"amdx" wrote in message
...
Please see subject line-- Help, Wifi Antenna-- on
alt.binaires.schematics.electronic
for a picture of my concept.
Looking to combine Helical antenna and Wifi adapter card in one unit.
My experience is limited to MW bcb. I know there are many pitfalls at
2.4Ghz, so I'm looking for feedback on how to do this properly.
I'm using the following page as my guide.
http://www.wlan.org.uk/jhecker.html

This is to extend the range of my laptop computer.

Mike

The Wifi Helical antenna is an awful lot of work, and the performance of
even long structures on PVC tubing is vastly disappointing. The easiest 15
dBi (my measurement) gain antenna is the Biquad. In fact, if you make the
biquad with circular instead of square loops, the construction is even
easier, and there's no problem measuring with all those bends - - just one
wavelength of straight wire in a circular loop for each section - -
http://www.wikarekare.org/Antenna/bicircle.html But try to keep a 50-ohm
coaxial configuration all the way to the feed points as in
http://homepages.ihug.co.nz/~redwood4/ It isn't necessary to keep the
polyethylene insulation - - for a short length of air insulated coax, the
tubing ID should be 2.25 times the center conductor OD for 50 ohms
impedance.

If you are like me, you will probably want to build the Helical anyway - -
just to see, and perhaps to compare against the two easiest wifi antennas
with decent performance - Biquad and Waveguide
http://www.saunalahti.fi/elepal/antenna2.html The easiest waveguide can is
the 83mm ID one you get with the 28oz size of Bush's Baked Beans or any of a
number of other products like canned spaghetti sauce or family size
Spaghettis.

See if you can get a USB Wi-Spy Spectrum Analyzer module, too - - try to
find one of the original (no external antenna - - cheaper) versions, and
just put it in your own shielding enclosure and make your own modification
to cut the path to the built-in antenna so that you can run a small coax to
a connector on the box for your own external antenna connection. This kind
of modification has been made by others - -
http://www.metageek.net/default.aspx...5&view =topic
scroll down to the post by pe2er on 9/9/06 showing how to connect a coax to
the board. I used a type N connector on my enclosure because it's universal
and strong, and filtered the three USB supply and signal wires with
feed-thru capacitors so no RF can enter the enclosure through these other
paths. Use Metageek.'s Chanalyzer software to run the Wi-Spy module - -
preferably version 2.0 before the current 2.1.4 came out, since the need for
compatibility with both the $199 Wi-Spy and the $399 Wi-Spy made operation
with the $199 Wi-Spy somewhat unsatisfactory. Maybe you can ask Metageek to
allow access to previous Chanalyzer 2.0 for owners of the older units. Why
do you want all this? So you can make accurate measurement of the
differences between antennas, using a reference 1/2-wave dipole, or the
standard RPSMA antenna you find on most Wifi Routers. The dB calibration of
the Chanalyzer display is very accurate.

Chuck W6PKP