[Hidden-tech] extended range wifi needed

[ussailis at shaysnet.com]

Here's some tips:

1. That cable form the antenna to the WiFi unit probably has more loss
(often MUCH more) than antenna gain. 

The larger diameter the cable, the less loss. So keep the cable very short
and of large diameter. For example, one foot of RG-58 has a loss of 1 dB at
the 2.45 GHz WiFi band. 

For most conditions this is loss on both transmitting and receiving. It is
a double whammy.

2. Antenna gain. The gain comes from focusing the signal. Using multiple
antennas to serve several users defeats the gain. However, properly phasing
two antennas to point at the same spot increases gain at the "expense" of a
smaller beamwidth.

Omni-directional antennas have a limited gain. About 6 to 8 dBi is it.

There is a lot of BS in the antenna gain / performance area. Gain rated in
dB is pure BS, as dB is a relative term. So what is it related to?? Older
antenna guys often a used 'wet noodle' as the gain relation for some poor
antennas. 

Gain should be given in dBi (dB with respect to an antenna that radiates in
all directions), or dBd (dB with respect to a dipole antenna). ANYTHING
else can be BS. 

Gain should also include antenna efficiency. Often it doesn't.

A Yagi antenna might be a good choice. The Pringles can is also a good
choice, except for the aluminum foil coating in the can which will corrode
and reduce gain over time. You might try a equivalent size copper pipe (if
you can afford it!)

Most of the 'flat panel' antennas that I have seen and taken apart are not
very good. You could make a 'patch' antenna from some sheet brass that you
can get at the model store. There is a program that will design a patch,
PCAAD. I have found it has a 6% error, design the antenna for a 6% lower
frequency, and it will work just fine.

I have even seen a snow-sled used as a reflector antenna at the WiFi band.
Worked fairly well. Do a Google search for HBO snow-sled antenna. [about 20
years HBO used a nearby frequency to transmit to apartment complexes]

3. Next get an amplifier. The maximum allowable signal level for most WiFi
setups is 1 Watt. (some conditions allow 4 watts). 

You need a 'two way' amplifier. This device works on both transmitting and
receiving. Be careful, the gain on the receive side should be no more than
the cable loss from the amplifier to the WiFi unit.

Again, the best way to do this is put the radio portion of the access point
almost at the antenna, with the amplifier. Those plastic freezer boxes are
good to keep the weather out.

Even though the cable between the amp and the access point is very short,
you will still need a 'two-way' amplifier as you need something to switch
between transmission and reception. 

Switching is done very fast. Most users don't believe that there is a
switch, but there is.

4. It is important to not seal the enclosure that houses the stuff at the
antenna. Always have a vent hole on the underside. This might be contrary
to what you read, but think of it as a hole to let the water out.

There was a company in Cincinnati, OH that made a two-way amp a few years
ago. The owner's last name is Janning.


Jim Ussailis
jim at nationalwireless.com

Original Message:
-----------------
From: Kiernan G-S greenearthcomputer at gmail.com
Date: Tue, 5 Jul 2011 20:23:36 -0400
To: dan at nachbar.com, hidden-discuss at lists.hidden-tech.net
Subject: Re: [Hidden-tech] extended range wifi needed


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