = http://www.usbwifi.orcon.net.nz/cellbear.jpg
& http://www.usbwifi.orcon.net.nz/wokaxim.jpg

This sure beats constructing Yagis,& 12" woks here in NZ are just
~US$5! Stan ( ZL2AJZ )


Hi Stan,

Mine doesn't quite fit a paraboloid. Here's some fun checking the gain:

Gain approx= 10 D(waves)^2

My wok is about 36 cm, or approximately 3 waves. Thus I would expect about a
factor of 90 in gain with 100% aperture efficiency.

You've possibly lost about 2-4 dB. But--you're cookin' anyway:-)

73,
Chip N1IR

Chip - "cooking " is right ! We're "reflecting" on a small front
screen to enhance illumination in fact. Of course mesh parabolas
typically only have 80% of the gain of a solid dish, but extensive
field trials have verified ~15dB for the 300mm (12") mesh scoop at
2.4GHz, & ~10dB for a 170mm at the same freq.At say 1800MHz cellular
freqs, gain only perhaps 2/3rd this =10dB for 12"?

Ref numerous pix & lab. notes = www.usbwifi.orcon.net.nz to support
things

Stan ( ZL2AJZ)

. Of course mesh parabolas
typically only have 80% of the gain of a solid dish,

I would seriously doubt the veracity of this statement and would be
gratified to see valid documented evidence of this. If the mesh openings
are under 0.1 lambda the mesh will appear solid. The problem may be
achieving good surface accuracy with a mesh dish.Those of us using mesh
dishes on 1296 MHz EME are seeing excellent efficiencies with mesh surfaces-
ultimately limited by the ability to properly illuminate the surface. For
EME we tend to underilluminate the surface to take advantage of lower side
lobes and less spill over, which means "seeing" less warm earth noise.

Dale W4OP

. Of course mesh parabolas
typically only have 80% of the gain of a solid dish,

I would seriously doubt the veracity of this statement and would be
gratified to see valid documented evidence of this. If the mesh openings
are under 0.1 lambda the mesh will appear solid. The problem may be
achieving good surface accuracy with a mesh dish.Those of us using mesh
dishes on 1296 MHz EME are seeing excellent efficiencies with mesh surfaces-
ultimately limited by the ability to properly illuminate the surface. For
EME we tend to underilluminate the surface to take advantage of lower side
lobes and less spill over, which means "seeing" less warm earth noise.

Dale W4OP

Hi Dale,

A wok has no focal 'point': it is not a true paraboloid. Its the imperfection
in shape, not mesh:-) Ergo the loss in aperture efficiency.

73,
Chip N1IR

Fractenna wrote:

. Of course mesh parabolas

typically only have 80% of the gain of a solid dish,

I would seriously doubt the veracity of this statement and would be
gratified to see valid documented evidence of this. If the mesh openings
are under 0.1 lambda the mesh will appear solid. The problem may be
achieving good surface accuracy with a mesh dish.Those of us using mesh
dishes on 1296 MHz EME are seeing excellent efficiencies with mesh surfaces-
ultimately limited by the ability to properly illuminate the surface. For
EME we tend to underilluminate the surface to take advantage of lower side
lobes and less spill over, which means "seeing" less warm earth noise.

Dale W4OP


Hi Dale,

A wok has no focal 'point': it is not a true paraboloid. Its the imperfection
in shape, not mesh:-) Ergo the loss in aperture efficiency.

For the purposes of radio signals, does the shape need to be a specific
paraboloid? Certainly at optical wavelengths a parabola is needed to
focus light from infinity, so a parabola is needed. But at radio
Frequency wavelengths a true parabola is not likely needed. In fact,
considering the difference between a sphere and a parabols, I would
suspect that anything out there is not a true parabola unless it is
arrived at by chance.

- Mike KB3EIA -