On Sat, 10 Apr 2010 09:07:51 -0800, Bruce in alaska
wrote:

In article ,
Bruce wrote:

A new one.

I'm now residing ashore as I sold my sailboat. The place I rented is
nearly a mile for the marina and I can sometimes log onto the marina's
free Wi-Fi net using the laptop's built in antenna.. I am using a
Wi-Fi transceiver that has some level of amplification, or at least it
is sold as a "high powered" Wi-Fi.

I have built a parabolic antenna which (according to the rather crude
signal strength meters included with Linux) seems to approximately
doubles the signal strength and allows me to access two additional, of
the five or six different circuits at the Marina.

Question: I am now building a larger parabolic antenna system. The
original was a ten inch dish and the new one will be a 17 inch dish.
Are there any formula to estimate the additional gain of the 17 " over
the 10"? In addition the first effort was screen and the second will
be solid aluminum. Again any estimates of gain increase - decrease .

I realize that there are many slip between the cup and the lip and
nothing is certain about antenna systems so am looking for estimates,
best guesses, text book "rule of thumb" basically any information
about parabola size or material and gain.

I do have the basic formula to calculate the focus point and some
recommendations for F.L. versus diameter.
Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

Yes, there are formula for calculating Parabola Antenna Gain.... Google
should get you those. The difference in parabola material is directly
related to Frequency in that The mesh size needs to less than 1/4 of
wavelength in order to be effective as a reflector. Solid is better.
Antenna Feed System is a critical point in the design, as well as
getting the feed system aligned with the dish's focal point. there are
literally hundreds of 2.4 Ghz Gain antenna designs around the net. I
would look at the Pringles Cantenna, and some of the cheaper Grid Corner
Reflector types with simple Dipole Feeds. I use some nifty little Patch
Antennas, on my 2.5 mile WiFi Links that provide LAN extensions, up and
down the beach, for my Close Neighbors. (close + 10 Sq Miles)


Had done some looking and read up on various types. Settled on the
parabolic as (hopefully) the type is not as directional as the
Pringles Can type. Aiming the thing is a bit iffy without a sensitive
signal strength meter. But of course, a tighter beam is higher gain
:-)
The parabolic is actually easier for me to build as "wok" type cooking
pans are a dime a dozen and in all sizes.

Anyway, will do more research and see whether I can locate the gain
calcs.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)