[NLRS] 2.4 GHz antenna

[Baker, Donn B]

'Morning, Ford.
One thing to try, and its easy to do, is a "corner reflector," with a 180° apex angle.  In other words, a simple flat metal sheet placed about 0.25 to 0.3 wavelengths behind the collinear.  Shoot for a spacing of 1.5" or just a little less (0.25 wavelength is 1.21"; 0.3 is 1.45").  The sheet needs to be at least 1 wavelength wide and should be about that both above and below the top and bottom of the collinear.  A piece of heavy duty aluminium foil will work just fine.  Tape or rubber cement it to a piece of cardboard for stiffness.

This won't provide a lot of gain, maybe 5-6 dB.  (My antenna books are at home, so I can't look anything up.)  Making the apex angle less than 180° will increase the gain (max of about 10-11 dB), but of course will reduce the beamwidth.

One other thing to look at is the orientation of the collinear with respect to the house.  For example, is the house above (or below) the height of the antenna ?

          /\
         /  \
        /    \
        |    |                                 /                     /
        |    |                                / \                   / \
        ------                            |  /   \              /  /   \ 
                      Max radiation <-----|  |   |             /   |   |
                                          |  |   |            /    |   |
                                             |---|                 |---|
                                       antenna IS         antenna SHOULD BE
 If so, try tipping the antenna so that its broad-on toward the house.  This might help.  (Same with the corner reflector).

Good luck... let us know how it works out

73 Donn
WA2VOI/0

> -----Original Message-----
> From: nlrs-bounces at mailman.qth.net
> [mailto:nlrs-bounces at mailman.qth.net]On Behalf Of Ford Peterson
> Sent: Thursday, August 04, 2005 10:38 AM
> To: NLRS at mailman.qth.net
> Subject: [NLRS] 2.4 GHz antenna
> 
> 
> 
> 
> I've got a problem looking for a solution.  It's my wireless 
> network at the home QTH.
> 
> I get my high speed connection from the top of the water tank 
> in Dassel, about 3.5 miles from the shack.  I use a 24dBi 
> dish to gather about -60dBm of signal for the connection.  
> That one works FB at up to 1.5MB/sec.  Connected to my LAN in 
> the shack is a 802.11G router with dual antennas.  A simple 
> mag mount collinear on the outside wall provides a local hot 
> spot for up in the house, some 200' - 220' away.  My XYL uses 
> the link to access the internet and my LAN in the shack.  The 
> trouble is, her connectivity on the laptop is poor.  Near a 
> window she gets 2-3 bars of signal (whatever that means) but 
> loses the connection from time-to-time.
> 
> So I'm looking for an antenna design that will provide decent 
> gain at 2.4 GHz, but has a beam width of about 30 degrees.  
> The 3' - 24dBi dish is too narrow to illuminate the whole 
> house.  Anybody got any ideas on a good design?  
> 
> Ford-N0FP
> ford at cmgate.com
> 
> 
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